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HANDtsOOKFOR RbVPILOTITECHNICIANS

By Chris Bell, Mel Baylissand Richard Warburton

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SABI.E Pfr -CIUGHSSIMD cabie ptoughs are n0w ths industry stanc1ari i Ti 'c. .sar-.rso{ ki iometres of cal i le have been bui ' ied on al l the malcr , r ; . , . .sT l rese p loughs are h igh ly deve loped re l jab le ma i ;h ines ar lp rov ide the bes t poss ib le cab le p ro tec l ion . w i th smal l s ize ,weight and pul l force. Larger versions nave been bui i t for theorlfield umi:il ical and power cable markets The conrprehensivecieci< equipment inciudes the unique and very ei fect ive Sl\ lDhandl ing system.

. : P T P E T R E T T I G H I N G P L O U S } I SThe EMC plough PL2 is the most aclvanced pipel ine pirLugh yetp r o d u c e d a n d h a s p r o v e d v e r y s u c t e s s f u l i n o p e r a t r o n .Diver less Ioading anci unloadrng is provicled by cornprehensivepipe handl ing equipment clesigned as an integral part of theplough Scphist icated iontroi and instrumentai ion providesmax imum i l ro tec t i0n lo r the p ipe l ine dur ing the t rench ingoperat ion. The equiprnei: t is provir led with the classic $MDstyle handling systen: tnai ensures safe and rapid cieploymcntand recovery.

T R A G K F f l t U E H I G I - E $T h e E u r e k a v e h i c l e f o i - B T M a r i n c i s L r ; " u i a r a n g e o fl ightweight , pourer fu l anLj versat i ie t racked vehi0 les designedand manufacturecl by Sl \10 for d iver less 0perat i0n. ThBSevehicles can be fitted v;ith a range of trenching ioois 1o provide

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rttech lnternational Ltd US Disttibutor :Slenesk. Kingswells, MECCOAbetdeen AB1 gQA. UK Tel : (206) 788 4522Tei : ++44 224 744111 Fax : (206) 788 0639Fax : ++44 224 741771

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Re-ordering

Addit ional copies of Handbook for ROV Pi lot / Iechnicians nray be obtained by

contact ing OPL direct at thc address, telephone and fax numbers given at the foot of

this page.

This Book has been carefully preparetl from the best eri.^titrg sources of ittformation

avai[able at the time of prepatution but O PL do trot guarantee lhe accuracy of the book

nor of the limits, exteilt or position of aill cartographicreprcsentation delineated thercitl

nor do OPL assume any responsibility or liability Jbr any relianu thereiin.

Homend House, PO Box 11, L.edbury Herefordshire HR8Tel: (01531) 64563 Fax: (01531) 634239

HandbookforROV Pilot/Technicians

@ Copyright

Handbook for ROV Pi lotvTechnicians, is the exclusive copyright of the publ ishers and

may not be reproduced in whole or part without the written permission of Oilfield

Publ icat ions Limited.

1BN, England

tsBN I 870945 67 0

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Foreword

Over the last 20 years or so, ROV Pilots and Technicians have had to master moreand more trades and skills. In these days of small operations teams, working withever more complex systems, usually far from home and 'the beach', they areexpected to keep all of their equipment at I00"/" availability as well as use theirspecial skills in navigating their vehicles safely and surely around all the hazards ofthe sea.

All ROV businesses have been built upon the professionalism of their Pilots andTechnicians. As new successful operations generate new skills, this in turn promptsadvances in vehicle technology, and this continuous cycle of change makes the lifedemanding and challenging. If there were any limits to the progress of ROVactivities they would be, in the end, set by the people who actually know and drivethem.

In this refreshing handbook, the authors have skilfully brought together a greatwealth of practical knowledge and experience of ROV operations, addressing all ofthe technical, operational and management disciplines in a clear and comprehensivemanner, as well as including plenty of 'hard to find' technical reference data. Nomatter whether you are a shore-based manager, operations supervisor, systemdesigner, interested bystander or actually at the sharp end "hands on the sticks", itshould be kept close by.

About Marcus Cardew

Marcus Cardew spent 9 years at sea as a Navigator. He then spent 2 years workingwith manned submersibles then 8 years as technical and operations director of SubSea Surveys before moving to Slingsby Engineering as technical director. For thepast 10 years he has been running his own business 'system Technologies' inUlverston , designing and manufacturing a range of underwater and vehicle systems.

/

About The Authors

ChrisBell isaCharteredEngineerwll! twelveyearsexperienceaSanRoVsuperintendenr. He h;$;";";il;;;ili.; i"i tr'J development of the presentlv

recosnised ROV training schemes'

uet-naytissisaMernberofthelnstituteofNon-destructiveTestingwithextensiveexperience in inrp""itJ"^oi'tu ir.aaitl*;;nbn;rpection- Heleaches on cswlP

FhiaseT approved courses at all levels'

Richard warburton is a specialist in ROV Electronics and Hydraulic systems with

extensive offshore exPerience'

\

Acknowledgements

The Authors are glad to acknowledge and offer their appreciation to the followingcompanies; all of whom have offered assistance with t1re preparation of this handbook.

Ashtead Technolog5.

Bowtech Products Ltd

BT (Marine) Ltd

De Regt Special Cable BV

Hawke Cable Glands Ltd.

Graham Mills, Oceaneering Ltd.

MacArtney Underwater Technology A/S

Slingsby Engineering Ltd

Systems Technologies

Teeside Valve and Fittings Co. Ltd.

TSS (UK) Ltd.

iIl

* ROV BATHYMETRY UNITSI 45 Units delivered I Digiquartz pressure sensors andMesotech altimeters I Fast update (6/sec) I Compactone-piece subsea unit fits most ROVs I 24v DC power forsubsea unit I Pitch/roll and conductiviry options

* VIDEO OVERLAY UNITSI Pal or NTSC I Colour text and graphics I Mulri channelI Expandable

* vtDEo slvtTcHERsI Desk top remote control I 8x 16 and l6x 15 matrrces

* INNOVATUM MULTI SYSTEMI Still the ONLY system for deep pipes and cables I Rentalunits always available.

* MULTIPLEXERS & CONTROLSYSTEMS

I For ROVs and other remote control applications I 45+systems delivered I Upgrade/enhance old vehicles

* MINI MANIPULATORI 4 Function I 220v AC powered I Integrated power unit andvalve pack I Microprocessor control I Complete with surfacecontroller I Fits most small/medium ROVs I Put hydraulicpower on electric vehicles

* I'' WIRE CUTTER AVAILABLEsooN *

* MERPRO SUBSEA HYDRAULICEQUIPMENTI Valve packs I Pan and tilt units I Manipulators lCamerabooms I Actuators

tf,RPR0 conrnol sysrEMs LtdUnit 10, Wellheads crescent Trading Estate, Dyce, Aberdeen, Scotland AB2 oGATel: (44) 1224n2150 Fax: (44) t224n2166

ITTDTRT'TRO CONTROL SYSTEMS Ltd

DEDICATION

TheAuthorswouldl iketodedicatethishandbookto:-

Sue Hamiliton

Sue Jones

Marion Else

without who'S hard work and timely assistance this manual would not have been

Produced and to their wives:-

Pam

Maria

Belinda

for their Support, encouragement and.patience without which this book would not have

been written.

\

Bib l iography

Underwater Inspection

Remotely Operated Vehicles ofthe World

An Introduction to ROV Operations

Pipeline Rules of Thumb Handbook

SUT Underwater Technology Vol18 No 2On-site Tests for Underwater VideoPicture Quality

SUT Underwater Technology Vol 6 No 2Snorrl Subsea Control System

SUT Underwater Technology Vol 15 No 4Advances in Underwater Inspection andmaintenance

SUT Underwater Technology Vol 17 No 2Application of a Remotely OperatedConstruction Vehicle

SUT An Introduction to RemoteiyOperated Vehicles Two Day Course23-24 February 1994

BT (Marine) Quality Manual

Implementing Quality Through BS5750

The Quality Management Manual

Electronics TEC Level II

D Shon, M BaylissE & FN Spon Ltd.rsBN 0-419-13540-5

D Gallimore, A MadsonOPLrsBN 1 870945 59 X

G Last, P WilliamsOPLrsBN | 810945 23 9

E W McAllisterGulf Publishing CorsBN 0-88415-094-1

RW Barrett, M Clarke,B Rav

P Jackson, D AshtonKogan Page LtdrsBN 074940797 2

J Waller, D Allen, A BurnsKogan Page LtdrsBN 0 7 494 0903 7

D C GreenPitman Books LtdrsBN 0273 01827 2

R L TuckerHeinemann NewnesrsBN 0 434 91978 0

Optoelectronic Line Transmis sion

Electronics Servicing Vol I

MTS Ooerational Guidelines for ROVs

K J BohlmanDickson Price PublishersrsBN 0-85380-166-5

r r r other useful reference books on underwaterworking from the offshore specialists

Remotely Operated Vehicles of the WorldThis new book provides for the first time a complete anddefinitrve illustrated relerence to

'what's what' and 'who's

who' in this hiqhly specialsed lield of underwater activity.

ln addr t ron 1o orv rng up to da te 'dnd hrgh ly de ta i ledlniormatrononevery ROV, including subseaploughs andother towed vehicles, it provrdes firll editonal listings ofmanufacturers, operators and vehicle developmentcompilies too. Other sections cover equipmenvsystemsmanufacturing companies and thetr worldwide agents,product listings covering lights, cmeras, manipulatorshandlirg equipment, buoyancy, flotation umbilicalscables and connectors, motors, thrusters, nav/tracking,sonar and acoustics and ROV support vessels. There arealso full dfectory listings of all compmies involved inROV operations and underwater contracting includingengineering and consultingr firms.

If you ae already familiar with our 'vessels of the world'series books then you'll know that we take theircomprlalion ver\, senously Thrs book rs no exceptron.so if you are interested in subsea operalions and rnparticular ROV's and thef related systems order you

copy today.

Paqes: 296 approximatelyPrice: S95 (inc p&p)

Product Order N": ROV,/W/ I

An Introduction toROV OperationsThrs book has proved so popular that we haverecently had to commission its first reprint, tosatlsfy the steady demand from readers whoappreciate its clear easy to read format andthe substantial amount of information itcontarns. Much of lts contents. because thebook's authors have ltrst hand prrctrcalexperience inthe field, is simplynot availableelsewhere, so if the facts on ROV operationsne rmportant to you order your copy nowyou won't be drsappornted.

Pages:300Price: i65 (inc p&p)Produa Order N": ROV/OPS

An Introduction toDiving OperationsOffshoreA comlete overuiew of today's offshoreindustry drving technrques, equipment andoperahons.

Pages:300Price:965 (inc p&p)

Product Order N": DIV/OPS

OrderingIi you would hke to order any of these books or would like a FfiEE copy of the OPL Catalogue listing over 400 maps, books,dtrectorres and databases contact us at the address given on the title page

10

Chapter LtChapter2Chapter 3lChapter 4"ehapter 5uChapter 6tChap|erTChapter 8Chapter 9

'Chapterl0Chapter 11Chapter 12

"Chapter13thapter14Chapter 15Chapter 16

{hapter17Chapter L8-Chapter19Chapter20

HANDBOOK FOR ROV PILOT/TECHNICIANS

TABLE OF CONTENTS

Introduction .. ... 13Offshore Safety ..- l7Types of ROV- ... 31Oiishore Structures ...... 39RovApp l ica t ions . . . . . .47ROV Ele-ctrical Systems .--... 79Use of Test Equipment Il7ROV Hydraulic Systems 131High Pressure Hydraulic F-ittings ... 167ROV Hook-Up, Pre/Post Dive Checks ... l7IElectrical Maintenance I75Mechanical Maintenance . I87Emergency Procedures 197Comriuniiations ..--. 203Underwater Video .. 207Underwater Photography .....- 213Seamanship . . . - . - - . - 237Drag, Buoyancy & Nav iga t ion . . . . . . . . ; . . . . . . . . 269fifofing St<ltts a tne Use of SonarQuality Assurance . 299

l

APPENDICES

The appendices contain useful technical information & Datasheets .. 301

11

Birh!

ffiThe [lnderwater World

Comes to Houston, Texas

January 16-78, 1995

Man & MachineUnderwater

The combined annucrl conference of theAssociation of Diving Contractors and the

ROV Committee of the Marine kchnology Society

D^n7n ;7^ ;+ - More than 1OO unde rwa te r con t rac to rs ,L X I L L U I . L ) e q u i p m e n t s u p p l i e r s a n d i n d u s t r yo rgan i za t i ons w i l l d i sp lay t he l a tes t i n new unde rwa te rservices, products and capabil it ies.

P r o gr am I;,:? ili=" f ff :J:? :fl? ?",:i n:: :J: Ttr1advar i -c i n g tec h nol o gy, ope rat ional exper ie nce, safety,regulations, commercial concerns and policy issues.

Tl , - , - L- A Dinner Dance, Exhib i tor 's Recept ion and gala

L y e n 6 c o c k t a i l P a r t y o f f e r r e l a x e d s e t t i n s s t oexchange information and review new ideas.

U n d e r w a t e r I n t e r v e n t i o n i s t h e n a t i o n ' s l e a d i n gcon fe rence devo ted to unde rwa te r t echno logy . Ove r3 ,OOO indus t r y pa r t i c i pan ts and the i r cus tomers w i l l be

t h e r e . . . . W i l l y o u ?

' - tggS -

Smtrurtion

ts$trcgtisn

hstallalion

FiFclines

HScs

Hdfirms

.,,,,hn1a Ct] .1 ' , , . . . . . , l , ' . ' .

,'',,.HEfnlaliun

i,,:-tir.iri.t:i.tt ..

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Exhibit - ParticQtate . Attend

Is reseiue lnlrg inflmation contact tltc Ul'$5 Gummittee at:

(713) e874808Fax (713) 987-4809

P.O. Box 130937Houston, TX 77219-0937 USA w

I

i

CHAPTER 1 INTRODUCTION

1.0.1

This ROV pilotflechnician Handbook has been written to compliment theAssociation of Underwgte-r Engineering.contractors (known as

'the AODC) recognised

RoV Pilotflechnician Inductidn and s[ills course, und ir the product or sJ"erar"yearsexperience. running__such courses. It is intended to be the first'in a series by the sameauthors to include Handbooks for: ROV Inspectors, ROV Systems/Survey E"gi"iriiand ROV Managers to include Offshore Superintendents. in addition to"beinglggliredreading for the, now well established courses, this handbook is likely tobecome a ref'erence_ bookfor ROV Systems Operators offshore and others suih as Sub!9.a EnSineers and Manufacturers who may hdve an interest in the work of an ROVPilotfechnician. The aim of this handbook is to present concisely the essentialinformationrequired py ROV Pilot/Technicians in their everyday'work that "*b1",thern to work both.to.fuly and effectively in the offshore induitri6s, in particutar, ttrepetroleum and cable laying industries, but also the growth industries of mine counter1t911urys (MCM), anti-terrorism and drug interveniion. Much of the technology ofROV design is_common to all typgl whidh is reflected in this handbook bylrre lrse orgeneric examples rarher than sp.ecific Boy types, where appropriut", "-pllusisingcommon features and the enabling technologiis. Practical tixeicises are.included toallow the reader to practice the mEthods desiribed in circumstances where suitableequipment and supervision are available. This enables the handbook also to be usedtor the structured training of personnel who started working in this industry prior tothe establishment of the present training programme.

1.0.2

A programme of training.modules and assessment is now established and, clearly$Pyn in Figure l. The first hurdle that must be negotiated is foi trre ptoifeaiueROV operator to become a Technician or Engineer

"*lttr at,itities in Electrical

Engineering, Electronics, Mechanics and Hydraulics. It is not normal in the UK forstudents to receive this breadth of training and it is therefore more usual for them tohave specific skills,and to rely on-the Indirction and Skills course (Module l) tointroduce them to the essentials of the other disciplines. Thorough cross training isthen achieved through experience and attendancsof further nrodlles of trainins ascareers pro.gress. At the time of writing it is expected that the AODC will beein aprocess to introduce a 'Certificate

of Conrpetenie' for ROV Operators basJ"on bothtraining. and experience, this will enable a'register of competent operators to beestablished, and may well prompt nrodificati-ons to this course structure. It isbglieye{' however, that thi.s proiess will take a significant ti-. ""J-th"t'ttrisianouootwtl l t tnd a place as essential reading for this scheme. A funher module beins acondensed version of Modules l, 7-and 8 containing essential -.f.;t i;i"rmu?Jn rnuythen be offered for the experienced -operator requiriig updatecl safeiy inrormaiion asan essential c.omponent.of the 'certifiaate

of competeice' scheme. There are anumberot recognised routes to becoming a Technician or Engineer and full details should be::,Yqll,ft9p the.Engineg.r^r.ng Council or other recogni"sed body, but ttrey inCfuOe tfretollowrng_ technical,cpalific.ations:- Degrees, HNCor HND, city and Guilds andNational Vocational Qualifications at le-vel 3'or above. Cornplirirent.y pi*1ir.fexperience, such as apprenticeships, may be required in acldition to thesequalifications but where sufficieni relevant expirience has been obtained, this alone..oy.bq acceptable to enrol for the ROV Pilot/Technician Induction anO Stitti Courrr,which is the first srep to comperency and to which this Hanclbook applies

13

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r.0.3

Ttre aims of the ROV Pilot/Technician Induction and skills course and this book aresrmilar and are to ensure that the Trainee Pilotflechnician has the essential knowledgeand skills to enable him to work both safely and effectively from his very firstoffshore tour of duty. This is essential in the modern ROV industry as therequirement for lower costs has reduced the crew sizes to the minimum, often onlyF^,o or three, and there is rarely an opportunity for extra-numerary trainees to beincluded. In addition we lay the foundations for future learning by explaining theprinciples of the enabling technologies such as; 'O'rings, video cameras, telemetryand hydraulics. Our industry is practically based and in this respect this Handbookacts as a guide to practical exercises and an identification of the skills required, theseexercise should be adapted to the training environment and equipment available.

1.0.4

The subjects that this handbook cover are wide ranging and diverse making itnecessary for the reader to have a grasp of scientific fundamentals such as electricity,hydraulics, and photography prior to reading it. There are many books availableexplaining these fundamentals and the reader is recommended to familiarise himselfwith these before taking up this course of study.

1.0.5

The technical levels described are equivalent to the National Vocational Qualification(NVQ) at level 3. The specific qualification recommended is the EngineeringTraining Authority (EnTra) NVQ Level 3 in Engineering Maintenance, Electro-mechanical option, adapted for ROV equipment. In addition to technical information,this handbook contains valuable information on Offshore safety, ROVs and theirapplications, Quality Assurance systems, photography, seiunanship and many othersubjects essential for successful ROV operations.

1.1.0 Backgr<lund To The Industry

1.1.1

As early as 1953 in the USA, the development of a diver propulsion vehicle by acompany called Rebikoff produced an ROV called Poodle which was used to locateshipwrecks. In 1966 CURV a US Navy vehicle assisted with the recovery of anumber of hydrogen bombs inadvertently dropped by the Americans into the Atlanticoff Spain. The potential of these systems was dramatically demonstrated in 1973when CURV 3 assisted in the rescue of a Pisces class manned submersible in 1575 ftof water off Ireland. The years 1973 to 1978 where dominated by fully autonomousbattery powered manned submersibles operating in either diver lock-out orobservation mode. In observation mode these manned submersibles where used forgeneral intervention work and surveys much as ROVs are today, and in diver lock-outmode they where used as a means of carrying and supporting divers in saturation.The years 1973 to 1977 saw a remendous developnrent of computer systems andtechnologies enabling the boom in ROV manufacture and use after 1977. The TROV(ISE) and as a result of US Navy backing the SCORPIO (AMETEK) and RCV 225were introduced to the commercial sectors. The SCORPIO was initially intended as amine recovery vehicle and the RCV 225 was designed to be 21 inches in diameter sothat it could be deployed though a torpedo tube. The 'classic' configuration of thesevehicles has since been reproduced with less expensive alternatives such as theHydrovision Diablo and Hyball ROV systems. There were around 20 ROVs inoperation by 1974, mainly in military or scientific applications, this had risen to 100by 1978 and is estimated to be over 2000 in 1994 with over 150 different typesavailable from over 60 different manufacturers. The development of ROVs has

15

slowed since the oil price fall of 1985 and there have been many recent criticisms of

itrr .Uifity of the offitoi. indutt.V 1o-{und future developments' Although much of

ifr. i"rtrn"ofogy is ,o**on to all ROVs these criticisms are not completely founded as

new deuelop"-ents are underway, pafiicularly in the areas of fibre optic telemetry'rrlgn Oenniiion tV sysrems, Sens6rs and other ancillary.euuil,menl. -1\:t l""*ffunaing markets in mine counter measures, anti-terrorism,-drug interdiction and for

AUVs (Autonomous Underwater Vehicles).

t.L.2

There are basically three main classes of ROV; The small observation class ROV, The

Work class ROV lna ttre Tracked vehicles/ploughs. These have been sub-dividedinto Low Cost ROVs (LCROVs) and Heavy, Medium and Light-work ROVs TanyU"in[proulAiA wittr a'survey opiion. _Ther6 are custom built ROVs for particularapplicitions, but ROVs ate oftdn modified to produce'hybrids'. For exampleSii";;bt E"gineerlng provided a TR_OJAN vehicte for intervention and drill suppo:tioi"i u'-oaltieA.,"riiloknown as CHALLENGER fo-r platform Inspection R"!{I-

and Maintenance finMl, and a tracked version for cableiepair work 5n9*l as ROV128. This same compuny no* provide a state-of-the-art vehicle that is designedarouna flexibility known as the MRV (Multi-Role Vehicle). More detailed .a"i.riptt""i of {OVi and their applications follow in later :.hapigrs: ili: tY_f.f,tlient to

t"V fii". itt.t the ROV industry.is i fascinating multi-disciplined industry, which has

enioved rapid growitr in a relaiively short peri-od of time, and.!p the potential for

"dhiii"".fi"u.R.tt to open up as it-matures. Central to the ability of the industry to-meer furure challenges'*itt 6. the knowledge and skills of its personnel. It is hopedthat this book will 6e able to make a small contribution to these.

t6

CHAPTER 2 OFFSHORE SAFETY

2.0 Introduction

The various operators in the North Sea take their responsibilities under the various Actsof Parliament and Government legislation very seriously. Before an individual isallowed onto any offshore worksite that worker must be medically fit and must hold avalid offshore survival certificate issued by an approved cenffe. Safe working practicesare encouraged and it is mandatory to wear the specified protective clothing andequipment. Failure to comply would result in dismissal. All new personnel are given aplatform safety briefing on arrival which is specific to that platform or worksite. Theoperators recognise that offshore worksites can be dangerous places and therefore doall they reasonably can to eliminate the dangers. As part of this safety philosophy apermit to work scheme is adopted generally throughout the North Sea., This scheme isoutlined later in the handbook in more detail but in essence the intention is to ensure thatalY work which is not of a routine nature is only undertaken with written permission.This ensures that all safety considerations are made before work commenCes. TheHealth and Safety at Work Act also places an onus onto individuals to be safethemselves and not to endanger work mates. It is most important that offshorepersonnel take note of these safety requirements.

2.0.1 Legislation, Codes of Practice and Guidance Notes in the UK.

Acts of Par l iament :

1. Health and Safety at Work etc. Act I974Pwt l2. Offshore Safety Act 19923. Mineral Workings (Offshore Installations) Act 19714. Territorial Sea Act 19875. Petroleum Act 19826. Oil and Gas (Enterprise) Act 19827 . Offshore Safety (Protection Against Vicrimisati on) Act 1992Statutory Instruments:

SI 289

SI 308SI 399S I 4 1 9SI 486

SI 608S I 6 1 1

SI 679sr 680

SI 702

SI 703

S I 7 1 ISI 835SI 840

S I 9 l OSI 923

The Offshore Installations (Construction and Survey)Regulations 1974Well Control (Amendntent) 1991Health and Saf'ety (Diving Operations) at WorkApplication of Statutory InsrrumentsThe Offshore Installations (Life-saving Appliances) Regulations1977The Diving Operations at Work (Amendnrent) Regulations 1992The Offshore Installations (Fire Fighting Equiprnent) -

Regulations 1978The Offshore Installations (Amendment) RegulationsThe Submarine Pipe-lines (lnspectors and Sifety) (Amendment)RegulationsThe Offshore Installations (Registrarion) Regulation s 1912(Amended by SI 679)The Offshore Installations (Managers) ReguIatiorr l9l2(Amended by SI 679)Asbestos (Prohibitions) (Amendment)Inspectors, etc.The Health and Safety at Work etc. Act 1974 (Applicationoutside Great Britain) Order 1989Asbestos (Prohibitions)Diving Operations Revoked by SI 1823)

17

F

SI971 The Offshore Installations (Safety Representatives and SafetyComnrittees) Regulations i989

SI 978 Included Apparatus or WorksSI 996 Diving Operations at Work (AmendmenQ ̂SI 1019 ttre Offshore Installations (Operational Safety, Health and

SISISI

SISISISISISISISISI

SISI

SISI

SISI

Wetfare)Regulations 19761029 EmergencyPiPe-line\alve1106 Prevention of Oil PollutionIZyZ The Health and Safety ar Work etc. Act 1974 (Application outside Great

Britain) Order l9ll1248 Control of Lead at Work1289 Employer's Liability (Compulsory Insurance)1331 Safety Zones1333 Ionising Radiations1398 Prevention of Pollution1443 Compulsory Insurance1513 Subnrarine PiPelines SafetYI53l Control of Explosives1542 The Offshoreinstallations (Logbooks and Registration of Death)

Regulation s 1972 (Amended by SI 679)1542 ttr[ Offsnore Instaliations (Emergency Procedures) Regglations. 1976

167 | The Offshore Installarions and Pipeline Works (First-Aid) Regulattons1989

1672 Operational Safety, Health and Welfare and Life-SavingAppliances.tisg The Offshore Insiailations (Well Control) Regulations 1980 (Amended

by SI 308)1823 Offshore Safety (Repeals and Modifications) Regu.latiols 1993

lB42 The Offshore Installations (lnspectors and Casualties) Regulations 1973(Amended bY SI679)

SI 1890 Freight Containers (Safety Convention)SI 1985 Subnrarine Pipelines Safety (Amendntent)SI 2002 The Merchant Shipping (Prevention of Oil Pollution) (Amendment)

OrderSI 2040 The Merchant Shipping (Prevention of Oil Polltrtion) (Amendment)

sr 2051s I 21 15sr2292

RegulationsThE Management of Health and Safety at Work Regulations 1992

Control of Asbestos at WorkThe Merchant Shipping (Prevention of Pollution by Garbage)Resulations

SI lZ32 and SI 1019 specifically refer to fixed installations and apply on or within

500m of these. The other regulations and Codes of Practice should be used asguidelines and although notln themselves legal requirements failure to follow an

ippi"""O "ode coulcl 6. .onrtru"d b_y_ a court-as faiiure to meet the recluirements of the

fiSnWn. Operations outside the UK will be govgrry{ Py ,lt. laws of that country

*fti.fr -uy not be the same as UK law. If in d=.oubt British Standards, Codes of Practice

and UK legislation are a good guide to saf'e working practice.

AODC Guidance Notes:

AODC 016 Crane HooksAODC 032 Remotely Operated Vehicle/Diver InvolvementAODC 036 ROV Handling Systems (UK)AODC 033 Responsibility for Underwater Inspection^AODC 051 Guibance Noie on the Safe and Efficient Operation of Remotely

Operated VehiclesAODC 060 Sifety Procedures for working on High Voltage Equipment

18

N

AODC 061 Bell Ballast Release Systems and Buoyant Ascent in Offshore DivingOperations

AODC 062 Use of Battery Operated Equipment in Hyperbaric ConditionsAODC 063 Underwater Air Lift BaesAODC 064 Ingress of Water into U"nderwater Cylinders Charged by Means of a

Manifold SystemCode of Practice for the Safe Use of Electricity Under Water

DMAC 06 Recommendations The Effect of Sonar Transmission on CommercialDivins Activities

Safety Notice2193 Crane Sling Hooks Used to Deploy Equipment Sub Sea

AODC/DMAC Publications mav be obtained from:

AODC,177 AHigh Street,Beckenham,Kent,UK,BR3 lAH

Government legislation and Statutory Instruments from:

HMSO

2.0.2 Medica l F i tness.

The Offshore operators require their personnel to be medically examined by anapproved doctor. There is a prescribed form to the medical and it is valid for:-

5 years for workers under 40 years of age.3 years for workers 40 to 50 years of age.1 year for workers over 50 years ofage.

The medical includes a dental fitness inspection.

2.0.3 Of fshore Surv iva l Courses

There are various approved offshore survival centres which are authorised to issuesurvival certificates. The centres offer 3 and 5 dav survival courses desisned to teachoffshore personnel the basics of fire fighting, survival in the sea, helicopier safety andevacuation and general first aid including EAR and CCM. The 5 day course certificateis valid for 5 years. The 3 day course is a refresher which lasts for 3 or 4 yearsdepending on the individual operator's recluiremenrs.Addresses of UK Centres:

For general information:

Central Training Register,Offshore Petroleum Industry Training Board,Forties Road,Montrose,Angus,DD1O 9 ET.

RGIT,Survival Centre Ltd.,Aberdeen

19

7

2.L Responsib i l i t ies

Under the Health and Safety at Work Ac(HSAWA) and the Offshore Installations(Operationai Safety, Healtti and Welfare Regulations); Statutory Instruments (SI) 1019.Th^e employer has a responsibility to ensure the health, safety and welfare of hisemployees and to provide "...such information, instruction, ffaining and suPervision asare^necessary..." to ensure these responsibilities are properly discharged- The employermust provid6 a written statement of his safety policies and procedures which must befreely available to employees. This statement is usually known as the Safety Manual.Empioyers also have a Ority to protect persons not in their employlnent a1d;9lf;emptoyea persons who may be affected by their operations. The Control of SubstancesHa2ardous to Health Regulations 1988 (COSHH) requires employers to take the stepsnecessary to minimise the risks arising from the use of dangerous substances. Theseregulations also place a duty on the employee to look after the health, safety andwelfare of himself and others he may be working with and to make "...full and properuse of any control nreasure, personal protective equipment or other thing of facility-provided-pursuant to these regulations and if he discovers any defects therein, he shallieport it forthwith to his employer...". The responsibility of the employee for safety is -considered to be of paramount importance and evidence of the employee's awareness ofthis must be demonstrated during the trainee's period of prinrary training.

2.2 At t i tudes

Poor attitudes towards safety usually come from a belief that accidents will only happento other people and not to oneself. Experienced operators who have witnessedaccidents, oi near accidents offshore are aware that accidents can and do happen andadjust their attitudes to"minimise the risk of accidents to thenrselves. A trainee mustimagine being in the same situation and be particularly careful to allow for anyinexperience, asking where necessary for assistance or instnlctions. The trainee mustimagine the worst case scenario in all situations, for example, posing the question,"Wliat happens if that lifting wire parts?" and taking appropriate safe action.

2.3 Operational Safety

Many factors combine when operating ROVs which make the potential for accidentsgreaier than for most other forms of employment. The major ones are listed below.

2 . 3 . 1

2 . 3 . 2

2 . 3 . 3

2 . 3 . 4

2 . 3 . 5

2 . 3 . 6

2 . 3 . 7

2 . 3 . 8

2 . 3 . 9

2 . 3 . 1 0

2 . 3 . 1 1

Electric:al Saf'ety.

Explosive Environments (Hazardous Areas).

Explosive and Radioactive Sources.

Mechanical Devices.

High Pressure Hydraulic Systems.

Lifting and Deploying the ROV.

Welding.

Gas Cylinders.

Restricted Areas.

Helicopter Operations.

Protective Clothing.

20

\

2 . 3 . 1 2

2 . 3 . 1 3

2 . 3 . t 4

2 . 3 . 1 5

2 . 3 . 1 6

Use of Tools.

Good Housekeeping.

Working with Divers.

The Nature of the Sea ltself.

Emergency Procedures.

These factors will be examined in more detail in the following paragraphs.

2.4. Electr ical Safety

ROVs usually operate with high voltages to reduce the current down the umbilical andhence the umbilical size. This fact coupled with the nature of the offshore workenvironment dictates close scrutiny of materials used in electrical installations in orderto avoid possible toxic effects in confined spaces should an electrical fire occur and theharsh conditions lequire that a high degree of skill and safe working practices go intothe installations. It is obvious that if we are to operate with high voltages in a wetenvironment there is a very real risk of electric shock and that precautions against thismust be taken. These precautions fall into three categories: peisonal precauiions;passive protection_and active protection. Personal precautions consist of applying goodwork practices and housekeeping methds and using correcr prorective ctoitiirig anOtools- Passive protection can be provided in 5 ways-. Active protection may bdprovided by either a residual currbnt device(RCDior a line in.sulation moniior(LlM).

2.4.1 Personal Precaut ions

1 .2 .

3 .4 .5 .

7 .8 .

9 .

6 .

only work on electrical systems if you are sure you know what you are doing.Be absolutely sure that the ground connection is made through the umbilical tothe ROV.Connect an additional external ground snap when the ROV is on deck.Wear rubber gloves if handling the umbilical during operations.Ma]<e sure that inexperienced personnel stand well clear during operational andmaintenance procedures.Do_not allow personnel and tools to become disorganised during maintenanceand repair procedures or take shon cuts due to operational pressures.Whenever possible stand on a rubber mat.Know the first aid for shock treatment and the medical evacuiition procedures ofthe vessel.Al l meters nrust be suitably rared e.g.l0tn V a.c. or 5000 V a.c.

2.4.2 Passive Protect ion

Piq fo"l of protection is provided by the use of: adequate insulation; providing a fixedbarrier using protective clothing; using shielding and suitabre earrhing.

2 .4 .2 . I I nsu la t i on

The primary means of providing passive protection against shock is by insulation of thepower system and the appliance it serves. Insulation is less effective underwater thanon dry land because a defect at any point might allow current to flow in the water andpart of this current nray be intercepted by the submersible or say a diver. Theeffectiveness of insulation as a means of protection may be improved by using twolayers of insulation with a conducting scrben in betweeh. Two defects ire the-n neededto constitute a risk. The first defect can be detected by continuously monitoring the

21

insulation level between the conducting screen and the load, and between the screen andthe outer casing. Entry of water could-however cause simultaneous failure of bothsections of insilation, consequently sealing arrangements such as 'O'rings andpressure balance terminations shouid be inCorporated if double insulation is to be moreeffective than single insulation.

, t | - _ - l t' Isolated Earth

cI

Figure 2. IIsolating Transformer

Insulation should be further improved by supplying the load via an isolatingtransformer. This electrical device isolates the supply current from the load thereforemaking it impossible for a fault to eafih in the supply causing a problem on the loadside. The w6ole of the electrical system including the transfonner secondary windingand all the appliances are thus insulated from eafih. It is then possible to make contactwith any point on the secondary circuit without receiving a shock. This prevents, forexample,tontact with a crane wire from the surface, the leg of a stee.l platform or aship's hull from fornting an earth return path and thereby creating a hazard. .If a firstdefect is not rectified, contact with the circuit or the occurrence of a second defect maycause current to flow through either the ROV or a diver. This can be avoided byincorporating an active proiection device for detecting the fir.st defect. The whole of thecircuit: transformer; secbndary winding; connected cable and the load should have ahigh insulation resistance to earth.

22

CurrentCarrying

Conductors

Figare2.2Double Insulation with

a Conductins Screen

2.4.2.2 F ixed Barr ier

When electrical equipment require^s direct contact with sea water to function correctlye..8. an impre-ssed curent anode a fixed barrier can be installed to keep the ROV ordiver a specific safe distance away from it. This barrier should be non-metallic andnon-conducting if possible. In addition to such equipment, high-power fixedinstallations e.g. cables and nrotors can feed large cuirents into the water if a faultoccurs. Again fixed barriers can be used to keep the ROV or a diver at a safe distance.The safe distance can be reduced by incorporating an impedance in the star point toearth line of the supply to limit the fault curent. Care should be taken to en.sure that allprotective devices will function at the low level. A fault current limit of 1 amp isrecommended by the AODC Code of Practice for the Safe Use of ElectricityL-nderwater.

2.1.2.3 Protect ive Cloth ing

An1' practice which limits the flow of current through the body is beneficial. RubbergJoves should be worn and should have a cuff to give the wriit area some degree ofprotection. Whenever handling the ROV umbilical these types of glove should be$orn.

2 . 1 . 2 . 4 S h i e l d i n g

Jhe el_ectrical equipment may be enclosed within a conducting shield to prevent currentfrrom flowing into the water. Where a shield is fitted it should be suitablv connected tocanh. to prevent a dangerous voltage by an internal fault. Protective scrbens should besonsrructed flom high conductivity material and have low resistance joints, otherwise afault current-flowing in the screen can produce a dangerous voltage gradient over itsexternal surface. However, this deficiency can be gr.eatly reduced by the use of a

LJ

double screen. The conducting screen, the external screen in double screened systemsshould also be in contact with the water to restrict the voltage difference between thescreen and the surrounding water.

2.4.2.5 Sui tab i l i ty o f Ear th ing

On any unit which operates at a voltage which is higher than the unprotected safe limitthe conductive stmcture or frame should be connected to earth to dissipate any faultcurrent. The connection should have a low impedance to minimise any rise of voltageon the conductive structure or frame, and sufficient mechanical strength to preventaccidental breakage when the equipment is operated within the stated limits. Theconnection should be through purpose designed conductors in the power cables. Theearth return path can be augmented by an area of bare metal, even corroded steel willdo, in contact with the water; such an ilrangement can be many times more effectivethan normal earth leads.

2.4.3 Act ive Protect ion

This form of protection incorporates devices into the circuit which cut off the supplywould a short circuit situation occur.

2.4.3.L Residual Current Devices (RCDs)

Commonly used RCDs have a typical operating time of 15 to 25 ms. The trip currentsof RCDs should be selected to be as low as possible consistent with freedom fromaccidental tripping which is inconvenient and can be dangerous. A trip current of 30mA at 20 ms. has been found to be suitable.

F igure 2.3Residual Current Circuit Breaker

Any imbalance in the curents flowing in the positive and neutral windings trips thebreaker. In a real device there is often only one turn as shown. The breaker is held'on'

24

I

by magnetic forces. Theneeded to divert the flux

magnetic circuit is designed so that only a small current isto an alternative path and release the armature.

Gonsumer's Load

TestButton

-l-Current

Transformer

TripMechanism

SuPPIY

Figure 2.4Residual Current Circuit Breaker

Type2

This type works in a similar manner but illustrates the situation when an earth isincluded.

2.4.3.2 L ine Insulat ion Moni tors(L lM)

A line insulation monitor (LIM) may be used to monitor the insulation level of anumbilical cable as it enters or leaves the water and any developing electrical leakage willbe detected. A read out of insulation level should beprovided with warnings of iowlevelsif appropriate. In order to use an LIM as part oi an active protection device itshould be connected to a circuit breaker to give suitable overall systenl operatingcharacteristics.

2.4.3.3 Toxicity of Materiats

In the event of a fire or even serious overheating, many commonly used electricalmaterials give off noxious and toxic fumes. aiit is oiten necessary to work inconfined sp€c_es offshore it is important always to use low-toxicity

-cables and other

materials. Full guidance on the selection of such materials is given in the AODC Codeof Practice for the Safe Use of Electricity Underwater.

TestResistor

Ph N

25

2.5 Instal lat ion Practice

To maintain the integrity of all fomls of protection, portable and fixed electrical

equipment should b8;'s"j;ii i;;il';;d 9v 'ory4tll:l:f.i onlv such staff should#"il;il.tu�li;;" or rewrrng, ano any temporary electrioal equipment used should

#;6 #;;;;Jil;Gal" ihe code'oinittl.Jror the Safe usl of ElectricitvUnderwater. Con,.u.io.r r"$."SUfe ioiuna"t*ater electrical equipment should

authorise staff in writing as competent toispecifii functions. Comrietent staff should

be familiar *itt prope, TniiatLatibn proceduies and be aware of the hazards and

problems particular to underwater work' Frequentilt!::"-,ont should be made for

iiens of mechanicar ;;G; on cabres and foiany gen^eral.deterioration of^equipment.

if;J#;;ffi;;;;-b" i-;orporated with the 6 minthly insulation test of the

il;iii;;i;tri.tr Ir uiuully completed to fulfil insurance requirements'

2.6 Batteries

In the past batteries have usually been considered to be electricallv'safe'' As in many

cases they are not used as ?-nrim* p";;; t;;;.", Uut rather as a reserve or back-up'

;il;; it"quently r*t*O ti"m el6arical safety assessments. ln practice. batteries can

;;;G;"".y r"at irur*as and considerable care'should be taken when using them'primary cetts (non-iect arg"uUf" batteriei) hav-e a limited life and when discharged are

nororious ror proouJ'i"n;;?;;;;ilp*d"cts. Short-circuitin'I of prinrary cells can be

potentially hazardous and adequat. tfton-.itcuii ptot..tion ino'ld be piovided'

|;;;"dfi r"rrr-t...t uigeaute'batte.ies) are nomially ofhigher power than primary

cells, so the same b;;ffr;;;;*nJuiiont qpplyi In additlon, however, there is an

;;;i;r*; hazard from hydrogen gar"s ptod^uced dutit'tg discharge and recharging'

$iil;""ff iifrorfA iormitty 5. t..i'tutg"d out on the surface in a properly

ventilated area.

2.6. t Submerged Batter ies

If fixed installations are required to have submerged recharging facilities' the charge

should be limited to a level below the gassing,roTtug., a' a"'etilt, extra c-ells may be

required to attain tfr. *otf.tng uottage-inO thirequii6d batterv capacitv' Where devices'"il

pt""r!J'i;;;h;,".;mUiiation"of ft* htd-''ten anO o^tioen. care should be taken

ro prevenr ou.r.nu.iii;;iri;h ;t;y f"ua t".'^"y?uet of the e'iectrolyte and malfunction

;ii;; i."ii.. If wa-terinters a baitery conrpafiment, an explosive or toxic gas mixture

*uV t. proOuced. Battery compartntents should be conrpletely wa.tertight' .Fusesshould be fitted in the battery compartment as close as possible to the batteries and

should be encapsuLrr.Jio;iru.niu blown fuse from igniting ,h"_p?.1:r-b^l,.P91ottn

;;;;ph;r; in iire .ontpu.ttn"nt. The state of batteries in battery-powered equrpment

should be checki;;iG;r;. Batteries should be handled with caution' Since a

battery cannot U" tur n"i tii it tonttitutes' even in a low-charge state,.a, shock and a

Uu-,1tt, if accideniaiy itrort-circuited by metal tools. Electrolyte sqtilage or carry-

over can utro proUOJ;i.;6g;puttt ftoniu high potenti.al,te'rrinal' Where there is any

p"r.iuiiirv oi ietatiue *ou"*Enibetween batte-riei, flexible electrical connections

should be used.

2.7 Explosive Environments

In UK waters, the handling systems of ROV's employed.offshore should complyrvith

the Offshore rnstatialions fbli"*tional Safety, Hedlth'and Welfare) Regulations 1976

SI 1019 which .dll-; ily'activity (as defined) from, by means of' or on, an offshore

installation o, Utfii,1 aiadius of 50bm. This relates to equipment located in hazardous

areas defined as; ;'...r;y p;Jof the insiutluion in which itt"te is likely to be danger of

Ft. o. explosion frc,-itie ignition of gas, vapour of volatile liquid.""'

26

The Pilotffechnician must therefore be aware if he is working in a hazardous area andsuitable precautions must be taken which might include the following:

2.7 .I No smoking or naked flames.

2.7 .2 Hot work permit may be required when working on the ROV

2.7 .3 Control and workshop containers may need to be approved for electricallyhazardous location by being configured to meet the requirements for purgedenclosures. Altematively explosion proof components and intrinsically safedevices can be used inside these containers, but the former is preferred. Forfurther infomration on the requirements of purged containers refer to the AODCOperational Guidelines for ROV's page 126.

2.7 .4 Winch slip ring, junction boxes and terminations may need the followingmodifications:i) explosion proof boxes, rigid metal conduit.ii) pressurise the electrical system with safe gas.iii) fill the existing sysrem with oil.

2 .7 .5 Use explosion proof electric motors for winches and cranes.

2.7 .6 Deck cables may not meet the requirements for steel armouring therefore a cagedeployed system may be required, altematively the vehicle nray only beoperated when a hot work pemrit has been issued.

2.8 Explos ive Handl ing

Explosives are used extensively during some ROV operations. It is imperative that thepersonal safety precautions for handling explosives are adhered to. The work itself willbe under the direct control of a qualified explosives technician who will follow a writtenprocedure and apply safe working practices. The role of the ROV must be fullyunderstood and the work itself must be detailed in writine. A common safetvrequirement for this type of work is to inrpose a radio silince as it is possible for radiotransmissions to trigger sonte types of detonator.

2.9 Mechanica l DevicesThrusters and manipulators on ROVs can be very powerful and may not behave asexpected. An electrical fault, for example can cause a normally placid manipulator tooscillate violently due to a phenomena known as positive feedback, causing immensedamage. It is important to stand clear of these during pre/post dive checks or wheneverthe vehicle is operated on deck. For example it is important to be sure that the system ispowere{ down before putting a hand into thrusters to clear obstnrctions or for any otherwork of this nature.

2.10 Hydraul ic Systems.

ROV hydraulic systems operate typically at 200 Bar (3000 p.s.i.) and, should a loosefitting cause a leak for example, serious injuries may be caused. It is importanttherefore that all personnel working on the hydraulic system should be qualified andhave attended the relevant safety seminars, and that non-essential personnel stand wellclear of ROVs whenever the hydraulic system is under pressure. The work area shouldbe isolated with signs in letters at least 5 cm high stating; "DANGER HIGHPRESSURE TESTING''.

),7

2.11. Lifting and Deploying the ROV

Many ROV Pilot/technicians have no experience_at sea nor3j lifting h.eavy loads withcranes or ruggers prior to going offshore for the first time. The procedures of liftingand deployii! tfre-nOV arE crucial to the success of the operation and can represent a""iy gi.uit aiety hazard if not implemented correctly and conscientiously. Procedurestoriifting equipment and ROV deployment methods are covered in the seamanship -secrion oT this irandbook. The obj6ctive here is to make the pilot/technician aware ofih. tirkr that are inherent during [aunch/recovery procedures to enables him to assistwith these procedures safely wi-thout exposing tiirirsglf or others to danger. At the timeof writing itudies are undenway by relevant authorities to determine the most suitabledeploymEnr system test procedures. Currelt practisg as.laid out in AODC 036 (Rev l)"The initial and PeriodiiExamination, Testing and Certification of ROV HandlingSystems" is:

a Initial and period examination and test of ROV launch and recoverysystems.

i) As New/Instal led:1. Manufacture to a recognised Code of Standard'

orB uild to Manufacturer' s S tand ard S pecifi cation.andVerify compliance with National Regulations.

2. Static load brake test at 1.5 x SWL.3. Function test at 1.25 x SWL.4 .Bo th tes ts to inc ludeanyadd i t i ona lequ ip r i l en twh ich

rnay be fitted to the ROV. NDT to be carried out oncritical items.

i i) In Service:1. Visual examination and function test at SWL'2. Static load brake resr at 1.5 x the weight at be lifted in

air. NDT to be carried out on critical items.

b. Initial and Period Examination and Test of ROV Lifting Cable/TVireRope and Terminations.

As New/Instal led:1. Verify compliance with National Regulations.Z. Load test to 1.5 x SWL.

In Serv ice:1 . Function test at SWL as an integral part of the Lifting

System and visual examination2. Static load test at 1.5 x SWL.3. Electro-mechanical umbilicals should be tested as above

and re-terminated at least once every 12 months.

These should be verified with the relevant authorities (DnV, Lloyds etc.) on eachmobilisation as standards vary.

2,l l . l Precautions

i )

ii)

i) Be aware of rigging safety in general and wear the appropriate safetyclothing i.e. safety boots and hard hats.

ii) Do notitand behihd tuggers etc.Thete have been maly nasty accidentsoffshore whereby the wlres have parted and personnel have caught thewhiplash. If necessary fit guards to tuggers.

28

Iiii) Practice launch/recovery procedures from a fixed platfbrrn before

attempting them at sea and make sure that all the personnel involved arefully aware of their roles.

iv) ROV's can weigh typically around 1 Tonne. When this weight is liftedfrom a moving platform it represents a significant hazard therefore; keepthe lifting pennant as short as possible, do not stand between the ROVand any fixed structure, and handle the ROV at arrns length to avoid ittrapping any pafi of the person if the lifting mechanism should break ors l iP .

v) Do not lean over the side of the ship and be aware of the location of lifesaving equipment. It is wise to practice the man overboard procedure infine weather conditions.

vi) Tie all the equipment down and stow it correctly during periods ofheavy weather.

2.L2 Diver Observation

ROV's have sufficient power to crush divers or to dras them fror.r.r their worksiteshould the umbilicals beconre entangled. Therefore th! following precautions must betaken when working with divers.

2 . I2 .1 P recau t i ons

i) Establish communications with the diving superuisor and be prepared toturn off the ROV power immediately on his instruction.

iD Fit guards to the thrusters.iii) Wherever possible work down current of the diver and take care to keep

the umbilicals apart.iv) Use rlinimal thiuster controls.

Reference: AODC Guidance Note Remotelv Ooerated VehicleiDiverInvolvement. (AODC 32)

2.13 The Nature of the SeaThe hazards of the sea are covered in the chapter on seamanship so suffice it to say heredo not underestimate the inherent dangers of wind, waves and tides.

2.14 Teamwork and Communications

Efficient and effective teamwork and clear and concise comnrunications are essential ifROV operations are to be safe and competent. These skills are emphasised throughoutthe industry and their inrportance cannot be over-sffessed. Effective communicationsmust extend to the ship's or platform's crew or any other group concerned in anyoffshore operation. It is important that everyone concerned knows when the ROV goesinto the water, when it comes out and what it is doing. Similarly it is essential the ROVcrew all know their task and what is required to conlplete it. Finally it should be notedthat Safety is a "core theme" throughout this book and will be found to be so on anyrecognised training course.

29

=F

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30

I

CHAPTER 3 TYPES OF ROV

3.0.0 Introduction

3.0.1

For the purpose of this book the term ROV shall mean an unmanned vehicle with acommunication and power link to the surface by means of a tether or umbilical.ROVs are classified in the "Guidance note on the safe and efficient operation ofremotely operated vehicles" (AODC 051 February 1989) into five classes:- Class 1Pure Observation Vehicles, Class 2 Observation with Payload option Vehicles, Class3 Work class vehicles, Class 4 Towed or bottom crawling vehiiles, and class 5Prototype or Development vehicles. In fact ROVs are a continuum of types andcapabilities from simple video cameras to 'flying bedsteads' with any number ofoptions, highly sophisticated work and survey vehicles, bottom crawling vehicles andspecial one-offs. Any attempt to classify all these possibilities leads to confusion atthe boundaries however, in this chapter we will list and describe some well knownexamples within these AODC classifications. Due to the ever growing number oftypes and manufacturers this list is by no means exhaustive but serves to demonstratethe range that is available.

J.0.2

Figure 3.1 shows the system components for a RCV 225 system. The basic systemcomponents will vary in their physical dimensions but are comrnon to all ROVsystems. They are; the Power Pack or Power Distribution Unit (PDU), the controlconsul or operator control Unit (oCU), the Sonar Control unit (SCU), the winchand Fiandling Systenr ('A'Frame), the launcher, Garage, or Tether ManagernentSystem (TMS), and the vehicle itself.

HandlingSystem

Power Pack

Figure 3.1ROV System Components

Figure 3.1 ROV System Components

3.1.0 Class 1 Pure Observation vehicles include; The Deep Ocean Engineeringphantom and the Benthos MiniROVER. These are theoretically physically limited to

pure video observation rasks although they have more recently been modified.with

ih. fit-"nt of grabbers to accompliJh retrieval tasks or calTy. Cathodic Protection (CP)

probes. FigurJ3.2 shows a MiniROVER and Figure 3.3 a Phantom 300.

Benthos, MiniROVER Mk IIFigure 3.2

Figure 3.3 Deep Ocean Engineering, Phantom 300

I

3.2.0

Class 2 Observation Vehicles with a Payload Option include; the HydrovisionOffshore Hyball, the Seaeye Surveyor, the Perry Tritech Sprint, and the BoforsUnderwater Systems/Sutec Sea Owl. These are vehicles capable of carryingadditional sensors such as stills cameras, cathodic protection (CP) measurementsystems, additional video cameras, sonar systems and wall thickness or floodedmember detection system. A class 2 system should be capable of operating withoutloss of its original function when carrying at least two additional sensors. Figure 3.4shows an Offshore Hvball and Fieure 3.5 shows a Seaeve Survevor.

Figure 3.4 Hydrovision, Hyball

Figure 3.5 Seaeye, Surveyor

-') -')

3.3.0

Class 3 Workclass Vehicles include; the Hydrovision Dia.blo' the Peny Tritech Super

Scorpio, SubSea OfT;h;;;;; pioneer and ;;il;;;,;nd slingstv Engineering's Trojan

and Multi Role Vehicle (MRV). fn.r"*fticfes aie large etioultt to be fitted with

additional sensors and/or special toot, fot"int"*tntion ind manlpulatiye 3^s$'. Class

3 vehicles will have a multiplexing .upu'Uiiii' ufn*i"g add.itionil sensors and tools to

be operated through ihe uehicle -sVste* The umbilical will also have spare

conductors to allow ;;;i;;ii'^.yr""o "q"igpg* workclass vehicles have

sufficient propulsive power (typically ut f"u'it'SO Hp) to op€rate at least one thruster in

each of the longituOiirf , rri#f-a ".ttiiui iii..tiont ylilst carrying additional

tooling packages. eig"i" :'O ifto*t" niuUfo-'figyt9t.3.'7,& 3'8 show the Super

Scorpio including ,1'f pii"it'.""t"r, iig"i"tl.rO-A 3J.1 show the Trojan including a

detailed drawing, Fi';"i;3.it;h";t ,h-"'Pi;.;; and Figure 3'13 shows the MRV'

Figure 3.6 rllgg:"':lglPhP*

SCORPIS

IE-,.

ww{wfrffafn,irl{;i&

figure :7-F...y Tritech Inc, Super Scorpio

Figure 3.tl Perry Tritech Inc, Super Scorpio Pilots C<lnsul

Figure 3.9 Slingsb,v Engineering, Trojan

?ROIAil

35

${*nipul*ttlrs

TlX,*l5t*f*. i , . . ,r , , , . , ' ' '

H-r.draulis*

RlecirieallX l**t:xrries

l.:nrliliL'lti

Tsriiii:l* l:.lilast

Figure 3.10 Slingsby Engineering Ltd'Trojan Detailed Schematic

Figure 3.1I SubseaOffshore Ltd, Pioneer

Figure 3.12SlingsbyEngineering,Multi RoleVehicle (MRV)

36

3.4.0

Class 4 Towed or Bottom Crawling Vehicles include; Soil Machine Dynamics (SMD)Eureka Tracked Vehicle, Sl ingsby Engineering's ROV 128 and SMD's ModularPlough. Towed Vehicles have no or little propulsive power off the seabed and aregenerally capable of limited manoeuvrability. They travel through the water by thehauling action of a surface craft or winch. Bottom crawling vehicles move primarilyby exerting traction forces on the sea floor via a wheel or track system although somemay be able to 'swim' l imited distances. Figure 3. l3 shows the Eureka, Figure 3.14shows the ROV 128.

Figure 3.13 Soil Machine Dynamics Ltd, Bott<lm Crarvling Cable Burial ROV

Figure 3.14 Slingsby Engineering, ROV 12tt Cable Burial/Retrieval System

3.5.0

Class 5 Prototype or Development vehicles are not featured here as they are beyondthe scope of his book. The reader is recornmended to read 'Remotely OperatedVehicles of the World' (OPL) for a full l isting and description of avail lable ROV's.

37

39

I

I

CHAPTER 4 OFFSHORE STRUCTURES

4.0 In t roduct ion

Offshore oil and gas are the most important natural resources to be discovered in Britainthis century. They are a vital commodity providing energy and chemicals to industryand providing revenue to the exchequer. There has been an enorrnous financialincentive for the oil companies to venture offshore, accepting the high risks involved,in order to exploit these reserves. Since the first licences for North Sea explorationwere issued tn 1964 over 112 production platforms have been installed; whichdemonstrates the growth of the industry in this geographical region. World-wide therehas been similar gowth in regions which have similar deposits of oil and gas.

4.0.1 Exploitat ion of Reserves

In the search for oil the usual procedure follows a set pattern. Initial surveys areundertaken using seismic techniques which produce data for interpretation by expertgeologists. When a likely area is pinpointed wildcat exploration rigs are dispatched tothe area to test if there are any reserves by drilling deep into the sea bed. If oil or gasreserves are found further pre-production drilling is undertaken to determine the extentof the reserves and prove whether full production is viable. Once commercial viabilityis proven production facilities ere designed and installed along with all the infrastructurethat goes with offshore oil field development such as, for exanrple, sub-sea pipelines,underwater manifold centres and offshore loadine facilities.

4.1 Of fshore Structures

Structures offshore come in a variety of shapes and sizes and in a variety of materials.Production platforms can be of steel construction or of concrete and some of the steelplatforms float and are tethered in place by cables. There are underwater constructionssuch as wellheads, manifold centres, emergency shut down valve igloos and linearblock manifolds. There are many hundreds of kilonretres of sub-sea pipelines.

4.1.1 Steel P lat fornrs

It should be remembered that offshore work is expensive and therefore productionplatforms are designed with a view to doing all the fabrication ashore and minimisingthe work involved in installation and repair and maintenance. In the main, productionplatforms are of steel construction and are designed to be easily installed andmaintained. There are several variations of design for this type of installation but themajority are of the piled structural type. Some of the variations are; tensioned legplatforms (TLP), jack-up platforms and semi-submersible anchored productionfacilities.

4.1.1.1 Pi led Steel Product ion Plat forms

An example of this type of structure is the Brent A Platfomr in Shell Expro's BrentField. Some facts about the nlatform are of interest.

a) Substructure

Water depth. 14mProduction capacity 100,00 b/d oil and 2OOmmscfd gasJacket type Self floating steel constructionNumber of legs 6Number of piles 32 skirt pilesWeight of jacket 14,225 tonnes

b)

Weight of piles 7 ,316 tonnes

superstructureHeight of deck above sea levelDeck areaDeck constructionWeights: Deck

Facilities on deckModules and equiP.

^-*

21.7m2,300m2Plate girder1,507 tonnes2,354 tonnes14,762 tonnes.

F igure 4 .1Brent A

40

4.1.2 Concrete Gravity Platforms

An example of this type of platform is Cormorant A in Shell Expro's Cormorant field.These structures are more massive than the steel platforms and are not piled into the sea-1,.

l. Hence the generic terrn " gravity" for this type of structure. Again some facts areof interest.

a) Substructure

Water depth 150mProduction capacity 60,000 b/d oil and 30 mmscfd gasStorage capacity 1,000,000 bblsCaisson shape SquareCaisson height 57mNumber of legs 4Weight in air 294,655 tonnes

b) Superstructure

Heieht of deck above water 23mArea of deck 4.200m 2Deck construction Box girderWeights: Deck 5,834 tonnes

Ecluipment within deck 3,593 tonnesModules and equip. 19,011 tonnes

Figure 4.2Cormorant A

41

4.1.3 Single Buoy Moor ings

World-wide there are a number of different variations on this type of loading facility.An example of an offshore SBM which was initially used by Shell Expro in the Aukoil field was the ELSBM (Exposed Location Single Buoy Mooring) and when in use itwas located approximately 1 nautical mile from the Auk A platform. It was kept inplace by 8 anchors, each weighing 15 tonnes placed in a 3000 foot diameter circle. Theanchor cable was 3" stud chain. The mooring hawsers and the hoses which carried theoil to the tankers were carried on large reels in the superstructure of the buoy.

Figure 4 .3Auk Field ELSBM

42

I

4.1.4 Pipel ines

There are thousands of kilometres of pipeline laid on the sea bed world-wide andalthough at first glance these structures appear to be simple they are in fact just ascarefully designed as all other types of offshore structure as the diagram, figure 4.4, ofa typical field joint indicates.

Sheet Metal Cladding

Concrete Weight Coat

Re-inforcement

Field Weld

Circumferential cutsin concrete to

minimise damagewhen pipe bends

during laying

Bitumen Wrap orDope Coating

Field Weld is coveredwith Black Bitumen

under the SheetMetal Cladding

Pipe Diameter up to 36"Wall Thickness 5/a" - 11/q"

Figure 4.4Typical Pipe Joint

4.2 Loading of Offshore Structures

Whatever type of offshore structure is considered the manner of its reaction to theloading imposed on it in service will be similar. The reaction depends on the propertiesof the materials used for any particular stmcture and as an illustration a briefdescription of the properties of elastic materials should prove helpful.

4 .2.1 Yie ld Stress

When any component is loaded, the material initially behaves elastically. This meansthat when the load is removed, the component returns to its original size and shape.This will continue while the component is in use, unless the yield load is exceeded.Yield stress is therefore the stress at which the material will no longer behave whollyelastically. If the loading is continued beyond the yield point, the material will deformand some of that defbrmation will be pemranent. Therefore, if a structure or part of it isdented o'r bent, it has been loaded above the yield stress.

4.2.2 Ult imate Tensile Strength (UTS)

If loading is continued well into this region, it reaches a maximum value known as the

ultimate tensile strength (o urs ) . Attempts to load beyond this value will result in thematerial failing by ductile fracture. Ductile fracture can be identified by a large amountof local deformation in the region of the fracture.

43

4.2.3 Brit t le Fracture

Brittte or fatigue fracture is by crack propagation without noticeable local deformationin the region of the fracture. Because of this lack of visible deformation, allY techniquewhich cin assist in making it easier to detect cracks needs to be considered, and thisneed has been one of the riain driving forces behind the development of the science ofnon-destructive testins. For tensile teit characteristics for ductile and brittle fracture seeFigure 4.5

Stress o

MN m-2

Figure 4,5Tensile Test Characteristics for

Ductile and Brittle Fracture

4.3 Stress Concentrat ion

It has been found that in a contponent under load where there is a change in shape just

locally at that change in shape,^the stress is very much higher than elsewhere in theco-ponent. This eTfect is quantified by the strbss concentration factor (K1 ) which is

the rltio of maximunt stress at the change in section to the average stress. This wasfirst developed by Professor Inglis when studying the cause of the formation of cracksfrom the .oinert of hatch coveri in the decks of merchant ships at the beginning of thiscenrury. The effect of this is best shown by considering the simple example of anelliptiial hole in a flat plate. The flat plate is loaded in tension in one direction only

with a stress, o, and in the plate is an elliptical hole as shown in Figure 4.6. The plate

is so large that the loss of area due to the cut-out can be neglected. At the edge of the

cut-out at point A the stress will be higher than the average stress o by an amount given

by the Stress concentration factor K1 such that the stless at A = omax. = K1X O . The

value of K1 for this case is given by the equation:

K 1 = l a 2 ab

44

E

Fracture 600 MN m -2

i.0olo strail Glass fibre UTS +00 MN m

Fracture 30% strain

Strarn

Figure 4.6Load on a Flat Plate

with an Elliptical Hole

It is worth examining this equation is a little more detail.Fig. 5.7 shows the variation ofK1 with the shape of the hole. It will be noticed that the shape of the cut-out and itsposition in the stress fleld is important. The longer and thinner the cut-out (or defect)the larger the stress concentration factor K1 and hence the higher the maximum stress atthe tip of the defect. The position of the cut-out or defect in the stress field isimportant. If the long side of the cut-out is at right angles to the maximum stress, thestress concentration factor is higher than if it runs in the direction of maximum stress.An awareness of the fact that stresses are higher at changes of shape alerts the inspectorto areas most at risk from cracking by fatigue. As there is seldom sufficient time toinspect the whole sffucture, this knowledge leads to a more effective inspectionprogramme. Some of the changes in shape that will give rise to stress concentrationsand hence lead to increase in stresses in the stricture are:

ab

defgD

Node joints;Cut-outs in members;Holes in drilling templates;Weld profiles (unless ground flush with the parent metal);Weld defects;Corrosion pits;Marks on the surface of the material caused bv accidental damase or badworkmanship.

i 3o

Figure 4.7Variation of Stress concentration

As a crack grows, the value of K1 will increase. Because the value alb increases, this is

sometimes iefened to as sharpening the crack. One of the standard engineering.emergency remedial proceduies whln a crack has been discovered, is to drill a hole atitre tlfi of ine crack, oflen referred to as crack blunting of -stopping.. The ryason for this

cun be understood because the stress at the tip of the crack will be high. Furthelgio*tfr of the crack will increase the value of K1 to an even higher value (for a long thin

J1ipr., this can be greater than 10). The drilling.of the hole.at the tip. of the clackredircei the high lodal stress at the tip of the crack, making the crack less likely topropagate, i.e. grinding out cracks reduces the a/b ratio.

46

\

CHAPTER 5 ROV APPLICATIONS

5.0.1 Introduction

The last ten yeius have witnessed a slow demise in the offshore diving indus0rybrought about, at least in part, because of the research and development put intomaking safer, more reliable, better tooled and cost effective Remote OperatedVehicles (ROVs). Cunently ROVs are employed on many sub-sea tasks which wereformally undertaken by divers, such as general platform inspections and sea bed scoursurveys. Reducing human intervention on many underwater tasks also reduces riskof injury or worse to personnel this is a further compelling reason for reducing thenumber of divers offshore and countries such as Norway have a government policy tolegislate against all diving on new projects without dispensation. It is the intention ofthis chapter to discuss the most common tasks carried out by ROV's these include:-

/ Pipeline Inspection

'/ Drill Support

r Platform Inspection

Intervention

I Cable Laying

I Construction

ROTV

Mine Counter Measures

Anti-tenorism/Drug enforcement

l

5.1.0 Pipeline Inspection

The annual inspection of pipelines in the North Sea forms the bulk of ROV operationsduring the summer months. Currently ROVs operate for periods of up to 70 hoursvirtually non-stop and the latest acoustic technology records details of the pipeline'sintegrity with great accuracy. These factors, along with improvements in sub seavideo cameras mean that ROVs are the prime pipeline survey method.

5.1.1 Normal Vehicle Fitment

A standard'Work class'ROV will normally have the following equipment andsensors:

Thrusters

Front and Back SIT Cameras

Lights

Ranging Sonar

Manipulator

47

Pan and Tilt Mechanism

Emergency Acoustic TransPonder

Emergency High Intensity Flashing Light

Gyro Compass

Power, Control, Instrumentation

Hydraulic Power Pack

Vehicle Depth Sensors

Vehicle Altimeter

5.1.2 Additional Fitment Specific to Pipeline Survey

In addition to the above a'survey package'will be fitted specifically to enable thevehicle to meet the specification r6quirements of a Pipeline survey contract. Thispackage will usually include:

Twin booms with full colour video and additional lighting

Still camera

Possibly stereo/photogrammetic camera

Strobe lights for still c:uneras

Side scan Sonar

Pipetracker

Sub Bottom Profiler

Current Density Meter/Contact CP Probe

Temperature and Salinity Sensors

Acoustic Responder

Odometer

This survey equipment is explained in the following paragraphs.

5.2.1 Twin Booms

Prior to undertaking pipeline survey work an ROV will be fitted with twin booms,these are fitted to each side of the vehicle. These booms are deployed and adjusted,usually hydraulically, once the vehicle is at the worksite and on the pipeline. Colourvideo

-czuireras and the associated lights will be attached to each boom. These can be

individualty positioned to achieve the best view of each side of t!9 pipe. _!he typeand model bf video camera will vary and these are described in Chapter 15Underwater Video. The lights will be of variable intensity. The maximum powerwill depend on a number of factors which are outlined in Chapter 15 also. As a. guide,however, at least 1000 Watts of power output will normally be required to obtain thecorrect lighting from a distance of 1 meter from the pipe.

48

Responder

Transponder

* Bathy Unit

Lights -+

-rrditional Equipment -='ont and Rear Sit CamerasS--:lls Stereo or PhotogrammaticS:ob€

0.25 metres l-

0.6 metres

(0m,0m)

Bathy

Responder

/Unit

\

Flower Pot

Transponder

-ptpETRACKER

\Addit ional Equipmenr

I0.72 metres

I

Colour Camera

,/Survey Sled

Figure 5.1

49

D.H.SS. PROTIIER

DIYE OOI

DATE I.I.92

Tlill 59-59-23

SOUND YEI.OCITY I43O M/S

HORTZ ttP l.2M

VTRT SEP ,OsM

SilID HIAD HIGHER

START AN9TE 035 DEG

STOP ANGTE I45 DEG

gTtP slzl .|.8 DEG

AUTOilAnC 00 SEc

PORT HEAD ON

'TBD HEAD ON

looolNo oFF

LL

6t

'.

?sr lkalD

9 "":-"''" n"'r. .l, , J \o ! ' i i'T i. ,l"ir. irr. :.r

.-:.'.rLC-r gl,d.ilr*,I l..r*irp4r.r ,6r.';;$ r. a r .o *q;-1 .;1:r!-tr;'!!rrl'l.

Figure 5.2

50

I:

l

nigry." 5.1 illustrates the various survey kit anached to an ROV during a typicalpipeline survey.

5.2.2 Stills Camera

The stills camera will usually be fitted to the pan and tilt mechanism, and may beeither a mono, sterco orphotogrammetic type-. These cameras are explainedin theC..hapte1 l6.Underwater Photogqphy. Wiitr tfre stills camera attached to the pan andtilt mechanlsq photographs can 6e taken from various angles as the Rov is'manoeuvred along and around the pipe and an indication of *re field of view will beobtained from the video ciunera on tfie same mechanism.

5.2.3 Side Scan Sonar

Side scan sonar is a. particular type of sonar that transmits in a sideways directionenablilg.a plal 9f tle sea bed topography to be plotted as rhe ROV nivels along thepipe. This enables the position of topogaphicalfeatures and debris such as bou-ldersor trawler gear to be recorded relative to tlie pipe.

5.2.4 Pipetracker

Pipetrackers usually operateon the principles of magnetism, hence, they are usuallyknown as 'magnetic pipetrackers'. An exdmple of th-is is the TSS 340 wtrictr is incommon use offshore These are fitted to ROVs to locate and tack ferromagneticpipg 9rd cables. They use a passive sensing technique to give the operator irelativeposition of the pipe or cable. some models have a'SEARCH' and 'StctgAtuReANALYSIS'mode which_allows any field anomaly to be pinpointed, and a fullsignature analysis made ifrequired. Pipetackers have a p^arti^cularly useful role intracking pipe that is buried and therefoie cannot be foilo*ed visualiv and versions arein use to follow and locate faults in buried telecommunications cabl6.

5.2.5 sub Bottom Profiler and rrenching Profiler (DHSS profiter)

The Dual Headed Scanning Sonar (DHSS) Profiler is an acoustic device that enablesa profile of the sea bed to be obtained. It accomplishes this by stepping twotransducers (one positioned on each side of the v:ehicle; fromihe ddtwira horizontalto the vertical downwards position. The distances from each head to the sea bed orother feature is recorded as a sonar return. The DHSS Profiler is essential fordetermining the^'Depth of Burial' of a pipeline, the depth of a Eench or the length of a'Free-span'. A 'free-span' is an unsuppbrted length of pipeline which may be citical ifthere is ?ny Possibility of movemen[ of the pipe. figtird 5.2 illustrates a crosssectional view of-p1pe anq sea bed recorded from a profiler system. Modern profilingsonar can be used for both sub bottom and tenching applicaiions and are available iriboth single headed and dual headed models.

5.2.6 Current Density Meter/Contact Cp probe

A Current Density Meter and Contact CP (Cathodic Potential) Probe are usuallyattached to the manipulator for use on exposed areas of pipeline or anodes. Thbprinciples of operation of these is that they monitor the potential to corrode of anyglposea metal on the pipeline and the effdctiveness of anodes. The Current DeniityMeter measures the Current Density which indicates the CP cover and the Contact'CpProbe measures the potential of theexposed metal with reference to the silver/silverchloride half cell in mv and is expected to be within the following ranges:

Unprotected iron and steel

Cathodically protected iron and steel

-500 to -650 mV

-800 to -900 mV

5 t

Zinc (Anodes) -1000 to -1050 mV

The contact CP probe is used because it is inconvenient to maintain an earthconne,ction with the pipe on a moving vessel as is required with the Proximity probewhich is normally used for platform inspections.

The above information is to enable the Pilot to have a basic understanding but fullinformation including calibration methods is included in the CSWIP 3.3u ROVinspectors course and handbook.

5.2.7 Temp and Salinity Sensors

These measure the temperature and salinity of the water during operations. Oftenthese are combined with an accurate depth fiansducer to form a Bathymetric system.

5.2.8 Acoustic Responderff ransponder/Pinger

An acoustic device will be attached to the top of the vehicle. There are three generictypes:-

Pinger - This repeatedly emits short pulses of acoustic energy at a setfrequency. This can be continuous throughout the dive or can be initiated inthe event of a power failure to the vehicle to enable the crew to locate it andeffect an emergency recovery.

Transponder - This emits short pulses in response to interrogation from thevessel or other transponders. Each transponder will have its own code andmany transponders can operate together each responding to its own codereceived acoustically and being displayed by individual symbols on thesurface display of the Hydro-acoustic Positioning Reference (HPR) System.

Responder - This is similar to the Transponder except that it responds to anelecffonic signal sent through the umbilical. This is'more accurate than thetransponder because there is only a one way propagation of acoustic energythrough the water. Calculation of through water range and bearings is subjectto errors due to variations in sound velocities due to variations in the watersdensity, temperature and other bathymetric conditions.

These devices will allow the surface vessel to track the vehicle and record the positionof the ROV relative to the vessel as the survey progresses.

5.2.9 Odometer

The Odometer is a device much like the wheeled devices that Surveyors push aroundto measure distances. For ROV applications these are typically used to measure thedistance of an area of damage from the nearest Field joint and to measure the depthand extent of the damage itself. Potentiometers produce signals tansmitted throughthe umbilical to the surface to indicate the number of turns of the wheel and itsdisplacement.

5.3.0 Additional Instrumentation Required for Pipeline Survey.

In addition to the equipment fitted to the vehicle it is necessary for navigation andcontrol purposes to have additional systems other than those already outlined above.

52

5.3.1 Surface Navigation System

The surface vessel will constantly fack its position with the aid of radio beacons orsatellite navigation systems. Examples of radio systems are; Decca, Sylledis, andPulse 8. These require land or platform based ffansmitters to accuately (Usually wellwithin I meter) position the ship usually in terms of 'Northings'and'Eastings'. It isbecoming more common recently to position the surface vessel with GPS (GlobalPositioning System) Satellites. These are updating quicker and becoming moreaccurate. Depending on the Global area the surface vessel is in, the particular systemin use and the number of satellites in use the accuracy can be between +/- 50m atworse +/- 10m as the norm and +/- 2m at best.

5.3.2 Telemetry System

This system enables conffol, instrumentation, sensor, and possible video signals to becommunicated between the surface vessel and the vehicle. Either electricalconductors or optical fibres are used to carry the signals in digital form. Fibre Optictelemetry has the following advantages over conventional 'Hard Wired' telemetry:-

a) A higher update (Baud) rate

b) No electrical interference

c) Negligible signal loss through the lengttr of the umbilical

Fibre optics have the disadvantage that the fibres may part and may consequently bemore difficult to join or re-terminate in the field. The paft of the telemetry systemthat switches the information onto the line in sequence is known as the multiplexer. Itis preferable to use a fibre optic telemebry system for pipeline survey work dueparticularly to the very large volume of data that is required to be ransmitted to thesurface and the enhanced video quality that is possible.

5.4.0 Drill Support

This section outlines the various stages of the drilling prograrnme and indicates theareas where the vehicle can provide valuable assistance. Before the programmecommences the operations controller should advise the drilling supervisor of thecapabilities of the vehicle and where it can assist the drilling operation. There is atendency to under estimate the assistance that an ROV can provide to a dritlingoperation. For this reason an overview of the tasks has been given, these will beexplained later in the chapter.

5.4.1 Overview Tasks

General tasks to assist with the overall operation will include:

a) Survey site and sea bed prior to spudding-in.

b) Acoustic beacon placement and recovery.

c) Guidance of packages and tools.

d) Observation and guidance during critical drilling sequences.

e) A-X ring replacement.

f) Emergency BOP or package release.

53

g) Debris removal.

h) Recovery ofdropped objects.

D Setting Wellhead charges.

j) Guide wire cutting and replacement.

k) Setting guidepost cutting shaped change.

5.4.2 Drilling Programme

The following section outlines a typical drilling prograrnme. At each stage of thedrilling operation a brief description of the vehicles assistance is given.

Drilling Programme

1) Rig on site

2) Drilling to set 30" casing

3) 30" casing stab-in

4) 30" casing cementing

5) Drilling to set 18 5/8"casmg

6) 18 5/8" casing entry

7) Drilling to set 13 318"9 518" 7" conductors

Vehicle Programme

Survey site and sea bedprior to'spudding-in'.

Place marker buoys to assist inwell relocation.

Observe relative position ofcasing to hole. Advise requireddirection to move. Use sonar toprovide distance of casing tomarker buoy and advise whenready to stab-in.

Monitor cement operation andcheck bulls eye on guide base.

Observe enffy to guide base andassist by pushing if required.

Observe entry to guide base andassist by pushing if required.Observe BOP latchingoperation. Check bulls eye andball joint inclinometer on stack.Carry out full inspection of stack,lower marine riser package andriser/conductor.

At this point in the programmethe vehicle changes from anactive to passive role. It isrecorrrmended that regular checkson the stack are carried out andthe distance and direction of thebeacon to the stack cross-checked by sonar. Other taskrequirements will depend largelyon the problems encounteredduring the drilling progranrmeand could vary from locating andrecovering dropped objects to

h54

;ilTf:ff I'*ii:,l',*"'ffi ffi"The programme outline may vary depending on the type of well, or rig and the depthbeing drilled. A copy of the actual well programme will be available in the drillsupervisors office.

5.4.3. Liaison with Drilting Staff

It is preferable that before mobilisation the drilling supervisor(s) and sub-seaengineer(s) are contacted. Not only to outline the assistance the vehicle can providebut also to verify the equipment installation, the type of stack in use etc. A great dealof time can be saved at this stage and possible problem areas ironed out. Also, it isworthwhile presenting optional equipment such as the emergency stack release paneland A-X ring replacement system so that fitting requirements, configuration andpositioning can all be verified in advance. A very useful preparation is to paint toolsand equipment that are to be used underwater with white markings to enable them tobe more easily seen by the vehicles video cameras.

5.5.0 Blow Out Preventer (BOP)

This is a safety device installed at the top of the well that can typically be 10 metresin height and weigh around 150 Tonnes.

5.5.1 Functions of BOP

Should a drill string reach an area of pressure that is higher than the hydraulic head ofpressure exerted by the drill mud then a blow out or'kick' will occur. This results inan unconfolled blow out of mud followed by oil or gas. The BOP allows the well tobe shut off whilst heavier mud is pumped down thereby bringing the well undercontrol.

5.5.2 Operation of the BOP

The BOP contains one or more pairs of rams made of steel or tough rubber. Should ablow out occur then the rams are hydraulically closed. There are two kinds of ramsPipe (choke) and shear (kill). The kill rams cut through the drill pipe and seal off thewell. Choke rams close and seal around the drill pipe. Both rams are held in place,once activated, by hydraulic pressure. Once this task has been completed heaviermud is pumped down the flow and choke lines to the drill string below the ramswhilst the drilling operations and BOP are shut down until the pressure due to thehead of mud is greater than the pressure from the gas or oil in the formation therebystabilising the situation

5.5.3 Tasks on a Blow Out Preventer

a) Check kill line connector

b) Inspect slip joint, flex joint and hoses

c) Guide line replacements

d) Align riser into BOP

e) Check connection of production conffol systems

0 Manually over-riding hydraulic connector for lifting BOP

55

g) Changing gasket between BOP and connector housing

h) Guiding BOP into place in wellhead

D Deployment and replacement of transponders

5.6.0 Detailed Tasks During Drilling Operations

The following are a possible set of detailed procedures for the various tasks thevehicle may be required to cary out during the drilling operations outlined above.Drilling suiport Task Procedures a.re described in detail here because.they do notappearln any of our other Handbooks, whereas, o,nlygqoleryi_ey of inspection Tasksis included as they are included in detail in the CSWIP 3.3u ROV InspectorsHandbook

5.6.1 Sea bed Survey

a) Locate the centre of the ar-ea t9 F lury.I"d. This is normally doneusing a mini beacon and the rig/ship Hydro-acoustic PositioningReference System (HPR).

b) Carry out a 3600 sonar search and enter the relative position of anytargets on the log sheet (see Fig. 5.3).

c) Locate and identify any significant targets. Note the dimensions andcomposluon.

d) Pass the information to the drilling supervisor. (see chart Fig. 5.3)

5.6.2 Place Marker Buoys

The reason for placing these buoys is to allow easy re-location of the hole after the36" bit is withdrawn and consequently reduce time required for the 30" casing stab-in.

a) Make up two markers. These should be single and double whitepainted Grimsby floats attached to suitable weights by approximately5 ft of line. (one 200 mm dia... metal Grimsby float gives about 4 kguplift).

b) Prior to the field string being recovered launch the vehicle and placethe marker buoys using sonar at the positions indicated. See Figure5.4

NOTE: The double buoy should be placed due North of the string and thesingle buoy due South for ease of orientation.

c) Ensure a video hook up with the bridge and the drill floor isfunctioning. Recover the vehicle.

56

(

re 5.3

-/

t l- t t -

t lt lt lIt lL_J

Figu

Drill String

Figure 5.4

57

Date: Dive No: Tape No: Seabed Survey

Vessel: Location:

Note: The Centre Axis is the Soud-in Location

t

Seabed

5.6.3 30"

1)

2)

3)

NOTE:

NOTES:

4)

5)

6)

7)

Casing Stab-in

When the 30" casing is 2 to 3 joints from the sea bed launch thevehicle.

Descend on the casing and when at the base carry out a sonar scan forthe Grimsby floats.

Pass the relevant directions to the bridge.

It is better to agrce beforehand on the procedure here and it issuggested that-"go to" directions are given. i.e. move the casing 30feet on a heading of2700.

Once visual contact is established with both the buoys and the base ofthe casing in view the vehicle should remain on a constalt hga{ing-either to lhe North or South of the casing. This will enable the bridgeto work from a known orientation and make the final adjusfinentsnecessary to bring the casing between the 2 buoys.

When the casing is between the buoys the vehicle should close up onone set of buoys and indicate the North or South movement required tocentralise the iasing. It should be noted that while not usually obviousthe hole diameter ai the sea bed is approximately 6 ft and providing theorder to stab-in is given when the casing is above the hole it willgravitate into the hble (a hundred feet of peneffation is_possible.iryithout there being a hole). It is possible for the vehicle to puqh,the.casing over the hole and this is often easier than moving the wholerigby adjusting anchor tensions. In order to accomplish this the vehicles6oul-<l havd a locating frame attached and the casing should be markedwith white rings to allow the carefully positioned cameras to observethe penetration.

While the casing is being fed in the vehicle can standby on the sea beduntil the guide base is inposition (normally 5 ft above the sea bed).The base should be checked to ensure it is level and, if required, thebull's eye can be recovered.

To allow removal of the unit on one occasion .an old A-X ring waswelded to a guide base and the bull's eye fitted to this

After checking the guide base monitor the string to casing unlatchingoperation and recover the vehicle.

5.6.4 30" Casing Cementing

1) Liaise with the drill supervisor to determine the launch time.

2)

3)

The vehicle should descend on the riser and take up a position upcurrent of the guide base to prevent the obscuring of the visibility.

Check the cement is over spilling around the guide base. Usually theexcess volume allowed is 100 - I507o.

It is quite difficult, especially where only monochrome video is used,to diflerentiate between mud, in filland cement however with practiseit is possible.

NOTE:

58

4) When-the supervisor is satisfied with the cementing operation recoverthe vehicle.

5.6.5 Drilling to set the 18 5/8" Casing

1) When the 30" casing has been cemented the bit will be lowered to drillfor the 18 5/8" casing, 3-4 joints off the guide base launch the vehicle.

2) Monitor the position of the string to guide base and direct as necessary.

3) Assist by pushing the string into the guide base if required.

NOTE: The deeper the sea yater depth the easier it is for the vehicle to pushthe string into position, but the Pilot should be wary during strongcurrents.

4) When the sning is in position recover the vehicle.

5.6.6 l8 5/8" Casing Entry

The procedure here is similar to that outlined for the 30" casing stab-in.

1) When the casing is within 3 joints of the guide base launch the vehicle.

2) Assist ir.t gujdilg the casing to the guide base, by pushing if required.The casing is fed in until it is approximately 4 te€t above the b6ttom ofthe.permanent_guide base. Monitor the sring being detached from thecasing ( a left hand thread connects the two).

3) It is normal to fit the stack at this stage. Check with the supervisor onthe time span aq{ based on this it may be worthwhile keeping thevehicle on standby on the sea bed.

4) Monitor the stack latching operation. Depending on how modernthe rig is this will be an 18_ 3/4" 10,000 psi unit or 20 3/4" 2000 psistack. In the latter case a 30 5/8" 10,000 psi unit is fitted at a laterstage.

5) Verify the degree of tilt on the bulls eyes.

6) Check the angleometer(s) on the ball joint (where the lower marineriser package joins the BOp).

7) Cany out a full inspection of the stack. Ensure sonar reflector andbeacon arms are in the correct position and that no oil leaks or damageis apparent.

8) Ascend on the riser/conductor and inspect this and hose lines fordamage and security of attachment.

5.7.0 Possible Tasks Requirements

The following-tasks occur lraphazardly during the course of drilling operations andmay be carried out only infrequently.

59

5.7.1 A-)VV-X Ring Replacement (Hydraulically operated units only)

The metal gasket which seals between the guide base and the BOP is usually calledthe V-X ring and the gasket that seals between the BOP and the Lower Marine RiserPackage is usually known as the A-X ring. If these fail two choices are oPe! to thesupervisor: round trip the stack and effect the change out on surface or lift the stackclear, eject the A-X ring and have the vehicle place a new ring in the guide base. Themethod chosen will largely depend on the depth of sea water and consequently theround trip time for the stack. However the recommended procedure for a vehiclechange out is listed below.

1) Fit the A-X ring carrying frame in accordance with the instructionsupplied.

2) Check out the system, fit the A-X ring in position and launch thevehicle.

3) Descend on the riser and move into the position over the guidebaselBOP.

4) Exact positioning of the ring in the guide base is critical so ensure thatthe self centring frame is level prior to ejecting the ring. Whensatisfied that the positioning of the vehicle is correct operate thevertical thruster pot to give 60Vo of down thrust and actuate the A-Xring tool.

5) Ascend clear of the guide base and video the unit in position.

6) Monitor the stack replacement and standby while it is latched.

7) Liaise with the drilling supervisor and recover the vehicle whenappropnate.

5.7.2 Emergency BOP or Package Release

This task will only be required if the stack or marine riser package cannot beconventionally released i.e. if the primary and secondary hydraulic systems fail.However, it only needs one such failure with worsening weather conditions tovalidate the need to have a separate back-up system, which can be independentlyoperated. The emergency stack release and lower package release panels must be pre-mounted on the stack and plumbed into the existing system. The following procedurecould be used when this task is undertaken.

1) Fit the emergency stack release panel tool to the manipulator.

2) Fit the rig supplied "hot line" to the quick connect and fit thisto the tool. Allow a reasonable amount of slack to allow for themanipulator rotation before taping the hose to the vehicle. (NB ensurethe tape can be broken after hose is connected to panel).

3) Launch the vehicle and descend on the riser. Once at the stack go tothe appropriate panel and turn off the valve

4) Insert the quick connect into the guide cone and ensure apositive lock before releasing the hose.

6L)

I

5) Once the hose is connected advise the drilling supervisor, break free ofthe tape holding the hose to the vehicle frame and standby to monitorthe unlatching.

6) When he stack is unlatched recover the vehicle.

5.7.3 Debris Removal

Small items of debris or transponders may be removed by the vehicle withoutassistance simply by taking hold of it with the manipulator however, where large,heavy objects such as dropped lengths of drill string require moving assistance fromthe drill floor will be required.

5.7.4 Recovery of Large Dropped Objects

This task may crop up from time to time and the item can vary from a drill string to acomplete stack. As the vehicle's lift capability using the manipulator is in the order of90 kg it will often be necessary to attack hooks or slings. This is a common-sensetask and the following guidelines are presented as a guide only.

1) Liaise with the necessary personnel to determine the exact shape of theobject(s), its approximate weight and suitable lift attachment points.

2) Based on the information supplied decide on the method of recovery,i.e. slings, single hook, net, multiple hooks or string deployed retrievaltool.

3) While the slings, wire ropes, hooks or string deployed retrieval toolsare being fashioned and lowered launch the vehicle and locate theobject. Mark the position relative to the well head and standby fortools to be lowered.

4) Attach the recovery tool and ensure the object is lifted clear of thesea bed before recovering the vehicle.

NOTE: It is good practise to ensure that the vehicle always remains above theobject being lifted in case the lifting device should disengage and theobject fall onto the vehicle, the speed of lift should be varied ifdifficulty in achieving this is experienced. Clear this point with therigger/charge hand prior to the lift commencing.

5.7.4 Setting Wellhead Chargm

This will normally be canied out from a ship after the well has been plugged andabandoned and the rig has moved location. The primary task of the team would be tolocate and mark the Wellhead then follow the explosive experts direction for placingthe charge. It is recommended that the ROV Supervisor is aware of all the necessaryprecautions for handling explosives and that the explosives expert gives a safety talkto the team prior to mobilisation. This talk should cover the method and proceduresfor placing and detonating the charge.

5.7.5 Guide Wire Cutting/Replacement

Where a guide wire system is used the vehicle may be required to cut and replace awire. It should be noted that the standard rig equipment can normally carry out thistask without assistance by using the remaining 3 wires. However, where equipment

6 l

I

5) Once the hose is connected advise the drilling supervisor, break free ofthe tape holding the hose to the vehicle frame and standby to monitorthe unlatching.

6) When he stack is unlatched recover the vehicle.

5.7.3 Debris Removal

Small items of debris or transponders may be removed by the vehicle withoutassistance simply by taking hold of it with the manipulator however, where large,heavy objects such as dropped lengths of drill string require moving assistance fromthe drill floor will be required.

5.7.4 Recovery of Large Dropped Objects

This task may crop up from time to time and the item can vary from a drill string to acomplete stack. As the vehicle's lift capability using the manipulator is in the order of90 kg it will often be necessary to attack hooks or slings. This is a cornmon-sensetask and the following guidelines are presented as a guide only.

1) Liaise with the necessary personnel to determine the exact shape of theobject(s), its approximate weight and suitable lift attachment points.

2) Based on the information supplied decide on the method of recovery,i.e. slings, single hook, net, multiple hooks or string deployed retrievaltool.

3) While the slings, wire ropes, hooks or string deployed retrieval toolsare being fashioned and lowered launch the vehicle and locate theobject. Mark the position relative to the well head and standby fortools to be lowered.

4) Attach the recovery tool and ensure the object is lifted clear of thesea bed before recovering ttre vehicle.

NOTE: It is good practise to ensure that the vehicle always remains above theobject being lifted in case the lifting device should disengage and theobject fall onto the vehicle, the speed of lift should be varied ifdifficulty in achieving this is experienced. Clear this point with therigger/charge hand prior to the lift commencing.

5.7.4 Setting Wellhead Charges

This will normally be carried out from a ship after the well has been plugged andabandoned and the rig has moved location. The primary task of the team would be tolocate and mark the Wellhead then follow the explosive experts direction for placingthe charge. It is recommended that the ROV Supervisor is aware of all the necessaryprecautions for handling explosives and that the explosives expert gives a safety talkto the team prior to mobilisation. This talk should cover the method and proceduresfor placing and detonating the charge.

5.7.5 Guide Wire Cutting/Replacement

Where a guide wire system is used the vehicle may be required to cut and replace awire. It should be noted that the standard rig equipment can normally carry out thistask without assistance by using the remaining 3 wires. However, where equipment

6 l

failure or other circumstances necessitates the use of the vehicle possible guidelinesfor this task are listed below.

1) Launch the vehicle and descend to the guide base.

2) Cut any remaining wire protruding from the post. This should be cutas close as possible to the post and the stub fed inside the post.

Place latch release tool over existing latch and lift unit clear.

Locate the new wire and grip immediately above the latch, the closerthe better.

5) Manoeuvre the vehicle into position above the post and place the coneof the latch over the post.

6) Release the wire, maintain position, raise the manipulator and bring itdown quickly and sharply onto the latch. This is necessary to forceback the spring loaded clip which holds the latch to the guide post.

7) When satisfied the latch is in position and connected to the guide postcheck this by tugging on the guide wire.

8) Monitor the latch while tension is applied from the surface and whenthis has been completed, recover the vehicle.

5.7.6 Setting Guide Post Cutting Charge

This may be necessary if a post has been badly bent and does not allow re-installationof the stack. As no shaped charges are carried the first action will be to contact thebase and iurange for the charge(s) and an explosives expert to be sent. Check withthe drilling supervisor that the lead times quoted by base are acceptable. On receiptof the charge(s) the action to be taken is as follows:

1) Discuss with the explosives expert the procedure to be followed forplaclp the charge. Use video previously takgn to- highlight any.significant areas of damage to enable him to decide the best positionfor the charge.

2) When the procedure is settled satisfactorily ensure each man is awareof his role and launch the vehicle.

3) Locate the bent post and place the charge. Video the placement andhave the explosives expert verify it is correctly positioned.

4) Recover the vehicle and detonate the charge.

5.7.7 Drilling Support (General)

The above section is by no means exhaustive and will not be relevant to everysituation. It is true, however, that ROVs are the normal method of providingunderwater support for drilling operations. It is good practice for at least one memberof the ROV crew (usually the Supervisor) to remain on the drilling rig for a numberof wells to allow him to become familiar with particular methods, as practised, inwhat is, undoubtedly, a specialised area of ROV operations.

3)

4)

oz

5.8 Platform Inspection

Legislation requires all offshore sfuctures have a valid certification of fitnessrenewed once every 5 years. Oil companies may have their sffuctures inspected on anannual basis, each yearly inspection is collated in order to apply for the 5 year'Certificate of Fitness'. It is not the intention of this sectionio discuss plaforminspection in detail as it is a specialised area that is described in detail in the CSWIPf.:g.$OJ Inspectors Handbook/Course and is normally required to be carried out byqualified personnel. The intention is to highlight the areas where ROVs play a key

-

role.

5.8.1 General Visual Inspection

9eneralYisual In_spectign (GVI) is normally undertaken on platforms annually byROVs. The ROVs used for platform inspection will be observation class compleiewith tether qanqgeqent systems operating from either a dive support vessel oi from{e^nlatform itself. _Typical types of ROV used for this purpose include; the Seaeye600, the Offshore Hyball and the Sprint.

The items that will be inspected include the risers and conductors which are ofparticular co_ngern as they carry the Hydrocarbons from the wells and away from theplatforms. Other key items to be inspected will include the anodes, the members,welds, the mudmats and other items such as clamps and pile guides.

The ins_pection will be planned from the'Workscope'provided by the client and willnormally include the following tasks:-

1) Assessing amount of marine growth deposits

2) Locating debris

3) Locating areas of general damage to structural components

4) Coating condition

5) Cathodic potential measurements using the proximity silver/silverchloride probe (CPP) ar anodes and other arbas of inierest.

6) The condition and integrity of clamps

7) Relative movement between clamps and risers

8) Flooded member detection

9) Mudmat surveys

10) Inspection of the spool piece and sea line flange

11) Anode condition

Resultsare logged either by computer systems or on data sheets and these togetherwith video tapes form the inspection report required by the client. Once the leneralIslal inspection has.been completed then a close visual inspection may be required.This is normally.carried-out by divers but ROVs are being d-eveloped tliat are c'apableof carrying out these tasks.

63

r5.8.2 Close Visual Inspection

Close visual inspection is carried out when defects have been highlighted by thegeneral visual inspection or as required by the workscope. Work class vehicles maybecome involved in this part of the inspection in the following ways:

Cleaning of welds and removal of marine gowth using rotating wirebrushes or water jets. Water jets can be either high pressure (HP) orLow Pressure (LP) and may be sand entained. It is extremelyimportant to adhere to any peftinent safety regulations where highpressure water jetting is being utilised. In general low pressure waterjetting will be sufficient to remove loose or soft marine growth prior toultrasonic flooded member detection or wall thickness measurement.High pressure water jets will be used where a bare metal finish isrequired prior to weld inspection or crack detection.

Photography of anomalies. If the anomalies are large they may bephotographed using'stand-off photography during the GVI but close-up photography using special NDT or Photo$ammetic cameras will berequired for weld or crack photography.

The practice of Non Desffuctive Testing (NDT) involves the testing of welds andmembers by ultrasonic, elecffo-magnetic and radioactive methods. These tasks arenormally ca:ried out by divers but more recently specially adapted tooling packageshave allowed work class ROVs to carry out these tasks.

1) Flooded member testing - The ultrasonic or radiographic testing of amember to determine if water ingress has taken place.

2) Wall thickness measurement - The ultrasonic testing of a member todetermine the wall thickness.

3) Magnetic Particle Inspection (MPI) - The inspection of a welds fordefects utilising magnetising coils or prods and fluorescent ink. Thismethod is usually undertaken by divers but has been accomplished byROV.

4) ACFM and ACPD are two methods of finding weld defects moresuited to ROVs as the electronic probes are smaller than the equipmentrequired for MPI. The probes use electronically sophisticated methodsto detect defects that are beyond the scope of this book.

The involvement of ROVs in platform inspection is constantly increasing and it isquite feasible that the whole inspection programme will be carried out by ROVs inthe near future. This is particularly so as weld inspections are becoming less frequentas weld defect predictability becomes better understood and ROVs and thereoperators are becoming more capable. This is due to technical advances andimproved operator standards with the emergence of the CSWIP 3.3u ROV Inspectorsraining courses and qualification.

5.9.0 Intervention tools

The main impetus for ROV Intervention has come from the fact that a fullyequipped ROV support vessel (ROVSV) will cost between 1/3rd and 1/10th of thecost of a dive support vessel (DSV), ROV intervention is therefore considerablycheaper. In Norway, Norsk Hydrois TOGI and Oseberg Development Projectsrepresent important milestones for remote intervention. These were the first projectsin which there were primary operations on the subsea installations which were

1)

2)

ho4

II

carried out solely by RoV. Until this point, ROV underwater intervention onpennanent installations had been restricted to back-up and override tasks in case theprime actuation systems failed. With the increased reliability and availability of ROVsystems, such operations could be much more cost effective. Typically suchoperations include opening and closing valves where the operation can be plannedsome time in advance and are not part of the installation control system operatedautomatically or via the sea bed umbilical.

5.9.1 Norway

Norway has taken a lead in remote intervention because exploration and productionoperations are occurring in ever increasing water depths and are already at andbeyond the reasonably practical and economic depths for manned diving (around 350to 400 metres or 1150 to 1310 feet). In addition ii is considered socially unacceptablein Norway for people to be taking the risks associated with deep divingoperatiohs.

5.9.2 Other Areas Of The World

Other parts of the world are also making progress with the development of diverlessintervention techniques. These include areas of the world where exploration andp:oduction are moving into water depths beyond the capacity of saturation diving.Operators in the Gulf of Mexico have set many records for such activities. Inparticular, Shell have drilled in 2,292 metres (7 5I7 ft) of water from the drill ship'Discoverer Seven Seas' with underwater intervention support provided by anOceaneering HYDRA 2500 ROV. Shell are also bringing theii Auger leg platform(TLP) on stream in 872 metres (2,860 ft) of water. In Brazil, Pero6ras aie operatingsubsea completion's tied back to production systems in over 1,000 metres depth.

5.9.3 Methods of Interventions

There are three main methods of carrying out remote intervention: the RemotervQperated Tool (ROT), the Remotelybpirated Vehicle (ROV) and the RemoteiyOperated Maintenance Vehicle (ROMV).

5.9.3.1 The Remotely Operated Tool System (ROT)

This is a development of existing drilling intervention techniques where tools aredeployed, via guide wfes, lowered from the surface. Once landed at the work site,the_tool can carry out its specific tasks. Usually such tools are controlled by separateumbilical cables from their topside control station. ROTs can deploy and operatelarger and heavier tool systems than would be considered using ROV methods. Alsothe tool is securely locked into the installation, providing a firm base for preciseoperations. The tools can be used to recover and replace large components, such asc.ontrol pods and valve inserts. ROTs have high reliability and are very task specific,they are also designed to require very little operator'skillt.

Rors are limited by water depth for guide wire operation, the need for a moresophisti^cated support vessel with the Increased associated costs. Also there is alwaysa risk of the tool 'dropping', and damaging the subsea intervention.

5.9.3.2 Remotely Operated Vehicle (ROV)

ROV operations are normally low-force, or more correctly, low mass. This is not tosay that high forces cannot be generated, only that the ROV tools are individuallysmaller. Typically a range of intervention tools could include; a subsea ROV winch,an interface system to a valve, a series of tool to remove covers, access valve inserts,an 'elevator' to recover the removed components, tools to inspect and clean insidevalve insert bodies, seal surface inspection, cleaning and refacing tools etc. The tools

65

can be fitted to the ROV or can be lowered to sea bed in a sepiuate basket, $ey arefittea wittr buoyancy material to reduce their in-water^weighi and then handled in turnLV G [OV. ttt" t6ols are usually job specific, but often.ian be used to addressseveral similar tasks in different locations giving cost savings.

The ROV tool spread is often cheaper to build and^operate, the surface support vesselr* GJorril"rdil.ty ROV DP sripport vessel, ofteir making tlg.o.pglatignl cfeaperthan with ROTs. Car6fU design with guides and latches to eitablish the tools in the;Ai did-;niuna i*olving-automad'c operationsthereafter can be used to minimisethl operator skill requirement and ensure repeatability.

5.9.3.3 Remotely Operated Maintenance Vehicle (ROMV)

The third method is where effectively an ROT is deployed into a subsea installation,where the tool can move within the itructure and carry out several tasks and is knownas i remotely operated maintenance vehicle (ROlVlV). An_example. of this is theSugnf"roleirm'Snone Subsea Production sys-tem. figg: 5.5 shows the Snorreiu6r.u production system. Figure 5.6 showi the manifold control module and ROMVend eff6cter which ii used to rlcover and replace all types of subsea conEol systemmodules.

't/.-2-'@*3 ' , 4'V"i

' ' / , ' '

,e

Umbil icalPorches

Figure 5.5Snorre subsea production system

L 66

c)

h)

i)

j)

ROMV End Effector No. 2External Can \ \ROMV GuideSleeves and

Pressure Comoensator

Latch Receptacles

Clamp Halves

< z \Hex Drive l-:-

- --G

Torque Wrench

Hydraulic Couplers

Inductive Couplers

Mounting Base --'

Figure 5.6Manifold conffol module and ROMV end effector

5.9.5 Typical intervention tasks by ROVa) Pull-in and connection using an ROV as the sole means of operating

the Pull-in connection (PIC) tool and other pull-in methods.- seeFigure 5.7

b) Inspection and cleaning by ROV tools. See Figure 5.8

d)

e)

f)

s)

ROV support for Blmote Operated Tool Packages. see Figure 5.9which shows an MRV with purpose built intervention pac[age addedat the rear for Mobil.

Electrical and hydraulic connector cleaning by custom Rov toors.

Electrical cable installation tooling.

Control system for a series of ROTs

ROV in_tervenliol panels for hydraulic "hot stab" operations. SeeFigIIg 5.I0_which shows a Tronic mini c-E conneitor and receptacreand Figure 5.11 which shows a subsea tree with stab-in panel.

Remote crack detection and sizing by ROV.

ROV based welding. See Figure 5.12

ROV based dredging. See Figure 5.13

o /

The above serve to illustrate the range of ROV intervention tasks, andis-not intended

to be exhaustive as this is a speciauied area of work with teams of tool designspecialists employed by all the major ROV Contractors'

Figure 5.7ROV Flow line Pull-in

Figure 5.8ROV Structural Cleaning

TRITON

L

Figure 5.9MRV With Tooling Package

Figure 5.10aTronic C-E Mini Connect

.T 'BAR

ROV PLUG

BULKHEAD MOUNTED RECEPTACLE

Figure 510bTronic C-E Mini Connedtor Tolerance To Misalignment

t

71

Figure 5. l lSubsea Tree With Stab-In Panel

Friction Welding Tool

Figure 5.12ROV Based Welding

:iAlternative Dump ...;1/Line to Surface ..iJ"

Dump Line iito Seabed \:.

Figure 5.13ROV Based Dredging

72

5.10.0 Telecommunications Cable Laying

Telecommunications Cable laying is a world wide operation carried out by companiessuch as BT (Marine) and Cable and Wireless (Marine) which is increasing infrequency as the telecommunications revolution gathers pace. Similar methods areused in the offshore oil industry for laying control umbilicals, flow lines andpipelines.

5.10.1 General Operations

In general operations a work class ROV may be required to crury out the followingduring the cable laying operarion:

1 Pre lay survey - The survey carried out before the cable is laid toassess the relief of the seabed.

2 Touch down monitoring - The ROV is required to observe the point atwhich the cable makes contact with the seabed. This enablesengineers to determine if the tension of the cable is correct during thelay down procedure.

3 Post lay survey - The surveying of the cable once laid, this taskresembles that of a pipeline survey and is to ensure that the cable islaid correctlv on the seabed

5.10.2 Burial

Often the cable or control umbilical is required to be buried. This is likely to berequired in shallow areas where there is a likelihood of trawling or similar activitiesd.utrugilg the cable. This is achieved in one of two ways; a plough is towed behind aship which ploughs a ffench and positions the cable in it, or a Trencher which is atracked ROV creates a trench with water jets and lays the cable in it. In both casesafter the cable is placed in the trench normal sea bed action is lift to fill the trench.

5.f03 Eureka Trenching System

f1r exampl^e_of the Eureka trenching system and a SMD plough are shown in chapter3; Types of ROV.

5.10.4 Modular Plough System

ligury 5.14 shows a description of the Modular Plough System taken from the BT(Marine) data sheet.

5.10.5 Submersible Trenching System

Figure 5. f 5 s_hsys a description of the Submersible trenching system similarlyoperated by BT(Marine) and taken from their data sheet.

5.10.6 Summary

lh9-information_presented here is intended as an overview of cable laying equipment.!ab]e laying_is, however, a specialised area and although the technologyis

'

fundamentally similar to all ROVs, due to their large size (often severi[Tonnes) theytend.to be operated_by large_r crews of typically 7 men for 24 hour coverage. Theywill be; a team leader, two Senior operatbrs oi shift supervisors and two o=perators pershift.. P]oqgh.s and trenchers are operated from dedicafed support vessels with heavylaunch facilities such as 'A' frames at the stern of the vessel. in both cases profiling

73

and bathymerric sonar (see chapter 19) are used to ensure that the cable is being laidin the trench and is entering the machine at the correct angle due to the very poorvisibility experienced during these operations. Detection coils are positioned-on eachside to aid location of buried cable and responder beacons are attached to enable thesurface vessel to 'track' the plough or trencher with its' HPR system.

5.11.0 Construction

Specially adapted trenchers similar to the one described in 5.10 prev^io-up have beenadiaptedio undertake sea bed construction work. A good example of this was thebuilding of a round concrete barrier wall around the central concrete_storag.e platformin the E-kofisk field operated by Phillips Petroleum (Norway). A full description ofthis project is described in the Society Of Underwater Technology (SUT) joumal'Undlerwater Technology' Volume 17 No.2 1991. It is sufficient to state here that suchprojects are possible by adapting trenchers with such things as; sea bed levellingtools, debris collection rakes and scraper collection tool.

5.11.1 General Construction Work

General construction work usually involves the installation of steel jackets. These arefloated off a barge and lifted into position on the sea bed by a Derrick Barge. TypicalROV tasks on such installations include the following:-

i) Pre installation sea bed survey

ii) Placing transponders and positioning the jacket

iii) Checking the mud mats

iv) Monitoring the pile driving and depth of penetration

v) Monitoring the cement returns at sea bed for pile cementing

vi) Diver Observation

vii) Post installation survey

Particular care must be taken with regard to safety when undertaking these kinds ofconstruction operations. Care must not only be taken not to harm divers that may bein the water but deck work must be done with care as many dangerous operationssuch as heavy lifting, welding and cutting will be taking place.

5.12.0 Remotely Operated Television (ROTV)

A good example of an ROTV system is the FOCUS (Fibre Optic ControlledUnderwater System) 400Inspector. This is a versatile, stable, controllable, towedsensor platform. The modular design approach permits designs to depths of 6000mwith cable lengths of up to 10000m. The innovative hydrodynamic 'box kite' designlends itself to carrying a multitude of sensors. These are commonly fitted with videocameras, obstacle avoidance sonar's, side scan sonar, sound velocity probe, stillcameras, lights, pan and tilt units and transponders. Everything in fact that a pipelinesurvey ROV might carry except the thrusters. ROTVs can offer a cost effectiveanswer to pipeline survey work. ROTV Pilots, however, need fast reactions as ROTVsurveys are often faster (around 2 knots) than normal ROV survey (around U4 - U2knot). Control is accomplished through control foils at the stern of the vehicle.Figure 5.16 shows the FOCUS 400 performance curves.

5.-13.0 Other applications

74

Other applications include the military use of ROVs for Mine Counter Measures.This is a specialised area where the ROVs in use are required to be; reliable, quietwith a minimal magnetic signature. ROVs are being widely used by customs officialsand the police to counter terrorism and drug smuggling where attachments may befound on the underside of vessels. Headline grabbing applications include the surveyof the Titanic and the MV Derbyshire. Other more romantic applications include thedredging for gold off South Africa and the harvesting of Pearls off Japan. There areas many applications of ROVs as man can imagine, and it has to be true that therewill be many more in the future as the explorations of the oceans is still considered tobe in its infancy.

.aut.,iauii,u:3t iut::a::

MPSCable Plough

&Fe$r -

Pre$ue nd$uces {4)i l , r : . r r r , r i l | r r laX : l . i 'l:ia :rr!rri..ri! ir!:iirr l l

rt:;:.r..iMr.rirr,

str'

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:!rk Snr:d iF.nn.i!)jr i l

l id. Lllr i j{ ir T$r 9rl : lFtu

tudtusEhyadMd

Figure 5.14

75

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> 6t h-:c ^"

(g

c(0

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c

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=)o o

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5 l^6= F Ei ; 6 9> o q )

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x _ >

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F 9 qt : v

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ge

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E(DID

ao)C

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Figure 5.L5

fuggm g€Hlga:gg*a?g**'76

FOCUS 4OO INSPECTOR

PERFORMANCE CURVES

t r '$

I

E

ro o)

c i

i 3

Figure 5.16

77

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L

Chapter 6 Electrical principtes

6.1 Introduction

In order to be able appreciate the Rov Electrical system thoroughly, a basicunderstanding of the Flectrical principles is essential. The first iption of this chapterconcentrates on revising these principles so they can be applied when carrying outmaintenance on any system.

6.1.1 Voltage and Current

In order to understand the nature of electricity and the basic electrical properties ofmaterials, a knowledge of the structure of atoms is required.All materials are made up of atoms and all atoms contajn tiny particles calledelectrons which orbit a central nucleus.

+ electron

+nucleus

metal,/

t,/

cI

@ /

Figure 6.1

Electrons have.a negative charge while the nucleus has a positive charge. Like chargesrepel while unlike charges attract each other, therefore the negative eleitrons areattracted to the positive nucleus and are held in orbit.

In conductors, electrons are not tightly held to their atoms and may break free and movefrom one atom to another. These Tree'electrons normally move around randomlv.

'free' -{

electrons 'e--Vgt @ +

of ^r@

Figure 6.2

If these free electrons are made to flow in the same direction, the result is an electriccurTent.

19

metal

'free'

electrons

@ +@+

@+ @+

Figure 6.3

Insulators are materials in which electrons are strongly bound to their atoms and theremay be few free elecftons. It is therefore difficult for current to flow. (For example,glass and rubber.)

Free electrons can be made to flow in one direction in a conductor by applying apositive charge to one end and a negative charge to the other. The positive charge at oneend will attract free electrons while the negatively charged end will repel electrons.

Current is the number of electrons passing any one point in a conductor in one second.In other words applying a potential difference (or voltage) across a circuit will cause acurrent to flow. The Potential Difference creates a force, known as Electro-MotiveForce which gives rise to current flow.The size of the current will depend on the size of the voltage and also the amount ofresistance in the circuit.

The symbol for current is I, it is measured in amps.The symbol for voltage is V, it is measured in volts.The symbol for resistance is R, it is measured in ohms.

6.1.2 Resistance and power

Resistance is an opposition to current flow that gives rise to power being dissipated andwork being done. The power may be dissipated in the form of light, heat or motion.Figure 6.4 illustrates a simple electrical circuit involving the basic electrical principles.

Distribution

Voltage Source istance

Figure 6.4

In this situation the current source develops a potential of charge, the units of which arecalled volts. It follows therefore that there will be a drop in potential across theresistance due to some of the electrical energy being converted to heat, light or motion.

Power

,/

L

Direction of Current

80

6.1.2.1 Relationship between voltage, current, resistancerand power

There is a mathematical relationship between voltage, curent and resistance.OHM's Law states that the curreni in a circuit is dlrectly proportional to the voltageand inv.ersely proportional to the resistance. These quantities are linked by thefollowing equation.

Figure 6.5

If the conductor is formed into a coil and a current is passed through it, a magnetic&F p produced which is similar to rhat of a bar magnet.This is known as an electromagnet.

VOLTAGE = CURRENT x RESISTANCE

( V = I R )

Power is the amount of work that can be done in a standard unit of time (1 second).Electrical power is expressed in units known as watts. One watt represents the powerused when one ampere of current flows due to an Electromotive Forie (EMF) of'1volt.Power is related to Voltage, Current and Resistance by the following equation.

POWER = (CURRENT ;z x RESISTANCE

P = I 2 R

POWER = VOLTAGE2 / RESISTANCE

P = V 2 l R

6.1.3 Electromagnetism

Figure- 64 shows an electric culrent flowing through a conductor produces a magneticaround the conductor, the direction of which depends on the direciion of current-flow.

conductor + -+I

direction of

magnetic field

conductor + <!-I

direction ofmagnetic field

8 l

F

bar magnet

Figure 6.6

The magnetic field is increased by:-

I increasing the number of loops in the coil2 increasing the current through the coil3 using a ferrous core

6.L.4 Electric motors

Direction of Rotation

Figure 6.7

Figure 6.7 shows the basic action of an electric motor. If a current 9?:rying conductoris placed in a magnetic field the conductor will move in a rotational direction that isdependent upon the direction of current flow. In practice a motor is made !p_gfthousands of coils wound on a former. The interaction between magnetic field andelectrical curent is stronger allowing the motor to develop a greater torque.

6.1.5 Direct current

Figure 6.8 illusrates the relationship between voltage and time. In this situation thecurrent has constant magnitude and direction .

82

time

IT

I

Figure 6.8

6.1.6 Alternating current

Figure 6.9 illustrates the relationship between voltage and time. In this situation thecurent varies in magnitude and direction. The current varies between a positive leveland a negative level oyer a period of time. The time taken for one complete cycle isknown as the periodic time, and the number of cycles that occur in one second istermed the frequency.

It follows therefore that:

FREQUENCY =

where 1= periodic time

The advantage of altemating current over direct current is that it is possible totransform alternating current by means of either a 'step up' or 'step down'transformer.

+ V

m a x + V

Figure 6.9

m a x - V

83

F!

Figure 6.10 illustrates how AC. current is generated. As the coil rotates it'cuts'thelines of magnetic flux resulting in current b-eing induced into the conductor. This isknown as single phase AC current and is commonly used for domestic supply.

External power sourcemechanically coupled to coilprovides rotation

Direction ofRotation

Figure 6. f0

6.1.7 Transformer action

A transformer is a device that transfers AC energy from one circuit to another withoutthere being any electrical contact between the two circuits.Transformers operate according to the principles discussed in section 6.1.3. If an ACcwrent is applied to a conductor then the resulting magnetic field will build up andcollapse in sympathy with the varying magnitude of the current. If this conductor isplaced in close proximity with another conductor then the magnetic field will induce asecondary current into this conductor. In practice the conductors are made up of coils ofwire known as primary and secondary coils .Figure 6.1 1 illustrates the action of the transformer.

PFIMAfr ! SECONOAFY COILSWOUNO ON THE SAME CORE

Figure 6.11

The relationship between the primary voltage and the secondary voltage is dependent onthe number of turns on the coils. Figure 6.10 illustrates the step up and step downtransformer. The output voltage is directly proportional to the number of turns in thecoil. The example shows an input voltage of 115VAC to a coil with 1000 turns.The secondary coil has 2000 turns and an output of 230VAC.

Direction ofinduced

84

I

I

6VDC

Example:

RATIO OF PRIMARY COL TURNS TO SECONDARy = I : 2

INPUT VOLTAGE =200 VOLTS.

Therefore

SecondaryVoltage - 2x.200 =400VAC' l

6.1.8 Relays

$q!y-q are electrical switches that operate on the principle of electromagnetism. Figure6.12 illustrates a simple relay circuii.The diagram shows the contacts when the relay is in its de-energised state. In this statetley.are referred to as bein_g normally open or irormally closed. When crrrent is appliedvia the controlling circuit the relay becomes energised and the contacts change to th'eopposite state. This in turn connects the high voltage source to the motor.

MOVINGARMA�TURE

CONTROLLINGCIRCUIT

RELAY CONTACT

N.C.

II n.o.

REI-AY J

Figure 6.12

HIGH.VOLTAGEHIGH-CURRENTPOWER SOURCE

220 VAC

CONTROLLEDCIRCUIT

MOTORRELAY CONTAST

LOW.VOLTAGELOW-CURRENT

POWER SOURCE

6.1.9 3-Phase electricity

ftgult 6.8 illustrated the relationship between single phase curent and rime. Thedisadvantage of single phase curreni is that it is noi suitable in situations where a highpower factor is required.Figure 6.13 illustrates the principles of generating 3-phase electricity. Three coils are>e t . 120.de_grees apart resulting in three separate phaies of current U6ing induced intoeach coil. It can be seen therefore that the phases are also offset from eich other by 120

85

degtees. In practice each coil is made up of man^y.thousands of turns, this being one ofthjmain faitors that influences the magnitude of the generated current.

A

tII,

Red, Yellow and Bluecoils

F igu re 6 .13

6.1.10 Transformer conf igurat ions

3 Phase transformers are normally connected in either Star or Delta configurationdepending on their specific requirements. Figure 6.14 illustrates the two modes ofconnectlon.

Phase 1 Conductors

Neutral

Phase 2

Phase 3

Star Configuration

Figure 6.14

It can be seen that in the star configuration that thereturn line as oppose to the delta connection where

Delta Confi

three windings have a commonno return is present. With star

I

86

transformers the line insulation is only required to withstand the phase voltage and notthe full output voltage. Also two choices of load voltage are available betweJn thewindings if the neutral line is used.

The main disadvantage of the star configuration is the transformers behaviour whenharmonics of the fundamental frequency exist in the secondary windings.The_delta configuration does not suffer the same disadvantages as the starconfiguration. In this situation the closed form of the delta piovides a path for theharmonics to circulate and prevents them flowing into the power system.The most common configuration on ROV systems is a star/delta Sivitching Mechanism.In the delta mode the output is ungrounded, the grounding of one phase will notseriously effect the operation of the power system as the fault cunent has no directreturn path to supply. If the output was in star then a fault current would have a directsea return path to the supply. Another advantage of this configuration is that anyunwanted harmonicsare prevented from propagating through the power system. It isusual practice to employ a srar / deltaconfiguraiion in the power supply. tnitially starconfiguration provides a low start up current for the electric motor, once running atoperating speed the system switches to delta configuration which runs more effiiiently.

6 .1.11 Power suppl ies

The mainparts of-a power supply unit (PSU) are a transformer, rectifier, smoothingcircuit and a stabilising circuit (see figure 6.15).

rnputF igu re 6 . f5

a) The transformer

The transformer tak€s an ac input voltage (e.g. mains) and 'steps' (converts)it to the.required voltage. A transformeimaylherefore be step-up'or'step-dg*L'depending on the turns ratio between the secondary and the primarywindings.

b) The rectifier

The transformer output is an ac. voltage. This is then converted to a dcvoltage by the rectifier, however this is not a steady dc voltage and assuch is not suitable for many applications.

c) The smoothing circuit

Most equipment and electronic circuitry require a constant and steadysupply voltage in order to operate. This circuit smoothes the rectifieioutput to give a steady dc voltage.

d) The stabilizing circuit

Because of internal resistance, the dc output of a PSU or battery decreasesfrom a maximum as the current drawn increases. The greater this decrease.the worse is said to be the regulation of the supply.

d.c.output

rectifier smoothing tabil ising

87

Figure 6.16 illustrates the effect of current loading on a power supply.

d.c.outputvoltage

REGULATIONCURVES

loadcurrent

Figure 6.16

The stabilising circuit overcomes this problem ensuring the output voltage remainsconstant.

Circuit Action.As the culrent drawn by the load increases the currentthrough the diode decreases and a constant voltage acrossR1 is maintained.

F igu re 6 .17

Figure 6.17 illustrates how a device known as aZ.ener Diode is incorporated into theoufrut stage of the circuit. The diode 'clamps ' the output voltage at the de.sired levelregirdlesiof the external loading. It is not ihe intention of this section to dwell on theciicuit theory of these electrical devices as there are mlny text books available that coverthe subject {uite adequately, but to provide sufficient information to cross-train amechanical itilotflechnician to be able to assist an Engineer with electrical tasks.

t-)

FD

z

RESISTANCE

88

Figure 6 .18 .

UMBILICAL

Aux 240 V

Deployment

89

6,2 Introduction To The System

In chapter 3 figure 3.1 illustrates the basic layout of a typical Rqy s_ys!gq. It can beseen that the system is comprised of a surface unit, winch, umbilical , TetherManagement System and vehicle. It is the intention of this section to discuss the basicprinciples of operation of these individual units.

6.2.1 Surface Unit

Figure 6.18 illustrates the surface unit of a typical work class ROy (SEL Multi RollVJtricte). There is one main power input which may be supplied from the vessel orinstallation or from a customised generator.An auxiliary input of 24AV is also providedas a domestic supply.

The main input, typically 440VAC, is fed via a junction box to the main PowerDistributionUnit. Power is then distributed to the following main units.

a) Purge System.

b) Deployment Crane.

c) Winch Power Pack.

6.2.1.1 Purge

Step up Transformer.

Control Console.

System

The purge system provides a pressurised safe area thus enabling the us of non-zonerelated equipment in the control cabin and winch junction box.When the system starts up a fan pressurises the cabin to 0.75 milli Bar, this ismonitored by the Purge Panel for a period of twenty minutes. After this period, shouldno problems occur then the vehicle system will be switched on. During operations,should cabin pressure fall below 0.25 milli Bar then the Purge system willautomaticallyshut down the system. It follows therefore that if the vessel or installationis in a situation where inflammable gas is present the positive pressure inside the cabinwill prevent the gas intruding, if the pressure falls then the power will be cut offpreventing any electrical arcing occurring and causing an explosion.

6.2.1.2 Deployment Crane

The crane hydraulic power pack consists of a 3-Phase electric motor, the power forwhich is taken from the PDU.

6.2.1.3 Winch Power Pack

The winch power pack operates on the same principle as the crane. A 3-Phase Electricmotor is directly coupled to a hydraulic pump. The motor receives its'power from thePDU

6.2.1.4 Step Up Transformer

The step up transformer is supplied with 440VAC which is converted to a suitable levelas to overcome line losses in the umbilical.Typical surface voltages for ROVs are as follows:

d)

e)

L 90

a) RECON IV I60VAC

b) scoRPro 1100vAC

c) HYDRA 1800VAC

d) RCV 1s0 950VAC

e) MRV 33OOVAC

6.2.1.5 Control Consote

The control console houses the surface elecronics control instrumentation and displaysthe vehicle sensor information.

a) Surface electronics and control instrumentationThe surface electronics processes the signals received from the vehicles primarycontrols (e.g. joy-stick, manipulator master control). The primary controlsproducg a varying dc voltage that may vary proportionallybetwebn t5vdepending on the system. These signals ari: algititized and multiplexed beforebeing transmitted down the umbilical to the vehicle electronics. Section 6.3 inthis chapter looks at multiplexing in more detail.Figure 6.19 illustrates the basic process of control and instrumentation.

over switch

Umbilical

\

Digital Signal

Figure 6.19

The remote box is a replication of the primary flying controls and enables the deckofficer to steer the ROV away from the vessej oi installation during the launchprocedure into a safe diving position. Once in position the controlis reverted back tothe main controls in the control cabin.

The joy stick potentiometer is simply a variable resisror that produces a proportionalanalogue voltage. There.is one porenriometer for each plane bf rhe joy-siicli.The surface interface unit amplifies the analogue signaf to a suitable t6vet to be appliedto the multiplexer (mux) unit.

b) Sensor informationChapter 5, section 5.2.2 discusses the various sensors that mav be found on a

" typical $OV. The vehicle electronics incorporates a'two way iata link'whichallows data to be transmitted to the vehicle-from the surface, as is the case for

Analogue Signal

SurfaceInterface

9 l

the control information, and from the vehicle to the surface, as is the case for

the information from the sensors.

The sensors consist of transducers that converts one form ofenergy (e'g'

pressure, rcmperature o. u"our,ir; i"iii.tti.ul energ.y. The electrical energy is in

the form or ri *ui.gue signal trriii converte{ tg &-gitat and tranqmitted in the

same mann"; u;ih;;;ntifi signat. rn" r"nror infoniation is displayed to the

pilot on the control console.

6.2.1.6 Switch On Procedure

It is important when switching the system on to follow the correct procedure'

a) Console Power

b) Vehicle Power

c) HYdraulic Power

If this procedure is not followed complications with the systems telemetry can occur'

The telemetry system works on the Master / Slave^princip.l9, the surface electronics

being rhe master and thevehicle being the slave. tf ttre v6trict: tly:l:t^:Yll:l* on

before the console po*"t then the sitiation arises whereby the slave is enabled and

receiving no ro*-und f.o* the surface master. This is an undesirable effect and can

fruJto p-ossible damage of the telemetry sy{em.. When powering down the system the

procedure should be followed in Reverse Order'

6 .2. I .7 Disp lay Uni t

As well as housing the vehicle control system the surface unitis rel"u{1!^t1{3laf

uiO.o unO sensor information. The system incorporates a number of vtdeo monltors

;[i"h ;r; capable oib.ing switched video cameras and sensors-asrequired' .Some ROV sysre;; h;;; S.if niugnostics Programm.e. All the

-circuit boards in

the system are continually monitored,Ihould a fault occur then a surface computer

allows the operato.;;G through a programme which will locate the relevant circuit

board.

6.2.2 Winch SYstems

All ROV systems require a system to-deploy the vehicle to the work site' Most winches

ar. "i..tt"-ttydraulic and are designed tocontrol the length of umbilical as oppose to

ohvsicallv liftine the vehicle. When submerged the vehicle controls its own depth, and

iliffi"fr^iir.;';ilil; il;-fis meChanism atiached to the crane lifts the vehicle out ofthe water. There."-r*" i,i.eptions to this in which case a more powerful winch is

fitted with a specially designed lifting umbilical'

Figure 6.18 shows the main units on a typical winch' .ffr? iyrrc. incorporates two junction boies connected together by slip rings'

6.2.2.1 Fixed Junct ion Box

The fixed junction box is a two way junction box that passes.power to the umbilical'uia"o rtgnlut from the umbilical and data signal in both directions.

92

6.2.2.2 Rotating Junction Box

The rotating junction box, as the name implies is attached to the main drum of thewinch and carries out the same function as the fixed junction box.

On systems where fibre optics are used (see section 6.4) the rotating junction box mayhouse fibre optic transmitters and receivers. This overcomes the problems caused whentransmining light energy from a fixed junction box to a rotating junction box. Thesignal passing between junction boxes remains electrical which is more compatible withthe slip ring assembly.

6.2.2.3 Sl ip Rings

The slip rings provide the interface between the fixed junction box and the rotatingjunction box.Figure 6.20 illustrates the operation of the slip ring.

_ WINCH MOUNI ING

Qr?-,!qA-I irr \r lv!!3 ?f PQ!E& S|GN{ & FrBER OqrC PASSI5

OFTIONAI PRESSURTCCMPTNSAiOR'

Figure 6.20

The unit consists of a number of contacts known as brushes (one brush per conductor)mounted on a central core which is static and directly connected to the fixed junctionbox. The core is mounted in a cylinder which is free to rotate and is directly coupled tothe winch drum. Inside the cylinder there is another set of contacts that make physicalcontact with the brushes on the static core. It follows therefore that electrical continuityis maintained at all times during the rotation of the winch drum. The slip ring in Figure6.20 also incorporates a fibre optic rotary joint which allows light signal from the staticjunction box to pass through a prism network which in turn directs the light onto a lens.The lens then converges the light onto a receptor in the rotary section of the joint beforeit is sent down the umbilical. It becomes obvious that the efficient functioning of thewhole system is dependent on the integrity of the slip rings and for this reason they aremanufactured to a high degree of quality. Correct maintenance is crucial, an outline ofwhich is referred to ln chapter 11.

IO ROIATINCJUNCIION 8OX

MODEL I?6ELECTRICAL SUP

I sEt oFllrL l

93

6.2 .3 Umbi l i ca ls

The umbilical provides the electrical link between the surface and the ROV Umbilicals-uy U" armouied depending on whether tlrey are required to lift the vehicle out of the*ui", during the rec6very o"peration. The fifling streirgth is provided by a steel wire*iup tttit srirrounds ttre rlmhtical. Umbilicals of this nature are heavy and requirededicated winches.Figure 6.21 illustrates a typical umbilical for a work class vehicle.

FibreOpticBundle Amrour

PowerConductors

Coaxial QuadsF i g u r e 6 . 2 1

6.2.3.1 Types of conductor

This umbilical consists of the following conductors:

a) 16 Power conductors, each phase being spread over 4 conductors. In this case 4conductors act as neutral line.

b) 4 Quads. A quad consists of two wires called'twisted pairs'. The twisted pair carrythe teiemery silnals and data up from the sensors. For this reason the twisted pairs arescreened to profect the signal from extemal interference.

c) I Fibre Optic bundle. These fibres may be used to carry video or any form of digitalsignal as required.

d) 2 Coaxial Cables. Coaxial cable is normally used to carry video signal from thevehicle to the surface unit.

t o,l

The Quads and coaxials are shielded by a copper braiding. If this was not the case thehigh voltages in the power conductors would lead to severe interference and comrptionof the data signals.

It should be noted that if fibre optic bundles are incorporated in the umbilical, becauseof their delicate structure, they are usually placed in the centre to minimise breakage dueto bending of the umbilical.

The conductors are enclosed in a plastic sheathing which provides insulation andprotection. This would be a standard umbilical and would not be suitable to lift thevehicle. By covering in armour the umbilical is then given its lifting capabilities.

6.2.3.2 Safety Factors

During launch and recovery operations the umbilical is often wavering at head height. Ifextreme care and attention is not exercised at all times then severe injury or even deathcan occur to careless personnel. It is the responsibility of the ROV team to makeeveryone aware of these dangers during the launch / recovery period.

6.2.3.3 Umbi l ica l Breakdown

Conductors within the umbilical can break due to excessive tension or severe twistingor bending. Faults of this nature can lead to long periods of down time and the pilotshould always be aware of the umbilicals state during diving operations.The maintenance and repair of umbilicals is covered in chapter 11.

6.2.4 Garages And Cages

Many ROV systems employ a Earage or cage which houses the vehicle during thelaunch / recovery process. In this situation the vehicle will be protected from possibledamage whilst passing through the 'splash zone'.

Small ROVs are limited at what depth they can work due to the drag factor of longlengths of umbilical. This problem is overcome by deploying the vehicle in a garage,once at the working depth the vehicle only has a short distance to 'swim' in order toreach the work site. By working from the garage the large drag factor has beeneliminated.

The garage employs what is known as a Tether Management System (TMS). TheTMS controls the paying out and reeling in of the umbilical during the diving operation.

The TMS is controlled by the pilot from the control cabin. The TMS control signalspass down an armoured lifting umbilical in the same format as the ROV control signals.They are then processed in the TMS electronics bonle and used to control theappropriate hydraulic valve. The ROV umbilical is housed on a hydraulically controlleddrum. From this the umbilical passes through a system of guides and rollers thatmaintain the correct tension on the umbilical whilst paying out and reeling in. A pan andtilt camera is also fitted to the system to aid the pilot when latching and unlatching theROV.

95

power

control

umbilical

power

control

YDRAULIC

PORTFLOATTANK

OPTICSruNCTIONBOX

PRESSURESENSOR

STARBOARDFLOATTANK

SONARSCANNINGI.JNIT

UMBILICALTERMINATION

Figure 6.23

96

6.2.5 Vehicle Electrical System

Figure 6.23 illustrates rhe basic electrical units of the ROV

6.2.5.1 Umbi l ical Terminat ion

The umbilical is terminated in an oil filled junction box which is compensated (seechapter 8). The signals are routed through iedicated subsea connectors to the relevantunrts.

6.2.5.2 Hydraulic Power Unit (HpU)

P{* phase powel is supplied to an electric motor which is directly coupled to thehydraulic pump. on some. sysrems the power signal may pass through d step downtransformer prior to-reaching the motor. When tfre hydrduiic power ii switclied on atthe surface a control signal is sent via the systems daia communication link an activatesa relay and applies the power to the electrii motor.

6.2.5.3 Port f loat tank

The actual layout of the electronics for ROVs varies from vehicle to vehicle dependingon.its workscope. For example an ROV that is intended for mainly survey operations"will possibly have.an extra pressure vessel incorporated into its d6sign to ho'use thenecessily electronics.This particular example of ROV incorporates two float tanks. The telemetry circuitsalong with the porv-er supplies sensor cards, and gyro will be housed in this tank. Theport ?.nd starboard float tanks are electrically coni.ected as the main system powersupplies also supply the equipment in the siarboard float tank.

6.2.5.4 Starboard float tank

The starboard tank may house the electronic circuits that control the survey equipment.This example illusrates the sona-r scan assembly power being derived frorir thestarboard float tank. There may also be power Juiplies housEd in here to drive variousother pieces of survey equipment such as profileis, pipetracker or sidescan units.

6.2.5.5 Opt ics junct ion box

The optic.s junc_tion box is a unit that is common to most work class /large inspectionclass vehicles. It is simply an oil filled junction box that may distribute ioweito thevehicle,lights, compass and other sensors. The diagram illuitrates the typical situationin which the power for each light.comes in on a common cable (typicatiy tZOVeC perlight), it is then distributed to various lamps situated around ttre'vetricte.

6.2.5.6 Vehic le l ights

The number of lights on ROVs varies consrderably and depends on the number ofcameras fitted and the task to be carried out. The operation is standard and consists of arelay or Powgr control module dedicated to each dmp. The relays are 'switched bycontrol signals from the surface and once energised cbnnect po*e. to the relevanr iamp.

6,2.5.7 Thruster control uni t

The hydraulic operation of the thruster control unit (TCU) has been discussed inChapter 8. The unit receives a varying analogue signal fiom the Servo Driver Cardshoused in the main electronics bottle or in thJcase 5f figu.e 6.7 . theport float tank. Theservo driver card consist of.a group ofamplifiers that bdost the contrbl signalto a suitable level to drive the servb valvei in the TCU.

91

6.2.5.8 Hydraulic control valves (HCU)

The hydraulic operation of this unit has also been discussed in chapter 8. This unitreceiGs analogue signal of a positive or negative polarity depending on the directionthat the manipulator limb or pan and tilt unit is required to move.

6.2.6 Auto control functions

The task of flying the ROV is made easier by the inclusion of Auto Control functionsinto the vehicie efectronics. These functions normally include Auto Heading and AutoDepth.

6 .2 .6 .1 Gy rocompass

The auto heading function operates on a similar principle to a ships auto pilot in thesense that it willremain on a pre-determined heading so long as the function remainsselected.

The ROV is fitted with a Gyroscope which is basically a 'mass' spinning on an axis. Ifa right angle force is applied to a gyroscope then the unit will ry to.exert an eqtral andoppbsite fbrce in ordei ihat it may ieturn io its cenral axis. In practice the gyro ispbwered by an electric motor an<i it is imperative that i1s speed is sufficient in order thatit does notiopple.It is also important thaf the gyro is aligned with the earth's magneticfield, this is achieved by incorporating what is known as Flux Gate.

A flux gate is a transformer with one primary winding and two secondaries. Thesecondiry windings are connected in

-opposition, the induced fields will therefore

cancel each other out. Each secondary coil interacts with the earth's magnetic field insuch a way rhat it is in addition with one field and in opposition with the other. Thisgives rise io a voltage being induced into the secondary windings. As the flux gate isiotated the magnitude and phase of these induced voltages changes in sympathy withthe changing earth's magnetic field.

It follows therefore that the difference between the phase of the primary and secondaryvoltage is proportional to the magnetic heading of the flux gate. The signal that isprodriced Uy ttris phase difference is mechanically coupled .to th_e gyro thus permanently^aligning

it io magnetic north. In general the gyro is 'slaved' to the flux g1te. and itsouiput ls conrolied by the earth's magnetic field. This situation is undesirable when theROV is in close proximity of steel structures whereby the magnetic field may becomedistorted. To overcome this the gyro may be decoupled from the flux gate and allowedto run in 'free drift' mode.

The output from the three synchro phases is converted into a voltage which is -proportibnal to the vehicle heading- This voltage is then input to the vehicle multiplexer^sysiem

and produces either a digital or analogue compass heading at the controlconsole.

6.2.6.2 Auto heading

On selecting the auro heading function the output of the gyro is constantly monitoredand comparid to a reference voltage. The resultant 'error' signal is processed and fed tothe thrusier control circuits. The thrusters act in such away as to reduce the error signaland thus maintain the vehicle on a fixed heading.

6.2.6.3 Auto depth

The auto depth function works on a similar principle to the auto heading in that avoltage thafis derived from a pressure sensor is compared to a reference signal. The

98

resulting'error'signal is applied to the vertical thruster which acts in such a way as tocounteract the change in depth.

Auto functions in their simplest form require the pilot to switch the device on at thesurface. The vehicle.istotally controlled-by the auto function in this state and the pilothas to physically switch the device off to iegain control. More complex systems illo*the pilot to make fine adjustment using trim confols.

6.2.6.4 Trim controls

Trim controls allows the pilot to apply a control signal to the ROV from a source other,h.T ltt jgystick. The sources are usually in the form of a single turn potentiometerwhich maintain a fixed control signal to ihe vehicle as oppose-to the pilot determinedsignal from the joystick. The commonest trim controls arb:

a) Forward / Reverse trim. (cruise control)

b) Vertical Up /Down trim

c) Lateral Port lStarboard trim

The principle of operation is the same for each trim in that the potentiometers 'add'asignal to th9 main input gonrol signal. They are useful when flying the vehicle into acurrent or if the vehicle is being subject to a cross current. fne pilot can use thesecontrols to make the flying operation less strenuouspoq: systems have heading trims which can be used in conjunction with the autoheading and enables the pilot to make fine adjustment to the-direction of the vehicle.

6.2.7 Sensor functions

It is essential that the vehicles overall condition of operation is constantly monitored inorder to minimise unnecessary breakdown time. The following items are monitored.

a) Oil Temperature.

b) Oil Pressure.

c) Oil level.

d) Water ingress.

e) Water ingress to connectors.

The sensors operate on a similar plnciple in that a transducer monitors the pressure ortemperature and converts this to a DC voltage. These signals are multiplexed and travelon the vehicles 'up'data link.

The water ingress sensors are located in the pressure vessels and usually consist of twocontacts located at the-lowest point of the veisel. Any water ingress wili short thesecontacts together and form an electrical circuit.

The resistance between all the conductors that are attached to the relevant subseaconnectors is also monitored. If water ingression takes place at the connector then theresistance will fall and provide a readout at the surface unit. The resistances mav bedisplayed 9n alq chart on the surface display and are commonly termed IRs. fheymay be AC or DC depending on the circuit b6ing monitored.

99

6.3 Telemetry

6.3.1 Introduction

Section 6.2 of this chapter discussed the basic electrical units and various sensors thatare found on ROV systems. It also discussed the method by which the vehicle iscontrolled from the surface unit.

It is now necessary to look at how control and sensor information is transmittedbetween the surfaie unit and the vehicle. The system that carries out this task iscommonly known as the Telementry System.

6.3.2 Analogue Signals

Analogue signals vary continuously with time and assume any amplitude level withinthe limitations of the electronic circuitry. It is these types of signals that are producedby the potenriometers in the joystick control. Figure 6.24 shows a typical o-utputsignal, in analogue form from a control joystick. It follows that the output from thejoystick potentiometer must be transmitted via the umbilical to the thruster control-circuitryon

the ROV. During this process this signal would be subject !g ling lossesand disiortion due to the physical properties of the conductors in the umbilical.

+5V

Il]*- +U Il YI

-5V \

JOYSTICKPOTENTIOMETER.

ALOGUE SIGNAL.

Figure 6.246.3.3 Digi ta l Signals

Digital signals are not continuous as are analogue they have two discreet levels, onelevel is a constant positive voltage and the other is zero volts. Figure 6.10 shows anexample of a digital signal. It follows therefore, that a simple on/off signal will still besusceptible to lihe losses and distortion but will however, be easier to re-shape'once ithas travelled through the umbilical. For this reason the analogue signal is convertedinto a 'train' of digital pulses known as a 'word', a particular output voltage level at thejoystick will have a dedicated digital code:

A T O DCONVERTER.

Figure 6.25

rLnrDIGITAL SIGNALOUT.

ANALOGUESIGNAL IN.

100

i

6.3.4 Line losses

Line losses is a condition that effects electrical signals when they are transmittedthrough conductors. Physical properties of metal conductors are such that they willabsorb some of the signal being passed through them, thus resulting in line loss.

6.3.5 Time Division Mult iplexing

So far we have discussed the use of digital signals to transmit the control informationfor the ROV. In practice however, the transfer of information for all thrusters andsensors is a continuous process. Ideally each thruster and sensor would require anindividual conductor in the umbilical thus allowing a constant stream of data passingbetween the vehicle and the surface unit. However, this would lead to the overalldiameter of the umbilical being large and therefore impractical. To overcome thisproblem the telemetry system makes use of Time Division Multiplexing (TDM).Instead of each function having a dedicated conductor, they in fact share twoconductors known as a 'twisted pair'. In order to overcome this problem the analoguesignals are converted to digital signals prior to being transmitted through the umbilical.Figure 6.26 illustrates a very simple telemery system.

, l Fo

Word I Word 2Cards in Surface Unit

l. Mother Board - Power Supplies2. ND Converter Board3. Timing/Program Board4. MIIX Board

6.3.6 Twisted Pair

Two wires twisted together, one wire is data up link, the other a data down link. Thewires are protected by a shield known as a screen.

fL

c h 3 - 1 6MF Sync

Figure 6.26

Shielded Twisted pair

t 0 l

6.3.7 Programme MicroProcessor

The programme microprocessor circuit controls the switching operation of the

;;ldpi"?;; rttunn"ri. 'rn

other words rvrUx Ctrannet 1 gpgni first, followed.by MUXcttanief 2, andro on. This will result in a train of 'words', each word containingdigital information from different functions on the system'

6.3.E Main Frame Synchronising Circuit

In order that the telemetry 'receive'circuits can distribute each word to the relevant;"ltipl.;;; cttannet a iyictrionisation pulse has to be added to-qcfr gloun of words'

This is added at the beginning of the gioup and the qn-d-py-lh" Main FrameS;;.-i;i;i"g Cir;?;. F# r*u-pi" a'64 "hannel MUX syqlgm will contain 64

*"oiar; these aie collectively known^as a'frame'. The system will transmit manythousands of frames Lurry i"rond. This gives rise to a constant flow of control and

rinioi information. Information is ransm'itted along the twisted P-arr in the form of a'frame'. Data from each function is allocated a "time slot" in this fiame thus allowmgttr" .onrtunt t ansfei ti information from all functions. Figure 6.1 1 shows a 'frame'

;;;fiG oi i *ords, each word containsdigital information from I particularfunction: firlr pto""rr it Ging carried out thoisand of times a second thereby allowing-uny functioni to "f.* uit"n. same time. In practice there is one word per channel.

6.3.9 Mult ip lexer Circui t (Mux Circui t )

The multiplexer circuit is simply a collection of electronic switches known as 'channels'

that allow^data conrrol information to pass on to the line. The switches operatei"qi*rii"ffy unO 3r. controtteO by a microprocessor. Itfollows that the output from thej;y-;iirfp"ientiomerer must be trinsmittedvia the umbilical to the thruster control"#*iii"g on the ROV. During this process thi^s signal would be subjectt-o.Jing lossesand distortion due to the physical properties of the conductors in the umbilical.Multiplexe. ,yrt"-i *uy "6ntuin'8, i6, 32 or 64channels {epelding 9l l!:

n_umber of

functibns beirig incorpoiated into the system and are very often incorporated lnto asingle IC.

6.4 Fibre Opt ics

6.4.1 Introduct ion

Line transmission has, over the years steadily improved. The last twenty years has

seen revolutionary innovations such as digitalisatibn and optoelectronics dramatically - -uii"i p"6nology ind cosreffective of datitransmission. Ifisonly recently that^the ROV

i;d"rrty tras tiiae use of Optical Fibre data transmission in the transmission oftelemetry and video signals.

6.4.2 Theory

The principles of optical fibre transmission makes use of theories that have been known

to man for centuriel .Fig 6,27 illustrates how a light beam behaves when it passes from

one medium to unoih"r 6f diffrr.nt densities. It dan be seen that when a beam of light

is directed ut u tru"tp**t medium (glass), although s^ome-of the light is reflected backi;t" rh" &ginatlng medium (air), a h-igh p.oponion of the light will pass into thatmedium.

102

Incident Rav

nl (air)

q = Angle of refraction

0 = Angle of Incidence

n2 (glass)

Figure 6.27

6.4.3 Refractive Index

Refractive index refers to the optical density of a material. It is a direct proportionbetween the velocity of light in a vacuum to the velocity of light in the material.

Velocity of light in vacuum = nRefractive index = Velocity of light in medium.

The refractive index is given the symbol n.

6.4.4 Snells Law

Willebrord Snell put forward a theory that claimed that the sine of the angle of

refraction (0 ) depended upon the sine of the angle of incidence (0 ). He claimed thatthe ratio of the sine of angle of incidence to the sine of the angle of refraction is aconstant.

S i n 0 = n !S i n d = n 2

Where nl and n2 are the refractive indices of the material through which the light ispassing.trig O.Za shows ho ugh a glass block.

n2 (glass)

nl(air)

Figure 6.28

l

103

Because the glass/air boundaries are parallel then ( 01 ) must be equal to ( 02).

Figure 6.29

Figure 6.29 shows the situation in which light is passing from a dense to a less densem#ium i.e. glass to air.In this situation n2 is greater than n1 and therefore the angle of

refraction (0 ) is greater than the angle of incidence(0 ).If the angle of incidence is increased still further then we can see in figure 6.29_that theangle ofiefracrion will eventually exceed 90 degrees. At this point the light willbecome Totally Internally Reflected.

: nl (air)

F igure 6.30

It is the principles of Total Internal Reflection that is made use of in the transmission oflight through an optical fibre. The glass tube acts as a guide for the light beam, as thelight is rapped iniide the glass, then any bends that occur in the glass are insignificant.Itls necessary however to surround the glass in a cladding, the refractive index ofwhich is slightly less than the glass, in order to minimise dispersion and therefore anysignificant losses.

Note: The angle of incidence that causes the angle of refraction to be greater than 90degrees is known as the critical angle and is roughly 42 degrees for glass, with arefractive index of 1.5.

n2 (glass)

Light source

cri t icalangle

104

n1 (cladding)

n1 (cladding)

Figure 6.31

Fig 6.31 shows a situation in which the light beam is totally internally reflected throughcladded fibre.

6.4.5 Light Transmitters

In order to convert electrical energy to light energy an Optoelectronic semi conductorsuch as a Light Emitting Diode (LED) or laser diode is used.

Note: Light that is emitted from an LED is quite safe to the naked eye, however lightemitted from a laser diode is potentially lethal and great care must be exercised whenusing such devices.

Fibre

Active Reeion G- n contactG n type GaAs

+p type zinc (diffusedGaAs)Silicon Dioxide

Gold Heatsink

Figure 6.32

Figure 6.32 shows the typical construction of an LED

The applied electrical signal gives rise to the Gallium Arsenide prod'ucing "excited"

electrons that travel from the p type to the n type material. During this process theyproduce light energy, a process known as Spontaneous Emission.

6.4.6 Advantages and Disadvantages of LED and Laser Diode

1) LED's are cheaper to manufacture than laser diodes.

2) Laser diodes have a greater optical power and can work at higher temperatures thanLED's.

3) Laser diodes are sensitive to overload currents, when they are required to operatecontinuously they can produce unfavourable thermal characteristics.

n2 (fibre)

105

6.4.6 Receivers and Photodiodes

A photo diode converts light energy back to electrical energy. They are similar toLED's in the fact that the photons (light energy) give rise to the flow of current betweenthe P-N junction.

6.4.7 Types of Fibre

There are two types of fibre commonly available, Stepped index and Graded indexfibre.

6.4.7.1 Stepped Index Fibre

As previously stated, propagation along paths is possible once the incident ray hasreached the critical angle, (approximately 42 degrees). However this situation gives riseto an increase in attenuation and dispersion losses.By making the fibre core extremely narrow (approximately 50 micro metres), andenclosing it in a cladding of refractive index which is only slightly less than that ofglass, we can not only reduce the critical angle but also reduce losses.A fibre constructed in this manner is known as step index fibre and is suitable for shortdistance transmissions as found in ROV umbilicals.

106

Outer l-ayer

Buffer ProtectiveCoating

Cladding

Figure 6.33 Stepped index Fibre

6.4.7.2 Graded Index Fibre

rn.9 aiy$vantage 9f sJgp index fibre is that the bandwidth of transmission is limited dueto the different optical lengths ca,usg$ by the various lengths at which rigrrt is piopagare.This can be overcome usiig graded inoi:x riure. - Gil;ii;jex fibre dif?ers fi.Lm stepindex fibre in the fact that tfiJcores refractive index a.r*ui"r paraboticatt/*iirr iaaiardistance.

The main advantage of using.graded index fibre is the low refractive index at the cenrreof the fibre. This is usefur tinl" ."rpiing ttre sharpit i*r*o beam of an LED withthe fibre.

t07

Figure 6.34 Graded index Fibre

6.4.8 Fibre Optic Connectors

It is not the intention of this chapter to list all the fibre optic connectors available. Thatis adequately covered in the appendix section.However it is essential that the conect procedure for re-terminating an optical fibreconnection is followed in order to minimise unnecessary breakdown time.The following section lays down the procedure for assembling a STRATOS SS430-01to a fibre opti-c bundle. This type of connector is incorporated in many of SlingsbyEngineering Ltd ROV fibre optic systems.

6.4.9 Umbilical Optical Termination - Vehicle

The following procedure relates to the assembly of the Stratos SS430-01 opticalfibreconnector to a figtrt jacket fibre optic bundle containing 900mm secondary coatedfibres, within an umbilical cable.-The following equipment will be required:

a Heat curing jig (temperature controlled);

r08

b Stratos tool kiu

c Micropolishec

d Optical Cable Fault l,ocator (OTDR);

e Connectors, leads and splices as required;

f Hot air gun;

g Disposable syringes, 5ml and lml;

h Stratos syringe needle;

g I9g syringe needle;

h Scalpel;

It will also be necessary to have the following materials:

a ConnectorStratos S5430-01- 1.0

b Heatshrink sleevingRaychem Atum 3/1,612,

c Solvents2-propanol (isopropyl alcohol)Dichloromethane (or paint stripper)White spirit or trichloroethylene

d Epoxy ResinEpo-tek 360

e Spiral Cable Wrap3mm

f Abrasive Paper360 grit wet and dry

g Abrasive Film30mm, 12mm and 3mm

6.4.9.1 Process Instruct ions

I2/4 and 1/16" RNF 100 or similar:

a Switch on the heat curing jig and ser ro 95 deg. C.

b Prepare Epo-tec 360 resin as follows:i. Draw up the required volume of resin (part A), into the 5 nrl syringe

(allow 0.5 ml per plug) noting that the calibration does not include thevolume contained in the nozzle. Withdraw the plunger further to leavean equal volume of airspace above the resin.

ii. Draw up the corresponding volume of hardener (part B), (mix ratio 10:1by volume) into the 1 ml syringe with the 19 g needle, ensuring thatthere are no air bubbles and that the needle is full when making themeasurement.

iii. Inject the hardener into the resin by entering the needle into the syringethrough the nozzle. Mix the resin and hardener by blocking the nozzleand shaking the syringe until an even colour is achieved. Pay particularattention to the material which may become trapped in the nozzle.

iv. Degqs the material by holding the syringe nozzle upwards and expel allthe air above the resin. Cover the nozzle and draw a vacuum bywithdrawing the plunger. Repeat this operation until only a few large

t09

bubbles form. Wipe the syringe nozzle and fit the Stratos needle. Leavethe resin to stand for ten minutes before use.The pot life of the mixture is approximately eight hours at roomtemperature.

v. Strii, 500 mm of sheath from the fibre optic bundle and remove the tapewrap and filler compound.

vi. Cut the centre strength member approximately 50 mm from the cut endof the sheath.

vii. Place 100 mm length of l2/4 heatshrink on the bundle and temporarilyposition out of the way, by sliding along the cable.

viii. Place onto each fibre in the following order:(a) 50 mm length of Atum 6/2;(b) 100 mm length of Atum 3/1;(d) 150 mm length of RNF 100-1/16"(e) Stratos nut (female thread towards end of fibre);(0 Crimp sleeve (shouldered end first if applicable);

viii. Strip 50 mm of coating from the fibre using 'No-Nik' tool (or similar)avoiding damage to the fibre.

ix. Immers6 the ex--posed fibres in dichloromethane to remove the remainingbuffer. If necessary wipe the fibre with a clean dry tissue' (,If qsingpaint stripper, rembve iesidue by wiping with tissue soaked with 2-propanol).Thd bare fibre is very susceptible to damage and contamination, do nottouch or leave exposed for any longer than necessary.

x. Check that the plug is clear by sighting through, if not, remove whiteplastic cap and then replace the cap and re-check, luppo1 the crimpsleeue at ihe end of the coating and assemble the plug, guiding itcarefully over the fibre and onto the crimp sleeve, up to the shoulder.

xi. Crimp flug in position: Place the plug in the small jaws. Operaqqtelever-to hotd ttie plug (do not crimp yet). Push the crimp sleeve fullyinto the plug. Crihp the plug without moving the plug., sleeve or fibre.Once the crimping operation has started, it cannot be aborted.

xii. Using the cleaving tool, touch the fibre flush with the face of themounting cap and remove the excess fibre by bending it away from thescratch.Excessive force when scratching the fibre will displace or damage thefibre inside the piug.

xii. Using the back of Cscalpel blade and the thumb as a lever, carefullyremove the white plastic cap. Remove the cap without twisting.Examine the end of the plug to check that the fibre is centralized betweenthe balls, then fit the moulded silicone reservoir cap.Do not attempt to refit the mounting cap after removal. If the fibre istrapped betwben a pair of balls, or outside them, carefully depress oneof llie balls with the tip of a scalpel to allow the fibre to return to thecentre. Do not touch the fibre.

xiii. Expel the air and a few drops of resin from the syringe to ensure thenoizle is clear. Hold the plug assembly vertical with the reservoirupwards and drop 2-3 drops into the reservoir, taking care not to touchthe fibre.

xiv. Clean the needle and insert it into the injection hole in the plug body.Withdraw the plunger to suck the resin into the nose of the plug, if -.yair enters the stringe remove the needle from the plug and expel the airbefore continuing. Inject resin slowly into the plug until it reaches thetop of the reservoir, tip out resin and repeat until three cycles with nobubUtes have been obierved. Remove the needle from the injection portand seal the hole with the plastic plug. Wipe away any traces of resinfrom the plug body.

1 1 0

xv. Check the temperature of the curing jig is 95 deg. C. +/- 5 deg. C.Clamp the plug(s) in the heating blotk.-Take care to avoid trapping theplastic plug. Do not move the reservoir, which, if moved, will-allowresin to contaminate the nose of the plug. Allow the resin to cure until1.5 to 2 mm of cured resin is visible above the plug (cured resin is ared/brown colour). Remove the plug and allow to cool to roomtemperature.

xvi. Carefully twist and pull off the reservoir. Wipe away the remainingliquid resin. The cured resin should not be allowed io extend furthErthan 3 mm nor should it be left for more than eight hours beforeremoving the reservoir, otherwise, difficulty will be experienced inremoving the reservoir without causing damage to the potting in the plugnose.

xvii. If the reservoir appears to be stuck, cut through with side cutting pliers2-3 ryy above the plug nose, and peel off the-remaining siliconemoulding. Do not exert any sideways force on the resin, which couldresult in damage to rhe fibre within the plug.

xviii. Remove the plastic plug.

6 .4 .9 .2 Po t i sh ing

a Using 360 grit paper, sand off the proruding resin until the 3 balls are just visible.

b Polish the plugs using Stratgs tools with 3M abrasive films in the following order:i. Tool number 491with 30mm film (green)ii. Tool number 492 with l2mm film (yellow)iii. Tool number 493 with 3mm film (pink)

c Thoroughly wash the plug to remove debris from previous operations and rinsethrough the polishing lool. Blow off excess water and assembl6 the plug into the tooland secure with the collar nut. Wet the glass plate and abrasive film ind-place the filmol th9 plate..Flood the surface with water and polish the plug using a figure of eight orcircular motion progressing.across the film suih that the abrlsiue i-s usei for one passonly. Keep the film wet during polishing.

d Light pressure.only is required on the tool; when cutting is complete a decrease inresistance to motion will be apparent and no track will be left on the abrasive. Rinse thetool under running water and remove the plug.

e Remove abrasive film and rinse off debris, store for further use, (an A4 sheet ofabrasive has sufficienr area for the polishing of 6 plugs).

f Repeat the operation using the tools and abrasives in the order listed in 6.4.9.1.To avoid damage to other plugs, ensure that the final polish with the pink film iscomplete.

g Dismantle andrinse the tool and,plug in water then re-assemble and polish again withthe final tool until no further material is removed. Dry the plug using a blean pipertowel paying particular attention to water remaining ih the nut and fii the white

'

protective cap.

i l l

6.4.9.3 F inat Assembly and Test ing

a Test each plug using the OTDR with at least 50 m launch length. Typical lossbetween theiwdtypeJof fibre will be 2 dB to 4 dB although the system will operatewith higher losses.

b When using light-source/power-meter test instruments records should be kept of

measured valiesTor referenfe when fault finding and re-terminating, allowance for

shortening of the cable should be made at 3 dB&m (850 nm) or 1 dB/km (1300 nm)'

c Slide the 1/16" heatshrink up to the back of the plug and shrink doyn tu\ing care not

to overheat the fibre. Slide the'3/1 heatshrink ovefthe crimped end of the plug allowing1 to 2 mm for Stratos nut movement and shrink down. Slid-e the 6/2 heatshrink onto theplug over the previous layer to the same position and shrink down.

d Identify fibres with number sleeves over the plug body, ensuring that the numbenco-incide"at both rop and bottom of the umbilical by reference to the wiring diagram ordiscarded umbilical end.

e Wrap the fibres, from the sheath onto the large heatshrink, with the 3 mm Spirawrapas far as the plug body.

f Lay the fibres back into the helix of the bundle and position the heatshrink over the

end of the sheath projecting 50 mm beyond the end and shrink down.Before making connectioni, ensure plugs and couplers are clean. If dirty, clean with apaper towel soaked in 2-propanol.ini couplers are fitted with an internal 'O'ring on the outboard side only. This is toallow thi connector faces to free flood with oil thus avoiding collapse under pressure.Couplers mounted inside junction boxes should have both internal 'O' rings removed.

6.4.10 Umbi l ica l Opt ica l Terminat ion ' Sur face

The following procedure relates to the assembly of Stratos ST optical fibre connector to

a tight jacket fibre optic bundle containing 900mm secondary coated llres, within anumb-ilical cable. The'same equipment will be required as laid out in 6.4.9 with thefollowing differences: a rubber-mat is recluired with the micropolisher; no 1 mlsyringe,lgg syringe needle, nor scalpel, is required. It will also be necessary to havethe following materials:

a ConnecrorSrratos ST-MC-128 (or ST-LC-121t) including white nylon crimp sleeve;

b Heatshrink sleevingRaychem Atum 612 and 1214,1116" RNF 1fi)or sinrilar

c Solvents2-propanol (isopropyl alcohol)Dichloromethane (or paint stripper)White spirit or trichloroethylene

d Epoxy ResinEpo-tek 353 ND

e Spiral Cable Wrap3 mm

f Abrasive Filml2 ntm, 3 ntnt, and 1 mm

t12

6.4.10.1 Process Instructions

a Switch on the heat curing jig and set ro 90 deg. C.

b Prepare Epo-tek 353 ND resin as follows:i. Open the sealed sachet and remove the 'squish Pack'. Inspect for

damage.ii. Remove the dividing seal between resin and hardener by pulling the

pack on either side, do not attempt to slide it as this may puncture thepack. mix the two components by kneading rhe pack gently with thefingers until the colour is uniform and no streaks remain.

iii. Remove the plunger from the syringe, cut the corner off the squish packand transfer the resin into the syringe, avoiding trapping air.

iv. Degas the material by holding the syringe nozzle upwards and expel allthe air above the resin. Cover the nozzle and draw a vacuum bywithdrawing the plunger. Repeat this operation until only a few largebubbles form. Wipe the syringe nozzle and fit the Stratos needle. Gavethe resin to stand for ten minutes before use.The pot life of the mixture is approximately four hours at roomtemperature.

v. Strip 500 mm of sheath from the fibre optic bundle and remove the tapewrap and filler compouni,.

vi. Cut the centre strength member approximately 50 mm from the cut endof the sheath.

vii. Place 100 mm length of l2l4 heatshrink on the bundle and temporarilyposition out of the way, by sliding along the cable.

viii. Place onto each fibre to be terminated (in the order shown):(a) 50 mm length of Atum 6/2

b) 100 mm length of Atum 3/l

(c) 150 mm length of RNF 100-1/16"(in oil filled junction boxes only - in dry boxes use boot suppliedwith plug trimmed to suit coating diameter)

(d) Crimp sleeve (for ST-LC-128 - white end first)ix. Strip 50 mm of coating from the fibre using 'No-Nik' tool (or similar)

avoiding damage to the fibre.x. Immerse the exposed fibre in dichloromethane to remove the remaining

buffer. If necessary wipe the fibre with a clean dry tissue. (If usingpaint stripper, remove residue by wiping tissue soaked with 2-propanol).The bare fibre is very susceptible to damage and contamination, do nottouch or leave exposed for any longer than necessary.

xi. Check that the plug is clear by sighting through, then fully insert thesyringe needle into the back of the plug and inject until a bead of resinaPPears through the other end of the plug. Remove the syringe whilststill injecting to leave resin in the back of the plug - approximately halffill the receplacle.

x. Support the crimp sleeve at the end of the coating and assemble theplug, guiding it carefully over the fibre and onto the crimp sleeve, as faras it will go without forcing it. Maintain light pressure until any excessresin flows out; carefully wipe resin off without moving the plug.

xi. Crimp plug in position: place the plug in the small jaws. Opeiate thelever to hold the plug (do not crimp yet). Push the crimp sl-eeve fullyinto the plug. Crimp the plug without moving the plug or sleeve.Once the crimping operation has started, it cannot

-Ue aUorteO.

1 1 3

xii. check the temperature of the curing jig is 90 deg. c. +/- 5 deg. c.Clamp the plu!(s) in the heating Utoct<. ettow the resin to cure until thebead bf resin on the end of the plug is a red/brown colour'(Approximately 20 - 30 minutei depending upon ambient temperature).Remove the plug and allow to cool to room temp€rature.

xiii. Using the cleavi-ng tool, touch the fibre flush with the bead of resin andremo..re the excess fibre bv bending it away from the scratch'Excessive force when scratching tlie fibre will damage the fibre insidethe Plug.

6.4.L0.2 Pol ish ing

a Examine the end of the plug for exposed fibre and, if necessary, lightly polish withdry 12 mm film to remove the glass only.

b Fit the plug into the polishing tool.

c Place the rubber mat on the glass plate. Wet the mat and 12 mm film and place on themat. Flood the surface with witer anO tlgtrtty polish the plug using a figurg of eight orcircular motion progressing across the film iuctr that the abrasive is used for one passonly. Keep the film-wet du-ring polishing. Regularly examine the plug face until only athin film of resin in the centre of the face remains.

d Remove the mat from the glass. Wet the glass and 3 mm film and continue polishing.Light pressure only is requirdd on the tool. Regularly examine the plug face until noresin is visible on the ceramic face of the plug.

e Repeat the operation for the remaining plugs.To avoid damage to the other plugs, ensule that the final polish is complete.

6.4.10.3 F inal Assembly and Test ing

a Test each plug using the OTDR with at least 50 m launch length. Typical lossbetween the two types of fibre will be 1 dB to 2 dB although the system will operatewith higher losses.

b When using light-source/power-meter test instruments records should be kept ofmeasured valies-for reference when fault finding and re-terminating, allowance forshortening of the cable should be made at 3 db&m (850 nm) or I db/km (1300 nm).

c Slide the l/16" heatshrink up to the back of the plug and shrink down ta\ing care notto overheat the fibre. Slide the-3/1 heatshrink up to the back of the plug and shrinkdown. Slide the 6/2 heatshrink onto the plug over the previous layer and shrink down.Ensure the final layer does not foul the sprung sleeve of the plug.

d Identify fibres with number sleeves over the plug body, ensuring. that.the numberscorrespond at borh top and bottom of the umbilical by reference to the wiring diagramor discarded umbilical end.

e Wrap the individual tubes from the sheath onto the heatshrink with the 3 mmSpirawrap as far as the plug body.

f Lay the fibres back into the helix of the bundle and position the I2l4 heatshrink overthe end of the sheath projecting 50 mm beyond the end and shrink down.Before making conne^ctions, ensure plugs and couplers are clean. If dirty, clean with apaper towel soaked in 2-ProPanol.

u 4

6.4.1J Optical Time Domain Reflector (OTDR)

The OTDR is probably the most common piece of test equipment used in themaintenance of ROV optical fibre systems.This instrument is used for measuring transmission performance, attenuation (i.e. lossverses distance) in situations where fibres have been repaired.The operation of OTDRs makes use of the principle that the time taken for a pulse oflight being transmitted and thus reflected can be measured. It is therefore possible tolocate faults over a known length of fibre.Figure 6.12 illustrates the principle of operation.

1 1 5

6.5 Fibre Optic Safety Guidlines

This ROV system includes a fibre optic transmission system which contains a Laserr.p"Ut" "f iititting harmful radiation at a wavelength not visible to the human eye. Thefoitowing guideliries must be understood to ensure the safety of all personnel.

1) Never Look Directly Into a Laser Beam from a bulkhead fitting or a fibre tailwhen the laser is switcheb on. Protective covers and/or shielding should be usedwhere necessary to prevent this possibility.

2) Never Use Optical Viewing Instruments (ie microscopes).when checking.6r optical power.'The ROV systEm will havepower meters and light sources suitablefor checking the continuity of an optical fibre link.

3) Never Inspect Polished Connectors or Terminations before ensuring^thatthe laser is switched off and the ROV OCU Power is Isolated and Locked Off atthe PDU.

When handling fibre optic cable the following safety information should be understoodby all personnel.

1) Never Casually Discard Glass Fibre Shards always use the "Sharp Safe"box supplied with each system for proper disposal.

2) Never Leave Spare Fibre Loose, always ensure that spare or disused fibresare sealed and protected with heatshrink.

3) Wear Safety Glasses when handling the exposed ends of tether and umbilicalcables containing optical fibres.

4) Ensure "Laser Warning" Labels are displayed on all junction boxes andenclosures containin g fibre-optic connection s and termination S.

l 1 6

CHAPTER 7 USE OF TEST EQUIPMENT

7.0 Introduction

It cannot be emphasised enough to the ROV Pilotflechnician just how importanr it isto have a thorough understanding of the basic test equipment ivailable. hi general,the vastarray of settings on a multimeter can be off iutting to the novice tedhnicianand confusion tends to arise when the new operator iails tdappreciate the basic theorybehind the various electrical quantities being measured.

7.1 Electrical Quantities

The quantities and qualities that are of interest to the technician are:

7.1.I

7.1.2

7.1.3

7.1.4

7.t.5

VOLTAGE AC/DC

CURRENT ACDC

RESISTANCE

CONTINUITY

INSULATION

The theory of those various electrical quantities that are measurable is discussed inchapter 6.

7.2 Measuring Voltage

The unit Volt refers to the potential of electrical charge at a given point in a circuitwith respecl tg 0v or ground as it is commonly knovin. Dep"ending on the iystembeing.tested the voltagemay.be AC or DC. T[re diagram btilow sh?ws u iyp'i"ursituation where voltage is b-eing measured:

+1 0V

uv (grouno)

Figure 7.1

10k ohms

5V with respect to ground

10k ohms

t17

7.3 Measuring Current

As with voltage, curent may be AC or DC and care must be taken to ensure that themeter is at thJcorrect settin!. tt may be necessary to re-insert the positive meter lead(red) in another socket for cirrent rneasurement. Current is a movement of electricaliharge through a circuit and therefore the circuit must be 'broken' and the meterinseied in s&ies to obtain the correct measurement. The diagram below shows anexample of current measuring:

Meter inserted inseries into circuit

7.4 Measuring Resistance

Measuring resistance is quite straight forward as the meter has only one ser of rangesas opposed to voltage. When measuring resistance it is important to switch off theequiphent that is being tested. Any components that are being tested should ideallybe out of circuit. This is due to the fact that surrounding components may be inparallel with the component being tested and will in effect produce a lower resistancevalue.

7.5 Continuity Testing

When carrying out fault diagnosis continuity testing tends to be one of the commonesttest procedures carried out by the technician. The test indicates whether or not thereis an electrical connection between two relevant points in a circuit. In the ROVindustrv continuitv testins is oredominantlv used in order to test subsea cablesindustry continuity testing is predominantly in order to test subsea cables forconducior breakage. Moit multimeters have a dedicated switch setting for continuitytesting. This position is indicated by a symbol depicting a diode and an audio tone.The diagram below indicates such a symbol. Figure 7.3.

Provided there is less than a certain value of resistance (varies from meter to metel,e.g.. 50 ohms, 100 ohms). This means it may not operate on a long length of cable.

/s\

Figure 7.2

1 1 8

->F- ,r))Figure 7.3

On placing the test leads on the relevant points in the circuit, a bleeping sound will beheard if continuity is present. The test can also be carried out by setting the meter toresistance. Obviously if continuity is present the meter will read close to Ohms. Thedisadvantage of this method is that the operator has to physically look at the meter asopposed to just hearing an audio tone.

7.6 Insulation Testing

Insulation testing is probably the most common form of test carried out in the ROVindustry. Subsea cables and connectors are under constant stress from factors such ashigh subsea pressure, vibration and corrosion. These factors can lead to a break downin the insulation between the conductors which will eventually lead to a short circuit.For this reason it is important to regularly test the insulation resistance between allconductors in a cable. The test meter used is known as a Megger Meter. It isimpofiant to appreciate that by just measuring the resistance with an ordinarymultimeter we could not determine how the cable would perform in a realisticsituation i.e. carrying high voltages. By using a Megger Meter we in fact apply ahigh voltage e.g. 500v and measure the resistance at the same time. In practice themeter has two test leads which may be fitted with crocodile clips in order to ensurethe safety of the operator. The meter can be set to measure in excess of 200Megohms, when connected up the operator pushes the test button which applies thevo-ltage. The resistance is indicated by a moving needle, a cable should ideally haveinfinite resistance between its conductors. The following precautions should be notedwhen using Megger Meter:

7.6.1 Disconnect all cables from any electronic circuitry.

7.6.2 Do not touch probe conductors when carrying out megger test.

7.6.3 Always discharge cables when test is completed. Adjoining conductors willhave capacitive properties which may store charge.

7.7 Types of Meter

There .ue two types of meter commonly available to the engineer.

(a) ANALOGUE METERS

(b) DIGITAL METERS

7.7.1 Analogue Meters

Analogue meters usually incorporate a pointer which can move over a scale and can,within limits, assume any reading i.e. they can indicate continuously any magnitudeof voltage or current. There are many types of instruments that fall into this category,but the most common is the moving coil meter.

119

t

Figure 7.4

The moving coil meter consists of an aluminium former which is pivoted at each endso that it is?ee to rorate in a magnetic field. Fine copper wire is wound around theformer through which cunent is passed. The magnetic field is produced by.shapedperrnanent magnets, the magnetic circuit is completeg bV I cyliryler of .soft iron, so^that

only a nariow gap remains through which the coil swing.s. Tt_r_e-.coil is therefore,positioned in a mafn6tic field of uniform strength and direction. When current is

fassed through the-coil it takes up a position depending upgn the magnitude. of the'current. The-moving coil meter uses the principles of the electric motor which is

covered in chapter 6 of this book. Obviously the accuracy of this meter depends onuser interpretation of pointer position. To reduce reading €rror a narrow needle isused and the scale fitt-ed with a mirror. The user simply aligns the needle with itsreflection. The magnitude of current that can be measured depends on.the resistanceof the coil. In order to measure larger currents a resistor is connected in parallel withthe coil, this is known as a'shunt'resistor. The moving coil meter may also be usedas a voltmeter by connecting a resistor in series with the coil, the resistor is known asa multiplier. With the aid of an internal.battery the moving coil meter is.capable ofmeasuring resistance. For electronic servicing work a meter that is capable ofmeasuring all electrical quantities is used, this is known as an Avometer.

7.7.1.1 Mult ipl iers.

This section discusses the principles of using a multimeter to measure voltage byincorporating a multiplier iesistor. In this example the meter has an internal resistance

of lkQ and a full scale deflection of 40pA. This simply means that the meter needlewill be deflected across the full range when a current of 40pA is passed through it.

Figure 7.5

Max voltage = 1kC) x 40PAV= 0.04VV= 40mV

Therefore this meter in its 'raw' state could only read up to 40mA or 40mV. If wewish to read higher voltages or culrents we need to adapt the circuit.

Placing resistors in series will increase the voltage measuring capability, resistors inparallel will increase the current measuring capability.

120

Example: If the above mercr was to measurerequired?

I Volt, what series resistance would be

Total resistance musr equal; 1 volt/40pA= 25ke 1 R = V/I )

Therefore a24kQ resistor is required in series with the lkQ resistance as shown infigure 7.6

This is termed a multiplier and enables use of the meter as a voltmeter.

7.7.1.2 Shunts

In order to read culrent, a parallel or shunt resistance is required in circuit.

Example: rf we wish the same meter to read 1OmA f.s.d., what value of shuntresistance is required?

1 = (10 mA) - (a0pA) = 9.96mA

V = 4 0 u A x l k O = 4 0 m V

R =V/[

R = 40mV /9.96mA

R = 4.02C1

Figure 7.6

121

Example: What value of shuntf.s.d.?

is required to make a 40pA, 10kQ meter read 1A

I = 1 - 4 0 p A

I = 0.999964

V = I x R

V = 4 0 p A x 1 0 k O

V = 0.4V

Shunt resistance = 0.4V I 0.99996A

Shunt resistance = 0.4 c)

7.7.2 Meter loading effect

The process of using shunts and multipliers means that our meters have a sp-ecificresistance value fortach voltage range on the meter. This resistance is conditional on

the range in use and is normally quoted in kQ /V e.g. an AVO Model 8 has 20 kC) ̂ /on both the ac and dc voltage ranges. This means that on the lV range the meter

system has 20kQ resistance, while on the 5V range it has 5 x 20kQ =100kf) .

This has serious implications when measuring small voltages across high resistance's.

Example: What voltage should be measured in the circuit below and what

voltage would be measured assuming that the meter is an AVO 8 (20kO f/) on the5V range?

122

Figure 7.9

Expected voltage: 5 V

Measured voltage:

Meterresistance = 5 x 20kCl = 100kQ

Totalcircuit.resistance=(1 /I20kO+ I / 100kQ)+ l20kQ

therefore it follows that 54.5kQ + 120kQ = 174.5kQ

Current drawn = 10 / l74.5kQ = 57.3LrA

Voltage across meter -- 57.31tA x 54.5kQ

= 3 . 1 5 V

7.7.3 Digital Meters

Digital meters give a direct read out that is free from human eror. The instrumentshave no moving parts and are generally less expensive that analogue meters.

aa a a aa oa aa a o ao .a aa a o a

Figure 7.10

b

e

a l 's l f

t23

The diagram above shows the typical layout for a digit on a meter. Each segmentmay be represented by four lighi emitting diodes (LED's). The LED's emit light whena suitable voltage is applied to them.

7.8 Safety Precautions

a) Check Test Leads for damage to insulation.

b) Always set meter to highest range before taking reading.

c) Ensure voltage being measured is within range of meter.

d) Remove any jewellery before working on live equipment.

e) If possible always work with somebody else present.

f) If possible carry out measurement using only one hand.

7.9 Oscilloscope

The cathode ray oscilloscope (CRO) is a measuring instrument in which thedeflection of an electron beam displays an applied voltage.An electron beam is directed through a vacuum on to a face plate that is coated withfluorescent powder. When the electron beam strikes the face plate it produces a spotof light on the screen. The oscilloscope incorporates a system of plates that, onapplication of a voltage, deflects the electron beam either horizontally or vertically.The resulting movement of the spot of light can now be used to measure the appliedinput voltage.The deflection system incorporates two sets of plates known as X and Y plates, the Xplates provide horizontal deflection and the Y plates vertical deflection. If the inputto the deflection system is rapidly varying , persistence of vision will make themoving spot of light on the face plate appear as a continuous line.

7.9.1 Advantages of the oscilloscope

a) Low inertia of electron beam permits the measurement of rapidlychanging input wave forms.

b) The deflection along two axis allows a graphical display of voltageagainst time.

c) Oscilloscopes have a very high input impedance which prevents thecircuit under test becomins loaded.

7.9.2 The basic system

All ROV systems will have an oscilloscope included in the tool kit, many differenttypes are in existence, however, the principles of operation are the same for allmodels. The oscilloscope consists of three basic blocks. These are :

a) A cathode ray tube (CRT).

b) Vertical deflection system ( Y Plates).

124

t

c) Horizontal deflection system ( X Plates).

7.9.3 Cathode Ray Tube (CRT)

The CRT contains an electron gun that consists of a cathode that when heated emitselectrons. The electrons are accelerated towards the face plate by electrodes that alsoregulate the intensity of the beam. It follows therefore thdt these electrodes determinethe brightness of the trace on the display.

The electron beam is focused_by an electron lens. The electron lens achieves focusingby either electromagnetic coils or field shaping electrostatic electrodes. Mostoscilloscopes use electrostatically focused iubes.

ELECTRONLENS

ELECTRONGUN

cathode

X deflectionr

intensity

Figure 7.l l

7.9.4 Yertical deflection system

The vertical axis is used to measure the magnitude of the input voltage and normallyrequires a voltage of between 20 and 30 vofts to produce a full scale-cleflection of theelectron beam. An amplifier and attenuator network allows a wide range of inputsignals_to be measured, the attenuator having a switched range that is rn'anuallycontrolled.

face platecoated inphosphour

focus

125

The oscilloscope screen is therefore graduated with a fixed number of centimetresquares, each square representing a fixed voltage level depending on the setting of theVOLTS /DIV control.The Y gain control is normally variable and allows the operator to make a wave formoccupy-a fixed number of squares. This function becomes useful yhgn Ising a dualtrace oscilloscope and comparison of two input signals is required. A dual traceoscilloscope, as the name implies, has two electron beams that are independentlydeflected allowing two signals to be displayed at once.

7.9.5 Horizontal Deflection System

In order to give a voltage against time display the spot must be made to sw^eep fromleft to right across the display. This is achieved by applying a ramp wave form totheX plaies. The ramp wave form is commonly known as a sawtooth wave form andis generated by an oscillator circuit within the oscilloscope.

Blanking period sweep tlme

Figure 7.12

The rising edge of the SAWTOOTH gives rise to the spot moving across the display.The sharp falling edge represents the spot returning to the left hand side of the displayand is known as the tfly back'period. During this period the electron gun is tumed offand therefore only the left to right trace is displayed.The sawtooth is generated by an oscillator known as a timebase oscillator. Thisoscillator can generate different sweep speeds thereby altering the time it takes for thespot to sweep across one squire. The timebase control determines the output of thisoscillator and is calibrated in TIME / DIVISION.

fly back

t26

7.9.6 Oscilloscope probes

Oscilloscope probes are used to detect the actua_l signal, they have fine metallic tipsthat allow measurements of signals to be made fronivarious components on a cir&itboard.The probe is connected to the oscilloscope via a screened cable. For this reason thelldg.ttut an eafth clip which must always be attached to a suitable earth point on theclrcult.It is also. necessary to calibrate the probe before use in order to compensate forthebuilt in reactance. This is achieved by connecting the probe to tfi" rqu6r.i *uu"gutlYt of the oscilloscope and altering the _adjustmeit scr6* on the acd;i probe. Thisis adjusted until the square wave has a unifonn shape as shown in rigure zlti--

TNCORRECT CORRECT

Figure 7.13

INCORRECT

7.9.7 Oscilloscope controls.

figurg 7.4 illustrates the controls on a typical dual trace oscilloscope. It is not theintention of this chapter to discuss euery'function aviilable as they are not normallyrequired for the basic test procedures cdrried out on an ROV syrte-. Uoweveithemain controls that are necessary are outlined below.

1) POWER ON / OFF: Turns oscilloscope on and off. Operatingcondition is indicated by an LED.

2) X POS: Controls horizontal position of trace.

l0) TIME / DIV: Selects timebase speed.

16) INTENSITY: Intensity control for fface brightness.

17) FOCUS: Focus control for trace sharpness.

19) CALIBRAToR: o.z.v peak to peak square wave outpur forcalibration of test probe.

r27

20) coMPoNENT TESTER: Enables a wide variety of electricalcomponents to be tested by connecting a jack plug. into th.e.CT socketand in earth connection into the ground socket. The resulting displayindicates the integrity of the component. The display scan is normallybe found in the oscilloscope manual.

2l) Y POS: Controls vertical position of trace.

24) VOLTS / DIV: Selects sensitivity in either mV /Cm or V / Cm.

26) DC - AC - GD: Selects input coupling to either DC,AC or

,tt"='". :

Figure 7.14

i

lll-

; 5\ d o ,* - l l i 9 ?r o r1 I in

"T-'l

d -

O U

-T-l"Ll

: l Iifl.;G$(-ilnFZAi*r ! \ \4;6>==t?rV / - : \

EEO//\r l.\J/.

'-'.\J,

t28

I

7.9.8 Typical uses of oscilloscope

Oscilloscopes do not come into everyday use as do test meters, however in certainsituations they become essential to the technician. Typical tests are as follows.

a) Monitoring of video signal during either calibration of camera orfault finding on the video sysrem. (See chapter 15).

b) Monitoring of telemetry signal during fault finding procedure.

Telemetry signals, being digital signals are best suited to being measured with anoscilloscope.It is not possible to interpret each digital pulse, however it is sufficient to be able tostep through a circuit and determine if telemetry signal is present. This enables thetechnician to be able to fault find to board level or if necessary to component level.

7.9.9 Measuring Amplitude of a Signal

The amplitude or, signal level as it is commonly known can be determined by makinguse of the screen graticule. By altering the VOLT/DIV control then we can ielect asuitable scale in order that the level of signal can be determined. For example if theVOLTIDIV is set to 2Y|DIY then in the example shown the peak to peak voltage is6V.

2V per division

Figure 7.15

Typical voLTiDIVISIoN sertings may range from 5 voLTS /DIVISIoN toSmV/DIVISION.

7.9.10 Summary

It is not the intention of this chapter to discuss every function available onoscilloscopes. There are many types available and the technician would be requiredto read the operators manual for the particular oscilloscope he/she intends to uie.However, the basic principles discussed in this section apply to all oscilloscopes.

t29

7.10 Self Diagnostics

Many ROV systems now incorporate a surface computer that carries out a selfdiagnostics piogra-*e. This ehables the operator tb monitor signals at various pointsin the system.

A typical self diagnostics programme is included in the_Hydrovision Diablo ROV-The lollowing pages are available in a typical data display system.

a) Multiplexer information: Up link and down link data for eachchannel c-an be displayed showing each individual data'bit'. When afunction is operated the data can be seen to vary accordingly.

b) Main display: This page is normally displayed during divingoperations and provides ttre pilot with vehicle heading, vehicle depth,pitch and roll, oil pressure and temperature.

c) Thruster demand and gain: The amount of thruster power that isbeing used is displayed graphically. Also the thruster gain is displayedas a percentage, it is possible to adjust the gain to suit the conditionsduring the dive.

d) DC voltages: The DC voltages at the control outputs are displayedboth digitally and graphically. It is also possible to 'null' the trimcontrols to zero volts in order to eliminate thruster spin when no inputis received from the joystick.

It can be seen that it is possible to diagnose areas of faults without touching the ROV.This can make the faulf finding procedure less time consuming The software alsoallows the operator to re-programme multiplexer channels, for example if some extraequipment is to be fitted io the vehicle a channel can be set up without any physicalre wiring taking place.

130

CHAPTER 8 HYDRAULIC SYSTEMS

8.1Introduction

SeqotgJV__QPerated Vehicles are, as previously stated divided into three classes.pJe.ball,Workclass and Large Inspection Ciass. The latter two are normallydedicated to work tasks and pipeline inspections. Due to the physical size of tlievehicle and the weight of the.equipment fitted to the Rov, the fower/size developedby the thrusters is critical to their operation. For this reason manufaciurers make useof hydraulics as their source of power.

8.2 Hydraulic Principles

Hydraulics can be defined as the transmission of power created by pushing on ac.onfined liquid. Figurg 8.1 illusrates a simple hydraulic press, cirrying o"ut exactlythe same task as a mechanical lever. A force of iOtU is aplpUea to a pision of an areaof I square inch, the pressure is defined as Force per Unit area, or:

Pressure=Force/Area

Then it follows that a pressure of l0lbs per square inch is developed in the fluidthroughout.the container. By_simple caltuhtion we can see that^the pressuredeveloped in the container will in fact support a load of l00lb suppoited on a pistonarea of 10 square inches. In comparison with the mechanical levei, we can see thatexactly the same task can be carried out by a fluid based system.

An input lorce of10lb. on a onesquarc inch piston

Ir Ivl.l/

3. This pressure willsupport a 100lb.weight if this is a10 sq. in. piston.

INPUT

2. develops a prcssureof 10 pounds per squarcinch (psi) thrcughoutthe container.

4. The forces arc proportionalto the piston arcas.

10 tb. =1 sq. in.

OUTPUT

100 tb.10 sq. in.

A. SIMPLE HYDRAULIC PRESS

Figure 8.1

l 3 l

A basic hydraulic system requires a pump to develop the oil pressure, a valve tocontrol the flow of oil to the actuator, which in turn carries out the work required bythe system. Figure 8.2 illustrates a basic system of this nature.

2. Llnee carry tho llquld toactuaton whlch arc pushedto cause a mechanlcal outPutto move a load.

TO RESERVOIR

3. Some actuaton openle lnI stralght llne (llnear actuatoF).They arc called cyllndon or ram8.They arc uged to llft vuelght' exerlforce, clamp, etc.

A. LINEAR ACTI'ATOR

Figure 8.2

132

I

8.3 Advantages of Hydraulics

Hydraulic systems have several advantages over non-fluid based systems.

8.3.1 Variable Speed

The speed of the actuator is dependent on the volume and flow rate of the oil beingsupplied to it. This can be achieved by either using a flow conffol valve, or byaltering the delivery of the pump, i.e. how much oil the pump supplies to the actuatorover a given time.

8.3.2 Reversible

It is possible to reverse a hydraulic actuator instantaneously without causing anydamage to the system. A directional control or reversible pump provides thereversing control, whilst a pressure relief valve protects the system from excesspressure.

8.3.3 Overload Protection

A pressure relief valve protects the system from excess pressure brought about by anoverload or torque, force in the actuator. For example should an ROV thrusterbecome fouled and seized, then the flow would cease and the pressure build up. Thepressure relief valve will activate and allow the oil to flow back to the tank, thusprotecting the systern from damage.

8.3.4 Stal l ing

If an electric motor stalls during an operation due to overload, it is likely that a fusewil l blow, thus preventing instant re-start. I f a hydraulic system stal ls, then thePressure Relief Valve will divert the oil back to tank for the period of time that thesystem pressure rentiiins in excess of nomtal working pressuie. Once normal pressureis resumed the system will continue to operate as normal. Stalling, therefore, doesnot pose the same problenr in a hydraulic system, as it does in a purely electrical ormechanical system.

1. In thls posltlon ofthe dlrcctlonal valve. . .

2. pump dellr/ery 18 dlrccted to thecap end of the ryllnder.

3. The plston rcd extends.

DIRECTIONALVALVE

4. Exhaust oll ls pushed outot the rcd end and dlrcctedto the tank.

Figure 8.3 a

133

5. In another Posltlon' ollls dlrccted to the rcd end ofthe cYllnder. ' . 6. the Pleton rod rctracts.

II!

8. The rcllef valve Protects the-' iwt". bY momLntarllY dlvertlngir6w to tank durlng reveelng'anO *rt en Plston |s stalled orlil,pi-ii6,ia ot strcke. Figure 8.3b

8.4 Pressure

Pressureiscreatedwhenevertheflowofliquidi '1.::Y:'g..Thismaybebrou.ghtabout bv a restriction in the piping' or the piestnce of an actuator with an applied

road. Figure 8.4 illi;r;;;..; tiie efiect "i'; i;;;; oil pressure. An 80001b load

srrnnorted bv a 10 sqLrare inch pisto' t;";;t;;;;;;"it of tt00 PSI Pressure' Force

;'d"Ar;;.;6 ii *.,t't y the fol l-ow i n g formul a'

Pressure = &IsgArea

Pressure = f(l0llD10Sq in

Pressure = 800 PSI

I t fo l lowstha t i f the load isuncreasedthenso is thep lessure .F igureS.4(B)illusrrares the effect "1" f..t on the t'ti"* pu" it" pitton' TheForce and Piston

Area remain unchanged and s9 the prrrr"#iJtuintih" sanle' However the oil flow

passses the piston ;';;t;il's-s'ir19"i fi;;il; .t*l: o"*p output flow is 10

Lallonsimins then i;[;;; *-OlS"guff9"r'prl minute to *ou" the piston' The overal]

Effect is that tfr" pi.to"riuii,ii"i"fJ* ttre t6ad will move much slower'

Exhaust ollfrom the capend ls dlrccted to tanx'

134

I

1. The force is 8000 tb. and. . .

4. ,19-112 gpm are lost thrcugha leak. . .

A. NO LEAK IN SYSTEM

Figure 8.4 a

2. the arca is 10 sq. in,

3. The pressur€ equals Force+Arcaequals 8000 lb.+10 sq. in. =800 psl.

5. the oil notlost must stillraise the piston.

6. Thus therc still is an 8000 lb.force on the oil andpressure is maintained.

B. LEAK IN CYLINDER

Figure 8.4b

135

8.5 Flow

As discussed in the previous section, it is pressure that gives the actuator its force.However, it is the flbw of oil that gives thb actuator its movement, flow is created bythe action of the pump.

8.5.1 Measurement of Flow

There are two ways in which flow can be measured.

Velocity - The average distance that the oil particles travel per unit and time.Units - Feet per second or metres per second

Flow Rate - Is a measure of the volume of fluid passing a given point in a given time.Units - gallons per minute or litres per minute

8.5.2 Flow and Pressure Drop

In order for liquid to flow, there must be a state of unbalanced force to cause motion.when fluid flows through a pipe of uniform diameter there will always be slightly lesspressure down stream wittr ieipect to the pressure up streanr. This is due to friction inlhe pipeline, and must be taken into account during the design of the system. Figure8.5 illustrates pressure with respect to flow through a unifornl pipeline.

1. Prcssure is maximum 4. Succeedingly lowerhere because of lhe level of liquld Inheight ol llquid. these pipes is a measurc

3. Frlction in the pipedrops prcssure fiommaximum to zerc

2. Pressurc is zerc her€as the llquid llowsout unrcstrlcted.

Figure 8.5

8.6 Hydraulic Calculations

By applying the basic laws of physics it is possible to determine the main componentsrequired by a hydraulic system.

8.6.1 Determining Pipe Size

By applying one of two formulas it is possible to calculate the size of hydraulic linesrequired. If gpm and velocity is known, it is possible to calculate the cross SectionalArea of the flow line.

Cross Sectional Area = gom x 0.3208( square feet) Velocity (fps) N.B. fps - feet/second

The Velocity in fps can be calculated by using the formula:

velocity (fps) = 3.r17ffiea

8.6.2 Work and Power

Work is carried out whenever a force acts through a distanc:e.

i.e. Work = Force x Distance

e.g. A 10lb load is moved through a distance of 5 feet.

Therefore Work = 10lb x 5 feet

Work Done = 50 ftllb

In practice we must take into account the rate at which work is done. This is referredto as power.

Porver = .Ee.tgg-E-Di$ltglgg or WorkTime Time

8.6.3 Horsepower in a Hydraulic System

One horsepower is described as being power required to lift 33,0001b, 1 foot in 1minute. In a hydraulic system speed and distance are represented as gallon/minute,and force is represented as pressure.

Horse Power = gpm x P.S.I x 0.0005tt3

Horse Power = gpm x Psi x 0.5831000

or hP = SP1IIJ-ESIt7t5

We can now calculate the exact horse power of a system using this formula, howeverthis formula assumes that the system is 1007a efficient. In practice a typical hydraulicsystem is only about 807o effrcient. For this reason we have to calculate on effectivehorsepower to compensate for losses.The equation is as follows:-

lf

137

hp = gpmxPSIx0 .000583

has to be modified to approximately

h p = g p m x P S I x 0 . 0 0 0 7 .

N.B. 0.000583 is approximately 80Vo of 0.0007.

Thus horsepower can now be represented

Power = sallonminute

T o r q u e = 6 3 0 2 5 x h prpm

8.7 Basic Hydraulic System

h . p = g a l l o n s x p A U X d Eminutes Sq Inches

As I gallon - 231Cubic inches

l2inches - l foot

x e1!in3 x Pounds xgallon in2

= 231 ft lb l mint 2

12 in

This gives the equivalent mechanical power of one gallon per minute flow at 1 PSI ofpressure. We can express this as a horsepower by dividing by 33000 foot pounds perminute.

++ rt rb / min= 0.0005tt3hp

33000ft lb / min

Thus 1 gallon per nrinute f low at I PSI ecluals 0.0005t13 hp

8.6.3 Horse Pnwer and Torque

Torque can be defined as a rotating or twisting force. There are two torque - powerformulas most commonlv used.

hp = fgrgue-:rlpxq6302s

Figure 8.6 shows the basic layout of the hydraulic system of a typical WorkclassROV. It is the intention of this section to discuss the various components that makeup the system.

138

t ,I!

I

6 :

{ t ;- 9 :

:

,3z

oa

o

i z< :

Fi

f

> r

i gi rt :

e {; ot 6

< =

i O

t

ffiHlill: : : 9F = : ir i 6 :' * : :

3

:;

Figure 8.6

a7

oto

oI

g 9e ,4 =

6

q,

oIa

=

2 .C a

a t

: e> 6

9 :- i9 . :

I

t: 5< r

3 ?

o l

rt:

c

r39

8.7.1Hydraulic Pump

The hydraulic pump is directly coupled to an electric motor and converts mechanicalenergy into hydraulic horsepower. The principle of the operation is that an increasingvolume is generated on the intake side and a decreasing volume (with increasingpressure) on the output side.

8.7.1.1 Pump Displacement

The flow capacity of a pump can be defined as the displacement per revolution, orsimply the output of oil in gallons per minute. Displacement is expressed in cubicinches per revolution.

8.7.1.2 Pump Delivery

The delivery of the pump is dependent upon two factors:-

a) Load Condit ions

b) Drive Shaft Speed

The pump will actually deliver more oil than it's specified rating, if it is running underno-load conditions. It follows therefore that the delivery will reduce under excessiveload conditions.

The amount of oil being delivered is also dependent upon the speed that the shaftturns. In order for the pump to perform according to it's specifications, the drivemotor must operate at the correct speed.

8.7.2 Types Of Pump

The most common types of hydraulic pump found in industry are positivedisplacement pumps. A positive displacement pump delivers specific amounts offluid per revolution, stroke or cycle. These pumps may be of fixed displacement, inorder to adjust this parameter, certain internal components have to be adjusted.

Some pumps have the facility to vary the size of the pumping chamber by adjustingexternal controls, these pumps are known as variable displacenlent pumps.

t40

8.7.2.1 External Gear Pump

4. Outlet pressune againstteeth causes heavy side-loading on shafts asindicated by arrows.

DRIVE GEAR

2. Oil is carried aroundhousing in chambersformed between teeth,housing and side plates. .

8.7.2.2 Vane Pumps

2. is carried aroundring in pumping chambers.. .

PUMPINGCHAMBERS

SHAFT

|NLET €>

1. Oil enters as spacebetween ring androtor increases. . .

OUTLET

INLET

Figure 8.7

3. and forced outof prcssure port asteeth go back intomesh.

1. Vacuum is created here asteeth unmesh. Oil entersfrom rcservoir.

ECCENTRIC ITY

A side load is exertedon bearings becauseof pressure unbalance.

As the teeth of the two gears un mesh a partial vacuum is created, thus, drawing oilinto the unit. The oil becomes trapped between gear teeth, and as the teeth meshtogether the oil beconres pressurised. Gear pumps can be ntounted in tandem, orthrough drive which allows separate inlet and outlet parts, thus, creating two separateisolated systems, possibly with two different types of hydraulic oil. Thls system doesoccur in certain ROV systems, typically where the nranipulator hydraulic system isisolated from the nlr in system.

ourLEr I.*+L

3. and is dischargedas space decreases.

CAM RING SURFACE

CASTING

141

Figure 8.8 illustrates the operating principle of the v?1e: puqq. The,unit.consists of a

sldtted spindle. The slots contain moveable vanes which are 'thrown' against the outer

casing oi the pump body. The eccentricity of the spindle is such that a vacuum is

creatJd on the infdt siOi, and as the volunie betweeh the vanes decreases, then the oil

pressure increases. Due to the vanes being in constant contact with the casing, they

ire subject to constant wear. As the vaneiwear down, then they extend further from

their slots and eventually replacements is necessary.

The vane pumps covers low, medium and high volume langes and. can operate at

;;;;t;;; i,p t,i fOoo pSr. T'hey are highly elficient with a low noise level and a long

life.

8.7.2.3 Piston Pumps

Piston pumps are contmonly used on ROV's and operate on the principle that.when a

piston in u bor. rerracrs it diaws fluid in and when-it moves out it expels fluid from

ihe bore. The second type of piston punlp:

There are two types of piston punlps:

a) Radial Piston Pumps

Radial Piston Pumps consist of a cylinder block inside a reitctiotl ring' (see fE g.gl.

The cylinder blockcontains bores in which free moving pi.stons are housed. The

cylinder block is offset in such a way that as i t .spins, the pistons are subject to.

clntr i fugal force. As the pistons nloue out, f luid is drawn into the. cyl inders. As the

distancjbetween thg s:ylincler block and reaction rirtg decreases, then the pistonsmove in towards the centre forcing out f l tr id in the process'

.ENTERLTNEx.--.1

CASE

PISTONS

CYLINDER BLOCK

Figure 8.9REACTION RING

CYLINDEB

t42

lNLETPORT

b) Axial Piston pumps

Figure 8.1-0 shows a.simple axia! pump. The cylinders rorare parallel to the axis ofrotation of the cylinder block. Th-e swash plate is at an angle that determines thelength of the piston stroke. The larger the stroke is, then tFe more oil is drawn to thebore and the larger the displacemeni becomes.

The ports are arranged so tha^t as the pistons pass the inlet, they are drawn back and asthey pass the outlet they are forced out. The displacement of ihe pump is determinedby the number of pistons and the length of the sttoke.

2.and are forcedback in at out let .

OUTLETPORT

VALVE PLATE SLOT

CYLINDER BLOCK BORE

PISTON SUB.ASSEMBLY

DRIVE SHAFT

SWASH PLATE

SHOE PLATE(RETRACTOR RtNc)

' i,:*"1'",:':liffi:, . . .Figure 8.10

lotg pistons are designed in such a way that oil is allowecl pasr the piston rings andinto the casing to facilitate lubrication of internal bearings. For this reason there hasto be a part, known as a case drain, to allow oil back to ihe tank.

8.8 Hydraulic Valves

Introduction

ligut" 8.6 illustrated a.basic.layout for an ROV hydraulic system. It can be seen thatthe thruster motors will requirea variable flow speed and direction, in order to meettheir requirements. The manipulators contain linear actuators, which requi.e only avariable direction, bur nomtally ody a constant flow rate.

143

8.8.1 Directional Valves

Directional valves feature in the ROV Hydraulic system in more than one form. Theyhave the ability to start, stop and control the direction of fluid flow.

8.8.1.1 Classification of Directional Valves

Directional valves are classified according to certain characteristics as listed below:-

a) Number of flow pathse.g. two way, three way.

b) Actuation methode.g. mechanical, pneumatic, electrical

c) Internal valve elemente.g. Poppet, spool, piston, ball

d) Size - Size of flange or part connections

e) Connections - Pipe thread, straight thread or flanged

8.8.1.2 Check Valve

Check valves feature in almost all hydraulic systems including ROVs Basically theyallow the flow of fluid in only one direction.

Figure 8. 1 1 shows a check valve serving as an in line one way valve. A spring holdsthi poppet in the nonrrally closed position. Fluid pressure forces the poppet againstthe Spiiirg, thus allowing flow in the appropriate direction. When the pressure ceases,the poppet retulns tct its seat and prevents any undesired back flow of oil.

Typical Uses On ROV

As on many hydraulic systems, a check valve is often used directly after the pump toprevent baik flow of oil, in the event of excessive pressure building up in the system.

SEAT BALL (OR POPPET)

FREE FLOW ALLOWEDAS BALL UNSEATS

FREEFLOW NOFLOW

FLOW BLOCKED ASVALVE SEATS Figure 8. l l

r44

8.8.1.3 Trvo Way Directional Valves

Two way directional valves are commonly found in what is termed the Hydraulic,Control Unit (HCU). This unit consists of a'bank' of two way directional valves,which control devices such as manipulator arms, and camera pan/tilt units. TheH.C.U generally operates at a lower pressure than the thruster hydraulic system,typically 1000 - 1200 PSI. As previously mentioned, the H.C.U may be completelyisolated from the main system, by incolporating two directly linked gear pumps intothe system (see section 8.7.2.I)

STATIC OIL

VALVECLOSED

otLouT

A I o t L t N

DrREcroN ffiO\E

OILOUT

DIRECTIONTWO

Figure 8.12

8.8.1.4 Actuation of Directional Valves

There are several methods generally used in industry to actuate the spool movement.They include, pneumatic, mechanical and electrical actuarion. The ROV industrymakes use of electromagnetism, and the particular valve is known as a solenoid valve.

t45

ENERGISED COIL

lSEDARMATURE

Figure 8.13

Fig 8.13 shows the solenoid valve in an energised state, by applying a voltage, thecoil becomes energised, moving the pin against the spool. Normally solenoid valvescontain springs, that centralise the spool once the coils are de-energised.

8.8.2 Servo Valves

The servo valve is a directional valve that is capable of being infinitely positioned toprovide control of the amount of fluid supplied to the actuator. ROV's make use oflhese devices to meet the requirements of the thruster motors, which are required torun at variable speed and in either direction.

8.8.2.1 Principles of Operation

Figure 8.14 shows the principle operation of a Electrohydraulic Servo Valve:-

IONOUE MOTOF ANO SERVOVALV€ ARE IN SINGLE UNIT

MECHANICALOF HYDRAULIC

P\

ENERGL.

DE-col

i

MECHANICALOFI HYDFAUL(

III

I

II

FEEOBACKDEVICE TELLSSER\IO v LvEIF OESIRED

l^E199.!Iv o_1

SPOOL

ACTUATORMO/ES AT

COiITROLLEDSPEED TO

CONTROLLEDPOSITION

Figure 8.14

r46

A control signal, which may comprise of an analogue d.c voltage is feed to anamplifier, which boosts the signal. This analogue voltage will represent the initialoutput from the joystick control. The electrical signal is applied to the torque motor,which is mechanically coupled to a spool that controls the fluid rate of flow.

If follows therefore that the load will move at a rate proportional to the electricalinput signal. A feed back loop may be incorporated into the system, whereby anelectrical signal is applied from the load to the servo amplifier. This feedback signalis compared with the original input signal, and any resulting error is fed to the torquemotor, which reacts in such a way as to cancel the error.

8.8.2.2 Torque Motor

Figure 8.15 shows the basic operation of the torque motor.

ARMATURE

PERMANENTMAGNETS

SUPPORT TUBE

FLAPPER

FEEDBACKSPRING

PERMANENTMAGNETS

Figure 8.15

The unit consists of a flapper, pivoting on a flexible support tube. The flapper iscoupled to armature, which is encased in a permanent magnet. Each armature issurrbunded by electrical coils to which the conrol signal is applied. On applicationof control sighal the armatures are shrouded by a magnetic field, the strength of whichis proportionlal to the input signal. This magnetic field gives rise to the movement ofthe armatures and therefore the pivoting of the flapper.The flapper is mechanically connected to the spool as illustrated in the_single.stageservo vaive (Fig 8.16). It follows that the spool will move proportionally to the inputsignal and thus create a fluid flow of equal proportion.

2. causes spoolto shift adistance proPortionalto electric signal.

hLECTRICALCONNECTOR

TORQUE MOTOR

1. Deflection ofmotor armatuc

VALVEBODY

SPOOL

PRESSURE MECHANICAL CONNECTION

Figure ft.16

8.8.2.3 Two Stage Sp<lol - Type Servo Valve

In most cases ROV systems require a larger flow rate than could be obtained fromsingle stage spool valve. For this reason the system makes use of the Two StageSpool - Type Servo Valves as i l lustrated in Fig 8.17.

148

1. When torque motormoves pilot valve to left.

3. Supply prcssure isopened to port'4". . .

6. Sleeve followspifot spool andcuts off flowwhen desired mainspool position isreached.

PILOT STAGESLEEVE LINKAGE FULCRUM

(vARtABLE)

2. large end of spoolrcceives increased controlpressurle and spool movesto right.

2ASPOOL

END AREA

TOROUE MOTORARMATURE

CONTROLPRESSURE

cotLs

7. Ratio of mainspool to pilotspool movementis adjustable.MAIN

SPOOL

1ASPOOL

END AREA 5. Feedback linkagetransmits spoolmovements to sleeve

Figure 8.17 (a)

4. and port "8"

t49

2. In neutral, largepilot end is blockedat pilot valve in thestatic condition. Thispnessune = 1/2 controlpressure (Pc).

3. Control pressuneis present here andat small end ofmain spool.

PILOT SPOOL

PILOT STAGESLEEVE LINKAGE FULCRUM

(vARTABLE)

ARMATURE

SUPPLYPRESSURE

1. l.arge spool endarea is twice the areaof opposite end whichis subject to controlpressune at all times.

FEEDBACK

MAIN SPOOL

CONTROL PRESSURE

4. Control pressune holdsmain spool stationaryagainst oil trapped atopposite end at 1/2 (Pc).P c x l A = 1 l 2 P c x 2 A

Figure 8.17 (b)

150

E

The principleof operation is similar to the single stage valve, excepr that the flapperis mech.anically_ connected to.a pilot spool, which coitrols the main supply spooi.^ Itshould be noted in this case that the feedback link from the main spoof ioitt.i flapperis mechanical. The most common type of servo valve used on ROV's is the MO'dF,the specifications and port configuration are available in the appendix section of thisbook.

8.9 Hydraulic Actuators

8.9.1 Introduction

The.h.ydraulic actuator is the unit responsible for converting the energy stored in thefluid into mechanical energy. They comprise of either motors, or rams; motorsproviding rotary motion for thrusters, rams producing linear motion for manipulatorsand camera pan and tilt function.

8.9.2 Hydraulic Rams

Figure 8.18 illustrates the typical construction of a hydraulic ram/cylinder.

ROD END HEAD CUSHION COLLAR

ROD BEARING

ROD END PORT

OPTIONAL AIR VENTS(FOR BLEEDTNG ArRFROM CYLTNDER)

PISTON SEALS

CAP END HEAD

END PORT

ROD SEALROD WIPER

CUSHION PLUNGER

BODYSTATIC SEAL

Figure 8.18

The^operatig! of the cylinder is basic in the fact that oil is clelivered to either port viathe Solenoid valve, and.the pressure acts up on the piston, rnoving it in theappropriate direction. The piston rod is connected to the 'linrb' of-a manipulator forexample and transfers the movement of the piston rod to the lirnb.

r 5 l

Figure 8.19 illustrates the various cylinder mounting methods

TAPPED MOUNT

EXTENDED TIE RODMOUNT-BLIND END

RECTANGULAR FLANGEMOUNT-ROD END

RECTANGULAR FLANGEMOUNT-BLIND END

SOUARE FLANGEMOUNT-BLIND END

EXTENDED TIE RODMOUNT-BOTH ENDS

CENTERLINELUG MOUNT

CLEVIS MOUNT CLEVTS MOUNT WITH

Figure 8.19

SIDE LUG MOUNT(FOOT MOUNT)

SOLID FLANGEMOUNT-BLIND END

SOLID FLANGEMOUNT_ROD END

EXTENDED TIE RODMOUNT-ROD END

TRUNNION MOUNT-BLIND END

TRUNNION MOUNT-INTERMEDIATE

TRUNNION MOUNT-ROD END

152

SPHERICAL BEARI

The main componenrs of the limb are as follows.

a) Seals' The seal between the piston and the cylinder walls is critical for efficientoperation. The seals mly qg manufactured frorncast iron or more commonly rubber.If these fail, then 'gre_ep.' will occur when the actuator is on load. This is cauied by oilby-passing the seal. Iris important to ensure that the rubber material is compatibiewith the oil, as the rubber may perish.

The integrity. of the rod seal is of upmost importance, as this prevents ingress of dirt,or sea water into the actuator. Rod seals may be manufactured from rub6er or teflon.The rod seal material must be compatible noi only with the oil, but in the case ofROVs in the sea water.

b)-.Cylinder Cushions - The cylinder cushions are situated at either end of thecylinder, in order to slow down-the movement of the piston at the end of it's stroke. Ifthis was not the case, the piston would hammer again.st the end cap and sufferpossible damage.

c) Ports ' The external openings to the cylinder allowing oil to and from the cylinderas appropriate.

8.9.3 Hydraulic Motors

8.9.3.1 Introduction

Motor is the term given to an actuator that provides rotary rnotion. All motors arecommon in the fact that pressure js exerted-on piston, vanes or gears which aredirectly coupled to an ourput shaft.

The motor that we are concerned with most in the ROV industry, is the axial pistonmotor. For this reason it is this motor that we will base our information.

8.9.3.2 Perf<lrmance of Motors

The performance of motors is based on the foilowing paranreters.

a) Ability of pressure exposed surfaces to withstand force of hydraulic fluid.

b) Efficiency of linkage method used to connect pressure surflce with output shaft.

c) Leakage Characrerist ics

8.9.3.3 Motor Ratings

Motors are rated according to torque, displacement, speed and maximum pressurelimitations.

a) Torque - Torque il lh" -r-urning, twisting function of the ourpur. Motion is atunctton of fbrce, and if sufficient torque is present to overcom^e friction, motion willoccur.

b). Displacement - ls the amount of fluid required to turn the motor I revolution, andit is expressed in cubic inches per revolution iCubic in/rev).

c) Running Torque ' The running torque of a motor is the actual torque a motor candevelop to keep the load turning. Running torque is a percentage of trieo."ti.aitorque.

153

d) Starting Torque - The starting torclue is the torque retluired to start the loadturning. Once again it is considered to be a percentage of theoretical torque.

e) Speed - Speed is the rotational velocity at a specific pressure that the motor canmainlain without sustaining damage. It is a funciion of volume of delivered fluid anddisplacement.

f) Slippage - Slippage is the leaking of fluid across the motor without any worktaking place.

8.9.3.4 Axial Piston Motors

Axial piston motors are probably one of the commonest type found on ROV systems.They fall into the class of High Speed, Low Torque Motors. Figure 8.20 shows theconstruction of a typical in line axial piston motor.

5. As the piston passes theInlet, it begins to rcturninto its bore because olthe swash plate angle.Exhaust l luid is pushed 4'into the outlet port.

OUTLET PORT

INLET PORT

The pistons, shoe plate,and cylinder block rotatetogether. The drive shaflis splined to the cylinder block.

3. The piston thrustis transmitted to theangled swash platecausing rctatlon.

PISTON SUB.ASSEMBLY

DRIVE SHAFT

SHOE RETAINER PLATE

2. Exerts a forceon pistons, forcingthem out of thecylinder block.

Figure 11.20

154

Fluid pressure acts up on the piston ends which transmit the pressure to the swashplate. The angle of the swash plate is such that a rotational movement is developed.The torque of the motor is proportional to the area, number of pistons and the angle atwhich the swash plate is positioned. The motors may be of fixed displacement orvariable displacement. The variation of displacement is brought about by externallyadjusting the angle of the swash plate.

8.10 Contamination Control

8.10.1 Introduction

It can be said that about 707a of hydraulic breakdowns are due to contamination ofhydraulic fluid. Contamination can be defined as the presence of solid particles in thehydraulic fluid. It is essential therefore to try and minimise this occurrence in the bestpossible manner.

8.10.2 Effect of Contamination on System

The following factors have to be taken into account when looking at howcontamination effects the system.

a) Purpose of Hydraulic Fluid -

To Cool and dissipate heatContamination fornrs a sludge on the reservoir walls and thus prevents effective heat

transfer.

- To Transmit PowerContamination blocks small orifices and consequently restricts the flow of oil torelevant units.

- LubricationThis can lead to disastrous consequences. All hydraulic components have toleranceswhich allow a certain amount of oil to flow through them for lubrication. Forexample, a certain amount of oil passes the piston rings in the axial motor in order tolubricate the shaft bearings. Build up of contamination in the cylinders will preventthis and lead to possible seizing of the shaft.

b) Mechanical Clearances

The clearance between hydraulic components can be defined as follows.

- 5 micrometers for high pressure units

- l5 to 40 micronreters fbr low pressure units

Note - one micrometer is one millionth of a meter.

r55

p m ln .

Gear pump(Pressure loaded)

Gear to side plateGear tip to case

1t2-51t2-5

0.00002-0.00020.00002-0.0002

Vane pumpTip of vaneSides of vane

1t2-1'�5-13

0.00002-0.000040.0002-0.0005

Piston pumpPiston to bore (R)"Valve plate to cylinder

5-40112-5

0.0002-0.00150.00002-0.0002

Servo valveOrificeFlapper wallSpool sleeve (R)"

130-45018-6314

0.005-0.0180.0007-0.0025

0.00005-0.00015

Control valve**Orifice*-'

--- l

Figure 8.21 shows the typical clearance value for various hydraulic components

Figure [1.21

c) Modes of Failure

particles that bring about contamination vary in size. It is this fact that determines the

degree of failure in a hydraulic system.

- CatastroPhic FailureBrought uUout'Uy large particles jamming acomponent. For example a particle may

nAgJU"t*een rhe tedth'of the two crowi wheels in the motor. This would cause.".frpf.t. seiuure of the motor and result in the ROV beconring immobilised.

- Intermittent FailureThis may occur in conrponents such aS relief valves. The contantinant maypreventItr" popp"t from re-seat'i,lg p.op".ly a1d the valve would temporarily dy.Pp back to

tun[. R's soon as the conffimin'ant is flushed away, normal operation will be resumed.

- Degradation FailuresOegra-aa?ion iuitui.r are caused by erosion of components by fine contaminants. Thisprocess may contlnue until catastiophic failure occurs if not checked by amaintenance procedure. (See chapter 12).

8.10.3 Summary of Contaminants

The table shown in tig tt.22 summarises the various contaminants in the ROVhvdraulic svstems.

156

Contamlnant Character Source and Remarkr

Acidic by-products Corrosive Breakdown of oil. May also arise fromwater{ontramination ofphosphatg-€st€r fluids.

Sludge Blocking Breakdown of oil.

Wator Emulsion Already in fluid or introduced by systemfault or breakdown

of oxidation-inhibitors.

Air Soluble

Insoluble

Effect can be controlledby anti-toam additives.

Excess air due to improper bleeding,poor s!€tom design or air leaks.

Othsr oils Miscible butmay r€acl

Use of wrong lluid for topping up, etc.

Grease May or maynot b€

miscible

From lubrication points.

Scale lnsoluble From pipes not prop€rlycleaned before assembly.

Melallic particl€s lnsolublewith

catalylicaction

May be caused by watercontamination, controllable

with anti-rust additives.

Paint flakEs lnsoluble,blocking

Paint on inside of tank old ornot compatibl€ with fluid.

Abrasive particles Abrasive andblocking

Airborne particles (remwe with air tilter).

Elastomericpartlcles

Blocking Seal brEakdor'vn. Check fluid, compatibility of seal design.

j Sealing compoundparticles

Blocking Sealing compounds should not be used on pipo joints.

Sand

-Adhesiv€ particles

Lint or fabricthreads

Abrasive andblocking

Sand should not be used as a filler for manipulating pipe bends.

BlockingBlocking

Adhesives or jointing compounds should not be used on gask€ts.Only linhlree cloths or rags should be used for cleaning or plugging

dismantled components.

Figure 8.22

r57

8.10.4 Prevention of Contamination

As a general rule ROV's incorporate-2 filters into the systenl. thev are Low Pressure

Suction Filters and High Pressure Filter. The Low Pressure Filtei is located after the

tank and before th" ;;";i *tti.ft isaeiigneA to remove any particles that T.u{ b"

sucked from the tank byihe pump. High pressurefilters, as the name lmplles

removes any conramination ift".itr. pu-b on the high pressure side.

Figure 8.23 illustrates a typical high pressure filter

5. Bypass valve oPensif f i l ter is tooclogged to Passlu l l f low.

r BODY

CARTRIDGE

2. flows downaround carlrldge. . .

3. through fi l terlngmedium to centerof houslng. . .

Figure [1.23

It is not the intention of this chapter to go into detail on filter changing as that is

amply covered in chapter 12 on Mechanical Maintenance'

8.11 Hydraulic Fluids

It has been mentioned previously about the properties required frgm a hydraulic oil'

tio*.u.. it is usefuiL'i,uu. an appreciation of which oils should be used in the

i'i,.* io suit the particular elviionment in which the ROV is working.

8.11.1 Viscosity

Viscosity can be defined as a measure of a fluids resistance to flow, or an inverse

measure of its fluidir'. it is generally viscosity that determines which oil is used in

;ily$;. Ii can neisaia if i nuiO fio*s easiiy, then its viscosity is low, a fluid that

does not flow easily is said to have high viscosity'

158

8.11.f.1 Choosing the Right Viscosity

One has to make a compromise when choosing oil of the optimum viscosity. A high

viscosity oil is desirabl6 for maintaining a seal between mating surfaces, however

there are disadvantages.

- High resistance to flow- High temperature caused by friction- InCreased power consumption due to friction- Sluggish operation- Air becomes easily traPPed.

If we overcome these factors by using a low viscosity oil, the following problemsmay occur.

- Excessive Internal Leakage- Pump efficiency decreases, slowing down actua.tor speed.- Brea'k down of oil film between moving parts gives rise to frictional wear.

8.11.1.2 Measurement of Viscosity

The viscosity of a given oil can be determined by measuri.ng th.e flow rateof oil at a

given tempeiutute."This value is termed the Kinematic Viscos^ity and has beenEatalogued by the Internarional Standards Organisation (lSO) for a variety of oils at

different temperatures.

Figure 8.24

Figure 8.24 illustrates the ISO figures for oils at 40oC'

rsoViscositYGrade

MidpointKinematic ViscositYcSt at 40oC

Kinematic ViscositY Limits

cSt at 40oQ

fsovc2 2.2tsovc3 3.2tsovcs 4.6tsovcT 6.8tsovclo 10tsovcls 1sfsovc22 22tsovc32 s2lsovc46 46tsovc6s 68tsovcl00 100tsovcl50 150

tsovc320 320

tsovcl000 1000tsovcls00 1500

159

l '

From this we see that one must bear in mind the conditions that the ROV is requiredto operate. For example whilst working in the Arctic regions-a low viscosity oil isrequired, e.g. ISO VG 30. When working in hotter climate-s, for examplg-T fgEaitern wa6rs, the vehicle may require oils of viscosity of around ISO VG 10.

Typical Oils are as follows:

BPESSOSHELLTOTAL

HLP 10NUTO H10 or UNVIS J13TELLUS RIO OT TELLUS TISAZOLLA VGlO

8.12 Manipulators

8.12.1 Introduction

Constant improvement in technology have given rise to ROVs carrying out more andmore subsea tasks that were at one time reliant solely upon divers. In order tocarryout these tasks, ROVs have to be fitted with robotics arn1s, commonly known asmanipulators. All nranipulators work on a master/slave principle, the pilots controlbeing the master and the manipulator being the slave. Manipulators can haveanything up to nine functions.

8.12.2 Principles of Operation

Manipulators are found on all classes of ROV - small 'eyeball' class are_ equipped withsingle function electronic manipulators, their purpose for exarnple would be to carry aCP Probe. As vehicles increase in size, the tasks become rnore complex, wherestronger and more functional manipulators are required. For this reason manrpulatorsof this nature are hydraulically powered.

The functions are nornrally only recluired to operate at a flxed rate and thereforesolenoid valves will be used to cont}ol the flow of oil. Norr.nally each function willhave its own dedicated valve, which will be one of a series of identical valves,collectively known as the Hydraulic Control Unit or H.C.U.

160

J

oo

'Tl

o

a

sa€(oooit-

CJ)-lmn

Fmn

(D

q)m

znt--

F -l l \ <

o - P

l €

s t, ^=E€ 5

o o

5

0)

1 0 - ^

J v . o - -- - = do P o =: X I ( / ): 1 x x 6= e. r, : 'R

5

t\)5

itU)c

€

s

A)

oc

t

^

o

O 6

o o

€g)

;o

:o

€

;

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('l

{q)

-i

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5fo

Figure 8.25 shows the layout of the Slingsby Engineering Ltd TA009 Seven FunctionManipulator.

(tl

€q)

-i

"J

o

I'Tl

ooNo

od

o

-

@cTTI

ommt-mo-T

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x x

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T iot r' N

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33X

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33x

33

161

Figure 8.26 shows the location of the relative feedback potentiometers on the masterand slave arms.

POTENTIOMETER LOCATION DIAGRAMSLAVVMASTER ARM

t

Figure 8.26

162

8.1,2.3 7 Function Manipulator

The TA009 Manipulator consists of two main groups of components which constitutea basic 7 function, closed loop positional feedback master slave manipulator system.

The Master Arm and its associated power supply and amplifiers are the minimumcomponents required in the master arm gfoup. (See Pictorial System Assembly).

The Slave Arm, Valve Pack, Positive Compensation System, Underwater CableAssembly and Slave Electronics Unit are the minimum required components in theslave arm group. (See Pictorial System Assembly).

The system is designed to be capable of operating in a variety of installationsituations. Typically, a remote piloted submersible, or manned submersibleconfiguration may be used as the Transporter Package.

A number of product options to the basic manipulator are available.

Among these are:-

A. Continuous Wrist RotateB. Tool Grip JawsC. Force FeedbackD. Tool Lock MechanismE. Freeze FacilityF. Parallel JawsG. Self Contained Multiplexer.H. 8th Function ExtenderI. Teach and Repeat Microprocessor based controlJ. Hydraulic Power PackK. Special Tooling InterfaceL. Debris Cutters.

The seven functions available in the standard system are, as configured in the humanarm.

1. Shoulder Slew (left/nght)2. Shoulder up/down3. Elbow pivot (left/nght)4. Forearm rotate5. Wrist Pivot (left/right)6. Claw rotate7. Claw open/close

163

The following is a brief overview of the system operation.. It is described with the

assumption tfr'at a basic system and freezefacilityare-fitted in a modern Type ROV.

Other installations would operate the same in principle.The motion of the manipulator is governed bythe master arm system which.is a

scaled-down version ofihe slave irm (underwater arm). Each position feedback joint,

on both master and slave arms, has a 5 kilohm servo potentiometer mounted on it, the

spindle of which is directly coupled to the motion of the joint itself. Refer to themechanical assembly drawings for further details.

Thus, to take a parricular joint, a signal is available from both the master and slavearms and these are nominally pre-aligned at the commissioning stage to corer thesame length of travel on the potentiometers, and hence to give nominallythesamevoltage.ing", as all potentiometers have +- 5V d.c. between the terminals. Some

variaiion e*ists in the forearm rotate, claw rotate and claw open/close functions as themaster arm is configured with rotary actuation potentiometers and the slave arm withlinear actuation pot6ntiometers. The electronis systems perform gain adjustment toensure matching of voltage swings, in these particular cases.

Both master and slave signals are fed to the vehicle electronics control box, thesurface master arni signa-is being carried via the optional 'Freeze' control card and thesysrem or vehicle datl link. The control box electronics performs a compal.sonb'etween the two signals and if an error exists between the two, supplies a drive signalto rhe relevant hydiaulic seruo valve (proportional control valve) in the slave arm.This serves to diive the slave arm joint to the required master arm position, tltgelectronics control rnonitoring conlinuously and progressively reducing the drivesignal until the two arm signals correspond. Atth.is point, the slave arm and masterar-m are in the same positidn, for that particular joint. Taking all seven degrees offreedom rogerher and all operating at ihe same time (if recluired) this means thatwhatever p6sition or attitude is taken up by the master arms, within the mechanicalconstraint.s of the systenl, the slave amr will be driven until it asstlnles acorrespottdin g posi t iott.

A 'freeze' switch is released, the electronics cause the slave arnl to track slowly, overa 10 second period, to any new position that the master arnt ntay.have.adopted. Ahydraulic isolate valve is fitted io the system and is used to switch hydraulic power tothe arm.

r64

Figure 8.27 shows the capabilities of the Slingsby Engineering Ltd 9 FunctionManipulator.

TA33-9 Function Master/Slave Manipulator

Rclat on

Slave

s\r$

i.

Master

Roiatron

340'Rotalron

.^- -.' : * . /

/ -\, .., ':

,l

3.10!'\>/../Potat ,on

\ 90'I

t . \ l -, i \ / 1

is- : .

. . ii a .

\ - . / t s ,

\ ' . \-x-

165

Figure 8.27

TA33 - Operating EnveloPe Specif ication

Shoulder - Up/Down190"Shoulder SlewL A < O

Elbow1'10"Forearm Rotation340"Upper Wrist Pitch80"Wrist Yaw+15"-65'Lower Wrist Pitch80"Claw Rotation340". Continuous OPtionalRotation Torque108. Nm B0 ft. lb.Claw Open/Close1SOmm (6 in . )Maximum Reach1 75m (69 in )Maximum Lift at Full Beach3akg (75 lb )Hydraul ic SupplY1381206 bar (2000i3000 p s . i . )2 9pm.Weioht of Slave ArmBB k6 (193 lb.) In Air. 56 kg (123 lb.) ln WaierWeiqht of Instal lat ionl iO [g Q42tb. ) In Ai r . 70 kg (154 ib . ) In Water

1M 1.51",1 2M

Sice elevalion

The TA33 is a nine function masierislavernanipulator designed primari ly for subseause on manned or remotely operated vehicles,as u'el l as being suitable for use in almostany hosti le environment.

The TA33 offers unrivalled dexteritycombined with the ruggedness essentialforr cmn to c r r hco2 r : ne r : l i nnq H i r r i r : r l i r ' : n r ir 9 r r r w ( g J v v r e s i v . ' ' , v ' v v , i v e , i v

electr ical service l ines run try i thin the arms' i ructure lo avoid the possibi l i ty of damageor snaggrng.

0.5h4

1 M

Figure 8.28

Designed as a general purpose subseamanipulator, the TA33 is part icularly suitedto dif{ lcult cleaning and inspection taskson structures where access is l imlted,such as welded nodal jo in ts .

The TA33 is a development of the provenTA9 seven function manipulator, now acceptedas the of-fshore industry slandard master/slavesystem, and therefore has the advantage of awell established spares and technical back-upservice.

8.12.4 Conclusion

This chapter has provided an overview of hydraulic theory and the componentscommonly found in ROV systems. The maintenance of the system is covered inchapter 12.

166

a)

b)

a

b

c

d

CHAPTER 9 PRESSURE FITTINGS

9.0 Introduction

work class Rovs alr make use of hydraulic po-wer.- The hydraulic systems thus!!!t-ovea,use pressure fittings to.oitnr.t together the high pressure pipe work andhoses used to connect to-gether the various components. High pressure fittings areproduced bv several diffErent manufacturer t ait swic ii6ki;;ig"ffi -?" urange of re-usable fittings that are very?opular gr{".d["* the indusny. These fittingswill be used ro ilustrate-the rypes oftitrinls availablel

9.1 Selecting Fitt ings

Before anv fittins is selected the tube outside diameter must be known and the fittingthread siz6 musti'e either, ttritGaloingw *ork, o.,nurct ia to existing fittings wheremodifications or mainteii:: is required. 1-t e ne*i conriJrruoon is the workingpressure. For hvdrauric systems thii may. F;r.i,-on il0'db;;.i.'ffi';;?ltiig ur"omusr be able to withstand this pressure #itf,tut Gfi;;;."""'9.1.1 Thread Size

Due to design considerations there are a number of different thread sizes and typesavailable. The thread may be tafred;rparallel

Japergd threads are designed so that a pressure-tight seal is made on thethreads. when using these lypes a seaiant such as stripTeeze or swakis required. These are manufaft*ra io gs ;1:'* v" eI" eeL

Parallel threads are used.where a pressure-tight seal is not made on thethreads. The seal is usually_maae'elttreimetit-to-*"tat "i *id, a gasketagainst the face of the.femite pun. irtiie may be 3 "*iul;;; on thesealing :urangement all being'coveredby BS 2779.

The first variation is a Mare paraller with Bonded Gasket seal.In this case_ a composite washer, "i"uffy metal and elastomer, isused to. seal againit the face or ttrJ remdre port. A machinedtaper directly behind the mare thread c"nt is trr" gast"t.-----

one variation is the Female paralrel. This type seals against theface of the female port metal-to-metal oi *itr, u gurt"tl---"- "

The third variation is the Female paralel Gauge. A gasket, meta]or fibre, is used inside the female pon uguinrt a flat surface. Thelating palejgTpgrynt exerts a load "fth. t;k;;";.li;;;.co.nnection. BS 1780 (19g5) is an additionuf ip".in;;r.;"f";this type.

i)

ii)

iii)

There are a number of different threads use for hydraulic applications some of the moreusual types are:-

American Standard pipe Thread (NpT)

American Standard Unified Thread

rso 7/1

rso228/r

t o /

BSP

BSPT

DIN

h JIS

i BSPP

9.1.2 Pressure Rating

It can be stated with confidence that Swagelok fittings are all rated to the maximumworking pressure of standard tubing. In their literature they state that Swagelok fittingsprovide a leak proof seal on all tubing connections. The onus is, however, on theindividual to ensure that he selects the correctly rated fitting for the job in hand.

9.2 The Swagelok System

These fittings are comprised of four precision-made components, all manufactured tovery stringent tolerances and under rigid quality conffol procedures. The consistencyand quality of these matched components is ttre reason that Swagelok can be soconfident in their being "fit for purpose". The four components are:-

The nutThe back femrleThe front femrleThe body

Special courses and training is provided by Swagelok on demand to teach the correctand safe use of their fittings. A selection of Swagelok fittings are shown in Figure

e

f

168

9.3 Advantages of Tube Fittings

The reasons for concentrating on these types of mechanical pipe fittings in this chapterare:-

Tube fittings are easier to install ttran threaded pipeLabour costs can tre significantly reducedW.ldirg,with the assoliated sp6cial procedures, is eliminatedNo specialist tools are required

Figure 9.1

r69

CHAPTER 10 ROV HOOK UP, PRE/POST DIVE CHECKS

f0.0 In t roduct ion

It is the intention of this chapter to outline the mobilisation of a typical ROV system anddiscuss the principles behind the pre and post dive routine.

As. $9 name implies the pre and post dive checks take place immediately before thevehicle is deployed and as soon as it arrives back on deck. It cannot beemphasisedenough how important a task the pre and post dives are. They form an integral part ofthe planned maintenance procedure in the fact that they identify any malfunclionimmediately and can therefore minimise any vehicle downtimb. For this reason it isimportant that a standard routine is laid down in the form of a check list that is madeavailable to all Rov personnel, especially newcomers to the system.

Becoming competent at carrying out a pre and post dive check is a skill that developsonly with practice. It is important to include every item on the list and a very imponantpoint is to be totally aware of the fact that the hydraulics have a limited running time inalr.

l 0 . l ROV Hook Up

ROV hook up basically refers to the mobilisation pro<;edure that takes place at thebeginning of the of the contract, the task usually takes between twelvs and twenty fourhours depending on the class of vehicle and the nature of the iob.

Mobilisation takes p!'rce initially in the base and will involve testing the system,carrying out a full inventory of spares and consumables and selecting a suitable crew tosuit the nature of the operation. Once this has been carried out the system will betransported to the vessel or installation by supply ship or helicopter depending on theclass of ROV being used.

The actual posit ioning of the conuol cabin, workshop, winch and crane requires acertain amount of liaison with the authorities on board as there are manv safetv factorsthat have to be taken into account.

Once in position the ROV team can start to connect up the appropriate cabling betweenthe relative units.

l 0 . t . l Deck Cab l i ng

Deck cable is atmoured, zone two rated cable that carries the necessary signals betweenthe control cabin, winch and wortshop. Typical exar.nples of these cables are asfol lows:-

a) Main power cable to supply the winch and crane power packs.

b) Domestic power supply to the workshop.

c) Cable to route power, control, video and optical fibre signals from the controlcabin to the winch fixed junction box.

d) If necessary any purge hoses between all the units.

e) Communication l ink between control cabin, winch nnd crane.

0 Vessel or r ig supply to the power distr ibution unit.

t71

During this procedure the cables will be routed in the safest r.nanner possible and once

"gui" Ef.r" iiuiron with the vessel or installation crew will be necessary'

The umbilical is also connected to the ROV during this procedure. During. the

"."rp"".iion ttre nOV is dir.onnr.t"d from the rlmbilibal, the loose conductors being

r"ru.!O to the winch which has a dedicated travelling container'

Once in location the conductors are feconnected, a task that can.be quite 1ime., ̂,-;;;;g depending on the system in use. The final stage in the operatton rs the

testing of the ,ytp. -unA

"nruring that ai1 the equipment i=n the contiol cabin is hooked

up colrectly.

Once the tests have been satisfactorily completed the control cabin, winch' workshop

and crane are weldeJ to ttre deck. ontompietion the welds are inspected and require to

be certified before the operations can proceed'

10.2 Pre and Post Dive Checks

Fisure 10.1 illustrates a typical pre and post dive check Iist for a Scorpio system' It can

;""# il;'h;;h*ktinciude the whole system and therefore any faults or defects can

be identifled immediatelY.

The list begins with integrity checks that ensure that the vehicle has not suffered any

physical damage o. ittui?nV equipment that is fitted to the vehicle has not worked loose'

These checks .nuv oiio riigfrify d.p"nding on what equipment is fitted to the ROV'

It can be seen that a generator is also included in the list. It may be the case that the

system is working "i " iftip that does.t''oi ttuu" a suitable source of power and therefore

the ROV .o-puny ii ;q;il"4 to supply a-generator. If this is the case then it is the

responsibility of the team to etlsure its safe operation'

once the integrity checks are cornplete it is safe to PoYel up the ROV. The

communication Oei*eenlne pitot iind deck officer is via haidwire comms with a

-i"-pt'one treadsei ur"JUyil. deck officer. The pilot will b:i.?:.o,l1g^the functions

from the control cabin whil.st the deck officer observing the vehicle ' An elltctent

method of communication is essential to ensure that the hydraulic power pack is not

*nning for too tong ,i period in air. Cood communication procedures takes time to

Oeuitofi, the basic ititis of which are discussed in Chapter 14.

During the dive checks it is the responsibility of the deck officer to ensure that the

p*.du.. does not endanger gy petsonnel who may be near by'. Jley ha.vg the right to

intercept anyone *ho irr"lir"el tir be pufting themselves or rhe vehicle at risk.

172

SCORPIO PRE AND POST DIVE CHECK LISTPost Dive No: Date

Pre Dive No: Dare

Submersible:

Post Vehicle Integrity Checks Preframe mee trom damase

cables & connectors secure

Pod suaps,caps & Plugs OK

KELLUM & Pennenr corrcct

Fixed buoyancy & Ballast OK

Thruster & props correct

Manipulator secure & correct

Cable cutter secure & correct

Pan & Tilt & carncra correct

on Lens cover - off

Lights secure

Sonar correct, comp full

Hyd. Term Securc & 80% full

Hyd. Fi l l Vv & Drain Plug OK

Hyd. motor securc

Hyd. Conps (x27) 807, full

Umb. Terrn. OK & Comp 807o

TCU oi l ind ful l . & cao securc

TCU Vv closed & cappcdHCU oi l ind. ful l , cap secure

Optics J/B comp diaphm full

Xenon flasher secure

Emergency pinger secure

off Sti l l camera & f lash sccure on

Sonardyne transrxrndcr OK

Ancillary eqpt. litted & secure

BALL-AST ADDITIONALFITTED kg BUOYANCY kg

10.3 Dive Logs

Post JENERATORCHECKPre

Fuel level

Water level

Anti-freeze correct

off Oil ievel on

Generator running

Record running hrs

[)ost CMNECHECKS Pre

Oil level in reservoir

Hook & Shackles OK

Lifr wLe OK

Start cranefest all functions

)osI VEHICLEPOWERONPre

Power ON - OCU

Hyd. Wng Lt ON

Leak indicator test lts

Power ON - Veh

Figure 10 .1

The pre dive and post dive log sheets are retained by the company and contributetowards the records that are kept regardl_ng lfq vehicle's history Another important logis the ROV dive log. The dive log records att the events that oicur from the moment t[eRov leaves the deck until the moment it comes back again. By carrying out thisprocess it is possible to keep record of the total numbeiof hours thai th-e vehicle hasbeen operating as well as recording specific events that occur during the dive. Fig. 10 2illustrates a typical dive log.

)ost VEHICLEPOWERON PreFlux gate to SLAVED

Leak locator to OPR

Reset cable twist ind.

Depth ind. to zero

Auto depth to MAN

Auto hdg to MAN

Veh lts check

Video system check

Sonar svstem check

Power ON - HYD.

Check HYD Dressure

HYD temp(100F max)

Thrusters functions OK

Pan & Tilt OK

Manipulator OK

Tools function OK

HYD - OFF

HDG - OK with ship?

Climb/dive rate ind - 0

Pitch ind veh atirude

Ancillary eqpt check

Emrgy Pinger test OK

off Xenon flasher tn

Check RCU

Post WINCHCHECKS he

Oil level in reservoir

Reset footage ctr

Brake operation

Buoy'cy floats ready

Comms working

Start winch

Test all functions

| /-')

SUBMERSIBLE DIVE LOGSheet of

DIVENO: DATE: SUBMERSIBLE SHIP/P[-ATFORM

CHARTER: JOB NO.: SEASTATE WIND:

OPERATIONTEAM

Ops Controllcr I

LOCATION: LAT.:

IONG:

Surface Officer

Pilot

DIVETASK:

EXTRA EQI.IIPMENT FTTTED:

Observer

Winch

aran"

BOTTOM CONDITIONS:

)eck \rlDEorAI,E No.: I utve ouRmoN'

TimeVideocounter

Evenl

Figure 10.2

CHAPTER 11 ELECTRICAL MAINTENANCE.

l l .0 In t roduct ion

A planned maintenance procedure (PPM) is, in the long term a cost effective way ofensuring the efficient operation of the whole system. tT ppV were not in place thenbreakdown would eventually occur and lead totime consuming remedial riaintenanceduring which the vehicle would be on DOWN TIME. Down Time refers ro the timethat the system is eff-ectively off hire due to breakdown.

Adhering to 3 PP{ is the respon_sibility of all ROV personnel and all pracricesshould be suitably logged. .A well organised fogging procedure will reflect the systemsoverall perfor_ma1ce and will, in certaln situatioiJ aid

^the technician in locating fiults.

Maintaining.the log.is normally the responsibility of the Sub Engineer as he forkssolely.with that particularsystem as opposed to certain personne'i who are contractorsand will constantly be moving between different systems. The Sub Engineer wiilensure.that the log.s are kept up to date and compil-e any 'handover'doiumentation

thatis required to be given to the new team on cre*^change.

A certain amount of time may be dedicated each day to carrying the routinemaintenance. It is the intention of this chapter to outline the valious electricalmaintenance tasks that nray be carried out as part of the maintelrance procedure.

l l . l Cables, Connectors and penetrators

As- a.general rule the vehicle electronics tends to be a very reliable part of the system.All the circuits are housed in watertight pressure vessels and requirb little main"tenance.However the connectors and cables that-interlink the various pressure vessels areexposed to the harsh environnlent and ere susceptible to danrage and wear. For thisIeasg.lt it is imperative that the technician be fully awilre of the"correcr methods ofhandling and maintaining such devices.

l l . l . l Connecto l .s and Penetrators

Connectors and penetrators fbrm the interf ace between the internal electronics of theROV and the external cabling interconnects the various pressure vessels. The efficientoperation of these devices depe.nds on their ability to preuent water ingress to thecurrent canying conductors. Figure 11.0 illustraies a-typical connecto-r and penetratorunrt.

Penetrator Lockinq Sleeve

Contacts

Figure 11.0

Locking Sleeve

Conductors

175

11 .1 .1 .1 Pene t ra to rs

The penetrator forms the interface between the intemal electronic circuitry and the

connector. Penetrators are normally manufactured from high quality stainless steel and

are bolted or screwed into the actual pressure vessel. The seal between the two mating

faces is created by a rubber'O' Ring and it is the degree of integrity of this 'O'Ring

that prevents water ingress to the pressure vessel.

The number of internal concluctors and therefore contacts can vary between one and

anything up to seventy depending on the requirements of the interconnection. The

,onturtr"u." normally gold phtedto ensure i ttigtt degree of electrical conductivity.. All

conductors and contids are chemically bonded-into a synthetic rubber matrix which

offers a high degree of insulation and resistance to watel ingress.

penetrators and connectors are manufactured in either male or female configuration and

a list of the many available types are included in the appendices of this handbook.

l l . l . l .2 Connectors

Connectors ere directly attached to the cable and have internal conductors and contactsthat are bonded in the .sa,rle nlan.er as in penetrators. The nray have a locking sleeve

that adds to rhe rigidity of the unit. The niain purpose of the locking sleeve however is

ro prevenr the con"necrbr being accidentally pulledout of the.penetrator during. .opirations. It is important to-realise that ih6 sealing_properties are not created by thei<icking sleeve and excessive over tightening will only lead to damage and eventualbreakdown of the unit.

t76

l l . l .2 Theory of Operation

$Su1e I 1. 1 illustrates the principle of operation of a single pin connector mating with afemale penetrator.

Synthetic rubber

F i g u r e l l . l

The diagram illustrates a typical connector / penetrator configuration. It can be seen thatthere is a tapered shoulder located at the base of the contact.-This forms part of theconnector synthetic body and it can be seen that when the connector and penetrator ismated then a seal is created along the face of the shoulder. It follows thai as the vehicleincreases in depth then the surrounding water pressure will increase. This has theeffect offorcing the rubber sealing facEs together and thus, increasing the sealingeffect. It is imperatjve therefore that the integrity of the sealing facesls maintainEd at alltimes as any breakdown will result in waterineiess.

Internal conductor

'O'r ing

Bulkhead

Male connector

177

11.1.2.3 'O ' Ring Seals

O Rings operate on n similar principlemechanical seal which is illustrated in

and penetrators. They form ato the connectorsf i gu re 11 .2

4

Waterpressure

+

=+

Air insidevessel

Air insidevessel

Un-distorted 'O'r ing

a). Nature of 'O' ring at shallow depth

Waterpressure----+>

+

+b). Nature of 'O'rirtg at depth

Figure l l .2

It can be seen that as the external pressure increases the O Ring becomes mis shapenand is forced into the gap between the two surfaces. It follows therefore that a greaterseal exists when the vehicle is at greater depths, however when working in shallowdepths water ingress may occur if the two faces are not firmly bolted together.

178

11.1.3 Maintenance of connectors, Penetrators and 'o ' Rings.

The efficient_operation of sub sea connectors is totally dependent on how well they aremaintained. It cannot be emphasised enough how important it is that the correctmethods are used when carrying out connector / penerator maintenance as failure to doso may result in many hours of unnecessary breakdown.

l f .1 .3.1 Connectors and Penetrators

Whenever a connector and penetrator are unmated the following procedure should befollowed.

a) Inspection of contacts.Electrical contacts are susceptible to corrosion . A defect of this naturewould indicate that there has been a possible ingress of water through afaulty or improperly mated connectoi. Contacts may also become iris-aligned due to the connector being 'forced'during the mating process.Contacts should also be inspectedfor evidence o-f 'arcing'. eriingoccurs when the contact is improperly mated in the female recepttcle,this gives rise to the current jumping'across the gap and causing thecontact to burn.

b) lnspect ion of synthet ic rubber .The rubber should be inspected for evidence of water ingress. Any signof nloisture on the rubber surface is unacceptable and the problemshould be addressed imrnediately. The possible causes of water ingressare inrproper mating of the connector and penetrator, rubberbeconring mis-shapen due to over tightening of the locking sleeve and,in extteme cases the rubber becoming cracked or perished. In exffemecases of water lngress an electro-chemical reaction may take placeresulting in a deposit fomring around the sealing face.s.

c) O Ring Seat .Connectors that nrake use of an O Ring to create the seal require the ORing to be thoroughly inspected whenbver the unit is un-mated. The ORing should be in-spected for obvious signs of damage, lack of integrityand perishing. It is not uncommon for an O Ring tobe mislaid and-theunit reassembled without the O Ring being in place. For this reason it isimperative that the technician checks that it is Correctly in position beforeassernbly.

1I .1 .3.2. Assembly Procedure

Once the above inspection has been carried out the following procedure should beundertaken when assembling the connector and penetrator.

a) The contacts and sealing faces should be cleaned with a suitableelectrical solvent cleaner in order that all traces of dirt are removed. ItTay b9 ne^cessary to use Q Tips in order ro remove any traces of dinfronr the o Ring groove. on some vessels or installatibns there mav be asource of compressed air available which can assist in the cleaninebfthe connector.

179i

b) Once the contacts, connector and peneffatol are clean it is necessaryro lightly grease rhe connecror. It is normal practice p apply a thinfild ofSiticon Grease to the maring parts in order to providelubrication. If this was not carried out then the mating parts wouldbecome dry and difficult to un-mate. The excessive force thatwould have to be applied to un-mate them would lead to possibledamage or distortion of the unit.

c) The connectol should be mated to the peneffator, taking great care asto align the two mating units correctly. Most connectors have a locatinglug tliat prevents any riisalignment iating pla9e.- Som.e connectors andpenetrators are manufacture-d with one pin, called a.polarising pin, ofbiffe.ent size which assists in correct location. In this situation great caremust be taken as to correctly align them. Figure I 1.3 illustratesconnectors of this nature.

Polarizing pin

Flange fbr captivatinglockine Sleeve

/ way connector 12 way connector

Figure 11 .3

/@ o\o o o

o @

o@o@o@ o o @

o @ @

180

d) . When adjus.ting the locking sleeve great care must be taken to prevent overtightening. If this occurs then the connector is liable to warp thus'destroying thesealing properties. It.is therefore only necessary to hand tighten the lockiig sleeveand no attempt should be- m1{g to use spanners or sffap wren*ches. Occasiona'ily it maybe necessary to use a tool of this nature to undo a connector locking sleeve. This isbecause the unit may have been subject to extreme pressure and thil has had the effectof tightening the connector. It may also be the case that the connector is somewhatinaccessible to the hand an a tool is required to release the locking sleeve.

f 1 . f . 3 .3 . Greas ing

It is important to fully appreciate the reason behind applying Silicone Grease to sub-seaconnectors. As previously stated it is used purely as a lubricant and does not create theseal. There are many misconceptions that exist ttnoughout the industry, some claimingthat if a large quantity of grease is applied then the grJater is the sealing effect of the c

"

Excessive grease allowspath for water intrusiorr

II

t

Grease

Figure I l .4

Figure 1 1.4 illustrates the effect of over greasing, in this situation the glease preventsthe connector and p€neffator from matinf coneclly. The grease actualiy allows a pathfor water,that may be under pressure, tolccess the conta6ts.

l l .2 Sub-Sea Cables

Sub-sea cables are especially designed to withstand excessively high pressures towhich.they are. subjected to in their working environment. They ari manufactured froma resilient synthetic rubber that offers a higli degree of protection and electricalinsulation to the conductors within. Sub-iea cibles contain varying numbers ofconductors depending o.n the specific task. It must be stated howeier that if they do notfall into a structured maintenance procedure then they are very susceptible to faiiure andconsequent breakdown of the system.

t

1 8 1

F

l l .2 . l Poss ib le Cable Defects

The following defects are likely to occur without regular maintenance taking place.

a) Breakdown of outer sheath ing.During operations the cables are constantly exposed to drag caused by themovement of the vehicle through the water. If they are not properly securedthen they become susceptible to wear. In extreme circumstances cables maybecome snagged on a manipulator or even sucked into a thruster. Toovercome thli problem it is-important to ensure that all cables are securelyfastened with Ty- Raps to the vehicle frame.In some extremb cases the insulation may perish causing the rubber to crack andexpose the conductors within. For this reason it is important to inspect allcables on a regular basis.

b) Breakdown of internal conductors.Extreme cable movement can also lead to the conductors within the cablebreaking down, particularly near the connectors which tends to be the mostsensitive point. Once again it is possible to detect these occurrences by regulartesting of the cable.

11.2.2 Test ing Sub Sea Cables

In order to monitor the integrity of the internal conductors we can measure theinsulation between each one using a MEGGER METER. This has the effect ofmeasuring the resistance between each conductor whilst connecting a high. voltage tothe condultors. (see chapter 7 Use of Test Equipment). Ideally the insulation should beinfinite between conductors, however ingress of moisture combined with eitherconnector or conductor damage can lead to an insulation breakdown that will requirerepair to be canied out.NOTE: WHENEVER AN INSLLATION TEST IS CARRIED OUT THE CABLESHOULD ALWAYS BE DISCON}{ECTED FROM THE PRESSURE VESSELS ORANY ELECTRICAL CIRCUITRY.

11 .3 Ma in tenance o f Umb i l i ca l s

Umbilicals are susceptible to both fatigue and overloading which can eventually lead tothe breakdown of the internal conductors. These factors may arise from poor pilotingtechniques which may lead to the umbilical becoming twisted or kinked. Damage mayalso occur due to mismanagement of the umbilical during the launch and recoveryprocess. When the vehicle is passing through the splash zone the umbilical may tend toisnatch'due to there being insufficient 'slack' available whilst latching and un-latching.

All these factors can result in the R.O.V. team having to carry out what is known as aRETERMINATION. Retennination can be a lengthy and tedious process, however itis important to follow the correct procedure in order to minimise the vehicle 'down

t ime' .The following sections outline the process for the re-termination of a typical armoured

umbilical.

182

11 .4 . Cab le Sp l i c i ng

{ stlylqiolmay often arise in which a sub-sea cable requires repair to be carried out inthe field. This may be due to insulation break down be^tween the internal conductors orin extreme cases, the severing of the cable by a thruster. In either case the cable can bere-joinedusing.either th.e quick splice method or the long splice method. Normallyspare cables will be available and the damaged one can be instantly replaced with aserviceable one. In this case time will allow the damaged cable tobe iepaired using thelong splice method. However it may be the case that the repair requires'immediateattention, in this case the quick splice method would be used.

l l .4 . l Long Spl ice

The long sp-lice method makes use of specially manufacturecl potting compounds toform arigid, water tight joint. It is the setting time of such compotinds tliat restrict this-?llod long..I periods of maintenance. Figuie 1 1.5. illustrares the procedure of cablesplicing by this merhod.

ll.4a. Staggering ofjoints

Sub-sea cable

ll.4b Pottedjoint

Soldered ioint

183

It can be seerr that the cores of the cable are staggered where they are joined in order tomainrain unifonn thickness. Staggering also pievents the soldered joints from cominginto contact with one another. Each soldered joint is normally covered with 'heat

shrink'to add to the insulating properties. Once this stage has been completed the cablecores and the outside insulatiod is cleaned with a degreasing agent. The cable is thenmounted in a mould into which the potting compound is poured.

There is a wide variety of potting compounds available, each having slightly differentproperties. The main difference-between the compounds is the specific depth rating and^the

guaranteed life span of the compound. Once the compound has been poured intothe mould the joint requires to be left to set for approximately [l to 10 hours.

L1.4.2 Shor t Spl ice

The initialjoining together of the conductors is the sarne for the short splice as it is forthe long splice. The only dit-ference with this method is the fact that no form of pottingcompound is used. Instead an insulating rubber tape known as self amalgamating tapeis used. When the tape is stretched it actually bonds with itself to form a strongwaterproof joint. The tape is wound around the conductors, starting from the centre ofthe conductors and working outwards. Between each layer of tape it is commonpractice to coat each layer with a resin that sets and fonns an electrically insulating andwaterproof coating over the tilpe.

l l . 5 Sub Sea lan rps

The quali ty of Sub sea l ighting is crucial to al l ROV operi i t ions, the principles of thissubject have been discussed in chapter 16. For this renson a correct ntaintenanceprocedure is essenti l l i f this clual i ty is to be upheld.

The most comlnon problem that occurs with sub sea lighting is the burning out of theactual filament. There are a variety of lanrps available to the indusffy, the maindifference being the power rating. They are mounted in a housing which offersprotection and a watet'tight environmerrt in which to operate. It follows therefore thatthe housing contains an 'o'ring seal which requires to be inspec:ted whenever a lamp ismaintained.

Lamps may burn out due to one or nrore of the following retlsorts.

a) Water ingress to the lanrp connector.

b) Breakdown of the 'o'ring seal allowing the actual lamp to becomeexposed to sea water.

c) Mis handling of the larnp during instal lat ion.

d) Being operated for too long a period in air.

If water ingress takes place within the lanrp connector then the connector should beundone and thoroughly inspected for darrrage. If necessary the cable should bereplaced with a serviceable one.

If the 'o'ring seal breaks down then it to should be replaced, if water does make contactwith the lamp connectors then a short circuit is likely to occur as well as corrosion andbreakdown of the actual contacts.

184

It is imperative that the lamps are not touched during installation as moisture from theskin can lead to 'hot spots'on the bulbs surface that can cause the glass to crack. Forthis reason the bulbs are supplied surrounded by a piece of foam that should be used tohold the lamp during installation.

It is important to realise that sub sea bulbs require to be water cooled. Should they berun in air for too long then they may overheat and bum out. During dive checkstherefore the lamps should only be operated for a few seconds.

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185

CHAPTER 12 MECHANICAL MAINTENANCE

12.0 Introduction

Throughout this handbook attention has been constantly drawn to the necessity for aplannel maintenance procedure. So far we have discussed maintenance as regard to theblectrical side of the RO, it is now the intention to discuss the routine maintenanceprocedures that should be carried out on the mechanical units of the ROV. It followsiherefore that this chapter will concentrate largely on the maintenance of hydraulicsystems, the basic principles of which have been covered in Chapter 8.

Maintenance of hydraulic systems is carried out on the basis of how long the systemhas been operating, this information may be obtained from the Sub Engineers log bookor an 'hours run'meter that may be incorporated into the control console.

Each unit will have a specified period of time that it can operate for, after which it willbe required to be removed from the system and serviced. As a general rule.the unitsthat require to be serviced will be swapped for a serviceable one. The actual servicingmay.require specialist test equipment and will therefore be sent ashore to a suitableservicing engineer. However, it is the responsibility of the ROV teant to ensure that theday to day running of the system is maintained and that if any units are to be removed,they are done so in the correct mallner.

l2 . l Hydraul ic Oi l Level

The function of hydraulic oil is initially to transfer energy throughout the system andthus give rise to work being done by the actuators. [t also provides lubrication andcooling to certain moving components. It is imperative therefore that the fluid bemaintained at alt optirrum level at all times otherwise serious detrimental effects couldtake place throughout the systenr.

l2 . l . l Loss Of Pressure

The toral energy that is present in the hydraulic fluid is nrade up of potential energy andkinetic energy. The potential energy relates directly to the system pressure and itfollows thatl? the opiimum oil level decreases due to leakage then the energy stored inthe fluid will be lost. This will become evident in the fact that system power will bereduced and the pilot may experience difficulty in controlling the vehicle.

L2.1.2 Lack Of Lubr icat ion

In extreme situations the optimum oil level may be reduced to such an extent thatinsufficient lubrication takes place. Situations may arise where certain high speedcomponents may seize. This may be the case with the pump which containscomponents such as pistons, gear wheels and bearings. Insufficient lubrication ofthese components could lead to excessive heat being generated and eventual seizurethus resulting in system failure.

12.1.3 Sea Water Ingress

Should the situation arise where virtually all the systems oil is lost then this will resultin the ingress of sea water. If this should occur it will becorne necessary to flush thewhole system out with fresh oil.

The ingress of sea water is caused by a positive pressLlre existing outside the systemwith respect to the.inside, if this should occur it can lead to such problems as corrosionwithin the system.

187

Any ingress of water to the system can be detected by draining off a sample of oil fromthe lowest point , the oil will have emulsified and will have a'milky' appearance.

12.1.4 Determin ing The Oi l Level

As a general rule the oil level is monitored via the systems electronics and is displayedat the surface unit. A transducer is mounted on the system which produces an electricalsignal proportional to the oil level, this is passed via the system telemetry to the surface.Should the oil fall below a certain level an alarm will be activated indicating to theoperator that a leak nray be present. Normally there will be two alarms, the first beingactivated at 660/o of the total oil level. This alarm may be over-ridden and will allow theoperators time to rec:over the vehicle before complete oil loss occurs. The second alarmwill be set to activate at a much lower value, for exarnple 337o, this alarm cannot beover-ridden and will cause the system to completely shut down. The oil level can alsobe monitored when the vehicle is on deck by noting the position of the compensators.

12.1.5 Compensation

As a general rule the ROV has several junction boxes which, when subject to extremepressure would probably implode. This is overcome by filling each box withpressurised static hydraulic oil. The internal oil pressure is nraintained by a piston thatis exposed to the external sea water pressure. The piston is directly coupled to the oilsystem via a spring that maintains the oil pressure at 3 to 5 PSI above the external seawater pressure. It follows that the pressure inside the junction box is positive withrespect to the external sea water pressure, thus preventing the inrplosion of the junctionbox.

This method of conrpensation is applied to the main hydraulic systenr. Should an oilleak occur the internal positive pressure will give rise to the oil being forced out asoppose to sea watel being allowed in. As the oil level drops the alarnrs will be activatedand the operators can recover the vehicle, hopefully before iiny sea water enters thesystem.

Whilst the vehicle is on deck it is possible to nronitor the oil level by noting the positionof the compensator piston. It is conrnron practice to nronitor the oil levels throughoutthe systenr in this manner during the pre and post dive checks. (see Chapter 10).

12.1.6 Oi l F i l l ing

The frequency of which the system requires filling with oil depends upon the leakagefactor of the various hydraulic units. However the method for filling the systemremains common for all ROVs. It is common practice to fill the system at the lowestpoint in order to minimise the trapping of air. The system is filled from a pressurisedcontainer which has a dedicated hydraulic fitting to couple to the oil inlet.Before connecting it is vital to ensure that the filler point is thoroughly clean in order tominimise the ingress of dirt into the systenr. Many systems nrake use of 'quick fit'connectors which simply snap on to the oil inlet. This minimises the use of spannersand consequent ly s lves t ime.

12.1.7 Ai r B leeding

Whenever the system is filled with oil it is necessary to bleed air out of the system.This is normally done from the highest point in the system. However it may be thecase that there are various bleed points around the systern located in the appropriatepositions. The bleed point rnay consist of a cap that when slackened allows the trappedair to escape. The bleed point should remain in this state until oil flows freely from thefitting. It may be necessary to bleed the system on a regular basis especially if a majoroil change or refit has taken place.

188

12.1.8 Oi l F i l ter Change

Oil filters should be changed whenever an oil change is carried out. Most filters requirethe element to be changed and therefore a spare should always be kept in stock. Th^eoperators should never be tempted to run the system without a filter element as thiscould lead to major breakdown due to contamination of the maior units. Beforechanging the filter or any unit for that matter it is important ro drain the system oil as theposlt lve pressure would result in a large loss of oi l .

12.1.9 Die lect r ic Oi l

As previously mentioned all junction boxes are oil filled, however the junction box mayhouse conductors or transfomrers that would not be compatible with siandard hydrauliioil. In this case it is necessary to use an oil that is inert. bielectric oil has high'insulating properties and is used in such enclosures. This oil is sometimes cilledtransformer oil and is c^ompensated in the usual manner. It is important that theinsulation properties of the oil is constantly monitored, this can be done by draining asample of the oil front the enclosure and checking for signs of water. In the case ofthetlectric motor the insulation is monitored elecrricilly, in ihis case a resistance reading isdisplayed at the surface unit and gives an indication to rhe integrity of the dielectric dil.

12,2 Component rvear

It is common practice to. have specialised engineers carry our the servicing of individualhydraulic units. The.task may iequire the use of specialist ecluipment and"skills thatdoes not fall within the requirements of the Rov personnel.'However, a basicunderstandilg q{ which conrponents are susceptib]e to wear could help the operator inthe diagnosis of basic faults. We will now coirsider rhe conrponents of the basichydraulic units that are prone to wear.

12 .2 .1 Hydrau l i c pumps and mo to rs

Hydraulic pqnJp.s itncl ntotors contain either gears,vanes or pistons which are requiredto.operate at high speeds. Irt each case the principle of operation relies on finetolerances between the chanrber wall and the moving component, any increase in thesetolerances can lead to loss of system pressure in thelase of pumps and reduced powerand excessive 'case' pressure in the case of motors. Pumps and motors are designed in;uc.!. a way.that a certain amount of oil is allowed passed ihe pistons, vanes or g"utr tofacilitate lubrication of.the bearings and shaft seals. For this ieason it is possibie tomeasure the output of the case drain over an interval of tinte, and, by consulting themanufacturers data, de,tem-Line the integrity of the internal conrponents. For eximple ifthe oil is in excess of the s.pecifications it would indicate that the piston rings were womthereby allowing excess oil into the case chamber.

Another cgrymox problem that can arise is wearing of the shaft seals. This is evidentby a visual check of the system whilst on deck. SJals have a specified worting life asstated by the manufacturer, however this can be drastically redirced if the systeirs oilbecomes contaminated. If any seals_are ever removed they should always be inspectedfor damage and any signs of break down.

r89

L2.2.2 Hydraul ic va lves

Valves generally contain minute components that are responsible for the flow rate and

dr""6;;nydrautic oil. For this reason their operation is dependent on 'ht - ,

ileanliness of the sysr; oil and the environmeni in which they have been serviced.

Typical faults that iould arise from blockages could be:-

a) Blo,cked relief valve leading to system operating at reducedpressure.

b) Blockage in solenoid valve leading to malfunction of manipulatorflnction.

c) Blockage in servo valve leading to either complete loss of oil flow to

thrusteirlotor or reduction in running speed'

12 .2 .3 Hydrau l i c rams

The operation of hyclraulic rants depends totally on th€ integrity. of the internal and

external seals. Any breakdown in tire tolerances can lead to leakage across the piston

and therefore reduction in operating perfgmrance of the driven unit. For example the

;;i;tp.;"i or tn. r-nanipulatoi may be reduced resulting in it being 'sluggish' in

ntovement.

As with all external seals excessive leakage is easily detected by visual inspection

during pre and post dive checks.

190

12.2.4 Fault diagnostics

ligure 110. illustrates a fault dilgn-osis procedure for a typical hydraulic system.Figure (12.0 illustrates thefault fi-nding procedure for a sitiration f;;;;y;rJ;irtat isgenerati ng excessive noise).

REMEDIES

A Any or ail of the followino:. Reptace di r ty t i l lers. Wash slranels in so/yenl compa/ib/e ,///, s/s,le/v //a/iy'. Clean ctogged inlet line

. Clean reservoi( b(eathe( ventr Qhange sys\em !\uid. Change to proper pump drive motor speed. Overhaul or replace supercharge pump. unecx ilutd temoeratute

B Any or a[ of the foilowino.'T ighten leaky in let coniect ions. Fill reservoir to proper level

- with few exceptions, arr return rines shourd be berow fluid rever in the reservoir.. Bleed air from system. Replace pump shaft seal

Also replace shaft if worn at seal journal.

C All of the tollowino:. At ign uni t. Check condition of seals, bearings, and coupling

O . lnstall and adjust pressure gauge

E . Overhaul or replace defective part(s)

Figure l2.l(a)

Selting too low orloo close to another

l 9 l

Figure 12.l(b) i l lustrates the procedure for a system generating excessive heat.

REMEOIES

Any or a l l of the fo l lowing:. Replace di r ty f i l ters. Clean c logged in let l ine. Clean reservoir breather vent. Change system f lu id. Change to proper pump dr ive motor speed. Overhaul or replace supercharge pump

Any or all of the following:. T ighten leaky in let connect ions. Fill reservoir to proper level

With tew exceptions, all return lines should be belowfluid level in the reservoir.

. Bleed air trom system

. Replace pump shatl sealAlso replace shaft il worn at seal journal.

All of the lollowing:. Al ign uni t. Check condition of seals, bearings, and coupling. Locate and correcl mechanical binding. Check for work load in excess ot circuit design

. Install and adiusl pressure gaugeKeep al least 125 PSI difference between valve settings

e Overhaul or replace defective part(s)

. Change t i l ters

. Check system fluid viscosity. Change if necessary.

. Fill reservoir to proper level

. Clean cooler and/or cooler strainer

. Replace cooler conttol valve

. Repair or replace cooler

Figure 12.1(b)

U

tr

F

Remedy: See columnD

Remedy: See columnD

Faul ty f lu id cool ingsyslem

Worn pump, valve,molor , cy l inder orother component

t92

I

i

i

Figure 12.L(c) illustrates the procedure for a system operating with an incorrect flow.

D

E

F

Any or all o, the following:. Replace dirty filters. Clean clogged inlet tineo Clean reservoir breather vent. Fill reservoir to proper level. Overhaul or replace supercharge pump

. Tighten leaky inlet connections

. Bleed air trom system

. Check for damaged pump or pump drive

. Replace and align coupling

. Adiust parl

. Overhaul or replace parl

Any or all of th€ tollowing:. Check position of manually operated controls. Check electrical circuit on solenoid operated controls. Repair or replace pilot pressure pump

G o Reverse rotation

H . Replace with correct unit

Figure l2.l(c)

Relief or unloadingvalve set loo low

RPM of pump dr ivemolor lncorrecl

Pump drive motorturning in wrongdirecl ion

Ent i re f low passingover relief valve

Worn pump, valve,molor, cylinder, or

REMEOIES

193

Figure 12.1(d) illustrates a system operating at an incorrect pressure.

REMEDIES

A . Replace dirty filters and syslem tluid

B . Tighten leaky connectionsFill reservoir to proper level and bleed air lrom system

C . Check gas valve for leakage. Charge to correcl ptessure. Overhaul if defective

D . Adjust part

E . Overhaul or replace part

Figure 12.1(d)

194

Remedy: See Charll l l , column A Remedy: See Chart

l l l . column A and B

Pressure reducing,re l ief or unloadingvalve worn ordamaged

Accumulalor defec-tive or has loslcharge

Oamaged pump,motof or cy l inder

12.2.5 Summary

It can be said therefore that the efficient operation of the hydraulics is dependent on thecleanliness of work environment. Should any maintenunrL be required the ROV shouldbe hosed down with fresh water and the unitin question removed'from th; vehicle andtaken to a clean, a_v_.worfntace. A high standaril of cleanliness should at*ays Uemaintained when filling rhe sysrem with oil so as to prevent ingress of dirt.

'- -

12.3 Planned maintenance

EYtry system should hulg I planned maintenance procedure that should be correctlyadhered to at all times. This would normally be kipt in log r".,n "i""-n"ppy oiir.The principle of the PMP is that it records the running timJof all the com6ffi;.Having this information enables one to ensure that th6 relevant unit is serviced afier theappropriate number of running hours. The running time is determined by themanufacturer and may have sfight variation depenling on the company.

'Figure l2.l

illustrates a typical log for the running hours of the mfin nyorartic syiiem o? a iypicarROV.

I\,,IASTER LOG HPU I,4OTOR HPU PUMP PORTTHRUSTER STBD.THRUSTER FWD.THRUSTER AFTTHRUSTER VERT.THRUSTEBDATE HOURS S/No HOUBS S/No HOURS S/No. HOURS S/No- HOURS S/No. HOURS S/No. HOURS S/No. HOUBS

Figure 12.2

195

Figure 12.2. illustrares a typical fault docket which provide.s.some detail of the actual*Iintenunce carried out. Documentation of this nature enables the operator to locatereoccurring faults more easily. For example certain units may break doYl more often

than normil, by consulting the docket it may be possible to_detect a nend in thesymptoms. This could indicate a fault som6where else in the system which can bea-ddr^essed and thereby minimise the overall repair maintenance time.The fault docket alsogives indication as to tha spares content on the ROV sy^stem. Thiswould normally have

-a separate log, but in this case it is possible to cross reference

between logs.

One of the main advantages of this system is that it makes maintenance easier for thevarious crews who may

-work with the system. It follows that it is in.everybody's

interest to follow the maintenance procedure as it minimises repair maintenance that canDrove costlv to the ROV cornpanies.

FAUTT D0CKET Ho.) ATE DIYE Ho . I l J08

] ATTGORY

:AUTT SYI1PTOTIS

tEt lovED FR0l" l SYSTIH 8qIEP A tR Y0RK c ̂ EE!!9_q!IJ

;P ARES USED; t 6nED ID ATE

lAcK l t l sYsTEl ' l

Figure 12.3

196

:AULT DoCKET Ho .D ATE DIYE t lo. I |JOB

C ATEGORY

FAULT SYHPTOHS I

i ixoveo rnoH svsrrx ev lREPATR Y0RK cARRtED ou r l

J P A R E S U S E D

; l ' t tED I io ̂ t 'tAcK tH sYSTEf4

iAULT DOCKET HoD ATE DtvE t lo. I lJoB

: ATEGORY

:AULT SYF{PTOI IS I

TEPAIR VORK CARRIED OUTI

SP ARES USEDS IGI iED IDATEBACK IH SYSTEH

CHAPTER 13 EMERGENCY PROCEDURES

13.0.0

The nature of ROV operations is such that despite careful preparation and adherenceto proven operational procedures, situations arise that endanger the vehicle andrequire the crew to take emergency action. The aims of this chapter are to describecommon emergencies, to focus on the crucial considerations of navigation,communications, and buoyancy in pre-dive planning and finally to describe actionsthat should be taken by the crew once an emergency situation has arisen.

13.f.0 The following is a description of possible emergency situations;-

13.1.1

Support Ship Entanglement is perhaps the most common form of emergencysituation and often results in the complete loss of the ROV. This can arise where theposition of the vehicle relative to the ship is uncertain and the ROV surfaces close toa propeller or thruster, where the ROV entangles with the taut wire of the DP system,or where the relative positions have changed due to a navigation error and theumbilical has moved 'under'the support ship. The key factor in these incidents isoften poor communications between the ROV crew and the suppoft ship's master.

13.L.2

Structure Entanglement is also very common but usually results in ROV or diverassistance rather than the complete loss of the vehicle. This often occurs because thepilot becomes disorientated, the vehicle becomes 'snagged', on debris or a structuralcomponent such as a pile guide, or the vehicle loses power in precariouscircumstances, but may also occur if the support vessel moves position without theROV crew being infonned.

13.1.3

Guide Wire Entanglement is common within Drilling Support activities and canresult in the crushing of the ROV as the Blow Out Preventer (BOP) Stack is landed.This can happen, for example, in remote locations where the Drilling Supervisor mayonly allow a period of time for the crew to disentangle the ROV beforerecommencing drilling operations due to cost pressures, particularly if there are noother ROVs or Divers available to assist. The most common causes of this are Pilotdisorientation due to loss of visibility possibly as a result of disturbed sediments ordisplaced drilling fluids, and unexpected changes in current strength and direction.

13.I.4

Anchor Chain Entanglement occurs when surveying the anchor chains of Barges orSemi-Submersibles platforms. This is the result of the ROV losing orientation due todisturbed sediments as the chain is lifting, the vehicle then passing under the chain asit lowers trapping the vehicle or its umbilical. This situation is also likely to occurwhen laying umbilicals and pipelines as the vehicle monitors the touch down point. Itis very important, therefore, that these operations are carried out in acceptableweather conditions where there is not excessive 'heave' of the vessel under survey,and that the vehicle is positioned facing into the current wherever possible, so that itbenefits- from optimum visibility and the prospect of being canied-safely away fromthe work area by the current in the case of a system failure.

:

197

13.1.5

Bottom Debris Entanglement occurs when an unseen hazard such as mono-filament

nrtting f*" o. nyton-ffi, which tend. to be buoyant where..they. are not anchored' are

drawn into the vehicle.ittrruster, or when the vehicle umbilical is 'snagged'around

htg"; items of debris. The besr advice is to travel slowly.in the vicinity of,these

hazards and in the event of soft line being taken into the thruster cease or slowly

reverse the thruster onA uit.nlpt to pull th"e vehicle free using the umbilical winch'

13.2.0

The above mentioned incidents can largely be avoided by careful planning of each

;Fil;" ;ittr particutai atrention beirig paiO to; currenta and weather conditions,

navigation, ,o.n*uni*tiont, and the bioyalcy of the vehicle and its umbilical' This

secti6n explains the importance of each of these factors'

L3.2.L

It is crucial to have an accurate prediction of the weather conditions and ocean

currents for the nl"*in.ruto expected duration of each dive. These should be available

io, tt e pre-dive meerings so that the support vessel can be,posilio".d f9l,T:I]1YT

safety, ind the dive can be planned t4ing the currentt 3nq weather condrtrons rnto

ur.olnt. The pre-div. to..ting should bJattended by.the ROV crew, the ships master

u"O-u"V otfrer participating peisonnel, the plan:rrived at will be a result of the

;;;i11G;onhitionr, the"srirface ship's and RoVs operating paranreters and the

experience of the personnei.

13.2.2

Consideration of the support ship and the ROVs navigation s-vstems is crucial to the

ftunnlng of the dive beiiuse rheaccuraci, of differenisyste.ts vary_considerably.

The shiis posit ion rf detemrined by Global Posit ioning Satei l i te (GPS) may.be

accurate to within -5 -10 metres <lepending on the location and satel l i te posit ions,

*harau, radio systents such as Decca or Fulse 8 are nruch tllore acctlrate' nomlally

within 1 metre. The Hyclro-acoustic Posit ion Referencirrg sy.stenl ( l- lPR),. used to

poiir ion th; ROV relative ro the s.pport ship, wil l also vitr ' f in accuracy.depending

ii imari ly on rhe depth of the vehicie and the. type of transdttcer f i t ted (Pinger,

irunrpond.. o. r.rpbnder). This nieans that incertain circrtt . t lstances,.panicularly on

or close to the surf i tce, i t may be expedient to judge the relative. po.sit ion of the

vehicle, with respect ro the sirrface itrip, t,y eye oi by f eel and tl're known direction of

the umbil ical leading away tronr the ship. The accuracy of the navigation systems(including the vehicies Gyro or compasi) is also a key factor in avoiding . lintungf.t i , .nts during the'dive, as is prior knowledge-of the posit ion.of l ikely.hazards'

When"working arogrid srrucrures or guide basis i t i i also inrportant that the pi lot is

ful ly briefed, i lrcluding the orientatidn ancl the posit ion of identif ication nlarks and

features to enable hirt l to rtavigate conlpetel l t ly.

13.2.3

Communications between ROV crew menrbers and the vessels crew are another

important consideration when planning and executing a dive. There have been

numerous nrisunderstandings i ind ' lack-of communications' leading to the loss of

ROVs. For exantple the R6V may surfac:e near an operational ships thruster.or main

propeller unexpected by the u.sr. is crew, result ing ir i the ROV being 'sucked in' and

hesiroyea. Alternativeiy a supply boat nray come alongslde a platform as the ROV is

surfacine. because tne orisrrore installation Manager (0tn,1) has not been informed of

198

i )

ii)iii)

the diving operation underway. These circumstances seem all too obvious, buthappen all too frequently due to poor communications.

13.2.4

The buoyancy of a vehicle and its umbilical can also be a critical factor in avoidingentanglements and easing subsequent rescue attempts. The situation of having anROV positively buoyant (usually about 30lbs for a work size vehicle) may well besuitable for a pipeline survey job where the vehicle can reasonably be expected tosurface clear of the surface ship in the event of a system failure. It may however bemore appropriate to have a 'heavy'vehicle for deep water work so that in the event ofa system failure or parted umbilical, it will sink to the bottom where it can be foundby the rescue ROV or divers. Considering the buoyancy requirements of the vehicleprior to each job can, therefore, significantly ease any rescue that may be attemptedsubsequent to an entanglement or parted umbilical situation and needs to be given dueconsideration at the pre-dive planning stage.

13.3.0

The first time that an ROV operator experiences a vehicle entanglement situation canbe unnerving. It is important to remember that these situations occur commonly dueto the nature of the job and the difficulties encountered in navigating in poorvisibility, avoiding unknown obstacles, and accurately predicti-ng wEathir conditionsand ocean currents. Whilst this may be a new and unnerving experience for you itwill be familiar to your supervisor who will have seen numerous such incidentspreviously and will know that they usually have a successful outcome. There is nosubstitute for experience in these situations but this section will describe proceduresthat may be followed to ensure the best chance of a successful outcome.

13.3.1

The first thing that a Pilot must do in the case of entanglement is to inform hissupervisor. If appropriate action is taken early there will be a much greater chance ofa successful outcome, whereas uninformed attempts to rectify the situation willinvariably make it worse.

13.3.2

If the vehicle suffers a loss of power on the surface, the following actions should betaken:

i)

ii)iii)

13.3.3

Deploy suitable fenders or buoys over the side to minimise contact betweenthe vehicle and the surface platform.Use the umbilical cable winch to move the vehicle into the recovery position.Perform the usual recovery procedure.

If power is lost while the vehicle is submerged the following acrions should betaken:

Manoeuvre the surface platform where possible so that the vehicle will notcome up under the platform.Deploy suitable fenders or buoys.If the vehicle is not rising, use the umbilical winch to haul the vehicle towardsthe surface.

199

iv)

v)

13.3.4

ii)iii)iv)

v)vi)

If it is dark the emergency flasher will activate when the vehicle reaches the

surface. Use the um6iticat winch to move the vehicle into the recoveryposition.Perform the usual recovery procedure.

If the vehicle is on the surface and the umbilical has been severed the following

actions should be taken:

i) Deploy suitable fenders or buoys.iil -anoeuure the surface platform close to the vehicle'iii) Deploy a rescue boat and attach lines to the vehicle.iv) Haul the vehicle into the recovery position.v) Perform the usual recovery procedure.

13.3.5

If the vehicle has become entangled the following actions should be taken:

i) Replay the 'Black-box'video recorder and with the assistance of the cable' twiit indicator attempt to determine how the vehicle came to be entangled and

the lay of the umbilical.Determine the degree of entanglement using the video camera.Plan a route out of the entanglement.Loosen the umbilical by unwinding the umbilical winch, and attempt tomanoeuvre the vehicle out of the entanglement.If step iv) fails atrempt to manoeuvre tlie surface vehicle to free the vehicle.If steir v) fails attenrpt to pull the vehicle free using the umbilical cable winch.Be careful not to exieed the breaking strain of the cable and to allow for thebend radius and safe working load of the sheave wheel and recovery gear.

13.3.6

If the umbilical is severed while the vehicle is submerged the following actionsshould be taken:

i) Estimate whether the vehicle will surface, float mid-water or remain on the

bottom by calculating the resultant buoyancy of the. vehicle and its umbilical.ii) Infom'r the ship's malter and record the ROVs last known position on the

charts.iii) If the vehicle is likely to remain on the bottom arualrge for an ROV or diver to

attempt the rescue.iv) tf the vehicle surfaces' perform the recovery procedure previously described.v)' If the vehicle is likely tb be fteta mid water then the ocean culrents should be'

predicted and if avaiiable an acoustic transducer should be deployed from the

iurface ship to 'listen' for and locate the vehicle through. the activation of itsemergency 'Pinger'. The vehicle should be 'tracked'and-grappling hooksdeplo-yed across its path to attempt to hook the umb.ilical or vehicle.

vi) Ori hdoking the ROV recover to ihe surface, immediately attach a line orsurface buoy and perform the usual recovery procedures.

It is very important in the above situation to act quickly. as the ROV can drift awayrapidly decreasing the chances of locating ald rescuing it. Grappling hooks, chartsund oih"r relevanirescue equipment should be made ready and the crew briefedbefore the diving operation comn'lences.

200

i)ii)iii)iv)v)vi)

13.3.7

In circumstances where a rescue ROV or divers is required it is necessary to give theClient's Representative and the onshore Operations Manager at least the followinginformation:

Last known location.Circumstances and degree of entanglement.Depth of ROV.Background information and manoeuvres already attempted.Likelihood of the vehicle drifting in the ocean currenrs.Urgency of the rescue i.e. is the vehicle holding up other platform or drillingoperations?

Finally, remember proper planning can often prevent these situations from occurring,but they do still occur from time to time due to unforeseen circumstances. Keepcalm and follow the relevant emergency procedures issued by your company and youare likely to have a successful outcome. If however, the outcome is the l,oss of thevehicle, remember that it will be covered by insurance and that it is accepted withinthe industry that a number will be unavoidably lost due to the nature of the work.These situations are not usually career limiting and can be put down to experience.

'l

{

I{

201

CHAPTER 14 COMMUNICATIONS

1 4 . 0 . I n t r o d u c t i o n .

ROV personnel will be required to use communication systems at various stages of thework programne offshore. This chapter sets out to indicate the procedures used forboth radio and "hard wire" communications svstems.

l4 .L Hard Wi re Sys tems .

This is the terminology used to describe the deck to conffol room wire linecommunication system. The common configuration is a headset containing a speechactivated microphone all connected to a wandering lead which is connected to a deckmounted control box. This method of communication is used daily and all ROVpersonnel must be familiar with its use. The procedure adopted for speaking on a hardwire system is based on radio procedure but is less formal . For example the Proword"Over" is not used. Radio procedures and Proword are outlined later in the chapter.

14 .2 Rad io Commun ica t i ons

Radio communications may be required to communicate between:a. Deck and control room;b. Vessel to platform;c. Vessel to vessel;d. Vessel to shore.

There are a variety of different radio systenrs used for these and other purposesoffshore. It is not nec:essary to have an intimate knowledge of these systems but a briefresume, highlighting the points affecting the user will be helpfLrl.

14.3 Radi< l Conrmunicat ion Modes

Radio_comrnunications systens are designed to be either Sinrplex or Duplex. In aSimplex system it is only possible to transmit and receive at the same time. If one radioon the designated frecluency or channel is transmitting it is not possible for any otherradio to talk back to the transmitting station until the transmit button is released. This isnot the case in a Duplex system where the transmitter and receiver are on differentfrequencies which nraintains the transmitting station's ability to receive incomingsignals. Thus on this type of network another station can talk back to the transmittingstation even while he transnrits.

14.3.1 Radi< l Frequencies

For a variety of reasons radios use different working fiequencies. The commonfrequency bands and comments on there uses are outlined below.

a. High Frequency (HF). Used for long range communications world-wide. Suffers from interference and is particularly bad forcommunicating at night. Used for vessel to shore communicationswhen more advanced systems are unavailable. Commonly usesduplex mode.

b. Very High Frequency (VHF). Used for short range, line of sight,comnrunications. Much less prone to interference than HF and clearvoice communication is possible 24 hours a day. Used for vessel tovessel, vessei to shore and deck to control roonr colrmunications.Conrnronly uses simplex ntode.

c. Ultra High Frequency (UHF). Used for shoft range, usually less thanline of sieht. and satellite communications. Verv clear voice

203

communications are possible 24 hours a day as there is little interf'erenceat all. Commonly uses simplex for line of sight and duplex for satelliteconlmunlcattons.

14.4 Radio Procedures.

Before using a radio for communication the frequency or channel to use, the callsign.ofthe transmitiing station, the callsign of the station called, the person required at.the otherend and the su6ject to be discussed must all be known. Once this information is knownall radio transmissions begin in the same way. There is the call, the text and the endingtransmission.

The Call: Polymariner THIS IS Stena MayoThe call consists of the calisign of the station required, followed by the Pro words ThisIs and the callsign of the station calling. Each callsign may be repeated up to threetimes if the initial call is made on international channel 16.

The Text: Either: Give me a working Channel; or The message.The text may be a request for a working channel if the original call was made oninternational channel 16 or it rnay be the information to be passed.

The Ending'fransrnission: OVER or OUT.The ending transmission consists of the Proword Over if a reply is required or Out if noreply is expected or recprired.

14.4.1 VHF Mar i t ime Cal l ing Procedure.

Calling on Maritin-re fiecluencies on VHF is the most cornnlon practise offshore. The

Tune to Chanrrel 16 and listen for a quiet period.Make your transnission as outlined above either requesting or stating aworking channel in the text.Wait f'or a lesponse front the station called for trp to 10 seconds. If thereis no response in this t inre make your cal l again.When a response is made change fretluency to the working channel andre-establishconrntunications. Do not work ott channel 16 which is usedonly tor distress and call ing.

14.4.2 How tn Speak

Whatever system is used for communication the following conlments will assist theuser in ensuring that a clear message is passed.

a. Always give precedence to distress or urgent callsb. Do not jam up the channel with un-necessary conversation or chat.c. Wait to respond until the transmitting station makes an ending

transrnission. Only try to interrupt if it is most urgent that you do so.d. Do not swear.e. Do not stammer.f . Remember RSVP

R Rhythm of speech - as normal but use pauses for effect.S Speed of speech - Slightly slower than normal'V Volume of speech - Slightly loader than nomral, but only

slightly.P Pitch of speech - Slightly higher than normal pitch if possible.

g. Reniember to press the transmit button and allow a short pausebefore speaking and continue to hold the button down throughout thet ransnt iss ion.

procedure is:

b .

d .

204

lIl

j

14.4.3 Prorvords

Numerous standard phrases, which have internationally recognised meanings, are usedin radio voice communications. These phrases are called Pro,iords. A table'of the moreuseful Prowords follows.

PROWORD USE OR MEANING PROWORDMAYDAY The distress signal. HOW DO yOU

Used when in FIEAR ME?imminent danger andlmnteolate asslstanceis required.

USE OR MEAMNGWhat is the strengthand clarity of my voicetransmission?

PAN

SECURITE The saf'ety signal.Mainly used fbrnavigation ormeteorological

ACKNowLEDGE ilil:'i5;.eceivect

ALL AFTER/ALL Used with a kevBEFORE word from the

"

transn]lsslon toidentify a parr of thetext.

OVER

The urgency signal. READ BACK Request to theUsed where safety is receiving station tothreatened but danger read baci the messageis not judged to be sent. Used to confiririmnrinent. the message has been

received exactly assent .

SAY AGAIN A request for all, or apart of the message tobe repeated.

I SPELL Used when a word orand understood this an abbreviation is speltmessage? out.

Transmission iscorrrpleted. and a replyrs requlred.

CORRECTION Cancels the word orphrase just sent.Normally followedinrmediately by thecorrect version.

OUT Transmissionconrpleted and noreply is expected.

I READ BACK The receiving srationrepeats back themessage as received toconfirm it is correct.

WAIT The station requirestime to consider areply this allows up to5 seconds unlessfollowed by a numberwhich indicates thenumber of minutes.

Message received and I SAy AGAINunderstood

Used when a messaseor phrase is repeatedfbr enrphasis.

ROGER

205

14 .5 . Deck Commun ica t i ons .

As stated above hard wire communications are frequently used by ROV personnel.They do have several advantages:

a. Headsets leave the hands free;b. There is no interferencec. Does not interfere with radio users.

A Typical conversation between; Deck Officer (DO), Crane Operator (CO), Pilot,Vessel Captain (VC), and Dive Control (DC) will illustrate the use of voice procedureon this means.

DO Pilot This is Deck Officer, Pre-dive checks are now complete standby to launchPilot Pilot, RogerDO Bridge This is Deck Officer, Please report the status of the vesselVC Bridge, Vessel is on station, Heading 1100, you are clear to launch.m Deck Officer, Roger.m Dive Control This is Deck Officer Please report stittus of divers.DC Dive Control, All divers are out of the water. You are clear to launch.DO Deck Officer, Roger.

The Deck Officer would then proceed with the launch opel'ation.

206

CHAPTER 15 UNDERWATER VIDEO

15.0 In t roduct ion

Remotely operated vehicles could not exist if closed circuit television was not available.In all types of vehicle it give a visual image to the surface showing what the vehicle islooking at and allowing topside staff to navigate around obstacles-or inspectcomponents or just generally monitor the underwater situation. There aie severaldifferent types of cameras available and in this chapter the most popular will beoutl ined.

15.1 SIT Cameras

The Silicon Intensified Target camera is used extensively for general navigation andobservation. The camera will operate in low light condiiions equivalent to night timewith a quarter moon showing this as a sensitivity of 1 x 10-a Lux. This in turn meansthat floodlights are not required and in turbid conditions bener visibility is achievedbecause there is no back scatter. It is the prime camera on most ROVs and is the pilot'sfirst choice. Osprey Electronics manufacture a compact SIT camera for ROV use whichis 100 mm in diameter and approximately 300 mmlong. It is rated to 1000 m waterdqpth and contains an automatic iris. The focus is fixed giving a depth of field from140 mm to infinity. One important operating point is to ensure the lens cover is put inplace as soon as the Rov is on deck to protecr the target. The picture is inmonochrome.

15.2 SDA Camera

The Silicon Diode Array canrera is specifically designed to be tolerant to high intensitylight and can, for exantple, be used to observe welding, the sensitivity of the camera isaround 1-10 Lux. This would be impossible with other types of cameras as the l ightfrom the welding arc would destroy the picture tube. Ospiey manufacture an SDAcamera which is 100 ntm in diameter and approximately 350 ntnr long. It is rated to1000 m water depth and contains an autonratic iris. Focus is by remoie control and it ispossible to get close up views of an object. This would be recluired for weld inspectionfor instance. This camera is used for specialist pllrposes where high intensity lilht is tobe observed.

15.3 CCD Cameras

This type of colour camera has become the industry standard for all types of inspectionand observation where good quality colour video pictures are required, sensitivitiesrangefrom +10 to 0. i Lux. Osprey once again manufacture thii type and they canprovide two models: one of which has a pan and tilt mechanism buili into the 6ead.The overall dimensions are 104 mm diameter and approximately 330 mm long. Theyare rated to 1000 m and have automatic irises. The focus is by remote control and is

-

from 10 mm to infinity.

15.4 Video Record ing

Whatever type of canrera is called for in the contract specifications the videoinformation will need to be recorded. There are several different standards for doinethis and Figure 15. I lays out in tabular form those curently available.

207

>400 260

Signalto 46 dB 46 dB 43 dB 45 dB 46dBNoise Ratio

Paramerer S-VHS Hi-g VHS

Resolution >400(TV Lines)

Max Tape 180 90 240Length (mins)

Cassette Size 500 90 500(Volume)

Volume per 166 60HourRecording

t 2 5 1 6 1 5 1 6 1 5

U-Matic U-MaticHB

Colour 250 Colour 270Mono 330 Mono 370

1 6 1 5 1 6 1 5

Signal Input conrposite composite composite conrposite compositeor S-Video or S-Video

F igu re lS . l

Most operatgrs are stipu.lating S-VHS (Super Video Home System) because it has goodresolution. To utilise this system to its fuli potential it is necessary to use 2 co-axialcables from the camera as opposed to the usual one . One cable carries the chrominancesignal and the other the luminance. The extra cable is nor usually ,r"J uipi.i"ni. rnorder to record the video signal from the camera.a recording suite nrust U" pui iogether.To indicate how this rrtay be.done a diagranrmatic layout rri,tr ,t, .outA b" ;;d;y "Scorp io ROV is shown in F igure 15.2-

208

Raw VideoPorr Raw Video

Pan and Tilt

Raw VideoStM

Figure lS.2

15.4.1 Record ing Qual i t -v

As a result of a study sponsored by several of the offshore oil producers; conducted byR.w. Barrett, M. clarke and.B. f.ay for the Marine Technology Directoiat., unopublished in Underwater technology vol. lg No. 2 four on siie resrs wererecommended:

a Check I Recorder playback and monitorUsing a tape pre-recorded to broadcast standards

b Check 2 Camera and transmissionExcluding the recorder from the system

c Check 3 Recorder and transmissionUsing a tape recorded on site in the previous check

d Check 3 Camera underwarcrA simple check for specific underwater problenrs.

These checks can only provide a measure of the video quality at the time they areimplemented.

1l9v can neither guarantee quality at a aiireie'nt time nor carittey tateacc.ount of.possible degradation if components of the whole system are changel oradditional items conne-cted to it. Theyire, however, designed for technicians who arecompetent in the use of relevant underwater equipment buj who have no specialiit videoor electronic knowled se.

Nav 2Monitor

Nav 1Monitor

SwitchMatrix

209

15.5 Video Signal

There are rwo main video systems in operation, they are PAL (phase alternation by titrc)and NTSC (national television system comminee) which was developed in the UnitedStates of America. It is not rhe intention of ttris book to go into great detail on theseformats as the subject is already well documented, but it is suffice to say that allsysrems are compatible with both types.

Video signal is an electrical signal that is produced by the caniera, that scans the object,and it is proportionai to the intensity of light entering the camera. Light is made up ofthe seven colours red, orange, yellow, green, blue, indigo and violet. However thehuman eye is most perceptive to red, green and blue, for this reason the camera isdesigned to detect these three colours which are recombined to form an image of theoriginal object.

The camera is made up of three tubes, each one designed to receive either red, green orblue light and produce an electrical signal which is proportional to the colour strength.The colour is then transmitted on the actual video sienal and decoded at the monitor toproduce the actual picture.

Figure 15.3 illustrates how video signal appea$ on an oscilloscope.

Typical Video Level I Volt Peak to PeakF igu re 15 .3

It can be seen that composite video signal is made up of synchronisation pulses, colourburst, chrominance and luminance.

15 .6 Luminance S igna l

Luminance is the characteristic used to provide picture detail by varying levels ofbrightness. Luminance is transmitted on the picture section of the signal.

Sync Pulse

2r0

15.7 Chrominance Signat

Chrominance-signal is- used to convey the colour information in the video signal. Ther9{, green and blue colours.produce an electrical signal that is proportional t6 the phaseshift between them. It is this electrical signal that forms the chrorninance signal.

15.8 Colour Burst

Colour burst is added to the video signal to provide synchronisation for thechrominance. This is added immediately after the piciure information, before thefollowing synchronisation pulse.

15.9 Synchronisat ion Pulses

The synchr^onisation pulses ensure that the receiver operates in step with the verticalscanning^o_f the camera. The TV monitor display is niade up of 625 scan lines that aresc^anned ?!_!ilttl per second. This means th-at each line is

^Ueing scanned at a frequency

of 15.625 KHz. It can be seen that the time period between eac6 synchronisation pulseis normally 64ps, the picture inforn-ration between the two consecutive synchronisationpulses therefore represents the inforn.ration applied to one scan line.

15.10 Cal ibrat ion Of Video Cameras

p.u.e to the length of umbilical, ROV systems are subject to the effects of line losses.This can manifest itself in the ROV video system.

The monitors on the system require a certain level of video signal to function correctly,if this is not the case then it may result in extremely poor pictlre quality.A situation may arise in which the umbilical may be-replaced for a muih longer one.For example it may be necessary to incorporate a TMS in to the system, this"wouldrequire the addition of an amroured umbiiical. This would obviously result in anincrease in the ovet'iill line losses. For this reason it would be necesstrv to carrv out acalibration of the vic'leo cameras.

By calibrating the camera we are in fact amplifying the canrera ourpur ro overcome theline losses. Normalll, the sjBna_l is monitorbd it th-e surface using an oscilloscope,whilst.the signal.is ldjq$qd at the camera output. This may invoTve the adjustnient of apotentiometer which will in tum alter the gain of an output amplifier.

It is important to adjust the gain at the canrera end rather than the surface as the videosignal will have'noise'.superimposed upon it, by carrying out amplification at thesurface we would amplify the nbise sighal as well. Nbis; may be derived from thepower conducrors that lie in close proximity with the video coax.

15 .11 Co lou r Loss

Due to the difference.in tiequency between the red, green and blue light it follows thatcolour absorption will take place to a varying degree over a fixed lenlth of umbilical.To overcome this it tla.y.be necessary to boolt an individual colour r.iith respect toanother. As red is of higher frequency than green and blue it follows that it is subject tothe highest absorption factor and may need to be amplified at the camera end.

2tl

15.12 Typical Faults With Video Systems

The most common faults that arise with video systems are caused by connectorbreakdown, this may occur at either the ROV or the surface. Should any faults developit would be wise to check that all the connections are serviceable prior to carrying outany major dismantling.

It may be the case that the video picture becomes impaired due to electrical interference.This can arise if the video system does not have an independent earth from the rest ofthe ROV electrical system. If this were the case'current loops'may be induced into thevideo system from the mains supply and give rise to picture flicker taking place atmains frequency. This fault can be proved by monitoring the video signal on theoscilloscope. It would be found that signals would be present at a frequency of 50 or60 Hz.

Many ROV systems make use of fibre optic transmission to convey video signal, thiswill illuminate any electrical interference. However the physical size of the conductorsmakes them susceptible to breakdown, especially at the connectors. This can lead to atotal loss of video signal.

212

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CHAPTER 16 UNDERWATER PHOTOGRAPHY

16 .0 In t roduc t i on .

Photography is used extensively offshore as a method of providing a permanent recordof the actual state of underwater components and structures. These photographs are incolour and may be stereoscopic. Engineers can then use them for structural analysisand other purposes and they iorm part of the permanent record for any particularstructure. Photography is also one of the prime methods of recording inspectioninformation during annual platform inspections and forms part of the final report forthis type of survey. Although video tape recordings are universally used for thepurpose of recording information on these same underwater constructions photographsstill have an important role to play and ROV personnel must be fully competent in theuse of underwater photography. It is appreciated that offshore personnel will probablynever need to apply the physics of underwater optical systems directly in a systemdesign way but it is still most useful to have an understanding of the basic principalsaffecting light in water.

16.L L ight in Water

Light entering the water is affected by reflection, refraction, loss of intensity, loss ofcolour and loss of contrast in accordance with the laws of physics. These same lawsapply when the light enters the camera housing from the water. As photography isbasically recording light images onto film a better understanding of these effects will beof benefit for anyone contemplating taking underwater photographs.

16.1.1 Ref lect ion

This is a straight forward effect; whenever a light beam meets a reflecting surface it isreflected, the angle of reflection equals the angle of incidence.

Angle of incidence

Figure L6.lAngle of Incidence Equals the Angle of Reflection

Angle of reflection

2t3

16.1.2 Refraction

As a light beam passes from water to air it is refracted in accordance with Snell's Lawwhich can be summarised by the equation:

Nwater Sin 0*u1", = Nair Sin 0u;t

Where N*",", = Refractive Index of waterNni, = Refractive Index of air

O*ut", = Angle to the Normal subtended by the light ray in water

Oui' = Angle to the Normal subtended by the light ray in air

In the case of light passing from water through a glass or plastic port into the.air glp ina camera housirig iiis posiiUte to look at the simple case w-here the Port consists of aplane glass with-parall^el surfaces. The Refractive Index of glass and perspex is verysimilar to water and in this case the equation evolves to:

Sin 0uir = N Sin 0waterWhere:

WATER (N watefl AIR (N air)

Plane Port

Figure 16.2Refraction from Water toAir across a Plane Port

As can be seen from Figure 16.2 the light rays emanating from the image after passingthrough the port appearto originate from the apparent image. This has the effect that,witho=ut conecting the lens, distortion, focus errors and field of view errors are caused.

16.1.3 Dis tor t ion

Rays from points forming a rectangle in water will suffer "pincushion" distortion,unless the lens is corrected for this underwater effect .

A

J

IMAGE oTA[?'

I L_ 3'4d_

LENS

^ t Az l +

ROVTECHNOLOGY

Figure 16.3Pincushion Dis tor t ion

Jhe d-iagram illustrates the effects of pincushion distortion which is more noriceable atthe edges o! qhe frame and less discernible towards rhe centre. The diagra- i;

-

exaggerated for emphasis.

16.I.4 Focus Error.

This effect is illustrated in Figure 16.2. The apparent image appears to be 3 larger and4 nearer.

16.1.5 Field of View Errors.

Objects in water are larger than those same objects in air by a factor of approximately4:3 refer to Fig 16.?. This means the lens lppears to have'a tongei f*;ii;;til1"water. The object fills more of the frame. Alio because of the r."ftu.tion-u;tii,ilr beamentering 4"pg{ at an angle other than the normal will leave at a wider ungr6. X lu*.ruhas a fixed field of view and therefore in these circumstancis its field oi ul"* in warerwill be less than in air.

16.1.6 Loss of Intensity.

Light passing through water is attenuated in accordance with the relationship:

I/Io = s'kx

Where Io is the initial intensityI is the intensity after icattering and absorptionk is the attenuation coefficrentx is the distance

The attenuation coefficient, k, is the sum of the absorption coefficient cr and thescattering coefficient B botl of which depend on rhe wavelength l. of the light and thetype and amount of suspended material.

215

16.1.7 Scattering.

Figure 16.4 shows the effects of scattering where suspended particles tl th! water.eflect some of the light at random angles dependant on the angle the reflecting surfaceof the particle presen-is to the beam. The more suspension the greater the amount ofscattering and ihe greater the reduction in light penetration.

Figure 16.4Scattering

Scattering is also responsible for back scatter which is a problem on the photographitself analogous to th-e effect of using headlights in fog. The light is reflected back andreduces the field of view.

16.1.8 Absorpt ion.

Fig 16.5 shows in diagrammatic form the effect of absorption which is to reduce thestrength of the light beam. The reduction in strength is dependant on the turbidity ofthe water and on distance travelled.The greater the amount of dissolved matter in the water and the greater the distancetravelled the greater will be the loss.

2 t 6

REDUCTION IN LIGHT DUE TOABSORPTION

Distance from Light Source (m)

Figure l6.sAbsorption

Both absorption and scattering cause problems when the stand-off distance in sizeable.Scalqryg is more troublesome as it adds background illumination as well as removingg1elul light. This background illumination is called "back scater" as shown in Figure"1 6 . 6 .

n os-O o< v o

Figure 16.6Back Scatter

In some circumstances it may..be possible to compensate for the loss of light byabsorption by using sffonger lighis, but if back sc^atter is a problem this o[tiorimay notbe possible due to the over?,ll degradation of the light caused by the increase in backscatter, rather like using full beam headlights in G.The effects of back scatter can be minimised by plicing the light source at an angle tothe plane of the lens of the camera as shown in Fieure-I6.7.

2 t 7

Strobe light angled to plane ofcamera lens to reduce back scatter

Figure 16.7Minimising Back Scatter

Even using this technique it is quite possible, especially in coastal waters, that usablephotographs can only be taken at a range of a meter or two at most.

16.1.9 Loss of colour.

White light is made up of the colours of the spectium and as it penetrates the water thevarious c-olou.s of the-specffum, which have different wavelengths, are absorbed atdifferent rates. The shorter wavelengths are absorhd at different rates with red light,for example, being absorbed approximately 6 times faster than blue light. This effectcauses underwatei long-range photographs to have little colour other than blue-green.Fig 16.8 illustrates this graphically.

218

Relative lllumination

COLOUR ABSORPTION IN WATER

Red 70004

219

1 5 2 U 2 5

Distance from Source in meters

'A Anqstroms

Figure l6 . t tColour Absorprion

The method for overcoming thi-s problerrr is to use a strobe that is powerful enough toilluminate the viewing area sufficiently. The basic advice therefoie, with any sr6be, isto get close to the subject.

16 . l . l 0 Con t ras t

When we observe art inrage its fonl and texture are nracle apparent to the eye by thedifferent intensities of reflected light conring from its surface. If the difference inintensities is strongly rlarked then the contrast is good and the inrage is said to be'crisp.

Jf l!. differences are poor then so is the contrasr ancl the iniage is said to be'Pu{dy'..Underwaterthere is alw.ays less l ight available than in air ir-nd with increasing

depth light intensity decreases. Thus the situation in water is that there is always poorcontrast and without introduc.ing artificial light this problenr gers worse with d6pth.The solution to this problenr is to use a powerful enough stro-be to compensate ior theloss of natural light and ensure you are as close as posiible to rhe subject.

16.2 Elect ronic Strobe L ights

All the problems associated with loss of light can be overcome or at least improved byllsing an.appropriate underwater strobe light. In air photography the output frorn stroilelights is indicated by the Guide Nuntber. This number is calculited generally for usewith 100 ASA filnr (filnr speed and the ASA system are discussed llter). W"hen a strobe

is to be used to provide the light the camera shutter speed control is set at the flashsynchronisation speed which is often 1/60th second. In these circumstances theappropriate formula is:-

GuideNumber=f XDf =f s topD = Flash to Subject Distance

hence to determine the f stop required with 100 ASA film and the shutter speed set at1/60th second the formula becomes:-

r Guide Number

16 .2 .1 . Gu ide Number .

In order to determine the Guide Number it is necessary to consider the flash rating andthe film speed, as indicated in paragraph 16.2. A general formula is:-

G N _v

BCPS = Beam Candle Power SecondASA = Film Speed Rating

Most film data sheets give the Guide Number for the film as a function of BCPS.The BCPS rating of a sffobe can be detemrined from the watt-second rating by theformula:-

s6p5 = !4r

WS = Watt Second RatingM = Reflector FactorLIW= Lumen Second/lVatt second Rating of the flash tube.

Normally 35 to 50.The guide number can be determined from the watt-second rating of the strobe thus:-

- \ , l o o o r \ w S \ , { S A X N l x Lt l t l = V

\ \ ,

For a nominal reflector gain of 2 and a 50 lumen second per watt-second flash tube:

GN = O.7 l r / \vS X ASA

and this means that in air the correct exposure is:-

16.2.2 Effects <lf Water Attenuation on (iuide Number.

Underwater the light fronr the strobe is attenuated which reduces the light intensity bythe factor

- c De

Where cr is the atterluatiorl co-ef ficient per foot of the water and D is in feet, thereturning light is attenuated a like anrount such that the total attenuation of light fallingon the film is:

0 ' xN rx# )

220

-2c rDe

Applying this to the f stop calculation gives for underwater work:

f = f u i . X e - 0 D

The attenuation function equals one stop for each object distance increment d, where:

e - 0 d = { t

d = I

= ,2.BB

O

For the remainder of this chapger this will be called the one srop attenuation distance'In the clearest ocean water "d" is 23 feet, however, the conditions usually encounteredare less than this and can be estimated as one tenth the limit of horizontal'visibility.Thus, in water with 50 feet visibility, the lens should be opened up one f stop foi each5 feet of distance to the object over ihe "in air" setting.

16.2.2.1 Est imat ing Hor izonta l Dis tance.

It is obvious that estimating horizontal distance is a guess but the analysis above willhelp in understanding the dlamatic difference in the ighting requirements of underwaterphotography versus dry land. As can be seen the "Un-derw"ater'Guide

Number" of astrobe light depends on power, reflector efficiency, water conditions and variesdramatically with distance compared to normal "in air" guide number calculations.

16.2.2.2 Estimating Proper Exposure

The chartreproduced_a-s figure 16.9 shows f stop versus object distance for variousfilm speeds using a.150 watt-sec strobe. This is i good rturiing point for estimitingg.oTec.t exposure. The chart is worked out assuming no ambient'light. In high ambientlight the iris should be stopped d.9*1 further than t"he serrings shoin to rffi.niut..The amount of iris adjustment will depend on rhe levels of a'mbient light in uiyparticular application but a rule of thunrb would be either one half or"on. f sio'p

221

.t6

1 1

f stop

100

22

t o

1 1

B

5 .6

4

2.8

1 6

l 1

F STOP vs OBJECT DISTANCE BASEDON 150 WATT/SEC STROBE

1 V 1oft )

\ 2 V)

20ft ) =estimiled vis mit

N 3 V)

40ft )

\ \ 4 V 80ft

For 'n r 'ma l 'o inore ! l ler usl V=20t

\ Fo reep o EAN US v:80f5.6

0 2 4 6 8 1 0 1 2 1 4 1 6 1 80 0 .6 1 .2 1 .8 2 .4 3 3 .7 4 .3 4 .9 5 .5

20 (feeQ6.1 (metres)

Oblect distance

Figure 16.9F St<lp Verses Distance

f6 .3 . Camera Cont ro ls

The amount of light entering a camera is conrrolled by the size of the aperture and thespeed with which the shutter op^e^n..s. Both these controls are adjustablebn the types ofcamera usedfor photography offshore. An understanding of hbw these controis'workwill be useful no matter whai camera is being used becaule there is a standard methodapplied by all camera manufacturers.

1 6 . 3 . 1 . A p e r t u r e C o n t r o l .

Thesize of thg aperture is.controlled by the iris diaphragm, which is adjustable, and rhetocal,length of the particular lens. This mgqls that a largt aperrure and a long focallength can transmit the.same brightness of light as a smail aperture and shorifocalleng^th. The scale used in.photography to relite focal length and aperture size ii tUt"Othe f number system. This systemis applied as a standar? method by manufaclri"rr rothat an aperture of, say, f4 will always Lansmit the same brightness of tigtiiwtraieverthe focal length. The series of f numbers as a whole is arranfed so rhat eich reductiono.f one f stop h.alves the amount of light admitted into the caile.a. nor exampli?4allows twice the amount of light as f 5.6 to enter but only half the anlounr dr n.g.fno. 22 16 l l 8 5.6

222

2.8 1 .4units of

Figure 16.10F stops

The size of the aperture affects the image definition of a lens. At maximum aperture thesharpness of the image in the centre of the picture is nearly always greater than in thecorners. Stopping down the lens improves central definition slightly and cornerdefinition much more. At small f stops such as f22 there is usually slight fall-off insharpness caused by diffraction, the scattering of light rays collected in the front of thelens as they pass the edge of the iris diaphragm, but this is not important in underwaterphotography.

1 6 . 3 . 1 . 1 D e p t h o f F i e l d

Depth of field describes the extent of the picture in focus at a given f number. Thelength ofthe zone on either side ofthe subject depends on the size ofthe aperture andthe focal length of the lens. In theory, only the subject in which you focus is completelysharp but m area of acceptable sharpness lies in front of and behind it. As the size ofthe aperture decreases, the depth of field lengthens, bringing more of the picture oneither side of the subject into focus. The subject focused on is not in the centre of thissharp zone which extends two-thirds beyond and one-third in front of the subject.

L6 .3 .2 Shutter Speed.

The shutter speed is set by adjusting the shutter speed control, which is calibrated inseconds and parts of seconds. Here, the relationship between stops is obvious andfollows the same method as f stops, the difference between one shutter speed and thenext is a ratio of l:2. A typical series is shown as Table 16. 1 .

I t lz U4 r /8 l f is U30 t l6o Utzs l lzs l 1 /500 l /1000

Tab le l 6 . lTypica l Shut ter Speeds

Here Vat passes /z as much light as T.ro but twice as much li-qht as X::.

223

Deoth of field at f l.4

SlstemASA 25 50DIN 15 18rso 25lts 50/18

Ilmage

Depth of field at f.l6

Figure 16 . l IDepth of Field

Using a Typical50 mm Lens

Film Speeds100 200 40021 24 27

rwlzl 200124 400127

Table 16.2

1 6 . 4 F i l m

Films vary from one manufacturer to another and there is a wide variation in choicefrom one photographer to another because each will present a different hue and onemay be mbre pleasing than another to different individuals. Underwater the choicetends to be more limited however because of the low light conditions.

16.4.1 Fi lm Speed

The speed of reaction to light for any film is rated on one of two international scaleswhicli have been rationalised by the International Standards Organisation (ISO). TheAmerican scale is referred to as the ASA (American Standards Association) method andthe European scale is refened to as the DIN (Deutsch Industries Norm) method. Thetable belbw shows the relationship between the two methods and the ISOrationalisation.

ti0030

800/30

1 1 4

As can be seen from Table 16.1 the ISo has grouped the ASA and DIN merhodstogether. loth methods apply the same rules and an examination of the ASA sysremwill show how both work. As the number increases the filnr's reaction to liehiis faster.The film speeds illusrrated are grouped inro slow films with ASA of 25 and-50,medium films, ASA 100 and 200 and fast films ASA400 and above. As the valueincreases by I step_th9 lighqerytion increases precisely twofold; for example 100 ASAis twice as fast as 50-ASA. This equates to one full stoil on the camera aperture orshutter lpeed con_trols. The reason that a film reacts more or less quickly to light is thesize of the silver halides on the emulsion. The smaller the grain th^e slower thJreactionto light. By careful selection of grain size the film manufacturer determines the ASAr-atin_g 9{ th9 film but as the film speed increases the grain size also increases and thusthe finished_print becomes more and more 'grainy'ai the ASA rating increases. Thus inselecting-a film speed it is necessary to balance the reaction to light alainst finishedprint quality. A sensible choice for most offshore work is EktaChrom--e 200 which is areasonably fine grain film with a moderate reaction to light.

16.4.2 Types of Film

There are basically two kinds of film;a) Negative film which requires a print to be made before you can properly

interpret the subject.b) Positive or Colour Reversal film which allows the subject to be viewed

directly on the film.

16.4.2.1 Colour Sensi t iv i ty

Films.also vary in their sensitivity_to different parts of the light specrrum. For exampleEktachrome is more sensitive to blue light, Kodachrome to ied and Fugicolour toryen. Some films are specifically balanced for artificial light and are niarked"Tungsten''. It is recommended that only daylight film be

-used for underwater

photography as these films are balanced for-use with strobe liehts which areexhaustively used in underwater photography.

16.4.2.2 Fi lm Format

Jltere are basically two filnt forntats to choose from in underwarer photography, either35 mm or 70 mm.35 mm is by far_the nrost popular filnr fomrat having the fbllowing advantages:

a) Cameras are smaller and lighter and less expensivJ than 70 irm.b) 35 nrm film is nrore universally available and less expensive than 70

mm.c) 35 mm is easier to process.d) 35 nrm film is less bulky ro srore.

7O p.q film produces a much larger negative than 35 ntnt, ils indicated in Fig 16.13 andfor high quality or photogramnreiy thisls a major advantage.

! ,1 ,t i1 j

1i; 1

l rI t1 :

22-5

35mm vs 70mm

Figure 16.12

It is unquestionable that 70 mm will give better quality prints than 35 mm the questionis whether 35 mm is acceptable or not.

16.4.3 Fi lm Selection

There is a wide selection to choose from and the basic recommendation is to experimentwith different films at first and then select the one that suits the requirements best andstay with it. Over time if one film is used constantly, better pictures will result becauseof the consistency of approach.

16.5 Framing the Subject

Manufacturers of underwater cameras nornrally list the angle-of-view (in water) of thecamera lens system, and fronr this infornration the area-of-coverage at variousdistances can'be calculated using sinrple trigonometry. Figure 16.13 illustrates this for a35 mm camera.

226

VIEWING AREA OF ATYPICAL 35mm CAMERA

24mm 1 vertical_ 6 r

36mm "'

1.5 horizontal

F i g u r e 1 6 . 1 3Area of View

This straight forward head-on situation gives the basis for calculation but in a realsituation it may be nrore cornplicated. For example if rhe canrera is looking obliquelydown the area of coverage is a trapezoid. This i.s illustrated in figure 16.1V.

'

35mm cameras cover a rectangular areawith the same ratio as the neoative

221

Area of view withcamera at an angleis a traoezoid.

Figure 16.14Area of View

When Camera is Ti l ted

This problem of framing a subject can be a difficult one to overcome but applying theprincipal shown here and with some practise a satisfactory solution should be found.Some camera systems are n'lore helpful than others and there are two systems whichuse the same lens system for both the Video and the Still carlera thus what you see onvideo is what you get on the still photograph.

16.6 Camera Systems

There are several carnera systems available for use on ROVs but one manufacturer,Photosea Systems Inc. are currently the nrost popular. They nranufacture severaldifferent types of renrotely operated canrera systems designed to take close up, stand-off or stereoscopic photographs. to complinrent their range of cameras theymanufacture compatible strobes and can offer total packages suitable for all ROVrequlrements.

16.6.1 Photosea 1000

These c:uneras can be fitted to ROV's and are also available for deep sea and diver heldmodes. Depth capabilities range from 6fi) m to 6000 nr. Standard features include:

a) 28 mm water-corrected lens system.b) Completely self-contained, weighs less than 1.1 kg. in water.c) Rechargeable internal power packs.d) Electronic filnr advance.e) Data chamber with time, alpha/numeric code and frame number.0 Daylight load film nragazine accepts standard 36 exposure or 250

exposure cassettes.

228

16.6.2 Photosea 2000

This camera is a single, completely self-contained stereo camera, incorporating a duallens system and a single film magazine. All problems associated with t^aking siereophotographs yitlr_a complex two-camera,/two strobe system have been eliminated. Withthe Photosea2ffi0 series cameras stereo-scopic viewing can be achieved with a systemas simple-as conventional single frame cameias. Stereo pairs are automaticallyregistered.and is a major advantage.over two-cameras stereo systems where developingand handling.two separate rolls of films and trying to match stereo pairs can be atedious and time consuming task.

16.6.3 Photosea 70 Series Cameras

These 70 mm cameras were designed for the offshore professional desiring the best inhigh resolution deep ocean photography. These cameras utilise large formit 70 mm filmwith more than32 times the negative aiea of 35 mm film. CombinEd with the highresolution water-corrected lens designed and built by photosea.

16.6.4 NDT 3000 Macro Stereo Camera

This camera has been ̂specifically designed to provide high resolution stereophotographs.at close distances to assisi in the detection crT cracks, pitting and corrosion9ygg^lgl-destructive testing and structural inspection. The most uniqJe feature of theNDT 3000 is the ability to take stereo photographs at a subject distance of l5 cm.

16.6.5 Combination Photo/TV Camera

Two companies manufacture 'combination photolfV cameras. These units include atelevision camera inside the housing, which is used as a 'viewfinder' for the photocamera.

f6 .6.5.1 Sub-Sea Stereo v iew 2000

This combination camera includes a colour television camera and a Photosea 2000'metric' stereo camera in the same housing. In addition to the ability to take 'rnono'o,stereo photographs, the stereo pairs produced by the camera can be irsed to take actualphotogrammetic measurements. The system also includes a data chamber. Thisequipment is available from

Sub-Sea Systems Inc.753 West Washington Ave.EscondidoCalifornia 92025USA

16.6.5.2 Osprey TVP Combination Camera

This system includes either a black and white SIT camera or a colour television cameraand a.'mono' single-lens reflex ph919 camera in the same housing. The rytt.* ulroincludes a data chamber with capability of remotely annotaring th? titm. ffi" syste. Itavailable from:

Osprey Electronics, Ltd.E27 Wellheads Industrials CentreDyceAberdeen AB2 OGDScotland

jl

l

) t o

L6.7 Strobe Lights

Almost all underwater still photography is accomplished using high-energy strobe,lightswhich are necessa.ry to offsit the ligh attenuation characteristics of light in water. Inudaiii*, u po*r*,it strobe will proiide the balanced illumination needed for high

a;;iit iotjur photographs since red light is virtually non-existent in ambient light atdepths beyond 4-5 m.

16.7.I How They Work

The srobe flashtube is essentially and arc-chamber made of glass, or quartz (for highoutput lamps) with an electrode sealed into each end. The size of the arc-chamber,wtrictr is normally filled with inert Xenon gas, is determined by its.operating.parametersunA ttr" upplications for which it is designJd. Flashtubes are available as straight tubes,or coiledinto a helix for greater conceniiation of light. A third elecffode, usual attachedto the extemal wall of thiarc-chamber, is needed to trigger the flash. An invisiblecoating oi Conauctive material on the tube, or a fine wiie wrapped around the wall ofid6;p is usually used. Flashtubes are used in a capacitor discharge circuit, see figure1 6 . 1 5 .

'X' sync switch incamera

Flashtube

R (Chargingimpdancc)

F igu re 16 .15Basic Strobe Ci rcu i t

The main components of the circuit are:a) DC power suPPly.b) Chaiging imp-edance - This limits the charge rate of the energy storage

capa&toi and allows the flashtube to de-ionise and extinguish after theflash.

c) Capacitors - store the energy for the flashtube.d) Hilh voltage trigger pulse circuit - This is usually a simple step-up

transformei, putied fiom the discharge of a small capacitor controlledby the camera shutter'sync'contact. The higli vo.ltage pulse activatesthe flash by ionisation of the gas in the arc-chamber.

e) The flashtube - changes electrical energy into light.

16.7.2 Strobe Power Ratings

As mentioned earlier the light output of most'topside' strobe lights are rated with aguide number, but because-of ttre wide variance in water clarity and its severe lightfttenuation characteristics, this guide number is useless in water, As a result, most

undr.*ut.r strobe lights are rate? in rcrms of watts per seconds (oules). This rating

describes the input power to the flashtube itself with:

High volrageDC powcrsupply

230

J w - t = 2 C V 2

C- = C_apacitance of the main discharge capacitor bankV =

!ol|a8e. to which the capacitor ii chaiged (which applies across rheflashtube).

16.7.3 Maximum Power Input

All flashtubes also have a specification called'maximum power input'. Although thisspecification is normally.only of interest to strove designers, users'of strobe tig'trtsshould be aware of what it means, because it can have ind impact on overall rirt"-design for a specific photographic.requirement where the flash frequency is i#portant.Maximum power input is the relationihip between the energy per fiash, ind maiimumflash frequency. For example, a'218'series flashtube (usel"in photosea 1500strobes), has a maximum watt per second rating of 200. At 150 w -s it has a maximumpower input rating of 5 watts.Therefore:

ll0 w s = 30 seconds maximum flash repetition rate

) wIf this particular tube operating on a power level of 150 w -s, were flashed at a ratefaster than I flash.per 30 seconds, it would overheat and prematurely fail. Thus the w -sraung rs actually the input power to the flashtube.

16.7.4 Reflector Eff iciency

The amount of actual light outpug and the parrern of light is affected significantly by thereflector design. The old styleleflectors wbre circulariross sections arid theref#efocused the lig^ht causing hot s_pots' which were very contmon in many unda.*ut".photographs. See Figure 16.16.

Figure 16 .16Circular Cross-sect ion Ref lectorsFocus the Light Causing Hotspots

New' reflector designs that are parabolic rlup. with coatings rhat diffuse the light givegood even illumination across the rield-of-view of rhe cam"era eliminating ttte.ie trotspots'. See Figure 16.17

23r

Figure 16.17Parabolic Shape

Provides Even I l luminat ion

16.7.5 Strobe Light Colour Output

Because of its spectral output, no other underwater light source can match the electronicflash for quality underwater colour photographs. All flashtubes have a continuousspectral distribution through-out the visible energy range. This visible radiation isapproaching 'daylight' which produces excellent colour in all parts of the spectrum.'Daylight'rated film should always be used when using an electronic flash. See Figure1 6 . 1 9

6000ANGSTROM UNITS

Figure 16 .18Spectral Distribution of aTypical 1000 v Flashtube

c <

=

I r ' \

r r'1

zr r l

f r ' l

FI

f l l

232

16.7.6 Strobe Units

Photosea supply the 15005 and 1500SX (external power)which both provide energyoutprt to 150 w -s and the 3000 series up to 300 w -s. All these units are lightweighiand have housing options to 6000 m deplhs and all have internal diffusingieflectors.

16.8 Operational Control of the Camera System

C*9* systems are commonly actuated by a contact closure which could be a remoteswitch initi-ated.bV u.n operator, or a 'bottom contact' switch which triggers the systemautomatically when it reaches the bottom, or by an intemal electronic t'iirer that tiiggetsthe system ar pre-set timed intervals. In each case some interfacing is required. Insituations where long cable lengths are used, or where there is thJpotent'id foi trignelectronic 'noise', from manipulator or thruster motors for example, it is always b-est to'actuate'.the photo_system wiih a relay located close to the camera, iuch as in i nearbyelectronic bottle. The reason for this is that most new camera designs include solid stitetimers which are susceptible to noise and can be 'false' triggered. if this problem isoccurring, it.will be obvious; the camera system will 'actuiie' itself. Thid problem iseasily cqed by using a voltage which actuates a relay which in turn actuatls the cameralVst*' Sory9 sy^stem designers have also used opto-isolators for the same purpose.See Figure 16.20.

Remote Actuate

Long cable orhigh noisepickup

Actuate

'X 'sync

mera

l1

fromfires strobe

-l-

]J

Figure 16.19System Actuation

16.8.1 External Power to Strobe

Stf:F lights can be operated from internal batteries or exrernal power. When operatinga high poryeled strobe light from external power, care should be taken when inierfacin-"gbecause of the higtr peak currents involved. The following comments apply to photosea1500 strobes but the principles apply to all electronic flasf, units which

^O'.a* ttigtr peat

currents when recharging.a) Srobes draw short peak currenls o! up to 10 amperes during recharge

(quiescent current after cut-off is 12 mA). Thereiore the poier sourceshould. be capable of supplying these peak currents, and it is alsoadvisable to fuse your srobe pbwer line with an 8-10 amp slo-blo fuseor breaker.

b) If possible, a remote ON-OFF switch should be installed in the powerline so the strobe is not operating during prolonged periods of timewhen no in use.

Relay oropto-isolator -

Srrobe light

Camera

a-'t-',

c) Input cable connections are critical when operating a high power strobfrom a remote power source.

No. 12 or 14 gauge wire is recommended to keep line resistance to a minimum. Forexample Photosea sffobes require at least 21 volts to fully charge and shutoff. With just1 ohm line resistance and peak currents exceeding 8 amp at 24 volts there could be an 8volt loss in the cabling to the strobe and it would never fully charge and shutoff. Thestrobe will simply keep turning itself ON and Off and oscillate erratically as the voltagesags below the l8 volt shutoff point and then rises after the current drain is removed.Typical curent drain of a Photosea 15005 strobe during its recharge cycle is a short,250-500 ms, peak of up to 10 amp at the beginning of the recharge cycle, averagecurrent of approximately 4 amp during the 3 second charging period, and 12 mAstandby current after shutoff. It is recommended that the external power source be abattery or a voltage source that will not 'sag'due to these short peak current loads. Youshould never connect a voltage source directly to a strobe light that includes internalbatteries or chances are the batteries will be permanently damaged.

16.8.2 Trickle-charging NICAD Batteries

NICAD batteries can be'trickle-charged'continuously during operations to keep theircapacity up. All NICADs must be charged from a constant current source. Typicallytrickle charge current is in the 25-50 mA range for a l-2 amp per hour battery pack.An important point to remember is that the voltage capability of the constant currentsource must be at least 4-5 times higher than the fully charged voltage of the batterypack or the battery will try to charge the charging circuit. For example, a24 V NICADbattery pack, 2o cells at 1.2 V per cell, will charge up to 28 V, I .4 V per cell at fullcharge. Therefore, if the charging circuitry requires 2-3 volts drop, the constant currentsource should have a voltage capability of at least 30-32 volts. Figure 16.20 shows asimple and reliable constant current source.

I to Bty

t0-12 v DC(Camera 6 V Bty)

Note: LM3l7T should be mountedon a heat sink

R1 Value

4 8 O 4 w2 4 Q 4 w

Trickle charge currentI

25 mA

50 mA

Figure 16.20Simple Charging Circui t

30-35 V DC(Srobe 24Y Btv

/.-)+

16.8.3 System Instal lat ion

Actual installation of a photo system will vary depending on specific applications, butthere are several guidelines that should be followed whatever the installation.

16.8.3.1 Camera/Strobe Posi t ion ing

Back scatter in turbid water can be the biggest enemy in taking quality underwaterphotographs. Suspended particles in the water will reflect light back into the ciuneralens resulting in a reduction of contrast. In turbid water this problem cannot beeliminated but separating the camera and strobe with at least-a 0.5 m distance will helpsignificantly. The least desirable strobe mounting position is directly adjacent to thecamera. The strobe, or strobes, should be mounted so that they intersect with thecamera axis at the approximate range of the required picture. Figure 16.21 illustratesthis.

Desired camera/subjectdistance

Second srobe if mounted

Camera/strobe separationat least 0.5 m

Figure 16.21Mount ing Strobes

16.8.3.2 Mount ing

The normal method of mounting a camera and strobe is to use a saddle type mount witha clamping device. If stainless steel hose clamps are used, the units should be securedwith at least two clamps, and the clamps should be covered with shrink tubing orsimilar insulating material. Remember that the camera and strobe should be accessibleand easy to install and remove for charging and film changing. It is also necessary tohave easy access to the ON-OFF switches. It cannot be over-emphasised as to theimportance of proper routing and connection of cables. A very high percentage ofproblems offshore are caused because of poor cable connections.

, J )

16.8.4 Pre/post Dive Check List

Some-important points are pre dive:- a) Fih installed properly and camera mechanism tested;b) Lens Focus/iris setting correct;c) Data chamber turned ON and properly set;d) Srobe and camera batteries charged;e) Power switches OFF until dive;0 System all connected and Test madeg) O rings properly greased and installed;

Post dive:a) All units flushed down with fresh water;b) Film unloaded in the dark and then labelled;c) All power switches switched OFF;d) Batteries charged;e) Housings ProPerlY stowed.

236

CHAPTER 17 SEAMANSHIP -...-'

17 .0 In t roduc t i on

In a handbook of this n.alurg it is not possible to cover ii vast topic such as seamanshipin any detail. Seamanship itself includes topics as diverse as th^e use of liftingequipment on one hand to the art of navigation on the other. It includes safe workingpractices, rigging, boat handling, weather prediction and all the many and varioustectrniques and skills which go to make up the art and skills of seamanship. Theobjective of this chapter is to cover in enough detail for operational use, t6ose subjectswhich will have relevance for ROV Pilot/technicians offshore.

1 7 . l L i f t i n g E q u i p m e n t

One operation that the piloVtechnician will certainly undertake regularly is thedepJoyment and recovery of the ROV. This entaili the use of lifting devices and as it issuch a regular task this aspect of seamanship will be covered first. the subject will bebroken down into three categories. Safety, which will be dealt with first, rigging andfillttY blocks and tackles which will give an insight into rhe nrechanical adiaitales oflifting equipntent.

17. l . l Safety Aspects

As stated in Chapter 2 safety in the work place is the subjecr of numerous Acts ofParliament and Statutory Instruments. The basic requirement is that everyone mustshoulder their own .part of the responsibility for ensirring a safe work place. On anywork site you are likely to go to it is no unlikely that yori will find locil safetyrequirements which have to be fol lowed. In the nraiority of cases these wil l be alonsthe l ines laid out here. One should be aware, however, that there is a possibi l i tv of

"

some local variations.

l 7 . l . l . l P e r s o n a l S a f e t _ v .

On a personal level one should always:a) Observe and comply-with all safety notices and instructions.b) Always wear the correcr safety equipnrent.

c g. Safety.boots, gloves, helmets, goggles, ear protectors, safetyhantesses, lrte preservers etc.

c) Be sttre of the correct operation of any, and all, tools and, or equipmentlikely to be required during any lifting operations. Read operatinginstructiotts before using any device for the first time or if in any-doubt.

d) Always use the right tool fbr the job. Never nrake do with the wrongone.

e) Always stand well clear of overhead loads.0 Understand fully what is required fcrr any particular task undertaken as

part of the overall operation.g) Avoid leaning over the side of the ship and be aware of the location of

l i fe saving equipment.h) Tie all ecluipntent down and stow it crorrectl)/ during periods of heavy

weather .

17 .1 .1 .2 L i f t i ng Ec lu ipmen t Sa fe ty .

All appliances and gear used for lifting, lowering and handling loads must be inspectedand tested at regular intervals. In the North Sea att such ecluiphent is tested every 6months by a competent person. The actlral testing is normally caried out by speiialistcompanies and certificates are issued once the equipntent uncler test has been approved.

:_1 I

It is necessarv to test to 1.5 times the SWL for load testing currently as outlined inChapter 2 paragraph 2.1. i.

17.1.1.3 Safe Working Loads

frflltj,:q.ruipment musr be marked with the safg wgrking load (swl-). If any item ofIlftlng equlpment ls not marked it must not be used. If the ltem is in apparently goodcondition it should F Pu., to one side and se.nt to a speciilist cornpany'fbr teiiiirg anocerrification after which ir may be put back into use.'

L7.1.1.4 Out Of Date Equipment .

It is commol p{a.ctlsq for lifting srops, shackles and other such lifting equipment to becolour coded with oaint in the coloui of the month. riris iimptifi;s-;fe j;t"oitlir.tingthat it is in date as ill that ls .equi.ea ii to.nr^ur. that only the correctly coloured stropsetc',are used. Any jQuipment which is out of date must not be used bit can be Uactloaded and re-certified by an appropriare aurhority.

17 .1 .1 .5 Sa fe P rac t i ses

If equipment becomes damaged during use rhe operarion nrusr be suspended and theoffending item replaced.

Inexperienced personnel and anyone under l8 years ofage should nor bg in charge ofpowered lifting equipment unleis under instruition, in wiich .ur" .r,rt. r"p.*ijion uya competent person is requir-ed at all times.

Controls of lifting ancl handling equipment should be pernmnently and legibly markedwith function and opera.ting diiection shown by arrows or other (i*pi. ri.u,ir.Make-shift extensiorls should not be fittecl to conrrols nor any unauthorised alterationsmade to them.

Foot-operated controls should have slip-resistant surfaces.

No lifting. appliance should be used with any locking pawl, saf'ety attachment or devicerendered in-operative.

If, exceptionally, limit switches need to be isolated in order to lower a crane to itsstowage position, the utmost care should be taken to ensure the operation iico.preteAsafely.

Any power appliance should always have a man ar rhe controls while it is in operafion,it should never be left ro mn with l control secured in the oN pos,t,on.

ff,any power.lifring equipment is to be left unattended with the power on, loads must betaken off and controls put in 'neutral' or'off positions.

- -

wh91e practical, controls should be locked or otherwise inactivated to preventaccidental restarting.

When work is compieted power must be shut off.

l;:i:"tt safety points may be summarised in a chart form which can be seen as Figure

238

Figure 17 . lPersonal Safety

START

Ii

T H I N K A B O U T T H E D A N G E R S

Weigh up j ob haza rdsWe igh upenv i ronmen t haza rds

Dec ide on p recau t i onsto be taken

P R E P A R E

Pu t on app rop r i a tesa fe t y c l o th ing

Assemble correctt oo l s and equ ipmen tinspect forserv icea b i l i ty

Remove any l ooseequ ipmen t f r om a rearvhich might cause ahazard. Erect safetyequ ipmen t as requ i redf i o ' n h i n n ' r : r r l

protect ive screen)

P o s i t i o n D A N G E RW A R N I N G n o t i c e s ,safety barr iers asrequ i red

Pos i t i on equ i pmen tand rou te anyelectr ic , pneumat ico r hyd rau l i c cab lesin safest posib le way

CARRY OUT TASK

Wear appropr iatesafety c loth ing

Always use correct toolN E V E R I M P R O V I S EO N T O O L S

C L E A R U P O N C O M P L E T I O N

F I N I S H

Retu rn equ ipmen tto store or bay

Rep lace anyloose equipmentmoved

Remove not icessafety barr ierssafety equipment

Col lect tools

239

17 . l . L6 Crane S igna ls

It is most colilnon these days to use some form of voice communication directly to thecrane driver but there may itill be occasions when it is necessary to use hand signals toindicate your requiremenis. The current standard Code of Hand Signals is reproducedas Figure 17.2.

Code of Hand Sigrals

E M E R G E N C YSTOP

H O I S T LOWE R

SIGNAL \ \O T H E R H

D E F R I

I T H O N E H A N DANO ON HEAO

J I B D O W NK I N G J I B

/ , ?i i \;=-

TRAVEL TO MESIGNAL WITF

T R A V E L F R O M M EBOTH HANOS

TWTSTLOC

ROTATE WRISTO F

LEFT HANO

KS ON/OFF

{?n_s,Hl ll t

C L E N C H A N DU N C L E N C HF I N G E R S T OSIGNAL

'TAKE

T H E S T R A I N 'O R ' I N C HTHE LOAO '

? - S LI N D I R E C T I ON I N D I C A T E D

S I G N A L W. O T H E R H

E X T E N D J I B - .I E L t r 5UL

T H O N E H A N D. N O O N H E A D

\' l

] I

. RETRACT J I

r P I N G J I B

T R A V E L I N D I RT C T I O N I N D I C A T E D

OPERATIONS CEASE

Figure 17.2

240

17.2 F ibre and Wire Ropes.

Tferg are a variety of both man-made and natural fibre ropes and several different typesof wire rope in use offshore on vessels and platforms. The intention here is tointroduce the common types of both wire and fibre ropes, indicating the way they areconstructed, their breaking strains and some uses.

17.2.1 F ibre Rope Construct ion.

All twisted or laid up ropes are manufactured in the same way. The selected fibres arecombed.into long ribbons which are then twisted into yarns. These yarns are thentwisted into strands which in turn are laid up into the finished three or four strand rope.In order to achieve a good quality rope it is necessary to select and blend the fibrescarefully to ensure unifomtity. The spinning into yarns must be cerefully controlled toachieve a uniform cross-sectional size, and with all the fibres twisted in at the correcttension and at the correct angle. Finally the laying up of the finished rope must also beat the correct tension and angle which is detemrined according ro the intendedapplication of the finished rope. Three strand ropes are referied to as plain lay and fourstrand as shroud lay. with the four strands conrnionly laid round a central heart. Boththese types of rope are nomtally laid up right handed.

17 .2 .1 .1 Va r ia t i ons

Both plaited and braided ropes are available but they iire nor so common as laid upropes offshore. Their construction is the sante as outlined above exceot that the finalstage of laying tlP the rope is achieved diff-erently. These ropes norrnally are put tospecial uses such as for ruooring warps or anchor ropes ancl therefbre the ROV pilot isless l ikely to conle into contact with thenr.

17.2.2 Types and Proper t ies < l f Ropes

Broadly speaking ropes rnay be divided into two categories: synthetic and natural fibreropes. Outlined below are the main properties of these ropes.

17.2.2.1 Natura l F ibre Ropes.

a. Manila - This is made from "abaca" fibre and n-ray vary in colour from darkbrown to ivory white The rope is smooth, glossy, strong, flexibre, very

. ly.able, easl' to handle and has a very high resistance to sea water rotting.b. Sisal - This is made from "aloe" leaves and is a creanry-white colour. ihe

rope is very brittle, glossy, swells up when wet ancl it has a hairy surface. Topgrade sisal is e.cpral to rnedium grade manila but it is an unpleasant rope tohandle due to its rough finish and is not used for pref-erenCe in marinb work if' manila is available.

-

c. Coir - This is made from coconut fibre and is a reddish colour. The rope isvery elastic, floats, is rough to handle and is extremely resistant to sea water

. rotting. It rf about one sixth the strength and half the weight of manila.d. H9*p - This is n-rade from the fibre of the Hemp plant and is a dark brown in

colour. It is ntainly found in sntall sizes or as seiziirg twin in marineapplications. It can be stronger than manila br.rt its u.ie is restricted.

?.41

17.2 F ibre and Wire Ropes.

Tferg are a variety of both man-made and natural fibre ropes and several different typesof wire rope in use offshore on vessels and platforms. The intention here is tointroduce the common types of both wire and fibre ropes, indicating the way they areconstructed, their breaking strains and some uses.

17.2.1 F ibre Rope Construct ion.

All twisted or laid up ropes are manufactured in the same way. The selected fibres arecombed into long ribbons which are then twisted into yarns. These yarns are thentwisted into strands which in turn are laid up into the finished three or four strand rope.In order to achieve a good quality rope it is necessary to select and blend the fibrescarefully to ensure unifom'rity. The spinning into yarns must be carefully controlled toachieve a uniform cross-sectional size, and with all the fibres twisted in at the correcttension and at the correct angle. Finally the laying up of rhe finished rope must also beat the correct tension and angle which is detemrined according ro the intendedapplication of the finished rope. Three strand ropes are referred to as plain lay and fourstrand as shroud lay. with the fbur strands commonly laid round a central heart. Boththese types of rope are nomrally laid up right handed.

17 .2 .1 .1 Va r ia t i ons

Both plaited and braided ropes are available but they are nor so common as laid upropes offshore. Their construction is the same as outiined above except that the finalstage of laying up the rope is achieved differently. These ropes norrnally are put tospecial uses such as for tnooring warps or anchor ropes ancl therefore the ROV pilot isless l ikel i , to come irrto corltact with the'.

17.2.2 Types and Proper t ies < l f Ropes

Broadly speaking ropes ntay be divided into two categories: synthetic and natural fibreropes. Outlined below are the rnain properties of these ropes.

17.2.2.1 Natura l F ibre Ropes.

a. Manila - This is rnade from "Abaca" fibre and nray vary in colour from darkbrown to ivory white. The rope is smooth, glossy, strong, t lexible, very

. 9ytable, easl' to handle and has a very high resistance to sea water rotting.b. Sisal - This is rnade from "aloe" leaves and is a creanry-white colour. the

rope is very brittle, glossy, sweils up when wet and it has a hairy surface. Topgrade sisal is eclual to medium grade manila but it is an unpleasant rope tohandle due to its rough finish and is not used for pref-erence in marine work if' manila is available.

-

c. Coir - This is made from coconut fibre and is a redclish colour. The rope isvery elastic, floats, is rough to handle and is exrremely resistant to sea water

_ rotting. It is about one sixth the strength and half the weight of manila.d. Hemp - This is made fiom the fibre of the Hemp plant and is a dark brown in

colour. It is nrainly found in snrall sizes or as seizing twin in marineapplications. It can be stronger than manila bLrt its use is restricted.

241

r

L7.2.2.2 Synthet ic F ibre Ropes

a. Polyamide (Nylon) - This is the strongest synthetic fibre after Kevlarwhich is only available for special uses. The rope is very elastic, soft, pliable,easy to handle, will not rot in sea water and is pest resistant. It will absorbwater however and will swell up if left for periods in the water. The rope driesquickly but should not be exposed to sunlight for long periods. Nylon is the duPont trade narne for polyamide.

b. Polyester (Terylene) - This rope is only a little less strong than nylon, forexample 6 mm Nylon would have a breaking strain of 750 kg. while 6 mmPolyester would be 550 kg., and it has low stretch, with some grades beingavailable pre-stretched. This rope has the same characteristics as Nylon exceptthat it will not absorb water. Terylene is the ICI trade name for polyester.

c. Polypropylene - This rope has almost the same strength as polyester. Incommon with Nylon it will stretch, in fact 407o before parting, and it willabsorb water but only 0.IVo of its weight. This rope floats and it will melt at1650 C. It is very common offshore.

d. Polythene (Courlene) - This rope is much less strong than polyester, forexample its breaking strain for 6 nrm would be 375 kg. This rope has lowstretch, it floats, it will not absorb water, it is resistant to sunlight, it is usuallyorange in colour and has a waxy, slippery feel to it. It is cheap and is widelyavailable. Courlene is the manufacturer's trade name.

17.2.3 Use and Care of Ropes

The Common causes of failure are: excessive stress; this danrages the fibres, abrasion;or cutting ;on a sharp object: exposlrre to chemicals and bad storage with inadequateventilation, particularly of wet ropes. Rotting often comn.lences on the inside of a ropeand is difficult to detect unless the lay is opened. Loose fibres or dust on the insideindicates dry rot. If the interior is darker than the outside, this is a sign of dampnesswhile a grey powderl, substance indicates ni i ldew and poor venti lat ion. Ropes shouldbe stored awav wherr dry, on gratings or hung on wooden or galvanised hooks. Thestoreroom should be well ventilated and dry, away f}om r.noist air. Artificially driedropes will becorne brittle, as nrost fibre ropes are spun with a srnall amount of lubricantintroduced at the tinre of manufacture to reduce internal fric:tion and increase rope life.If left on deck, ropes should be protected from sunlight, rain and frost (as the iceparticles cut.through the frozen rope ). Ropes should also be kept away from allchemicals, such as cleaning nraterials, paint thinners, etc. After use in salt water, ropesshould ideally be hosed down with fresh water. Knots and kinks should be avoided asmuch as possible. When coiling rope, as most ropes are laid up right-handed , theyshould be coiled right handed i.e. clockwise. When heaving on a rope, ensure that itdoes not chafe wherr passing through fair leads or over the rough edge of a dock wallashore. Sharp edges must also be avoided. Mooring lines (warps) may have shortlengths of plastic hose tied onto thenl to reduce chafe. When a rope passes around asheave, the sheave diameter should be nine to twelve tinres the rope diameter.When using winches with ropes, ensure that a laid rope is put onto the winch in thesame direction that it should be coiled down. The lead onto the winch must be suchthat the furns on the drunr do not ride over the followir]g turns. See Figure 17.3

242

wire ropes gre ysed extensively,for all type of standing and running rigging, cranewires, winch wires and strops. In any o{shorg app[cltion where F.oVs #e ueingdeployed wire ropes in one form or anottrer will G used.

Figure I7.3Lrading a RopeOnto aWinch

17.2,4 Wire Ropes

17.2.4.1 Selection

when selecting a wire rope four main factors should be considered:a. What job is it to be used for?

i) If th. wire is required for standing rigging it witl be less flexible, f9r example, than if it is to be used foi running rigging.

b. What safe working load is required?i) This will effect either the diameter or the material properties of

the pp9. If.it is ryquired ttrat the diameter of the rope be aparticulal size, for example, it may be necessary toselect a hightensile type of wire rope.

c. Will the job require specialist properties form the wire?i) A Tirfor wire needs to be wire core instead of hemp core for

example.d. Will it have adequate resistance to the corrosive factors present in the

environment?i) Standing rigging is often galvanised to provide some corrosion

protection because of the aggressive environment it has towithstand.

17.2.4.2 Construction

All specialist handling qualities a Iopq possesses are introduced into the rope in themanufacturing stage. Therefore, it is important that we know how a rope is formed asthe material properties are selected to match the method of lay. There are three basicforms: Ordinary Lay;

Lang's Lay;Preformed.

a. Ordinary \uy - { roqe of.ordinary lay has its strands laid up togettrer right

handed, in the gpposite direction of their constituent wires, whiih aie Uia upleft handed to form a srrand. See Figure 17.4

-+-l

ORDINARYLAY

Figure 17.4

b.. Lang's Lay - A rope of Lang's lay has its strands laid up together in thesame direction as their constituent wires are twisted. This means that ca.re isrequired when handling Lang's Lay as it tends to unlay itself. See Figure 17.5

LANGSLAY

Figure 17.5

c. Preformed rope - This is a modern development in the manufacture ofwire rope. The manufacturers form individual strands into spirals before thestrands are laid into the rope. This is known as preforming and results in eachsfand laying in its correct position in a completed rope without a tendency tospring out should the rope break of be cut. Preformed ropes are safer to handle.

L7.2.4.3 Specialist Qualit ies

Three factors which determine a rope's specialist qualities are:a. The type of core that is used in the wire rope;b. The size and number of individual wires used to form a sffand;c. The number of strands used to form the wire rope.

a. Cores - The type of core used in a wire rope plays a part in the whe'sflexibility, rigidity and resistance to crushing.

1) Flexible Steel Wire Rope(FSWR) and Extra Special Flexible Steel WireRope @SFSWR) generally have a core of manmade fibre, occasionally natural,which is impregnated with a lubricant to reduce corrosion. ESFSWR isgenerally stronger than FSWR, as it is made of better quality steel.

ii) Steel Wire Rope (SWR) frequently has a steel core and contains fewerwires in each strand than flexible ropes. trt is generally used when strength is agreater need than flexibility.

. , A A

b . Wires. Steel wires are often described as being of , for exanrple, "6x37"construction. This description means that the wire consists of 6 strands, eachcomprising 37 wires. There is a wide variety to choose from, as an illustration:

i) 6 x 24 Galvanised. Figure 17.6 illustrates a Round Strand Rope, righthand lay, which is 6 x 24\aid over a fibre core. This type of rope wouldcommonly be used for topping rope and cargo runners. The maJority of wireropes have six strands which form the rope. There are, howevei, multi-stranded ropes, used for their non-rotational properties and as many as l6strands rnay be used to form a rope.

6 x 24 Galvanized

Figure 17.6

ii) 12 x 6 over 3 x 24. Figure 17.7 shows diagrunntaticly a Multi-strand,right hand Lang's lay rope which is 12 x 6laid over A 3 x24 core. This type ofrope would comnronly be used fbr, cargo purchases on derrick cranes, anddeck cranes where non-rotating properties are desirable.1 2 x 6 o v e r 3 x 2 4

17.2 .2 .4 Hand l ing

Wire. ropes should always be treated with the utmost respecr. The following pointsshould be noted:

a. Never handle wire ropes when wearing rings on the fingers.

b. Neverkeep l wire ropg turned up around a bollard for a long period, especiallyif you have a pull of 50o/o or more of the breaking strain ofthe rope. fhis wiildeform the rope.

c. A wire.rope which is under a load near to the linrit of its breaking strain will91xt a high pitched whining note, it may vibrate and it r"nay show signs of oilbeing squeezed out berween the wires. A rope in this state in under 6xtreme

Figure 17.7

stress and the loading should be eased at once but in a controlled way, notsuddenly.

Always inspect before use. Look for distortion of strands, as this is a result ofkinking, crushing or serious crippling. Broken wires are a result of fatigue andwear. A rope with a good external appearance but with a dry powdery heartshould be discarded.

The diameter of any sheave over which the rope will pass must be correct. Thesmaller the sheave, the greater the friction and the smaller the bend radius. Thesmaller the bend radius the greater the stress concentration factor. See Chapter4 paragraph 4.3. The greater fiiction is caused because the strands and wiresfurthest fronr the centre of curvature move apart whilst those nearest movecloser together. This results in friction between the wires and strands and thesmaller the sheave the greater this friction will be. Generally the diameter of thesheave should be at least 6 times the circumference of the rope.

Coiling. Long lengths of wire rope should be stowed on reels. Wire rope isless able to absorb turns than fibre rope, so when coiling down it is sometimesnecessary to use left handed loops called "Frenchmen". Frenchmen serve tocounteract any twists caused by coiling down right handed. See Figure 17.8

Figure 17.8

Opening a coil. A coil of wire nlust not be opened up in the same manner as acoil of rope or a mult i tude of "kinks" wil l be the result. Instead, i t should beunrolled in tlre opposite way to which it was nrade up. Small coils can be rolledalong the deck in the sante nrAnner as a hose is unrolled, but larger ones requirea turntable. No special turntable is kept for the purpose, so one has always tobe improvisecl. This is best done with two substantial pieces of wood lashedtogether to fomr a cross. Two bridles are attached by nraking an end fast oneach leg of the cross, about midway between the centre and the ends, and thebights must be long enough to reach through the centre of the coil when it is laidon the wooden cross. The bridle is then suspended from a suitable position, ora small crane if one can be dedicated for this purpose. The wire can then be un-coiled and it will revolve freely if the crane hook or nrethod of suspension isfitted with a swivel. Otherwise the coil must be landed occasionally to take outany turns put into the suspension device.

Cutting. Befbre cutting whipping or strong tape must be put onto the wireeither side of the cut, otherwise, once cut, the strands nray fly apart and spoilthe rope for some considerable distance. A few sharp blows with the edge ofthe hammer in the space between the whippings (about 25 nrm) will flattJn thesurface, so that the sharp cold chisel will cut more evenly. Cutting must bedone on a good, solid foundation, so that a clean cut is achieved.

d .

f .

ttD '

246

17 .3 Sa fe R igg ing P rac t i se

Rope manufacturers will provide infbmration on the safe working loads for theirproducts and tables are available which can be consulted. For general use, however,laid out below as Figure |J.9, are the recommended safe loads which can be usedwith fibre rope, FSWR, stud and open link chain. These formulas can be used innormal working conditions.

METRIC FORt',4ULAE FOF BREAKING STRESSES OF NATURAL AND SYNTHETIC FIBRE ROPE,STEEL WIRE ROP€ AND CHAIN

FIBRE ROPE 3 strand hawser laid

FLEXIBLE STEEL WIRE ROPE

STUD LINK CHAIN

OPEN LINK CHAIN

MATERIAL

Grade 1 mani l la (7mm to 144mm)High grade mani l la (7mm to 144mm)

Polylhene (4mm to 72mm)Polypropylene (7mm to 80mm)

Polyester Oerylene) 4mm to 96mm)

Polyamide (Nylon) (4mm to 96mm)

6 x12

6 x24

6 x 3 7

GRADE 1

GRADE 2

GRADE 3

GRADE 1

GRADE 2

(4mm to 48mm)

(8mm to 56mm)

(8mm to 56mm)

(12 .5mm to 120mm)

(12.5mm to 120mm)

(12 .5mmto 120mm)

(12.5mm to 50mm)

(12.5mm to 50mm)

FACTOR{Breaklng Strajn)

zDz/3oo

3D'l3oo

4D'/300

5D'�l3oo

1 5d'1500

zoD'�l5oo

21D'�/5oo

2oD2/600

3oD2/6oo

43D'�/6oo

2oD2/600

3oD2/6oo

SWt., Ereaking Strain

The drameter D is expressed in mill imetres, the breaking stress in tonnes.

Figure 17.9

I 7 .3 .1 Shack les

Shackle sizes and types vary ranging frorn about 25 mm in length to over 1 m. Theydo have one thing in common for offshore use; all are tested and stamped with theirsafe working load (SWL). It is also common practise in the North Sea , as has beenstated previously, for all lifting equipment, including shackles, to be colour coded toindicate that it is in date for test..

17.3.1.1 Safe Use of Shackles

In any situation where a shackle is employed as part of the rigging only tested shacklesshould be used. This will elinrinate any risk of failure of the rigging and thus ensuresafety of personnel. Whenever shackles are being used they rnust be moused toprevent them beconring accidentally un-fastened. Figure 17.10 Shows diagrammaticlyhow this is done.

1,1'7

Mousing

Figure 17. l0Moused Shackle

L7.3.2 L i f t ing Strops

Similarly whenever lifting strops are employed they must never be doubled over andthe recommended nrethod recluires the lifting hook to be placed centrally with the stropforming an angle of 1200 where it hangs over the hook. Figure 17.11 i l lustrates this.

F igu re l 7 . l lSafe Use of a Lifting Strop

17 .4 Knots, Bends and Hi tches and Thei r Uses

In the normal course of work around an ROV spread it is probable that you willfrequently need to secure objects in place and the most likely way of doing this is byusing rope or some form of cordage. If the term "knot" is then accepted as the generalwork for a fastening made with cordage, some more precise definitions follow:

a. The standing part. Is the main part of the rope above a loop or bight. Itis the part opposed to the end.

b. The end. Is the end or unsecured part ofthe rope.c. A bight. Is a half or open circle in a rope and also refers to the middle

part of a length of rope.d. A loop. Is a closed circle in a rope.e. A knot. In the precise meaning of the temr , is any knot other than a

bend or a hitch. The best known knots are "stopping" knots, such as theFigure of Eight knot, which is used to prevent the rope running outthrough a cleat or fairlead.

f A bend .ls the knot used for tying one rope to another.g. A hitch. Is used for fastening a rope to another object, such as a spar, or

tent peg. See the fol lowing diagrams. Figure 17.12 to 1l.25.

248

Figure 17.12

249

Stopping tail end of rope runningthrough a sheave of a block

Figure 17.13

General purpose knot for joining twoof equal sized roPes together.

Figure 17.15

FIGUREOF EIGHT

KNOT

Used on tail ends of sheets, to stopends running through clews

or sheaves of blocks.

Figure 17.14

KNOT

250

Figure L7.16

: SHERMAN'S: =ND

Sheet bend orswab hitch Double sheet bend

Figure f7.18

To secure boats painter to buoy ring

Figure 17.17

( i i )

Blackwall hitch

To secure lifting pennant to lifting hook

Figure 17.19

2 5 1

Used in life-saving situations, i.e.securing a lifeline to a diver, or

man working from heights

Figure 17.20

To join two uneven sized ropes together

Figure 17.21

252

-----ar

IIII

IIl

CLOVE HITCH

t l i l l lGeneral purpose hitch. Can be usedfor securing boats painter to mooring

ring for short durations.

Figure 17.22

ROUND TURN AND TWO HALF HITCHES

General purpose hitch for securinqlifelines to anchor points on barge'or harbour wall. Boats painters to

bollard or mooring points on jetties,

Figure 17.23

:

TIMBERHITCH

c l i f t pi l ings, t imber or any roundcylindrical objects.

Figure 17.24

Lifting slippery, shiny cylinders,scaffold poles. etc.

Figure 17.25

2_53

1 7 . 5 B l o c k s

This item of rigging is in comnron use in many different lYPes of lifting equipment such

as cranes, launching sy;i";;, winches "t.. bJ"uute it is in'such widespread use.the

various parts which go to making up a "on1-on block are shown in Figure 17 '26

F igu re 17 .26Parts of a Block

17.5.1 Types of B lock

Blocks are put to nany uses and there are specialised. ty.pe.s.available, obviously for

ip.riri puipor.t. Tw'o type^s which may well be included in ROV deployment systems

aie snatch blocks and lead blocks.Snatch blocks f,aue one itreet< hinged ancl held in place by a locking pin' They can

therefore be insertecl into a working line and this is their purpose.

Swollow

Sheave Pin

254

Once in place they can then be employed to change the direction of pull on the load andthus become Lead blocks. Common blocks are frequently used foi this purpose whenthe rigging is first being set up and they can be threaded onro rhe falls oi working line.

1 7 . 6 T a c k l e s

A brief introduction to tackles will illustrate the method employed by all cranes andsimilar lifting devices. A tackle is a sin-rple device which givei incr6ased power by aconrbination of blocks and ropes. The number of sheaves in the block, the manner inwhich^the rope of fall is rove through them, and whether or not the standing part ismade.fast tg. the. top or bottorr.r block are all distinguishing features of the uiious typesof tackle. The theoretical power gained is proportionate with the number of sheav'es inthe tackle and typically varies from two to nine times according to the type of tackleuseo.

17 .6 .1 Gun Tack le

The name for this sirnple tackle is derived fiom the fact that these tackles were used torun out the guns on sail ing tren o' war. I t simply i l lustrates the principle involved inusing p.urchases to ittcrease lifting power whiihis why it is illusirated^here. Thetheoretical pow^er gain is two or three depending on whether it is rigged to advantage ordisadvantage. See Figures 17.21 and 17.29.

DIRECTIONOF PULL

DIRECTIONOF TRAVEL

Gun tackle rigged to disadvantagePower gain ratio 2:1

Figure 17.27

DIRECTIONOF TRAVEL

Gun tackle rigged to advantage.Power gain rat io 3:1.

Figure 17.28

DIRECTIONOF PULL

255

Figure 17,29

" :

Figure 17.31257

17.7 ROV Deploynrent Systems

ROV's can be operated fronr the following:

a Monohull vessels;b. Semi-submersible vessels;c. Fixed pliitfornts.

ROVs are launched either over the side or through a moonpool and may be deployedwith or without a cage or garage. There are several handling strategies bn_t fourexamples will adequately ilhtstrate the possibilities and these are outlined below.Whatever the method, however, it will require the use of either a crane or a winch toconrrol the vehicle. See Figure 17 .29 unO tZ.lO. If a winch is used it wil l commonlyemploy an A frame to suspend the ROV clear of the deck and move it inboard andout'boatO. The crane has the advantage of being able to cover a larger area on the deckand is more flexible. The A frame is-more rigid and there are fewer controls whichmakes operating easier. Both cranes and winches must be designed within the ̂requirements ofan approved classification society, such as: Anterican Bureau ofShipping; Lloyds Register of Shipping or Det Norske Veritas. Winches are verywideiy Jsed anO are 'ilost often controlled directly by the ROV teanr as opposed tocranei which most often have a dedicated operator. Some specific points on winchestherefore will not go amiss.

17.7.1 Winches

Of the numerous factors considered when designing or choosing a winch the mostobvious is the line pull required. This is determined by the weight to be recovered andwill not be more than the 6reaking strain of the cable, taking account of the fPPropriatesafety factor. Another factor is the drum diameter which will be determined by theminimum bending radius of the wire. The number of wraps to be stored on the drumwill also be considered. This will be detennined by the length of the umbilical to beused and the cable cliameter, this in turn will detemrine the clrunt flange diameter. It isbest to use a winch with a Ievel wind to ensure the unrbilical is evenly spooled. If thisis not possible a goocl fleet angle is required which is not always possible when deckspace is at o p.etiirm. Anothdr important factor is the braking method. Two methods-e co--on. Manual braking is used during normaloperations and an automatic brakewill be applied in an emergency situation, such as a rapid drop in oil pressure.

17.7.2 Pick-up Hook Recover-v

In this case the umbilical usecl is medium and lightweight and nray be winch or handtended. When this approach is used simple cranes are enlployecl,often o-n an.opportunity basis. Thjs method of launch and recovery is generally employed whenl ive boat ins. See Fisure 17.31

258

17.7 .3 Speciat is t Latch ing

A specialist "grabit" or "go-getter'is

run down the umbilicarl and latches a pick-updevice to the top of trre vehidle. The vehicle is ttten .i.or.r.o using a dedicated crane.This method is generally used *iihort a cage and in a live boat situation.

17.7.4 Umbi l ica l Launch and Recovery

This method is occasionally used with large vehicles which have sufficient power tomanoeuwe with the amroured cable that iJnecessary to tu[. tne weigtrioiiti. u.r,i.t.during the launch and recovery. once more this -etnoa is mainly used when liveboating and without a cage.

17.7.5 Cage and Winch Deployment

The frameworkSpooling drunrSlip r ingsPower source.

Additio-nally some cages are tltted with a depth gauge and a T'v canrera. This enablesthe Rov's position relative to.thecage to beass"essJo. ir'. ,,nrhrilical_f'rom_the surfacewinch to the cage is annoured and hJavy duty to take the *,1.rr., and strains of thelaunch,,anp recoie+ anci the vehicle un.,uiti.ri iirigrrLi. rrlls vehicle umbilical may beneutral ly.buoyant in sea water. This neutral uroya'ncy ir iur ' t i t . ty to rotl [o*.u., u,any small cut itl the cable outer will allow sea water to enter ancl the neurral buoyancy isdependant on the specific gravity of the warer anyway. The cage merhod of launch andrecovery provides several advantages cornpared io oti.r metirois. These in.ruo.,

Vehicle protection during launch and recovery:Isolation of unrbilical drig from the vehicle;

'

A merhod of carrying tools down ro rhe *oikrit.:A nreans of kcepin-e ihe main unrbir icar .te'oiourrr ircrions.

fr:.^t:.::,"l1rl]"g the vehicre is lowered from a dedicated winch usin.q an A frame.- - - - - - - - - . r . . . i ^ : . ._ : : " rJ rvvywruu r rv r r r d usu lu i . l r . so w lncn usrng an A t rame.

:T,ttji"l:1s: yflligi,'3s.. arrangemenl yl'.f the vehicle is pa.[eo inio-it'or. itT:l:::;,:*1{^f::,,r:ryll thgre"th.e uer,icie ii r,*r,.j ",i;,fi;:#:'"rfi;i.';.,type of cage is employed ir will contain the fbllo*in*r ilig ntaJor elenrents:

111.":X;,::11,-o^Y.:'::19_.|:.iJ,?,::,.d by fendering to absorb rhe strains imposed by1:-:glly:k whi,9l is ine,vitabt. t,, no"'1ri;p;;;;,,; ti;. ffiJi';.Ji't:minimised by caref,r handring paying til*rr;;;;;iil i" ,rrii"irrrs lng swlnglngmot ions. See Figure l j .3Z.

-

Figure 17.32

2-59

II

17.8 Navigation

The nature of the work undertaken by ROVs is such that an understanding of^someaspects of navigation are an asset. Being able-to.follow a. compass.c.ourse, fore*lmpte ,is a sf,ll that is required of any-ROV p1lqt. Similarly the ability to be able to

interpiet intormation availabie on chartiis a helilful technique to have when planning a

dive in a new location.

17 .8 .1 Compasses

Tradirionally compass cards were marked in points (one point is i i4 o; but now they

are marked in degrees. It is often adequate when steering an ROV . to gi by the-"o-pitr points ind for this reason the compass. rose is ieproduced as Figure 17 .33. lfit is necessary to steer a more accurate course it is conventional practise to use 3 digis

to indicate the bearing, as in l80o or 0300'

$'l{1y;V V t(),,1-l

\: ll

Figure 17.33

260

17.7.3 Speciat isr Latch ing

A specialist "grabit" or "go-getter'

is run down the umbilical and latches a pick-updevice to. the top of the vehidte. The vehicle is then recovered using . oraiJui"a crane.This method is generally used without a cage and in a tive uoat situation.

17.7.4 Umbi l ica l Launch and Recnvery

This method is occasionally used with large vehicles which have sufficient power tomanoeuvre with the armoured cable that iinecessary to tu[. the weighioiirie uenicteduring the launch and recovery. Once more this *"thoO is mainly used when liveboating and without a cage.

17.7,5 Cage and Winch Deptoyment

A cage containing the vehicle is lowered from a dedicated wrnch using an A frame.The actual, cage rnay be a garage *r*g"nl.nt where the vehicle is parked into it or itmay be a "top hat" arrangenrerit wherc"the vehicle is larched ,no.rirr'. tog"."wt ur.u",type of cage is enrpr.yed it will corrain the fbllowing "r;.i"i elenrents:

The tiameworkSpooling drunrSlip r ingsPower source.

Additio,nally some cages are fitted with a depth gauge and a'fv camera. This enablesthe ROV's position reiative to, the.cage to t',e as#ssJo. i6e unrt,ilical-from_the surfacewinch to the cage is anrlourecl and hJavy duty lo iot. trr. yresses and strains of thelaunch and reco-veu ancl the vehicle un.,bili.ni iirigrrLi. iiris vehicle umbilical may beneutral ly.buoyant in sea water. This neutrar uroyiniy is i i i rr i tely to lasr however asany snrall cut in the cable outer will allow sea warer ro enrer ancl ihe r;;;;i bJoyuncy i,dependant on the specific gravity of the warer anyway. The cage method of launch andrecovery provides several advantages compared io otirer metho"ds. These in.l-uO-",

Vehicle protection during launch and recovery;Isolation of unrbilical drag fronr the vehicle;

'

A method of carrying tools down ro the *oikrit.:A nreans of keeping ihe main unrbir icar ctea. oiourrrucrions.

The cage and RoV 'should be protectecl by fendering to absorb.the strains imposed bythe odd knock which is inevitiible in nomial op..atl3,ii. ih.r. knocks can beminimised by carefirl handling payirrg particulir attentiorr to nrininrising swingingmot ions. See Figurc 11.32. " '

i

:I

I

261

17.7.6 Mot ion Compensat ion

Occasionally motion compensation is required for the system. One technique used inlive boating is to attach floats to the umbilical; this essentially decouples the vehiclefrom the surface forces. Active and passive winch compensation is also available butthese methods are complex and involve the use of: high response drive systems;counter weights or accumulators. A different approach has been used which involvesthe aeration of the moonpool. This permits the safe launch and recovery of the vehicleup to force 5/6.

17.7.7 Launch Hazards

If motion compensation is not used the homing and docking of the ROV with thelauncher can be both difficult and hazardous. Small ROVs, up to 500 kg, normallyrespond adequately to a little application of appropriate shock absorption and bruteforce. Where ROVs are being deployed without cages they are normally connected tothe handling arrangenrent at the surface and hazardously close to the vessel. Abrupt,dynamic loading to the hoisting system often occurs when lifting the vehicle clear of thewater in these cases. If motion compensation is not used this calls for careful timingand a good deal ofexperience on the part of the winch or crane operator.

17.7. l l Porver Requi renrents

Normally this is 440 volts 3 phase and most often,the power train on the winch iselectro-hydraulic which allows for good speed control. The size of the power supply isdictated by the line speed and pull. This is established by distance per unit timernultiplied by force (the units of power). The number of wraps of cable around thedrum must be taken into consideration as this affects the torclue required and startingcurrents, which are higher than working current, must also be considered.

17.7.9 Locat ing the Launch Si te

A centrally located site on the vessel places the ROV near to the pitch and roll centre andmaximises safety ancl efficiency during launch and recovery. A central location willalso provide shelter frorn the elemerrts which is of benefit during nlaintenance periods-If a false deck can bc provided it will allow access under the deployment system and itwill help to isolate the system fronr sea water. It will also give access for cables andhydraulic lines. Finally if a winch is being used in conjunc:tiolr with a crane ofopportunity it nray tre necessary to use lead blocks to ensure a c:orect lead ismaintained.

17.7.10 Operat ing in T ide or Weather

Unless_an ROV weighs several hundred kilos with power to match it is not expected tooperate on the surface or in the splash zone in any adverse weather conditions. Thefirst point about operating in these conditions then, is to get below the surface asquickly as possible. 'fhe

second point is that the effects of current will be morenoticeable on the unrbilical than on the vehicle itself. As a guide "eyeball" ROV's willgenerally operate in 1 .5 knots of tide or current but, because of the current effects, it isprudent to pay particuler attention to the reduction of drag on the umbilical. This iswhere the garage method of launch and recovery is such an asset and why it hasbecome so favoured.

262

E

1 7 . 8 N a v i g a t i o n a l

The nature of the work undertaken by ROVs is such that an understanding of someaspects of navig.ation are an asset. Being able to follow a compass cou.Ie, forexample ,is a skill that is.req-uired of any ROV pilot. Similarly ihe ability to be able tointerpret information available on charts is a helpful techniqueio have when planning adive in a new location.

17.8.1 Compasses

Traditionally compass cards were marked in points (one point is 114 o) but now rheyare marked in degree.s. It is often adequate when steering an ROV to go by theco.mpass points and for this reason the compass rose is ieproduced asFigure 17.33. Ifit is necessary to steer a more accurate course it is conventional practise tJ use 3 digitsto indicate the bearing, as in l80o or 0300.

+Itr

+ r

NYle/ LJti

f p

rfAr)ir ) - : )\:,\Y/v / , 67 V

% ' (

(?\

i"*c

\ , , 'a\.- t lE Is//:l/ c

//,

nq"

f .c

; *

E,.

5 . ;

lui,, ( \ r )\ ; . l L

\: l/

ffiFigure 17.33

263

17.8.2 Magnet ic Compass

The magnetic compass responds to the earth's magnetic field by way of a magneticneedle, which is freely suspected, aligning itself North South. On the bowl of thecompass is a "Lubber Line" and connected to the magnetic needle is a compass card.The compass is suspended in gimbals so that movements of the ROV do not interferewith the swinging of the needle. As the ROV then changes direction, the compassbowl moves with the vehicle, while the card is held in a North/South direction by theneedle. The relative movement between the lubber line and the card can then be readoff directly in degrees which indicates the heading of the vehicle.

17.8.3 Gyro Compass

Most ROVs are fitted with gyro compasses which use the properties of gyroscopicinertia and precession. A child's conical top, when not spinning, will topple over. If itis made to rotate rapidly it will not deviate from the upright position. This is anexample of gyroscopic inertia, i.e. the axle of a rotating body tends to remain pointingin a fixed direction. If a force could be applied to the rotating parts of a spinning bodyin such a way that it were not slowed down, it would be seen that the object wouldmove in a direction contrary to that expected. This is the property of precessionexhibited only by rotating objects. These two propenies of rotating bodies areharnessed in the gyro compass to produce a mechanism which continuously points toNorth, provided its sensitive rotating parts are kept energised from a suitable electricalpower supply. The gyro compass ideally seeks to align itself in the true north-southdirection, but, in common with most mechanical apparatus it is subject to small errors.These must be al lowed for when the conrpass is in use.

1 7 . 9 C h a r t s

The chart is an important and reliable source of infonrration, which is available to theROV pilot as required via the ship's bridge. The most conlnlon charts available in theNorth Sea are Admiralty charts, but word wide there are a great nrany variations. Allcharts use similar methods to indicate various features and objects on what is aconventionalised picture on a flat surface of a portion of the curved surface of the earth.

17.9. I Scale

The natural scale of a chart is the ratio of the area of the picture to the actual arearepresented therein. The larger the ratio, the smaller the scale and the less the extent ofthedeta i l thatcan be shown. Thus achar t hav inganatura l sca leof 1 :72,000 (1" to 1nautical mile) shows more detail than one with a natural scale of 1: 393,000 (5 " to 1nautical mile).

17.9.2 General lnformation

The general information in charts is given by means of standardised synrbols andabbreviations, which are listed in a key chart. In the case of Admiralty charts this isknown as chan 501 1 and is available is book form. This kei,chart will be available inthe ship's bridge.

264

17.9.3 Char t T i t le

The title is much more than a mere label and should be read carefully, since it containsmuch key information. The contains, in addition to a statement of the area charted,such key information as the natural scale, the way in which bearings, soundings, andheights of land, drying banks, or rocks are given and the datum levels from whichsoundings and heights are measured. The surveys on which the chart is based are alsoincluded, and often further information, such as the exact positions of prominent landfeatures.

17,9.4 Correct ions

Always see that a chart is up to date and so far as possible keep it so. Charts as sold bythe agent are corrected up to date at the time of sale and the corrections incorporated areshown by a string of numbers outside the frame of the chart at the bottom. Theyrepresent the year and numbers of the Admiralty or similar organisation's notices toMariners which are issued regularly. These notices, which are nunrbered in sequence,are careful, plain language statements of changes in harbour lights, positions orremoval of wrecks etc.

17.9.5 True Cornpass Roses

Circular notation. Several compass roses are usually provided. Each rose alwaysincludes an olrter circle or true compass rose, which is divided in degrees from 0o atTrue North, clockwise through East, South and West to 3600. The even numbereddegrees being indicated by radial lines, with the odd nunrbered degrees indicated bydots between them. Every tenth degree is indicated by a longer radial line marked withthe number of degrees. These trlle roses are so oriented that a line between 0o andl80o is the t rue Nor th and South.

17.9.6 Magnet ic Compass Rose

Quadrantal Notation. These are concentrically within the tnre compass roses and areoriented so that the North point corresponds to magnetic instead of true North, Degreemarkings are given in the same way as on the true rose.

17.9.7 Magnet ic Var ia f ion

A magnetic rose is twisted in relation to a true rose, for the North point of the former ismagnetic Nor1h, whereas, that of the latter is true North, the angle between North andtrue North is called the variatit'rn. It is not consmnt, but varies all over the surface of theearth. It also changes slowly with tinre. This can be ascertained from the informationprinted across the E-W line of the rose.

17.9.9 T idal Diamonds

The direction and rate of the tidal streams is given at selected points on the chart, in theform of a magenta diamond if it is an Admiralty chan. The chart shows a number ofletters, tidal diamonds, with printed details referring to the dianrond's position given ina box on the chart.

17.10 T idal In fornrat ion

There are many occasiorts when ROV's operate in areas subjected to tides. thefollowing information should be of use in these circuntstance.

-ll

iiJ

26-5

17.10.1 Causes of T ides

The tides are caused by the gravitational pull of the Moon and the Sun, the moon hasthe greater effect. The-ration of the effecis of each body is roughly l:,3 \.e. the Moon'spulftccounts for 7 "units" and the Sun's for 3 "units". The planets also exefi muchsmaller gravitational attractions. Both the earth's atmosphere and the watersurround.ing the earth are free to move in response to the motion of the sun and moonaround theiarth. The atmospheric motion is not significant, causing only a smallchange in pressure through the day, but the water; being more dense, ubulg^es"

signiEcantiy towards the attracting body. The bulge occurs on both sides of the earth,as shown in Fisure 17.34

Hw Sun--)

F igu re 17 .34Tidal Bulges

Generally there are two high watel and two Iow water times in each24 hour periodexcept in the Pacific. The earth rotates about its axis anticloc:kwise once every 24hours. The moon orbits around the earth, in the same directiort as the earth's rotation,once every 292 days (approxiniately). This means the lunar day is longer than an earthday by about 50 minutes due to the nroon nroving in the sanie direction as the earth'sroiation. This in tllnt nteans the interval between two high waters or two low waters ison average 12 hours ?-5 minutes, giving a "semi-diurnal" t ide i .e. twice aday. InEuropean waters the tides are alnrost invariably semi-diurnal in character. In the pacificthe tide is diurnal with only one high and one low each day. Local anomalies do occur,at Southampton for exan-rple there are four high and low waters each day caused by thetidal streani flowing around the Isle of Wight. The range of the tide is much affected bythe shape of the sea or ocean, the gradient of the sea bed etc. If a sea or ocean has anatural period of oscillation near to the period of the tidal forces, then a greater rangeresults.

-The North Atlantic has some of the greatest ranges in the world, particularly in

the Bay of Fundy where a 17 rnetre range occurs at spring tides. In the Mediterraneanthere is very little tidal moventent; generally less than 0.7 nletres.

17.10.2 Spr ings and Neaps

The Sun and Moon ntay act together or at 900 to each other. They act together at Newand Full Moon and at 900 to each other at flrst and last quar"ters. At New and Full moonthe tides are higher at High Water and lower at Low Water than the average, givingspring tides. At first and last cluarters the High Water is lower and the Low Water islrigher than the averilge, giving a smaller range than averagel termed neap tides. SeeFieure 17.35

266

New Moon

oSprings

LWN bw Water Ncaps

LWS Low Water Sprints

Last Quaner

CNeaps

{ Earth }\-/

Ncaps

cFirst Qua,rter

Full Moon

oSprings

Figure 17.35Spring and Neap

TidesThe Sun and Moon move North and South above and below the Equator. The Suntakes a year to make a full cycle front 2320 N to 2320 S and back again, while theMoon takes about 26 days to move from 2820 N to 2820 S and back again. When theSun is at the Equator it gives the most direct pull to the senti-diurnal tides and thus thegreatest tidal range. The same applies to the Moon. The Sun is at the Ecluator onMarch 21 st. and Sept. 21 st. and the New or Full Moon nearest to this date gives riseto the most extreme tidal range; pru-ticularly with the Moon also at the Equatoi. Thespring t ides near March 21 st.. presunrablv give r ise to the narle fbr the t ides having thegreatest range.

17 .10 .3 T ida l De f i n i t i ons

A number of terms have to be understood before calculations are caried out on heightsand tintes of tides. These are best explained by the use of a diagrant showing a tidepole in a coastal area. see Figure 17.36.

HWS High Watcr Springs

HWN High Watcr Ncaps

Height of tide MSL Mean Sea Levcl

SpringRange

[TJ,;"*'CD Chart DatumThis is a lcvcl choscn such that the sealevel rarcly fal ls bclow it . This isapproximatcl1, thc low'csI predictab'lc tidelevel undcr avcraSc nrclc\)rologicralcondit ions.

Figure 17.36Tide Temrinology

::I

I

III

I

267

17.10.4 Times ancl Heights at Stirndard Ports

A number of ports throughout the word are known as Standard Ports' At these'

observations have been made over a nu*l"ioiye-ans and the effects of the positions of

rhe Sun, Moon anO G Planets naue Ueen ditermineO for each Port' so that predictions

can be made for many years ahead for the tidal heights.which will occur at these ports

and the times of HW'.fi;W:'Tht;l;i;rmation iiavailable in tabular form various

sources such as tne nimiralry, R'eed's Af-unut or the Macmillan Almanac' The way in

which the tide rises and falls has atso U.en-iattfullyrcxamined to allow curves of rise

and fall to be produced for Spring ana Niai tides.'These ap Rlodugq{ 9y u number of

asencies the best t.nown of ifricfr is ttre'nimiiuft' These bobts of tidal curves can be

c6nsulted when the tidal height is required'

17 .11 Weather

In any operation undertaken at sea the weather must be considered' Weather

forecasts are available world wide and the local forecast should be consulted

before conducting oPerations.

268

CHAPTER 18 DRAG, BUOYANCY AND NAVIGATION

f8.0 In t roduct ion

There are two purposes for this chapter. The first is to introduce the effects of twoforces that effect ROVs in the working environment; namely drag and buoyancy. Thesecond is to discuss navigation on the ROV in practical terrns.

18.1 The Drag Force

One importan-t factor that should be appreciated when considering the effects of drag isthat.the drag force itself is still imperfectly understood and a great deal of empirical

-

work is undertaken, in wind tunnels and test tanks, at the design stage for newdevelopments because of this. This does not mean that ROVs are thus tested nor doesit imply that nothing is known theoretically about the drag force. It is simply statedhere to underline the complex nature of drag.

l 8 . l . l F lu id F lo rv

In considering drag the first consideration has to be the type of flow of the liquidcausing the drag. This can be either LAMINAR or TURBULENT and many detailedexperiments have been undertaken to study the effects of flow notably by O.sbouneReynolds who published his results in 1 883. His nanre is used to denote the non-dimensional REYNOLDS NUMBER that is decisive in deternrining the type of flow.The Reynolds number is deterntined thus:

R e =

Re - Reynolds nurnberp - DensityI - Selected Dimension

tt - Viscosity

The density of fresh water is taken to be 10tX) kg m-3 and sea warer about 1025 kg m 3.The viscosity of fresh warer is 10 3 Nsnr 2 (1.0 mPa) (Pa - Pascal and 1.0 pa = 1.0Nsm-2)An exanrple should illustrate the use of this formula

Example :-

What is the Reynolds nurnber fbr sea water flowing at 2 knots over a I m lengthof pipe?(i Kt approximately equals 2 nrl)

T h u s 2 K t = 2 X 2 = I n t - I

R e =

1 0 2 5 X 1 X l?

1 0 -1 02500

l

p u l

l.r

p u lu

269

At low Re the flow is said to be laminar but at high Re it is turbulent. The actualReynolds number separating these two states depends 9n l 1nd the ge_neral flol.andFigure 18.1 shows t6,e transition from laminar to turbulent for a ttrin flat plate alignedwith the flow to be at about Re = 500000.

18.1.2 Boundary Layers

The concept of boundary layers which was first inroduced by Ludrvig.Prandtl has ledto ttre development of FiuidMechanics as a science. This concept has been the subjectof much experiment especially in the aircraft industry and many-advances inunderstandi:ng have ociuned. There is still much that is not understood and workcontinues in tiris field. To illusfiate crurent knowledge consider a thin flat plate alignedwith the flow. The drag coefficient associated with this flow w-ould ngrmally !edenoted C6 but experinients have concenrated on the drag-coefficient for a singlesurface asihis siniplifies the study. The drag coefficient for a single surface is oftendenoted Cr (Ca = 2 C) and is callid the friction coefficient. The simplest generalboundary-layer case is summarised in Figure 18.1

c"̂ 0.010

0.008

0.006

0.005

0.004

0.003

0.002

0.001t d z s t d z s 1 0 6 z s d z 5 to8 z 5 toe

Re

Figure 18.1

As indicated on the diagram the Cp at low Re (less than 500000) is laminar and_ Cgdecreases as Re increas-es. Above Re = 500000 the boundary layer is likely to benrrbulent. The more turbulent the flow the better it resists separation from the plate.Separation generally causes high drag and to minimise this and give an attached flow astreamlined shape as illustrated in Figure 18.2 is employed.

FigureThis shape is obviously far removed from thewhich must be considered as a "bluff" shape.

18.2shape of a typical underwater vehicle

\\t

\

\

\

l e f\

\ I\

\ IC l l ' uvr

210

-!

Figure 18.3

This section has a wake typically.about the same width as the section containing flowthat may be; very turbulent, varying in a regular manner, or some combination

"of these

1wo. F^or a variety of sections, particularly circular cylinders the wake is often in thetorm of vortices in a regular pattern called the "Karman Vortex Sffeet" as shown infigure 18.4

d

+ot

18.1.3 Bluff Shape

Bluff shapes have detached flow at the rear and such a shape is shown in Figure 18.3

Flow-+Y = 1 . 2 6 d

Vortex street at Red 2000Figure 18.4

von Karman was able to demonsffate the arrangement in Figure 18.4 was a stable one-Ug t$t is-by no means the usual case as most such aoangeirents are unstable.Whether the vortex sffeet is stable or not, however, it cauies violent lateral motions ofthe fluid behind the object and is associated with a high drag coefficient, which iorbluff shapes is often denoted cap (this being c6 based on fr6ntal area).

a. A standard equation used throughout studies into fluid flow isBernoullie's equation :-

P = p * 2 p u z x + p g zP = Total Pressurep = Static pressurep - Densityg = Gravityz = Height above datum

P Ez= Potential pressure termu = Velocity2 = Constant of integration

l - -=4 .5d-J

O H

)::

271

This equation and practical experiments show that fluid dynamic fgr-ces ale proportionalto the rqu*" of th6 speed. It is a common practise to express fluid force by a non-dimensional force coefficient C and:-

F = 2 p u 2 C AWhere A is a reference area. A common example of the force coefficient C is the "drag

coefficient" denoted C-6.A useful device to redice drag is a " splitter plate" behind the object. The effects of thisare illustrated in diagrammatic form in Figure 18.5.

Car

1.03

Shape

o

Effects of Splitter PlateFigure 18.5

18.5 Effects of Drag in Practise

To illustrate the practical aspecLs of the effects of drag consider a neutallY byo131tt;;tk;6rJ ROV operating in 150 m of water on a pipeli3e inspection. Lh. ROV isdeployed from the dect aid locates onto the pipeline. th" diugt*.n q Fig. 18.7. showsa;fsnapsfrot" in time at a moment when ttre vesielis stationary vertically.abqy" Strtution'*y ROV with the tether also rising vertically. .This is not a realistic situation butit does gine a start point for a simple analysis o.f th9 t?S forcgl at this point in time.The drig coefficieirt can be found from ihe table in Figure L8.6

0.59Flow4

0.62

3D SHAPES

SHAPE co,

0.4

0.8

1 . 1

272

Support Vessel

Umbilical

150 m

Diameter = 40 mm

Frontal area

-/

{___

Tidalcurrent=2kts( Approx I m-l)

1 . 5 m x 2 m = 3 m 2

<|--Fr

Figure 18.7

Consider first the force on the umbilical.Fr=2 p u2 Cas A

= 2 x 1 0 2 5 x 1 2 x 0 . 4 x 1 5 0 x 0 . 0 4

= 1230 N

Now consider the force on the vehicle.Fz=2 p u2 C61 A

= 2 x 1 0 2 5 x 1 2 x 1 . 1 x 3= 1691.25 N (1690 I{)

F"tg figures demonstrate that the force on the umbilical is considerable and for longlgngtlts the dragon the umbilical is greater than the drag on the vehicle. The umbilicildrag is effectively reacted 50Vo atthe vessel end and 56Vo atthe vehicle. This meansthat the total force reacted by ttre vehicle is:

615 + 1690 = 2305 N

This in turn means that whatevel polver is available to the vehicle a percentage of thatpowelis required to overcome this drag force thus reducing the power availible forother functions such as manoeuvring. In the situation bein! coniidered here the ROVmust achieve a rate of advance along the pipeline of approximatnly lD ms-I. This willimpose^greater forces onto both the umbifi&l and the vitricte and iequire even morepower.from the vehicle just to go forward, T!" situation posed in this simple exampleis obvio-usly far frgm the real case where the forces on the umbilical in particular witi Ueimposed in a much more complicated manner as indicated in Figure 1g.g.

: t - 1

Support Vessel

Umbilical

F F r =40mm

Tidalcunent=2kts( Approx I m-l )

i

150 mFtn0 r

a,n

G-Fz

Figure 18.8

In this situation the force on the umbilical reacted bv the ROV must be resolved into itstwo components thus:

Fln = F1 Sin 300

and

Fth = F1 Cos 300

In this case which is slightly more realistic some vehicle power is required for bothhorizontal and vertical reactions. The real situation is even more complex of course butthe fwo points to bear in mind are; ttre drag force on the umbilical is considerable andwill always affect the vehicle handling, and the total available vehicle power is never allavailable for forward motion because a proportion has to be used to counter the dragforces. In any situation this puts an onus on the pilot to navigate accurately and thusminimise the need for manoeuvring and conserve power. The drag force on theumbilical is also an important reason for employing a cage or tether management systemwheneverpossibie when deploying the ROV.

18.8 The Buoyancy Force

This force is encapsulated in Archimedes'principal, which states, "An object immersedin a fluid is subjected to an upthrust equal to the weight of the volume of fluiddisplaced". Quantitatively it is easily evolved by considering a vertical cylinder filledwith air immersed in a liquid as shown in Figure 18.9

274

Znro gaage pressure

Cylinder cross-sectionalarea is S and length is I

z

I

Figure f8.9

From the diagram:-Buoyancy forceB=Fz-Fr

F z = P B h z S and F r = P g h r S

. . . l = p E h z S - p g h r= p g S ( h z - h r )

but h 2 - h 1 - l

h e n c e 3 = p g S l

h o w e v e r S l = V

T h u s B = p g V

It can also be seen from the diagram that the buoyancy force acts vertically upwardsthrough the centre of gravity i.e. it opposes gravity.

18.2.1 Practical Applications

In practise the application of the buoyancy force to ROVs is in either fresh or salt waterand it revolves around balancing the weight of objects. This allows a simplification tobe made substituting weight for mass. It is then possible to assume that 1l of freshwater is equal to 1 kg weight. and if 11 of fresh water is displaced the buoyancy forcewill produce an upthrust equivalent to 1 kg of lift. In order to apply thesesimplifications the basic equation is:

Weight of Object - Displacement of Object = Lift Required

j \t l

275

18.2,1.L Examples

Suppose that a block of concrete 2m x 1.5m x 3m is to be lifted from the sea bed inlSffaipttr of water. An inflatable lifting bag is to be used. How much free air will berequired?

Weight of Object - Displacement of Object = Lift Required

a. DisPlacement (D) =2x1.5 x 3 = 9m3

now 1m3 = 10001in fresh water and 10251in salt water

henceD=9x 1025 =9225k8

b. Weight of concrete =2200 kg m-r

henceweightof block =9x2200 = 19800kg

.'. 19800 - 9225 = 10575 kg

Now if 10,5751 of warer is displaced the upthrust will equal this. Thus an airbaq full of10,5751 of uir will displace thii amount of sea water. If ahis concrete block is to bemted trom the sea bed however the lift bag will have to be full of this amount of air attftut a"ptft. Boyles Law must therefore be ap4ied- to determine the reqqrgd amount ofair thaf has to

-be supplied from the surface. Boyles Law may be stated thus:-

Pt Vr = PzYz

The pressure at the surface is p1 an4 the pressure at the sea be{ is-p.z1nd tl.thgecalculations it is easier to woihin Bars ( I Bar is approximately I4.7 p.s.i.). Thus theamount of free air required will be:-

p " vV = ' -' p t

At 35m water depth the Absolute pressure is 4.5 bar (approximately) and Pt = 1 Bar

.'. Vr = 4.5 x 10575 = 47587 '51

It would be an usual ROV task to place such an air bag but it could be done.a more usual example may be to piace Eansponders on the-sea bed for a site survey.Soppot" the transpbnders-weigtr (;O tg_1n aii and a:! gflindrical in t!ry".yog udiineter of 0.2 mand a lengtfi of lm. How many Grimqby buoys of 5l displacementare required to make the tansponders neutrally buoyant?

Weight of Object - Displacement of Object = Lift Required

a. Displacement = lt t2l=TI x 0.12 x 1 =.0314 m3 = 31'41

60 - 31.4 =28.61

In this case the displacement makes very little difference to the amount of lift requiredbut the calculation is included for completness.

iIt

L _2'�76

b . The number of Grimsby buoys required will be: -

628.6 =5

18.3 Navigation

Navigating a1 Rov can be very straight forward operation as, for example, whenfollowing a nrnglile o1a survey when'the nltiguti6l *iii u" ir the handi oi a ipeciatistteam. It may also be difficult as it can be whei working off a plaforminath; sonilrand compass go unserviceable.

18.3.1 Open Water Navigation

The. task in.open water i,q made straight forward by the provision of the vessel,snavigation information displayed on-a VOU is ttre hOV'connol room. fne n-OV wittbe provided with a sonar transpondelwhSh is interrogar"a Uv trte stript iiyoioa"ourti"Positioning Reference SystemiHPRS). The ."tponrl"r.o- tttr RoV is the'n displayedon the electronic chart and the pilot can see at a glance his fosition relative to the vessel.Navigational targets are_displayed on the chart a"na ttr. piioi can ,,read,, his coursedirectly from this. The ROV will normally have itsow'n sonar and will be providedwith a magnetic compass and probably a gyro compass ur *Jr.

-rrt. .t-pt r"rl, "r.ato maintain course yhich is checked by th6'track on the Vou and as ttte ta'ne" to tlretarget closes the Rov sonar is.used to-pinpoint the rarget. Th" pil"t;;;"d;;

information to negotiate the vehicle in itre most enicieii way to the."quir.a porition.

18.3.2 Navigation Without Electronic Aids

On occasiol^it^TayF necessary to navigate onto a target without the aids outlined inpagagraph 18.1.1. In this case it will be teggssary to resorr to under*ai". pilo[g"using visual information_gained from the ROV cl6sea ctcoit television. The basiccourse can be maintained_using the compass but to establish the course -aO" eooa th""set and drift" of the RoV mus=t be estimated. This can u" u.rri"uJ;r;.u*f,;%vel byfacing the ROV intothe current, centralising ttre ca-era anJ tunng the bearine when thegl9ryq sggpgn$ed sediment is observedio be comine aiiedtrv it;h;;;#. Th"rectprocal of this bearing is the current direction. Havin'g established ttre sii the drift:T,T::l_llP9_!r adjusting the RoVs position so tttatitte,suspended particiei arednrnng clrectly across the front of the camera. The time taken for a sel6ctedparticle topass a known distance can be recorded. The known distance can be the lendh of amanipulator or some.other visible part of the ROV. Using trt. ii-fr" .quu-ii|,itrr'utdistance divided by.gme equals s.peed ?nd^the apppxrmlion that z -t

'uppro*i-ut"ty

equals I knot the drift can be estimated. As exlirience is gained ttte curienirpe"o *adirec ti on can be esuy,led"in tui tively bul.in i tialiy ryhit" dd;p;;;;";;, u"i"i g"i *athe foregoing should be of some.heip.- The set ind drifroith" .uo.nt togethei ioitt tt "vehicle speed can then be applied to a Vetocity Vector rriangre and the ri*ii *a ti-"to the target can then be estimated. These meihods.-.nri" that the Rov isnavigated onto a target using only its compass.

f83.3 Navigating Around a Structure

It is most important thatthe pilot makes himself familar with the structure by consultingthe platrorm drawingp. Some platforms have underwater identification --t"wrricrr9d ngvigalion and where these are in use the pilot -uit *uti himself aware of wherethey have \en placed. A hazard to navigation *ound u ,t utt*" is debris andsometimes fishine line, where this is likeiy to be^a-probtem iimust U" antiiipat"A beforethe dive. once th"e ROV is on tt" ituiiurc itself the_compass may nor be of anyassistance as it may

f {rgcte$ uy ft9 magnetic field of trr!- it ucture itself and the pilotmust rely on navigating visually much mdre than is the case-in open water.

271

The sonar can still be of great assistance provided the pilot is prepared to sit the vehiclein one position and allow the sonar pictue to build. It is vitally important that the routetaken around the structure by the ROV is memorised by the pilot. This will ensure theis not umbilical fouled up. The pilot needs to cultivate the skill of spatial awareness inthis type of operation much more than for other ROV operations because of this hazardto the umbilical.

i

218

E

CHAPTER 19 PRINCIPLES OF ROV PILOTING & SONAR

19.1.0 Piloting Competencies

19. l . l

This chapter is concerned with the principles of piloting ROVs which is oftenconsidered as something of a 'Black art'. The aims of this chapter are to explain assimply as possible the competencies (a competency is a combination of bothknowledge and skills) that an ROV pilot should have if he is to succeed in what is avery diff icult operar ional environment.

19.1.2

Piloting an ROV is often considered too difficult to teach, but rather as a set ofcompetencies that only 'talented' people can learn, and only then by years of operatingexperience. It is clearly true that work experience is required for the Pilot to be fully-capable, but we have found that the learning process can be considerably acceleratedby init ial Pi lot training in these fundamental -ompetencies.

r9.1.3

Although each principle is easily understood in isolation, the ful ly capable ROV Pilotmust incorporate thenr all at once and this can only be acconrplished by practisingthem. It is also true, that the progress of the trainee Pilot is bound to b-e impeded-ifthese principies are not properly understood during his initial training period as theyform a valuable 'frarnework' to build upon througlipractice.

19.2.0 Teamrvork

t9.2.1

The ROV Pilot is otte nrenrber of a snral l team of usually three people. For the Pilotto be able to operate successfully he nrust be able to uncierstancltheroles of, andcommunicate with the other team menrbers. The pilot depends on and mustcommunicate with the supervisor to take care of overall safety and the operationalplanning, the observer to keep track of the vehicles position and keep records, andthe winch man to adjust the umbilical length according to the vehicles circumstances.

The first fundamentul p,rincipLe is therefore that the Pilot c:an only be successful withthe assistance of the other team members and that clear uno,mbiiuous communicationmust exist between ettch of these team members..

19.3.0 Navigation

19.3.1

Navigating an ROV can be anything from very straightforward to extremely difficult.In open waterthe task is_made straightforward by the provision of a ships navigationdisplay showing the ROVs position relative to obstaclbs and targets using infoimationfrom the ships surface. navigation systern and the Hydroacoustic-Position"ReferencingSystem. This system ts however often unavailable and the Pilot may be required to

-

navigate in open water. This is again straightforward if the target is"large enough tobe displayed clearlv on sonar, i t is nruch more diff icLrlt , howevEr, i f thel i lot is 'searching for a small target such as a well-head or a transponcler, part icularly i f i t is

279

necessary to estimate the ROVs'Set and Drift' to the target, allowing for the currentdirection and speed as outlined in Chapter 18.

i) Once the currerlt is known, provided the through water speed of the vehicle is

kno*n allowing for umbilical lengih, then the Set, Drift and time to target can beestimated using nonrral methods of Triangles of Velocities'

19.3.2

When navigating around structures the Pilot needs to be familiar with the structureand any ide"ntifiJation marks an Chapter l8 gives more information on this subject.

19.3.3

Navigation is assisted by planning the dive to ensure that work is carried out with theoptirium visibility. Wheiever poisible the task should be undertaken with the vehicleficing into the current to prevent sediment disturbed by the vehicles own thrustersfromibscuring the work .site. In addition sediment must not be unnecessarily.disturbed from-the structure itself or the seabed. Although irt many cases this is'easier said than dgne' careful planning and care during dives can appreciably improvethe situation.The seconclfunclamt:ntal principle is that the pilot must be u.ble to navigate.effecttvely-in open *aie, or arountl'structures taking uccount o.f current, visibil,ity and umbilicalresirictions making use ofnu,t;igational aids effectively, incLutling where necessary'Dead Reckoning'.

19,4.0 Spatial Arvareness

19.4.r

In addition to being capable of Navigation, the ROV Pilot r.nust develop_a fig! degreeof spatial awat'etres=s. fhat is, he muit not only be able to go from A to B, but he mustbe able to visualise his relative posit ion in three dimensions with reference to A andB. It is very comnton for ROV Pilots to be aware only of the video monitors and todetermine the vehicles posit ion on this alone during tasks.

The accomplished Pilot wil l however develop a sense of spatial awareness thattranscends lhis and enables him to visualise the whole situation in three dimensions,rather like he was able to look at a model of the situation without the water beingthere. In this way he is able to reference everything to North and know the lie of theumbilical through or around structures and obstacles.This essential a6ility comes ntore naturally to some than to others, but in all cases itcan be improved by clrawing the support vessel, ROV and Umbilical onto workingdrawings at regular intervals during dives.

The rhird principle is rhat the Pilot must have a hi44hl,v developed sense of spatialawareness.

19.5.0 Vehicle Geometry and Systems

19.5.r

The position and power of vehicle thrusters, and the position of the umbilicalattachment points are particularly relevant to the understanding of the vehiclesperformanci. fhe geonretry of the thrusters affects the pedornlance of the vehicle in

280

EIiI!

]

:the most fundamental way. It is clear that a vehicle in the standard configuration oftwo stern thrusters, one vertical thruster, and one lateral thruster will behave quitedifferently to a vehicle having three vertical thrusters, and one horizontal thruiter ineach corner of the frame at 45 . The latter configuration is more effective inc.ountering the upward pull of the umbilical and enabling uniform manoeuvrability inthe horizontal plane. The attachment position of the umbilical to the frame is alsoimportant because, as will be seen later, the umbilical pull is often very substantialand the point of application of this pull can severely effect manoeuvrabitity.

L9.5.2

A.knowledge of the vehicles technical systems is again essential. As an example ofthis;.take a hydraulic vehicle that has a pump capable of providing an output o? IOOOPS.I.hydraulic pre^ssure at a maximum flbw rate of 15 Gallons perfuinute. tf tnisvehicle has four thrusters each requiring 5 Gallons per Minute at full speed, then it isclear that the Pilot will not be able to demand full speed from each thruster at thesame time. In this situation it may be inappropriate to attentpt to manoeuvre thevehicle in turbulent conditions around srructuies with the Automatic Depth andHeading Circuits engaged, as the total oil demanded from the thrusters may be morethan the 15 Gallons per Mirtute available resulting in a severe drop in oil piessurehence thruster power. The informed Pilot may well decide to disengage theAutomatic circuits whilst ntarroeuvring in these condit ion to ensurehaximum powerat the thrusters wherc it is nrost recluired.

r9.5.3

Clearly a knowledge of all the vehicles systems is essential for efficient and effectiveROV operations ancl the Pilot must be well aware of the vehicles capabil i t ies.

The fourth principle is tlut tha Pilot must know the vehtr:les geometry', systems andpe rformanc'c ca pu h i I i r i c s.

19.6.0 Effects of Controls

19.6.1

The effects and secondary effects of the controls must be appreciated by the ROVPilot and these are not.alwavs as straight forward as it first seenrs. For'example iflateral thrust.is lpplied to a vehicle it nray be expected to sintply traverse laterallymaintaining its heacling. However i t is unlikelylhat the lateral ihruster is posit iohedin the exact metacentre of the vehicle, and there is therefore likely to be the secondary9{fu-cJ of a heading c:hange, or roll which will be required to be counteracted.S.imilarly, if a pilot is endeavouring to change the h^eading of a vehicle he may wellfind that the vehicle creeps forward as the siern thrusters-nlay well be more eifectivewhen operating in the forward direction than when operating in the reverse direction,this may need to be counteructed by the application of rever^-se thrust in associationwith heading controls.

Thefifth principle is; thereJore, that the Pilot must know the effects and secondaryeffects of the control inputs. This is often best established iniiialty in a test tank or onthe surface, where the Pilot can see the vehicle and cun monitor ihe eXects directly,but can be quickly ttppreciated by the experienced Pilot in the work siiuation.

2 8 1

19.7.0 Vehicle Momentum

19.7.1

The significance of the vehicles momentum is very often not appreciated sufficientlyby PilSts as ROVs behave very differently to cqq il this respect. Whenturning aco.ner in a car the steering is simply applied until the desired new direction isachieved, then removed. iire coritrot input and resultant effect on the car is shown inFigure 1. The Same control input to an ROV would not, however, have the sameefiect. Because the car is in contact with the road, the momentum effects areminimal. The ROV will, however, continue to turn after the control input has beenremoved, due to the high momentum and low drag forces (particularly in the case ofheavy compact vehicles).

19.7.2

A similar control input to an ROV will therefore result in overshoot as shown inFigure 2. The required control input to affect a heading change of an ROV would beas"shown in Figuie 3. The ROV Pilot is therefore required to put in an oppositecontrol action io every initiating action to achieve the desired vehicle movements.This is a very important skill for the ROV Pilot to attain and becomes apparent as the

vehicle descendi to seabed, when the Pilot is required to cotlnleracl Ihe rrehrc\e

momentum by applying up-thfust on seeing the seabed, if he is to avoid touching

;;;;;"d rp,iifing t'f'e iisiUifity. If the Pil6t.simply removes the down thrust, the

momentum'of thJvehicle will ensure it continuei downwards until either dr.ag, the

umbilical or the seabed prevents it, often obscuring the visibility by dislodging

sediments.

The sixth principle is thereJore, that the ROV Pitot must be dwore ofthe vehicles

momentum ond be prepured to countcruct each inititttirtg t:rtntrol ntovement with an

opposite rno\)enrcnl.

oO

Z

1&3

STEERINGWHEELPOSITIONS

I

i

Figure 19.1

19.7.0 Vehicle Momentum

19.7.1

The significance of the vehicles momentum is very often not appreciated sufficientlyby Pilots as ROVs behave very differently to cars in this respect. When turning acorner in a car the steering is simply applied until the desired new direction isachieved, then removed. The control input and resultant effect on the car is shown inFigure 1. The same control input to an ROV would not, however, have the sameeffect. Because the car is in contact with the road, the momentum effects areminimal. The ROV will, however, continue to turn after the control input has beenremoved, due to the high momentum and low drag forces (particularly in the case ofheavy compact vehicles).

19.7.2

A similar control input to an ROV will therefore result in overshoot as shown inFigure 2. The required control input to affect a heading change of an ROV would beas shown in Figure .1. The ROV Pilot is therefore required to put in an oppositecontrol action to every initiating action to achieve the desired vehicle movements.This is a very important skill for the ROV Pilot to attain and becomes apparent as thevehicle descends to seabed, when the Pilot is required to counteract the vehiclemomentum by applying up-thrust on seeing the seabed, if he is to avoid touchingdown and spoiling the visibility. If the Pilot simply removes the down thrust, themomentum of the vehicle will ensure it continues downwards until either drag, theumbilical or the seabed prevents it, often obscuring the visibility by dislodgingsediments.

The sixth principle is theref'ore that the ROV Pilot must be uwore oJ'the vehiclesmomentum und be preparetl to courLtcrut:t each initittting control movement with anopprtsite tn( )\'(tttc ttl .

STEERINGWHEELPOSITIONS

cO

z

1&3

CONTROL INPUT

Figure l9.l

282

5I

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j:

Q zQ ras

JOYSTICKPOSITIONS

n'aq())RSHoor' l o l R o v

MANOEUVRE

Figure 19.2

@ sQ +Q ,Q zQ r

JOYSTICKPOSITIONS

'/Y ,lffHfiB\ . /

2 , 3 & 4 | \ r /

Figure 19.3

283

19.8.0 Drag Effects

19.8.1

Perhaps the most crucial factor effecting vehicle p-erformance is the effect of drag onthe vehicle and in particular the fact thai the dragforces on the umbilical can be muchgreater than the drag on the vehicle itself. The example shown in Figure 19.4 showsElearly the relative iize of these drag forces on a typi-al medium sized work vehicletraveliing at ll2 a knot at a depth of300m. The example also shows the effect of theumbilical length, hence angle at the vehicle, on the direction of these forces.

19.8.2

In this example the drag on the vehicle itself is shown to be 20 kg whereas thehorizontal component of tne umbilical drag is 120 kg. This correspoqqs to^a tensionin the umbilicai of 140 kg at 30 to the horizontal and 240 kg at 60 . SiglLftllntly theupward component of this force is 70 kg in the first case (Figure 4.) and207 kg i1 thesecond case (Figure 5). This neans that in many cases the primary force at a vehiclemay well be the upward pull of the umbilical and not a backwards force as may beexpected. For further inforrlation on the rnethod of calculating drag forces seeChapter 18.

The seventh principte is that the forces J'rotn the umbilical can be at least ten times thedrag force on the vehicle itself , and the length of the umbilical is significant as a 'tight

stri"ng' tends to pull the vehicle up off the .iob, rather than exert a purell' horizontal

force astern as tnay otherwise be expected.

1Depth 300m

ITension 240k9

+II

a-- Drag (Vehicle) 20kg

Speed:72 knot

-+

Fh:1 20kg

<-

Figure 19.4

284

Figure 19.5

F

lf9.9.0 Hand/Eye Co-ordination

19.1.0

Hand/eye co-ordination is a skill that is partly hereditary and partly developedthrough practice. Co-ordination is generally over rated as a Piloting skill, as it is justone of the many required and not an end in itself . The difference in co-ordinationabilities between one Pilot and another is often inconsequential as very few ROVtasks demand a very high degree of co-ordination. It is generally preferable that aPilot has a good grasp of all the principles mentioned here, rather than simply havinghighly developed Hand - eye co-ordination.

The eighth principle is that the ROV Pilot must develop a high degree of Hand - eyeco-ordination.

19.10.0 BE IN IT!

19.10.0

ROVs are difficult to fly because they are Remotely Operated, that is , there is no'feel ' associated with them. The capable Pilot wil l , however, imagine that he isactually onboard the vehicle, to the extent that he nray actLrally lean when turning and'duck' as the vehicle approaches obstacles. This is a good trait as being able toimagine. ones self to be ac:tually in the vehicle assists greatly with navigation andonentatl0n.

The ninth principle is that the ROV Pilot should be able to imagine that he is actually'in' the vehicle, particulurll,wlrcn navigating and attempting to orientate himself.

19.11.0 Fami l iar i t l , and Exper ience

19 .1 l . l

To be ful ly competent the ROV Pilot must have ' internalised' the principles and ski l lsmentioned in the previous nine sections. This can onlv be achieved by thoroughinitial training, as provided at Wray Castle, followed by fanriliarity of the ROVsystem operated and experience of the job in hanC. The pragnratic ROV Pilot willalways take the time to familiarise himself with a new vehicle or task in a shelteredenvironment prior to undertaking the iob for real.

The tenth principle is that the ROV Pilot will be familiar wirh the ROV he is operatingand will have experience of tlrc task in hand wherever possible prior to the offshoreoperatbn.

19.12.0 Diffi cult"v Comparison

19.t2.r

The following comparison is used at Wray Castle as a method of explaining thedegree of difficultl, experienced by ROV Pilots as compared with airline Pilots:-

Imagine you are to f1y an airline from London to New York. Firstly replace theaircraft 's high resolution radar systems with i ts sonar equivalent, a system that ismany thousand t inres iess accurate. Then l imit the Pilots visibi l i ty to around threemetres. Arrange for the wind to blow at around 300 Knots with directional changes

i

iII

, !

'6-\

every 6 hours. Finally arrange for a massive steel structure in the middle of theAtlantic ocean and attach the aircraft to a tether anchored to the ground at the otherend. Effectively you will be reducing the information available to the Pilot andincreasing the external forces acting on the aircraft.

This comparison serves to enable the trainee to understand the nature of the job and tocomprehend the reasons for fully 'internalising' the l0 Piloting principles explainedabove.

19.f3.0 Sonar Interpretation

19.13.1

In order for the ROV Pilotftechnician to be able to understand and interpret thesonars that are typically used during ROV operations it is necessary to review thetheory. The depth of this review is sufficient to allow the scientifically educatedreader to gain an appreciation of the complexity of sonar theory and the factors thataffect the ability of a Sonar and its Operator to detect a target. This review is notintended to be exhaustive and the interested reader is recommended to read theappropriate scientific literature.

19.13.2

SONAR is an acronym for Sound Navigation and Ranging. The term is used forsystems that utilise underwater acoustic energy for obseruation and obstacleavoidance. Sonar is preferred to Radar because of the extremely high attenuation andscattering that Electro-Magnetic (EM) radiated energy suffers in a highly conductivemedium such as sea water.

The Acoustic Triangle has the sanre purpose as the Electrical Triangle used for Ohmslaw and is to show the relationships between the fundantental quantit ies responsiblefor sound transfer:-

Figure 19.6

Where:- P = Acoustic Pressure (Equivalent to Voltage V) in micro Pascals.

U = Particle Velocity (Equivalent to Current I) in m/s.

Z = Acoustic Impedance (Equivalent to Resistance R) in Acoustic Ohms.

286

Then the acoustic ecluivalent of V = IR is P =UZ and the acoustic equivalent ofElectrical Power is:- Instantaneous Acoustic Intensity = PU.

The sound velocity (C) at or near the surface in a water temperature of 15.5 C and asalinity of 34 parts per thousand is 1500m/s. This value can be taken to be reasonablyconstant throughout normal operating conditions, but allowances should be made forits variances when undertaking detailed survey work or similar.

19.14.0 The Sonar Equat ion:

The generally accepted equation for the signal to noise ratio (Ns/N) at the transducerof a sonar is:-

Ns/N = (SL - 2PL + TS) - (BN - DI)

Where:

SI- rs the Source Level in dBs. This varies from l0dBs to over100dlls dependent on the power capability of the sonar transmitter,type , size and the directionality of the transducer array.

PL is the propagation losses for which there are the following types:-

i) Spreading loss.i ;) Attenuation Loss.i i i ) Scattering and Absolution.iv) Heating by absorbtion.vi) Seabed and surface reflection and absorption.v) Reverberatiorrs.

'IS is the Target Strength and is the echo level fronr an actual target in

dBs uhove the echo level of a reference sphere. The value ofTarsetStrength is dependent on:-

i) Size of targer.i i) Shape of target.i i i ) Orientation of tarset.iv) Internal constructlon of target.v) Extent of Anechoic coatingl.vi) Frequerrcy of transntission.

BN is the Background Noise and consists of the fol lowing types:-

i) Self noise is that noise produced by the receiver and itsplatform, it can be decreased by good design and maintenance.

ii) Ambient Noise is from; Thermal, Sea Surface, Biological,Traffic, Rain, Surf. and Turbulence sources.

iii) Reverberations are the portion of the scattered soundfrom any reflecting surface in the ocean which returns to thel is ten ing t ransducer .

DI is ihe Directivity Index of the receiving array which is dependenton the frecluency and the length of the array. Directivity is forexanrple better when the length of the array is twice the wavelength ofthe ri:c:eived signal than a quarter of the wavelength. Put another way,the transducer array needs to be longer at lower frequencies to obtainthc sr rnre d i rect iv i tv .

l

:!

i

:l

II

i:

287

The operators ability to detect targets is also a factor which should be taken accountof by the Recognition Differential RD where the RD = NsA.{ when there is a 50Vochance of detection by the operator.

The above serves to show the complexity of the Physics involved in Sonar operations.In practice, although it is important to be aware of all these factors, the experiencedoperator will become familiar with his equipment, the optimum settings and thedisplayed information in order to identify targets.

19.15.0 The Transducer

The Transducer is the name given to devices which convert energy from one form toanother, in the active (rather than the'Passive'i.e. hydrophone) case this is theconversion of electrical energy into sound and vice versa.

There are two main types of transducers:-

Electr ic Field Types

Piezo-electric - Crystal Microphones, Transnritters etc.

Electrostrictive - The alteration of physical dinrensions when underthe action of an electric field.

Magnetic Field Types

Electrodynamic - moving coil .

Elec:tnlnragrrel ic - nrovirrg iron.

Of these the Electric: Field types are most conlmon. With all Transducers theamplitude of the signal output depends upon the signal strength over the frequencybandwidth.

OutputSignaldBs

Figure 19.7

288

Frequency

I

l

Q is the Quality Factor Q = fRBandwidth (W).

Q is important in the design of transducers and in an active Rx hydrophone thebandwidth W should be wide enough to accommodate the transmission frequency andthe full range of Doppler shift while maintaining a high quality factor to attainsatisfactory output signal levels. Transducers of the Electrostrictive type havecapacitance and the only way to measure transducer deterioration is to measure thecapacitance plus insulation and noise. Transducers are generally constructed fromseveral smaller elenrents rather than one larger one for several reasons but primarilyto enable directional coverage to be shifted from Mechanical Steering to ElectricalScanning, and to improve dependability although it also improves diiectivity andeases manufacture.

f9.16.0 Trade-off:

19.16.1

In all cases the losses are higher the greater the frequency, this means that the Sonarswith the highest frerluencies have the shortests range. However the higher frequencysonars have greater Directivity enabling greater resolution to be obtained. This meansthat there is inevitably a 'trade-off to be made between Resolution and Range whendeciding a Sonars operating frequency.

19.17 .0 Transmission pulses:

There are two basic types of transmission used in modern day Sonar:

19.17.1

The first transntits a f)'ecluency ranrp and conrpares the frecprency of the returningsignal with that being transrl i t ted (the difference frecluency) ro obtain the range.

19.t7.2

The ramped frequencies are contained within a pulse and there is a blanking periodbetween pulses.

19.t7.3

The pulse repetition frequency (PRF) is increased as the range is decreased enablingthe^display (usually PPI) to use the sarne graticules on the CRT and simply to use adifferent scale.

t9.17.4

A major advantage of this type is the fact that the difference signal can be amplifiedand listened to by the operator who can then judge the range of targets by the-flequency; the lower the frequency the less is the difference frequency airO thereforethe closer the target. The disadvantage is that these are often more efpensive than thesimple pulse alternative.

t9.17.5

The simp_le pulse t1,pe simply sends short pulses of sound at one fiecluency. Therange is determined fronr the t ime taken forthe pulse toreturn. I t is-usuaiforthe

289

receiver to be blanked as the transmission pulse is transmitted to protect the receivercircuits. The head can either be mechanically or electrically scanned and the returnsare usually displayed on a computer monitor where they can be logged on computerdisks.

19.17.6

The advantages of these are that they are cheap, small and because the datacommunications protocol allow muliiple deviCes such as altimeters and profilers to beconnected to a single twisted pair, simple to install and versatile.

19.17.7

The disadvantages are that they transmit only one frequency making them acompromise beiween range and resolution, and also ir is not possible to judge therange by an audible output.

19.18.0 Example of Ramped Frequency Sonar

19.18.1 An example of a ran.rped frequency Sonar is the Ametek Sea Probe model2504 as fitted ro many Scorpirc vehicles. The transmitted pulse is a frequency ramp-from 107 to l22KHz. The iransmitting and receiving heads are fitted to the front ofthe vehicle and scanning takes place as the head is turned either in sector scan modeor continuously by an electricai motor. The audio output represents sonar returns thathave been converied into audio difference frequencies by the receiver and fed into thespeaker. The same receiver output is further processed in the.analyser and {itpluycircuits and is presented in PPI forrnat on the CRT. Figure 19.8 shows the displayunit for this sonar.

r x a { S x C r t O / / r ( ( u r r i ^ r t O i

/tY rx".v...".K/. ',r/t\

..Ill,. \y' f,.i'

u\( ?.;N\_'.(J IUIe ^ N 6 t . r r g J /f t P t 5 a c v i G r x

(\vorwt \t/ -)i€^

lOOt L 15O^ SOiato {

^ r t I t ( r t I l A 2 ^ O l v

Figure 19.8 Ametek 250A Sonar

290

19.18.2

The operating controls of the Ametek 250,4 have the following functions:-

1. CRT: 7 inch CRT that represents target data in PPI format. Equipped with anilluminated graticule and filter. Graticule is graduated in 5 degree inciements andm^arked every 45 degrees from 0 degrees relative with range rings for determinationof target range.

2. Threshold cnntrol: Adjusts the level of intensity at which targets aredisplayed and sets the level for rejection of low amplitude video signals that are in theoutput^of the.analyzer. This control is effectively used to improve the signal to noiseratio of the displayed infomration by rejecting the low level iignals and noise leavingonly the stronger signals displayed.

3. Illumination control: Controls the brightness of the control panel andgraticules on the display unit.

4. Scan Srvitch: Selects the transducer scan mode:

ON posit ion: Transducers scan continuously in a clockwise direction.

OFF position: TransdLlcer scan is halted.

SEC_p^ositiort: Transducer scanning is a preset 90 degrees scan angle cenffedon (X)0 degrees automatically reversing at the scan liritits

5. REV button: When depressed, causes the scan to rotate in thecounterclockwise direction. When released, scan is in the clockwise direction.

6. RCVR GAIN: Controls the gain of the Sonar and marker receiver circuit,thereby controlling the level of its output to the analyzer and audio circuits.Increasin_g the gain increases the level of the signals and the noise togetherthereby does not improve the signal to noise raiio.

7. POWER Srvitch: Controls the power ro the Display Unit.

8. VOLUME control: Controls the loudness of the sound heard via the speakeror headset.

9. RANGE FT: Selects rhe operating range of the sysrem or rhe Markermode. Selectableranges are; 0 -20f t ,0 - 75f t ,0 - 2( [ f t ,0- 750f tand 0 -2000ft.

10. MKR Channel: May be tuned to any frequency. Displays the direction butnot the range to marker beacons.

The basic functions of these controls such as gain and threshold are similar for allSonars and a full understanding of these functions are reqLrired by the operator.

291

19.19.0 Mechanicall-v Scanned Simple Pulse Sonar

l9.19.r

Examples of Mechanically Scanned Simple_Pulse Sonars.are the Tritech ST325, 525

ina iS Imaging and Obsiacle Avoidance Sonars. A typical display _f91tle1e isinoluded ur Fig.ir. 19.9 and the specifications are included as Figure19.10 It is

important to n6t. the 'trade-off b-etween.range and resolution with these so that the

correct Sonar san be selected for each job. For example the ST325 KHz has a range -of 200 metres and a beamwidth of 4.5

"degtees, the ST725 KHz has a shorter range.of

100 metres but a grearer resolution with ibeamwidth of 2 degrees. In.both cases the

resolution can belmproved by increasing the size of the transducers which narrows

the beamwidth.

{RE€

{oes€E

V)

Figure 19.9 Sonar DisPlaY

FrequencyBeamwidth, normalBeamwidth, Big ToPMaximum rangePulse widthScan rate

Overall lengthOverall length, Big ToPDiameterMaximum diameter, Big ToPWeight in airWeight in water

Depth ratingCommunicationsLong line driveProtection

Power requirements

Gonnector / penetrator

Figure 19.10 Tritech

ST325325kHz4.5" x24"2.5" x24"200 metres60 - 1000p sec.8 - 40" sec.

195 mm199 mm70 mm123 mm1 k g0.5 kg

3000 metresRS485, RS2322,200 metresOpto isolationZener clamping18 - 30 VDC@ 900mA maxTritech 6 pin

Sonar Specification

sT525525 kHz2.5" x24"1.2" x24"150 metres60 - 1000p sec.8 - 40" sec.

195 mm199 mm70 mm123 mm1 k g0.5 kg

3000 metresRS485, RS2322,200 metresOpto isolationZener clamping't8 - 30 vDC@ 900mA maxTritech 6 pin

sT725725 kHz2" x24"N/A100 metres60 - 1000p sec.8 - 40" sec.

195 mmN/A70 mmN/A1 k g0.5 kg

3000 metresRS485, RS2322,200 metresOpto isolationZener clamping18 - 30 VDC@ 900mA maxTritech 6 pin

292

19.20.0 Electronical ly Scanning Sonar

19.20.1

An exanrple of an Electronically Scanning Sonar is the Tritech SE500. An exampleof a display fbr this is shown in Figure 19.1 1. This has rapid Sonar image updaterates bJt has the disadvantage of only allowing a 60 degree scan angle rather than theful l 360 degrees. Figure 19.12 shows the Sonar head itself and the systemspecifications.

Figure 19.11 Tritech SE500 Electronical ly Scanned High ResolutionDispla-v

Sonor inrage of platform risers

- rpact, high speed imaging sonar for. ROTV, MCM and other subsea

.:tions that require very fast sonar image. J \ .

Sonar head

Figure 19.12 SE500 Head and Specifications

Sonar update rate, maximumFrequencySector WidthNumber of sonar beamsVerticalscan angleOptional vertical scan anglesHorizontal beam widthMaximum rangeRange resolutionBeam forming methodData protocolData transmissionLengthDiameterPower supplyDepth ratingWeight in airWeight in waterMaterials

Sonar

4 per second500 kHz

60'64

13.4"3 ' - 13.4"

2.7"75 metres

100 mm (depending on range)Fast Fourier Transform

SDLC @375 kBaudScreened, twisted pair

265 mm100 mm

24 VDC @ 2A300 metres

2.5 kg1.25 kg

Anodised aluminium, polyurethane

!

!

193

19.21.0 Multibeam Bathvmetric Sonar

t9.2r.r

An example of a Multibeanr Bathymetric Sonar system is the SeaBat 9001, shown inFigure 19.13. This Sonar systenl displays and updates the sonarimage and aful ldigitised profile of the seabed in real time. The high data density allow total areacoverage within a 'footprint' of 90 by 1.-5 degrees making it suitable for suchapplications as sea f loor mapping.

Figure 19.13 Reson, SeaBat 9001 Multibeam Bathymetric Sonar System

294

19.22.0 Scanning pnrfi l ing Sonars

19.22.1

An example of a nrultihead (usually dual) Scanning Profiler display is shown in19.14. The Sonar is used to scan vertically downwards to determine the profile of thesea bed and any feature such as a pipeline that may be across it.

i

n.i.

ar

a

{.-4\

Figure 19.14 Tritech STl000 Multi-Head Scanning profi ler Display

19.23.0 Altimeters

19.23.1 Figure 19.1-5 shows an example of an acoustic altinreter. Altimeters are usedon ROVs to detemrirre the heieht of the vehicle fronr the sea bed.

Figure 19.15 Tritech sT200 and ST500 Precision Altimeters

195

19.24.0 Doppler Sonar

L9.24.1 The Doppler Sonar works on the principle that their transmitted frequencyappears to increas-e or decrease if there is relative movement of the Sonar with respecttoine water column or seabed to precisely determine speed and distance moved.Figure 19.16 shows the Tritech DS30 Doppler Sonar and Figure 19.17 shows thetechnical specifications of this sonar.

Figure 9.16 TritechDS30 Doppler Sonar Unit

Operatingfrequency """"""""""" 1 MHz

Transducer "" 4transducerJANUSanayOperating mooe .. . . . . . . . . . . . . . Pulse Doppler

Operating range (for seabed tracking) 2 metres to 30 metres

Tracking modes ....'..-.... Seabed and Seawater

Operating voltage .""" 12 VDC to 48 VDC

Velocitv +o to 3'75 m/sec

VelocitY accuracy +2'5 cm/sec

Velocity resolution +0'5 cm/sec

Uodate rate .. . . . . ." . . . . . . . """ ' 5 updates/secLength (inc. connector) 365mm

Minimum diameter ' 95mm

Depth rat ing """" ' 3,000m

Weight in a i r . . . . . . . . . . . . . . . . . . . . " " " " " - " " " " skg

Weignt in water . . . . . . . . . . . . . " " " " " " " " " " ' 2kg

Communications .. . ' . . . . . . . . . . . ' . . RS-232/RS-485Ana logueoutpu t . . . . . . . ' . . . . " " " ' 0 -3 '75VDC

Figure 19.17 Tritech DS30 Doppler Sonar Specifications

296

:19.25.0 Use of the Sonar

19.25.1 It is important to ensure that the Sonar is correctly installed and maintainedprior to testing. In particular the transducer heads should be_wiped clean as-grease orbit witt impair performance and if the head is oil filled this should be kept clean andwater free.

19.25.2 Sonars can be tested in air by turning them on and observing that the headscans correctly, placing targets in the beam path in close proximity to the_head shouldindicate Sonai tiansnrii and receive circuitry is operating correctly. The Sonarmanual should be referred to, prior to these tests, as some models will overheat ifoperated for too long in air.

19.25.3 After a successful surface test the vehicle can be deployed. Sonars will onlyshow echoes that reflect sound back, such that hard shiny surfaces are sometimes onlyseen when they are at right angle to the Sonar head, and rough seabed textures canblot out smaller targets completely.

19.25.4 The plan view also does not show how high an object is unless a shadow iscast, in which case the length of the shadow is related to the height of the object, i tsrange, and the height of the Sonar head. Interpretatiorl of Sonar data devellps withexpirience. Sonar reflections of isolated small objects give no indication of shape orattitude. Man made structures, such as Platforms or Pipelines tend to have regularpatterns which are easier to identify.

19.25.5 Using a Sonar is rather like looking at a world made of shiny black plastic, inthe dark, witlionly a narrow torch beam for illumination, targets only show when thebeam shines on thent directly at r ight angles.

19,25.6 Renrember that when close to large objects, or in a depression in the seabed,that the viewing range ntay be severely linrited. Very strong ref-lectors may givenrult iple echoes along a bearing l ine and are identif led by being equispaced in.range.If they persist, reduc:C the Gain. Fish also produce excellent echoes due to their airsacs and can often obliterate targets.

19.25.7 When searching fbr objects, keep the vehicle heading as steady as possible tostop the image blurring.- Sit on the sea bed if necessary. If using a sidescan mode forsealching, keep the vehicle steady, at longer ranges f1y the vehicle a few metres abovethe sea bEd to improve the detection range and quality. Depending on water depthand vehicle depth, there nray be ring like echoes. These can be caused by surface orsea bed direct reflectiorts and may be difficult to avoid.

19,25.8 Experience with Sonar will enable the operator to be able to quickly set theGain, Threshold ancl Range controls to give as even a background as possible, withoutswamping the display, thu.s nraxinrising the Sonars perfornrance <;apabil i t ies.

1

I

297

CHAPTER 20 QUALITY ASSURANCE (QA) SCHEMES

20.1.0 Background to QA Schemes

20.r.r

The revolution in the quality of Japanese products, and their consequent increase in

Global market share, has brbught about the general belief throughout business. that'Quality Marters'. This belief fias permeated into the Offshore industry and.it is now

ndr-ui for Operators to require thbir suppliers to be registered_fo1 1 recognised

euality Assuiance scheme. The standaid that is relevant to ROV Contractors isuir.rt6d by the British Standards Institute, a British National Accreditation CouncilC"rtifi"A dody and is known as B55750 Part 1 which is the same as internationalstandard ISOEQQ1 and the European standard EN 29001. This standard firsr appearedin 1979 as BS5750 which was based on the ministry of defence 05 series of standardswhich was updated with a less prescriptive, more flexible framework in 1987. It is

this standard that is now accepted as the international standard ISO9000 whichprovides a practical action plan for managers to implement quality. standards withoutbecoming ionfused by the intangibles and vagaries of .the so called 'management

experts'. "The

remainder of this chapter will refer to this standard as IS09000.

20.1.2

These Quality Assurance standards are a means of ensuring an agreed level of.qualitythroughbut the service contract from bidding through to job completion/rep.orting andr"*eio reassure the client that the performance of the contract will be carried out toagreed performance and reporting slandards. There is a general conception.offshore,tliat these Quality Assuranie schemes are a 'paperwork exercise' and 'something thatonly affects the office'. It is the intention of this c!ap19r to explain the quality.managemenr sysrenl and its relevance to offshore ROV work as a means to raisingoperaiional standards and reducing equiprrlent'downtime'.

20.1.3

ISO9000 is fundamentally a set of quality policy statements, nlanagement proceduresand work place references, this is the accepted standard of Quality Assurance but isonly part of totat Quality Management (TQM). TQM is an all e.ncompassing idealthai includes attitude assessmenf and a commitment to total quality throughout anorganisation. Companies that have achieved IS09000 can further improve qualitythiough the implementation of TQM and many ROV contractors are striving toachieve this.

20.2.0 The Quality Management System

20.2.1

The quality management system can be thought of as a three level structure as shownin Figure 20.f. fne three levels are linked together by quality records and theauditing process.

20.2.2

Level 1 is the Senior lnanagement level where policy, plans and strategic decisionsare made. The Quality poticy manual covers ihe quality policies and plans comingfrom the Senior level of managentent..

299

20.2.3

Level 2 is the middle or operational management level which will include theOffshore Superintendent or Team Leader and the Onshore Project Manager. This keygroup will bi responsible for the interpretation and implementation of -th-e quaryy

ioliiies and the development of workable procedures for gyeryonelo follow. The

Quality Procedures Manual covers all the procedures which are developed andimplemented at this middle level of the organisation.

20.2.4

The Quatity Policy Manual and the Quality Procedures Manual together with aguide-to workplace references are often referred to by the generic term:- The QualityManagement Manual

20.2.5

The third level is the workforce whichworkforce will follow the proceduresDocuments.

includes the operational team itself. Theand consult the Workplace Reference

Documentatiott

Level I

Level2

Level 3

FIGURE 20.1

20.3.0 The Quality Policy Manual

20.3.1 This is usually divided into six sections:

i) Introduction

ii) Policy Statements

Organisational lcvel

Planningand Polic.v

QualityPolicyManual Quality

Management

ManualManagementandProcedures

Qualityprocedures orOperationsmanual

TaskWorkplaceReferences

300

-----l

iii) Organisational Structure

iv) Management Responsibility and Authority

v) Management Review

vi) The Quality Managemenr system and it relationship to ISo9000.

20.3.2

The organisations quality. programme is put into context in the introduction byintroducing the organisation and its quality management sysrem.

20.3.3

Thgjt are usually two Policy Statements, the Mission Statement and the QualityPolicy Statement

An example of a Mission Statement might be:- Company 'x' undertakes to deliverthe highg_s1 technology service possible to the custo-ers iatisfaction uny *fr"ir in theworld. 'World-wide

service attempted with perfection'.

An exampl.e_of a Quality Policy Statement might be:- It is the Policy of Company'x'to: Provide products and services which nreeiourclients recluirements, by theimplementation and maintenance of a cost effective Quality Mbnagemeni ryri"-based on the concept of 'Total

Quality' in which euery nrenibe. of itaff has 'and

accepts.a personal responsibility for q.uality. These policy statements are usuallysigned by the senior management of the organisation to indicate their commitmentand support for them.

20.3.4

The organisational structure section of the Policy Manual will describe how theorganisation works. This wil l include an organisaiional chart which wil l show:-

i) How the lines of authority throughout the organisation are organised aroundprojects or functions such as; sales or oplrations.

ii) How many lines of authority there are, and the titles of the roles in thehierarchy.

iii) What formalised direct and cross-reporting relationships exist between lines ofmanagement respon si bili ty.

In addition to showing managentent roles the chart will show the roles which arerpPortant for the Quality Management system such as the Quality vfunug"i anOQuality Inspectors.

20.3.5

The.Management Responsibility and Authority secrion will describe in furtherdetail.the.responsibilities and reporting relationships of the roles identified in theorganisational chart.

20.3.6

The Management Review section will describe the systenr by which seniormanagement wil l evaluate the Qualit l , Management systent.

:i

3 f ) l

20.3.7

The Quality Management system and its conformance with ISO9000requirements section will describe the scope of the Quality Management System andits ielationship with ISO9000 requirements. The scope may be limited by the factthat only some divisions of the company are registered and by the fact that productsupply and design companies are covered by ISO9001/BS5750 Part 1 whilstProduction and Installalion companies are covered by ISO90028S5750 Part2. In thecase of ROV contracting companies; the whole company is usually covered byISO9001/8S5750 Part 1.

20.4.0 The Quality Procedures Manual

20.4.1

The Quality Procedures Manual is often referred to as the Operations Manual Itis primarily intended for the use of the organisations 'nriddle management' and willdefine and describe the management processes in the organisation and the proceduresthat must be followed to make these processes work smoothly. This manual is theoperational heart of the quality management system and sets up a detailed model ofhow the organisation should operate.

20.4.2

The Management processes section will describe the main groups of managementactivities such as:- Sales and marketing, conffacts, project management and the role ofthe offshore supervisor or Team Leader who may be considered as a member of themanagement team. The management processes for service providers such as ROVContractors are usually 'customer driven'. This means that the management teamswill behave in a way that provides the maximum satisfaction for the client. Someareas of the organisation may also be 'technology driven' such a research anddevelopment.

20.4.3

The Quality Management Procedures section of the Quality Procedures manual areoften referred to sinrply as: 'the Procedures'. The procedures are there to informpeople how to implement all the n'lanagenrent activities that are to be done in theorganisation. The procedures are there to ensure that all the people across theorganisation do things in the same way which fits with how other people are working.The procedures will include:-

i) How all the managernent activities are carried out.

ii) Who will carry out all these activities.

iii) How the activities are to be docunrented.

iv) A list of the workplace instructions that will be needed for reference and theirlocation.

Procedures will be focused on management activities, such as; ensuring that contractsare carried out to the requirements of the client, and personnel selection, training andreward structures.

Training standards are considered to be extremely important, if quality procedures areto be followed, personnel must know how to follow them. It is preferred if training

302

standards are verified by some form of external assessment to recognised standardssuch as National Vocational Qualification (NVQs). NVQs can be extremely useful asthey are partly assessed on the ability of employees to follow workplace instructionsas required by Quality Assurance schemes.

An important part of the operations manual will however be a description of theduties and responsibilities of personnel at every level. An example of a typicaldescription of the duties of an ROV OperatorMaintainer (This is the same asPilotfiechnician and is the term preferred by Cable laying companies such as BT(Marine) Ltd from whose Operation Manual this was taken) is given below :-

JOB TITLE: OPERATOR/MAINTAINER

PURPOSE OF JOB: To undertake the safe operation of Equipment asdirected by the Team Leader or Senior Operator/lMaintainer.

ACCOUNTABLETO: SeniorOperatorMaintainer

DUTIES AND RESPONSIBILITIES

An Operatorfit4aintainer has a responsibility to:-

i) Protect personal health and safety, and to take all steps to safeguard others, inline with the BT (Marine) Health and Safety Policy.

ii) Understand the company concept of Total Quality Managentent, and tocontribute to the continning process of improvement.

iii) Have an awareness of the potential damage that can be caused by the variousforms of environmental pollution, and to ensure that all work is carried out inaccordance with the company policies on environnrental protection.

iv) Undertake the safe operation of subsea Equipment as directed.

v) Undertake breakdown and routine maintenance work, as directed by theSenior Operator.

vi) Assist in maintaining records as rerluired.

vii) Undertake nraintenance and modification work on Equipment, as directed bythe Senior Operator.

viii) Assist in mobilisation, as required

ix) Assist in the production of operating instructions.

xi) Assist in applying company quality assurance procedures.

x) Update stores and maintenance records as necessary.

NOTE: Equipment in the above case refers to the Trencher, Plough, Scarab andother specialised tools and associated equipment operated by BT (Marine) Ltd. Thiswill vary from contract to contract and company to company depending on theequipment operated.

30-3

20.5.0 Workplace References

20.5.1

The Quality Policy and Quality Procedures manuals are provided primarily for themiddle and senior management level of an organisation, and as suth are unlikely tobe referred to regularly by the ROV Pilot/Technician, except to gain an understandingof the policies and management procedures as they affect his job. Whilst it isimportant for the Pilotffechnician to be aware of ihese it is the workplace referencesthat will be most essential to ensuring that he carries out his responsibilities to theprescribed quality standards.

20.5.2

The ISO9000 standard requires that personnel know exactly what reference materialsthey are_likely to need and where to find them. It is also extremely important thatthese reference documents are kept up-to-date and complete.

20.s.3

Workplace references can be either internally or externally generated. Examples ofinternally generated workplace references are:-

i) Forms

ii) Technical Manuals

iii) Technical Instructions

iv) Technical Drawings

v) Instructions and Checklists

VI) Internal Specifications and Standards

vi) Methodologies for Testing

vii) Reference and Research Materials

20.5.4

Examples of Forms would include: Daily reports, Dive Logs and Equipmentmaintenance logs.

20.5.5

Examples of Technical Manuals would include: the Manuals provided bymanufacturers for specific equipment.

20.5.6

Examples of Jgghnical Drawings would include: working drawings for theequipme^nt. NOTE: It is particularly important to modify these drawings and manualsas modifications are undertaken on the iystems, for the benefit of otheicrews.

304

20.5.7

Examples of Instructions and Checklists would include: Pre/Post Dive Checklists.

20.5.8

Examples of Internal Specifications and standards would include: videoacceptance standards and calibration standards.

20.5.9

Examples of Methodologies for Testing would include: calibration and equipmenttest procedures, and procedures for handling non-conformance's.

20.5.10

Examples of Reference and Research Materials would include: Details ofequipment and methods under development, and areas of specialist knowledgeavailable within the organisation. These would also include relevant periodicals andresearch reports.

20.6.0

Externally Generated workplace References are the laws, standards andguidelines set by bodies which are outside your organisation, but which influenceaspects of what you do. Exarnples of externally generated workplace references are:-

i) Legislation.

ii) Industry standards, codes of practice and trade association guidelines.

iii) Customer Specifications

iv) National Vocational Qualifications work instructions or books such as this.

20.6.r

Fxamples of legislation would include Health and Safety legislation such asStatutory Instruments (SI)1019, the health and safety at worl iact SI 840and theControl of Substances Hazardous ro Health regulations (COSHH).

20.6.2

Examples of Industry Codes of Practice include those issued by the AODC such as'The Safe use of Electricity underwater' and 'ROV Handling Systems'.

20.6.3

Examples of Cu.stomer Specifications include 'Scopes of Work' on Inspectioncontracts or similar specifications for Ploughing/Cable laying or drill supportactivities.

20.6.4

Examples of National vocational Qualifications might include the EnTraengineering. maintenance work instructions or similar if developed for this specificindustry. They may also include training notes or handbooks such as this.

305

20.7.0

It is important that a guide to workplace references exists and is easily available atevery work site. It is also important that the Quality Procedures Manual refers to theworkplace references wherever they form part of the procedures and further specificprocedures for modifying and updating these workplace references.

20.8.0

In conclusion it is essential for the ROV Pilot/Technician to understand theimportance of following procedures, consulting workplace references andinternalising the concept of 'Total

Quality Management'for the successful completionof contracts to the satisfaction of the client, to ensure the safety and proper operationof the equipment and to safeguard their own welfare.

306

Appendices

. l; ll =t :-307it

Appendix A Resistor Colour Codes

COLOUR

RED

ORANGE

YELLOW

GREEN

BLUE

VIOLET

GRAY

WHITE

GOLD

SILVER

NO COLOUR

FIRST

Drcrr (A)2a-)

4

5

6

7

8

9

SECOND

DrGrT (B)2aJ

Aa

5

6

7

8

9

MULTIPLIER(c01001,00010,000100,0001,000,00010,000,000100,000,000

TOLERANC(D)

+l- 5Vo

+l- l07o

+l- 20Va

308

Appendix B Electrical Formula

RL Circuit (Series) Impedence

z=" ,1n2* 61p

1) Sine-Wave Voltage Relationships

Effective or r.m.s Value

Eeff =Ema^ = E*a*=0.707Emax

AC Circuit Voltage

E = l Z - P1 x P . F

2) AC Circuit Porver

Apparent Power

P = E I

Power Factor

P . F . = P = c o s 0

EI

cos 0 = -------!MSSIapparent power

3) Transformers

Voltage Relationship

E p = N p o r E . = E p x \

Es Ns Np

Current Relationships

s = Secondary

p = Primary

N = Number of turns

Parallel Circuit Impedance

I p = N tIs Np

R, C, and L Circuit (Series) Impedance

Z =. ,1R2+ (Xt - - xO2

Maximum Value

Emax = {Z Geff) = l.4I4Beff

AC Circuit Current

l = E = PZ E x P . F

True Power

P = E I c o s 0 = E I x P . F .

Z = Z ZZ t + Z z

309

1 .

z .

A

1 1 .

12.

1 A

a a

1 8 .

Appendix C Formulas and Data (Hydraulic)

Hydraul ics is a means of t ransmit t ing power. l t may be used to mult iply force or modify motions'

PASCAL'S LAW: Pressure exerted on a conf ined f luid is transmit ted undiminished in al l d irect ions

and acts with equal force on al l equal areas and at r ight angles to them.

To f ind the area of a piston (circ le), square ihe diameter and mult iply by .7854. A = D2 x '7854'

The force (pounds) exerted by a piston can be determinedby mult iply ing the piston area (square inches) by the pressurea p p l i e d ( P S l ) . F = P x A

5. To determine the volume of l iqu id (cubic inches) requi red to move a p is ton a g iven d is tance, mul t ip ly

the p is ton area (sq. inches) by the s l roke requi red ( inches) . Vol . = A x L.

7 .

2 3 1 c u b i c i n c h e s = O n e U . S . G a l l o n

Work is force act ing through a d is tance.Examp le : Work ( i n . l bs . )= Fo rce ( l bs . ) x

Porver is the rate of doing rvork. Power

W O R K = F O R C E x D I S T A N C EDis tance ( i n . )

Work Force x Distance= - - =T ime T ime

o .

9 .

1 0 .

Hydrau l i c o i l se rves as a l ub r i can t and i s p rac t i ca l l y non -compress ib le . l t w i l l compress app rox -

lma te l y 0 .4 o f 1o /o a t 10OO PSI and 1 .1920 a t 3000 PS I a t 120oF .

The weight of hydraul ic o i l may vary rv i th a change in v iscosi ty . However, 55 to 58 lbs. per cublc

foot covers the vtscosi ty range f rom 150 SSU to 900 SSU at 100oF.

p ressu re a t t he bo t tom o f a one foo t co lumn o f o i l r v i l l be app rox ima le l y 0 .4 PS l . To l i nd t he

app rox ima te p ressu re a t t he bo t tom o f any co lumn o f o i l , mu l t i p l y t he he igh t i n f ee t by 0 .4 .

A tmosp i t e r i c p ressu re equa l s 14 7 PS IA a t sea l eve l .

Gauge read ings do no t i nc luce a tmosp l -e r i c p ressu re un less marked PS IA .

The re mus t be a p ressu re d rop (p ressu re d i i f e rence ) ac roSS an o r i f i ce o r o the r res t r i c l i on t o cause' f l o r v t h rough i t . Conve rse l y , i f t he re i s no i l ow , t he re w ' i l l be no p ressu re d rop .

A f l u i d i s pushed , no t d rawn , i n to a pump.

A pump does no t pump p ressu re ; i 1s pu rpose i s t o c rea le f l o r v . Pumps used l o t r ansm i t power a re

usua i l y pos i t i ve d i sp lacemen t t ype .

p ressu re i s caused by res i s tance to { l c r v . A p ressu re gauge i nd i ca tes t he l vo rk l cad a t any g i ven

momen t .

F lu ids t ake the cou rse o f l eas t r es i s tance .

Speed of a cy l inder p is ton is dependent upon i ts s ize (p is ton area) and the rate of f lovr in to i t .

Veioc i ty ( inches/mrn.) - F lorv (cu jnches/min ' ) oR

Area ( sq . i n . )

F l o w = V e l o c i t v x A r e a

t o .

3 1 0

Flow veloci ty through a pipe var ies inversely as the square of the inside diameter. Doubl ing theins ide d iameter inc reases the area four t imes.

Frict ion losses (pressure drop) of a l iquid in a pipe vary with veloci ty.

To f ind the actual area ol a pipe needed to handle a given f low, use the formula:

Area (sq . in . ; = GPM x '3208\JN

Veloci ty (Ft. /Sec.)

Veloci ty (Ft. /Sec.) G P M3.117 x Area (sq . in . )

The actual inside diameter of standard pipe is usual ly larger than the nominal s ize quoted. A con-vers ion char t shou ld be consu l ted when se lec t ing p ipe .

Stee l and copper tub ing s ize ind ica tes the ou ts ide d iameter . To f ind the ac tua l ins ide d iameter ,subtract two t imes the vral l th ickness from the tube size quoted.

Hydraul ic hose sizes are usual ly designated by their nominal inside diameter. With some excep-t ions , th is i s ind ica ted by a dash number represent ing the number o f s ix teenth inch inc rementsin the i r ins ide d iameter .

One H.P. = 33 ,000 f t . lbs . per minu te o r 33 ,000 lbs . ra ised one foo t in one minute . One H.P. =746 wat ts . One H.P. = 42 .4 BTU per minu te .

To f ind the H.P. requ i red fo r a g iven f lo l ra te a t a known pressure , use the fo rmula :

Pump Output H P. = GPlv' l x PSI x .000583 = GPli la lqL1 7 1 4

To f ind the H.P. requ i red to d r ive a hydrau l i c pump o f a g iven vo lume a t a known pressure , usethe fo rmula :

G P M x P S l x C 0 0 5 8 3 G P M x P S IP r r m n l n n r r t l _ _ l p _ - v r r v r A I u r , \ . u u u J Q J v r

Pump E f f i c i ency 1714 x Pump E f f i c i cncy

l f ac tua l pump e f f i c i ency i s no t knov rn , use l he f o l l ow ing ru le o f t humb fo rmu la f o r I npu t H .P .

I n p u t H , P . = G F l . l x P S I x . 0 0 0 7

T h e r e l a t i o n s h i p b e t y / e e n T o r q u e a n d H P . i s :

4 3 0 2 5 x H . P .Torque ( lb . in ) = t :Ar i , '1- ' - OB

u o T o r q u e ( l b . i n . ) x F P \ 1n . r . =63025

To de le rm ine the pump capac i l y (GP l ' , 1 ) neu .Ced to ex tend a cy l i nde r p i s ton o f a g i ven a rea(sq . i n . ) t h ru a g i ven C is l ; , nce l , r l chcs ) i r r a spu ' c r f i c t i n r c ( s t - ' conds ) :. 1 -o^ t _ P j s ton A rea - ( so ._ in , ) 4 Lqng in ( l pc fes ) x Q0 sg .q ,

u T t v t =

T i rne ( scco r :ds ) x l - r 1 cu , r r .

20.

2 1 .

23 .

z + .

22.

z o

27.

2 8 .

-1 I I

Density

Appendix D Meteric Unit For

QUANTITY NAME

Acceleration

Angle, Plane

AreaConductivity,Therr.nal

Current, Electrichydraulic fluids& other liquidsgasessolids

Di spiacement pneumatlc

(unit discharge;hydraulicEfficiencyEnergy, HeatFlow Rate, Heat

Flow Rate, MassPt teu t r t i t t i c

Flow Rate,volume

hydrarr l icForceForce per Length

Freciuency (Cyclel

Frequency (Rotattonal )HeatHeat Capac:ity, Specif ic

Heat Tran sf er, Cocffic: ic rr t

inert iu. Montettt ot

Fluid Porver APPlication

METRICUNITSmetre per second squareddegreeminutesecondsquare millimetrewatt per metre kelvin

amperekilogram per litre

kilogram per cubic mgram per cubic cmcubic cn-tI i tre

l l l l l l

percelltki lojoulewattgranr per secondkilogranr per secondcubic decinretre per seccubic centinletre per sec

Litre per ntirtLltenri l l inretre per nrinutene\.\'tollnewton l)er l l " l l l lhrrrtz_

leciprocal t t t i t tutereciprocl t l t t t i t t t t teki lo. jouleki lo. joule pe r k i logratt tk c l v i n

\\' ittt l)er s(ll.l i lre ll letrek e l v i n

ki lognrrtr nlctrc sclul t rct l

U.S. CUSTOMARYSYMBOLS

ft/sec2

:

mm2

SYMBOLSm/s"

oI

mm2

K g ' l 1 t l

mLo/-

KJwg/skg/sdnvr/scm/r/s

L/minnrL/rlirt

NN/nrnr

HZ1/rtr in

I /mink.l

k . l /kg 'K' Btu/lb. 'F

W/n r t ' k

ln3Va

BtuBtu/minlb/minlb/s

ftr/min (cfm)in:/min (cim)

gallmininr/min

tblb/in

Hz (cps)cpm

rpmBtu

w/m .K Btu/hrft oF

A Akg/L lb/gal

(Note 1)kg/m: lb/ft:g/cm: lb/ft:crn3 in:

L gal

Btu/hr . f tz 'uF

lb. f t2

3 1 2

::

Appendix E Hydraulic Symbols

1) L ines

{

L tNE, WORKTNG (MAtN)

L I N E S C R O S S I N G

LtNE, PTLOT (FOR CONTROL)

L I N E S J O I N I N G

L I N E . L I Q U I D D R A I N

L I N E W I T H F I X E DRESTRICTION

\,,

C O M P O N E N T E N C L O S U R E r-_lt- - ----r

FLEXIBLE \JHYDRAULIC FLOW _)_

STATION, TESTING,MEASUREMENT. POWERTAKE.OFF, OR PLUGGEDPORT

PNEUMATIC FLOW ----+-

FLUID STORAGE

RESERVOIR. VENTED l lLINE, TO RESERVOIR

. A B O V E F L U I D L E V E L

. B E L O W F L U I D L E V E L

IJ

R E S E R V O I R . P R E S S U R I Z E D V E N T E D M A N I F O L D{

3 l . i

2) \ /ar iab le d isp lacernent l lumps

MANUAL, HANDWHEEL CONTROL

PRESSURE COMPENSATORCONTROL

PRESSURE COMPENSATORA N D T O R Q U E L I M I T E R

L O A D S E N S I N G C O N T R O L

LOAD SENSING ANDP R E S S U R E L I M I T E RCONTROL

ELECTRO-HYDRAULICCONTROL

3 1 4

3) l i i xed d i sp lacen tc r r t pun rps

SINGLE, POWERSTEERING PUMPWITH INTEGRALFLOW CONTROLAND HELIEFVALVES

SINGLE,PISTON TYPEWITH DRAIN

SINGLE. VANE& GEAR TYPE

S I N G L E .WITH INTEGRALPRIORITY VALVE

S I N G L E ,WITH INTEGRALFLOW CONTROLVALVE

I\ A-r-\-,/ I

t w

I

DOUBLE.VANE ANT)GEAR TYPE

- j l5

1) Di rec t i o t ra l con t ro l va l vcs

TWOTWO

POSITIONCONNECTION S P R I N G

CENTERED,AIR OPERATED

TWO POSITIONTHREE CONNECTION

S P R I N G O RP R E S S U R ECENTERED,PILOT OPERATED

TWO POSITIONFOUR CONNECTION

TWO POSITIONI N T R A N S I T I O N

S P R I N GC E N T E R E D ,S O L E N O I DOPERATED

| , r * r , Post r toN

I roun coNNEcrloN

I vnlves cAPABLEi or t rur l ru l rEI postr torutruc1 (HontzotlrAl BARSi t t ' rotcnrr lNFlNlrE] rostrtorutruoI ABlL l rY)r _

S O L E N O I DCONTROLLED,PILOT OPERATED

N O S P F I N GDETENTED,MANUALLYOPERATED

S P F I N GC E N T E R E D ,S O L E N O I DCONTFOLLED,PILOT OPERATED

SPRING OFFSET,MECHANICALLYOPERATED

SPRING OFFSET,LEVEROPERATED-TWO WAY

I r _ L _ |

t l

P F E S S U R EC E N T E R E D ,S O L E N O I DCONTROLLED,PILOT OPERATED( s n 4 P L l F l E D S Y M B O L )

N O S P R I N GWITH DETENTS,LEVEROPERATED

o . . _ | 1 . . . . q ., 1Y lH l l l u| /\ tl I il tt;:J

l l r

3 1 6

5) P ropo r t i ona l r i i l ves

SERVO VALVES

CHECK VALVES

DECELERATION VALVES

HYDRAULIC MOTORS

CYLINDERS

SINGLE END, ADJUSTABLEC U S H I O N , C A P E N D

I

PROPORTIONALVALVE

TWO.STAGESERVO VALVE

PILOT OPERATEDCHECK VALVECHECK VALVE

ADJUSTABLEDECELERATIONVALVE WITH CHECK

NON-ADJUSTABLEDECELERATIONVALVE

VARIABLEDISPLACEMENT,DUAL DIRECTIONAL

F I X E D D I S P L A C E M E N TDUAL DIRECTIONAL

S I N G L E E N D ,N O C U S H I O N S

SINGLE END, ADJUSTABLECUSHIONS, CAPA N D R O D E N D S

SINGLE END, ADJUSTABLEC U S H I O N , R O D E N D

S I N G L E E N D ,HEAVY DUTY ROD

-1 I /

D O U B L E E N D

6) P ressu re con t ro l va l ves

P R E S S U R ER E L I E F

I

COUNTERBALANCEVALVE WITHINTEGRAL CHECK

P R E S S U R ERELIEF VALVE,S O L E N O I DCONTROLLED

UNLOADINGRELIEF VALVEWITHINTEGRAL CHECK

Hl -1 t ) ) u11 t r

RELIEF VALVE,REMOTEELECTRICALLYMODULATED

P R E S S U R ER E D U C I N G

r h t r ) ) u n ERELIEF VALVE,CARTFIDGEVALVE TYPE

II

I

I

P R E S S U R ER E D U C I N G\ALVEW I T HI N T E G R A L C H E C K

P R E S S U R EF E D U C I N GVT\LVE,CARTRIDGEVALVE TYPE

I

III

r-- . li t r 5

ffir-? -j

r y i iSEOUENCE VALVE

SEQUENCE VALVE,AUXIL IARY f ]EMOTEC O N T R O LOPERATION

I

r-T-_lI l f l - - ei |l_l-l--I IFTI* [ - t -

3 1 8

7) F lo rv Con t ro l va l vcs

FLOW CONTROL, ADJUSTABLE-NON-COMPENSATED

-*-

FLOW REGULATOR WITH REVERSEFREE FLOW

FLOW CONTROL VALVE

=I -OW CONTROL VALVE WITH CHECKSI | '4PLIF IED SYMBOL)

iE iUOTE CONTROLLED, ELECTRICALLY. . IODULATED WITH CHECK VALVE

FLOW CONTROL AND OVERLOADBELIEF VALVE

:RESSURE COMPENSATED CARTRIDGL.:ALVE TYPE

3 r 9

A p p e n d i x F E n g l i s h \ l e t r i c Co t t ve rs ion Fac to rs

To convert Into ....----_---> MultiPlY bY

ln to To convert D iv ide by

U n i t Symbol U n i t Symbol Factor

Atmospheres Atm bat bat 1.013250

BTU/hour Blu/h kilowatts kw 0.293071 x 10-3

Cubic cent imetres c m 3 l i t res 0.001

Cubic cent imetres c m 3 mil l i l i t res ml 1 .0

Cubic feel tt3 cubic metres m 3 0.0283168

Cubic feet tt3 I i t res 28.3161

Cubic inches i n3 cubic cent imetres cm3 16.3871

Cubic inches i n3 l i t res 0.0163866

Degrees (angle) rad rans rad 0.0174533

Fahrenhei t Cels ius (cent igrace)

Feet tt melres m 0.3048

Feet of water tl HzO bar 0.0298907

Fluid ounces, US US f l oz cubic cenlrmetres cm3 29.s735

Foot pounds f. tr lbl joules J 1.35582

Foot pounds/minuto t1 Ibf/min wails 81.3492

Gal lons, US l l Q c : l la t res 3.78531

Horsepower h p kilowails 0.7457

Inches of mercury i n Hg m i l l i b a r moar 33.8639

Inches of water in HaO m i l l i b a r mDar 2.49089

I n c h e s t n cen l ime i res cm 2.54

l n c h e s l n m i l l r m e t r e s mm ?5.4

Kr logram fo rce Kgl ne\l1ons N 9.60665

Ki logram f . n re l re kEt m newlcn mei res N m 9.80665

Ki logram f . /sq cent i retrs ba r U J d U C O J

Ki lopasca ls kPa L . r ba r 0.01

Ki loponds kp n e,rlo n s N 9.80665

Ki lopcnd metres k p m ne! \40n mei res N m 9.8066s

Ki loponds/square cen l imet f e kp icmz b a r ba r 0 980665

l , ' l i c rc inches ] l l n m t c r o n s pm 0.0254

l ,4 i i l imelres of mercury m m n g m r l l r b a r mbar 1.33322

l ,4 i l l ime l res o f wa ler m m H a O m r l r r b a r mbar 0.09 t06

NeMons/square c€ntrmelre N/crn2 oar 0.1

Newlons /square mel r9 l 'J/n2 ba r 1 0

Pascals (newtons/sq melre) Pa D a r D a r 10 -5

P in i s , US US i i q p t l r i r e s 0.473163

Pounds (mass) t o k i t o g r a n s xg 0.4536

PounCJcubic loot tb/l i l k i iogr ;ns /cub ic rne i re kg/mr 16.0185

PoundJcubic inch lb/ i ' i l k i lograms, 'c u b rc c en1 im e i rs k9.1c mJ 0.0276799

Pounds force l b l ne$ ions N 4.44822

Pounds f . feet tbf h nes ion mui r€s N m |.35582

Pounds f . inchcs l b l i n newion nre l reS N m 0.112985

Pounds l . /square tnch l b l i inz 0.06894

Revo lu t iongrn inu lo r /mrn raCians 'second raols o.104770

Square feel squa re ne l r es 1p2 0 092903

Squa ro i nches i n e sQUare me l res m 2 6.4516 x 10-a

Square inches i n e s q u a r e c e n l i m e l i e s cm2 6.4516

"C = 5( "F-32) /sF lu id power equ iva len ts1 bar = 105 N/mz1 bar = 10 N/cnr2 = 1 dNimmzl p a s c a l = 1 f J / m 21 l i t re = 1000.028 cm31 centistoke (cSt) = 1 66:751 joule = 1 wattsecond (Ws)Hertz (Hz) = cycles/seccnd

For mul t ip iesP r e l i x e s d e n o t i n g d e c i m a lm u l t i p l e s o r s u b - m u l t i P l e s

For sub-mul l ip les

320

E

Append ix G H1 'd rau l i c F lu ids

Contamlnant Character Source and Remarks

Acidic by-products Corrosive Breakdown of oi l . May also arise fromwater-contamination ofphosphate-ester f lu ids.

S ludge Block ing Breakdown of oi l .

Water Emuls ion Already in f luid or introduced by systemfault or breakdown

ol oxidation-inhibitors.

A i r So lub lo

lnso lub le

Etfect can be control ledL . , ^ ^ r ; , ^ ^ - ^ f , r i . i ,oy ani l-roam aooruves.

Excess a i r due lo improper b leed ing ,poor system design or air leaks.

Other o i l s Misc ib le bu tI r r d y I v d u (

Use of wrong f luid for topping up, etc.

Grease fu1ay or maynot 0e

misc ib le

From lubrication points

Scale lnso lu b le From p ipes no t p roper lyc leaned be fore assembly .

Meta l l i c par t i c les lnso lub lewi th

cataiy, l icac t ion

May be caused by watercon lamina i ion , con t ro l lab le

wi th an t i - rus t add i t i ves .

Paint f lakes Inso lub le ,b lcck ing

Pa in t on ins ide o f tank o ld o rno t compat ib le w i th f lu id

Abrasive part icles Abrasive andb lock ing

Ai rbo i 'ne par t i c les ( remove w i th a i r { i l l e r ) .

Elastomericparl icles

B lock ing Sea l b reakdown. Check f lu id , compat ib i l i t y o f sea l des ign ,

Sealing compoundpart icles

B lock ing Sea l ing compounds shou ld no t be used on p ipe jo in ts .

Sand Abrasive andblocking

Sand shou ld no t be used as a f i l l e r fo r man iou la t ino o ipe bends.

Adhesive part iclesLint or labric

threads

Block ingBlock ing

Adhesives or joint ing compounds should not be used on gaskets.Only l int-free cloths of rags should be used for cleaning or plugging

d ismant led comoonents .

:i

i

-r_ I

2) ISO Viscosi t -v gr l r les for H1'4 l 'au l ic Oi ls

I ISO Midpoint K inemat ic Viscosi ty L imi ts

I V iscos i ty Kinemat ic Viscosi ty cSt at 40oC

I Grade cSt at 40oC Min imum MaximumI ' r

2 .42 |l__l!eYG2 z.z t.sa ,I tsovcg s.z z.Bs 3.s2 iI l sovcs 4 .6 4 .14 5 .06 i' 'l l s o v c T 6 , 8 6 . 1 2 7 . 4 8 j

I

l l s o v c l s 1 s 1 3 . 5 1 6 . s j

I |SOVG22 22 19 .8 24 .2 II tsovcsz sz ze.s ss.z jI rsovc46 46 41.4 s0.6 iI lsovc6s 58 61,2 74.8 jI | S O V G 1 0 0 1 0 0 9 0 . 0 1 1 0 i

;I 199vG220 220 1s8 242 _iI tsovcszo 320 2Bs gs2 i

I lsovc460 460 414 506

I rsovc680 _680 612 748I l sovc1000 1000 __ 900 _ 1 100

3 ) C o n r p a t i b i l i t l ' o f I { 1 ' d r a u l i c f l u i d s a n d s e a l i n g t n a t c r i a l s

WATER-BASE FLUIDS NON.WATER.BASE FLUIDS

MATEBIALSUNDERCONSIOERATION

P E T R O L E U M O I L S

OIL ANDWATER

EMULSION

WATER.GLYCOLM I X T U R E

PHOSPHATEESTERS

ACCEPTABLESEAL ANOPACKINGMATEBIALS

N E O P F E N E ,E U N A N

NECPREN E ,BUNA N ,(NO COFn

NEOPBENE,BUNA N ,(No coFn

8UTYL, VITON',VYRAM,s rL t coNE,TEFI.ONFBA

ACCEPTABLEPAINTS CONVENTIONAL CONVENTIONALAS FECO[4TlENDED

8Y SUPPL IER

, 'A IR CUBE"EPOXY ASFECOMNIENDED

ACCEPTABL EP IPE DOPES CONVENTIONAL CONVENTIONAL PIPE DOPES AS FECOI, , !MENDED, TEFLON TAPE

ACCEPTABLESUCIIONSTRAINERS

100 r" lEsH wtRE1.1/2 T[ ,1ESPUMP CAPACITY

1O h , lESH !V IRE4 T I I , IES PUh, lPCAPACIry

50 ' \ .1ESH WIFE. 4 T I | t , lES PUMP CAPACITY

ACCEPTABLEr t L t E h 5

CELLULOSEFt8EF , 200 -3CO MESH WIRE,KNIFE EDGEOB PLATE TYPE

9 U 5 5 t i t t H

?00-300\V IFE , KN IFEE U b t r U H

PLATE

CELLULOSEFIBER, 2OO-300 |"IESH WIRE,KNIFE EDGE ORPLATE

CELLULOSE FI8ER, ?OO-3OO MESH WIRE, KNIFEEDGE OR PLATE TYPE (FULLER'S EARTH OR MICRONICT} 'PE MAY BE USED ON NONADDITIVE FLUIDS.)

ACCEPTAELEMETALS OFCONSTRUCTION

CONVENTIONAL CONVENTIONAL

AVOJDGALVAI.lIZEDMETAL ANDCADMIUMPLATING

CONVENTIONAL

J Z L

Append ix H Hydrau l i c P ipcs

1 ) P ipe s i zes by schedu le number

(STANDARD) (EXTRA HEAVY)

SCHEDULE40

S C H E D U L EBO

SCHEDULEt o u

DOUBLE EXTRA HEAVY

S C H E D .1 6 0

DOUBLEEXTRAHEAVY

COMPARISON

IAMETER

1tB1143/81t2314'|

t - v +

1-1t2

z - vz3

3-112A

56B1 01 C

.405

.540.675.840

1 .0501 .3.15L C O U

1.9002.3752 8753.5004.0004.5005.5636 6258 625

10.75012.750

, z o J

,c o4

.493

.622

.8241.0491.3801 . 6 1 0

/ , u o l2.169. r .uo63.5184.0265.047o .uo37.981

10.02011 .934

.215.302.423.546.742.957

t . z t o

1.500L Y - l y

2.3232.9003.3643.8264 .8135.7617.6259.564I l . J / o

.466.614.B 15

1 . 1 6 01 .3381 .6892 .1252 624

3.4384 .3135 .1896.8138.500

1 0 .1 26

.252,Z+ J '+

.599

.896'1 .100

1 .5031 .771

4.063

2) Pressure ra t i l rg o f p ipes

Working pressures for various schedule pipes are obtained by dividing burst pressure by the safety factor.

Nomina lP ipeSizei n .

Ou ls ideDiametero t P ipe

. in .

Numbero t

ThreadsPer Inch

Lengtho f

Eflect iveThreads

- i n .

Schedu le 40(Standard)

S c h e d u l e 8 0(Ext ra Heavy)

Schedu le1 6 0

Doub le(Extra Heavy)

P ipelD- in .

BurstPress-

PS I

Pipel D - i n .

Bu rstPress-

P S I

Pipel D - i n .

Bu rstPress.

PSI

PipelD- in .

BurstPress-

PSI1/8

1 t 43/81 t 23t4

1

1-1 t2

1 - t I Z

0.405

0.5400.6750.8401 . 0 5 0

t . J t c

1 . 6 6 01 . 9 0 0

z , J t 3

2.8753.500

27

1 B1 8

1 4

1 1 - 1 t 21 1 - 1 t 2I t - t t 1

| 1 -1 t2A

tt

0.26

0.400-410.530 . 5 5

0.680 . 7 10.72

0.76

1 . 2 0

.364.493

.824

1 . 0 4 91 . 3 8 01 . 6 1 0

2.Q672.4693.068

16,000'13.5001 3 , 2 0 01 1 , 0 0 0'10 ,000

8,4007,600

7,0006, '100

.302

.423

.546

.742

.9571 . 2 7 81 . 5 0 0

1 . 9 3 92.3232,900

'13,600'1 1 ,50010,500

22,00019,00017,50015,000

9 ,1 009,6008,500

1.689z . t z 32.624

.q6s

. 6 1 4

1 . 1 6 0I . J J d

:21 ,00021,000

19,00015,00014,800

14,50013,00012,500

; ^.434

.599

.896r .100I ( n e

,.!,

35,00030,000

27,O0023,00021,000

19,00018,000

-11-1

3) Oi l f lorv ve loc i t ] ' in tub i l rg

Figures in chart ale GPN4 florv capacity of tubing, and were calculated frorn fornrula

C P I \ 4 = V x A0 . 3 2 0 8

V = Velocity (feet

A = Inside square

/ second)

inch area of tube

Tubeo.D.

WallTh ick .

2Ft/Sec

F iqures in Body o f Char t a re GPM F lows

l c l l o l l sI rvs"" I rvsec I rvsec

z vFt/Sec

30Ft/Sec

112

n ? q

.042

.049

.058

.065

.o72

.083

.905 GPM

.847

.791

.670

.620

. 5 4 b

1 . 8 1 G P M1 . 6 31 . 5 81 . 1 41 . 3 4

1 . 0 9

4 .52 GPM4.233 .95J . O I

3 . 1 0

6 .79 GPMO . J J

5 . 4 1

4 .654 .09

9 .05 GPM6.477 .917 .22o . / uo . 4 v5 .46

1 3 . 612.71 1 . 91 0 . 8'1 0.19.308 . 1 6

518

.UJf,

.049

.058

.065

.072

.083

.095

. 5 1,43,36.27.20

.03

.9 26

3 . 0 12 .852 .722 .542 .10

z . v o1 . 8 5

7 .547 . 1 66 .606 .346 .005 .665 . 1 6

1 1 . 310.710.29 . 5 19.008 .497 .73o . Y f

1 5 . 11 4 . 31 3 . 61 2 . 712.01 1 . 31 0 . 39 .26

22.6

20.4r o n1 8 . 01 7 . 01 5 , 51 3 . 9

3 t4

.049

.058

. U O J

.072

.083

.095, 1 C 9

2 . 0 81 . 9 71 . 8 81 . 7 51 . 6 71 . 5 31 . 3 9

4 . 1 73 .933 .763 . 5 13 ,343 .072 .77

1 0 . 49.8.+9 . 4 18 . 7 78 .35

6 .93

1 5 . 61 4 . 8

13.212.51 1 q

1 0 . 4

20.81 9 . 71 8 . 81 7 . 51 6 . 71 5 . 3

n a t

29 .62e .226.41 3 . v

23.020.8

7 t 8

.049

.058

.065

.072

.083

.095

. 1 0 9

2 .952 .822 .72z . c <2 .462 .302 . 1 1

) . v l

5 .435 .234.-424 .604 .22

1 4 . 8

1 3 . 61 3 . 11 2 . 31 1 . 51 0 . 6

22 .22 1 , 1

1 9 . 61 8 . 517 .21 5 . 8

28.227 .226.221.623 .021 .1

44.342 .310.739 .2

34.4J t . ,

I

. 049

.058

.065

.072

.083

.095

. 1 0 9

.120

3 .98J . O a

3 7 03 .59

J . Z I

3 .00z . 6 J

7 .967 .657 . 1 17 . 1 76 . 8 1o . \ z

6.005 .65

1 9 . 91 9 . 11 8 . 51 7 . 91 7 . 01 6 . 11 5 . 0

29 .9

27 .8l o . t2 5 . )

2 4 . 1

39 .838.237 .0

34 .0a ) 1

29.928.3

3 V . /57.4

5 1 . 118.244.942 .4

1 -1 t4

.049

.058

.065

.072

.033

. U Y J

. 120

6 5 06 .29o . t q

6 .005 . 7 55 .50J . Z I

5 .00

1 3 . 01 2 . 612.312.01 1 . 51 1 . 01 0 . 41 0 . 0

32 .53 1 . 530 .730 .028.8z t . 3

26.125 .0

48.7

46 .014 .94 3 . 14 1 . 23 9 . 137.4

64.9o z . t6 1 . 4

5 5 . U\ ) 1

97.494 .492.189.8d o . J82 .5I O . a

74.9

1-1 l2

.065

.o7?

.083

.095

. 1 0 9

.120

9 . 1 99 .008 .718 .408 .47 .77

1 8 . 41 8 . 017.41 6 . 81 6 . 11 5 . 5

45.945.043 .542 .040.238.8

68 .9o / . f65 .3o J . v60.3c o . J

9 1 . 990 .087.184 .080.477.7

1 3 8t ? (

1 3 1126

1-3t4

0650720830951 0 9120| -1+

12.81 2 . 61 2 . 31 1 . 91 1 . 511 .210.7

25.71 J . Z24.623.823.01 1 , O

21.5

64.263 .1o l . $

s9.657.43 f . d

53 ,7

Y O . J

94.792 .189 .386 .183.780 .6

'1 281 2 61231 1 9 .1 1 5112107

'193

1891 8 41 7 91 7 2167'161

2

.065

.072

.063

.095

. 1 0 9

.12Q- t J {

1 7 . 11 6 . 91 6 . 5i o , u1 5 . 51 5 . 214 .7

34.233.732 .9J Z , I

J t - l

30 .329.4

b f , . o

84 .382 .380.277 .77 5 . 873.4

1 2 81 2 6l z J

120117

1 1 0

1 7 11 6 91 6 51 6 01 5 5152

Z J Tz 3 J

247

Z J J

220

324

Append ix I C l , l i nde r s i ze se lec f i o r r

This chart l ists the theoretical push and pui l forces that cyl inders wil l e.xert when supplied with various working pressures, plus

ir i i i "* irc j i pi"ton vetocit ies when supplied with 15 Ft. lsec. l luid velocity through scH 80 size pipe'

O i l . " ^ r , ^p t io " in ga l lons per minu te = Ga l lons per inch x inches per minu le o f p is ton t rave l '

i ; ; i l ; : ZSt cuOic inches . Cy l inder bore d ia rne ters and p is ton rod d iamelers a re in inches .

cvl.BoreDia .

PislonRodDia .

WorkArea

S q . I n .

HYDRAULIC WORKING PRESSURE P.S.I.F lu id Required

Per ln . 0f Stroke PortSize

Fluid Velocity6 15 Fl./Sec.

FlowGPM

PistonVel.

ln./Sec.500 750 1000 1 500 2000 3000 Gal. C u . I n .

1-112 5/81

1.7671.460.982

8837304 9 1

1 3251 095736

17671 460982

265121901473

353425201 964

530143802946

007650063200425

1.7671.460.s82

1t2 1 t 024.029.043.1

2 r-1 -3/8

3 .1 412.3561 656

t J / |

1 178828

2356li67

31 4123561 656

47 1135342484

628347 12331 2

942370684968

0136001 02000717

3 . 1 4 12.3561.656

1t2 1 1 . 013 .518 .025.6

2-112 i -1 -3l81-314

4.9094.1243.4242.504

. ^ F A

206217 121252

3682309325681 878

4909412434242504

736361 8651363756

981 882186848s00B

1472712372102727512

.0212501 785.01482.01084

4.9094.1243.4242.504

1t2 1 1 . 0

8 .610 .3t a . q

t o . Y

3-114 t -S, t1-3t4

B 2-466 . 8 1 15.8915 . 1 5 4

41 48340529452577

6222510844183865

8296681 1589 151 54

1 ' / A A

1 0 2 1 6BB367731

65,Q2362217E20308

24888204331767315162

.0359

.0295,0255.0223

8 2966 . 8 1 15.891( 1 ( , {

3t4 2 0 3

9 .41 1 , 5I J . J

15.2

4 1-31422-1t2

12 566' 1 0 . 1 6 1

9.4247 657

6283508047 123B2B

"q425r- 6217068

1 25661 0 1 6 194247657

BB4952414 1 3 61 465

25132203221 8B1Br ( 2 1 1

3769830483282722297 1

.0544

.0440

.0408

.033 1

12 5661 0 . 1 6 1I 4247 657

3t4 2 0 3

6 .21 1

8 ,310.2

5c

2-11233-112

19 6351 6 .4S214.7261 2 . 5 6 61 0 . 0 i 4

961 B8246736362835007

t \ l l l )

1 2369

94 21751 0

963561-o247262566001 4

29.1532'!73822089188.1915021

3927C32984295422513220c28

5390549476441 t'B3769830c42

0850071 4063705440133,

'19 6351 649214.72612.566' 1 0 . 0 1 4

3t4 20.3

4 .04 .75 .36 27 .8

o 2-1t2

^

28.27423.365T.24515.708

141371 1 6 8 21 06027854

212451 /- 5241 59041 1 i 8 1

2827 423365212051 5708

l a . 4 1 1

350473 1 8 0 723562

5654846730A24103 1 4 1 6

8,1822700956 3 6 1 547 124

1224101 1091 80680

28.?7 423.36521.20515 708

3 3 8

4 .65 .6o . I

8 3

I2

38.48531.4162 5 9 1 918 850

I J L 9 '

157081 29609425

23861235621 913911137

38,1853 1 1 i 62 5 9 i 91 8850

57i28471243887828275

769706283251 83637700

1 1 5455942487775756550

1 6661 3601122081 6

38.46531.41625 .91918 850

I 1/4 602

6.07.48.9

12.3

I 3-1t2^5-1t2

50.26540 64437.69926.507

251 33203221 88501 3253

376"09304832827 41 9880

50265$61,43769926507

75398609665654839760

1 0053081288753985301 4

1 507951219321 1 309779521

21761 7591 632

50.26540.64437.69926.507

t - U z 83.0

6 .47 .98.5

12.0

1 0 o , n5-1t27

78.51062.63654.78240.055

392703 1 3 1 82739120027

5890546977410863004 1

785106263654i8210055

1 1 7 8 1 0939548217360082

1 570801252721 0956480110

2356201 879081 643461 201 65

3400271123711734

78.54062.63651.78240.055

139

o . o8 .59 .8

13 .4

12 5-1127I

1 1 3 . 1 089.3474.6262.84

56550446703i31 031420

848256700s55,o6547 130

1 1 3 1 0 0893407 462062840

1 696501 3401 01 1 1 9 3 094260

2262401 786E01 192401 256E0

3393002680202238601 88s20

4896386732302720

1 1 3 . 1 089.347 4.6262.84

a - U L 199

6 .88.6

10 .3I t . t

14 781 0

153.S41 15.46103.687 5.40

769i05773051 84037700

r l q / ( (

865957776056550

1 539401 1 51601 036t075400

23091 01 73i 901 555201 1 3100

3078802309202073601 50800

161 82034638031 1 040226200

.6664

.4998

.4488

.3264

1 53.94I 15.461 03.68

1 e / i

2-1t2 1 9 9

J . U

6 .67 .4

10.2

32-s

Appendix J Heavy, Medium and Lightweight ROVs (As vesse-l specifications are

tiaUte to change, please refer to manufacturer for current specifications.)

a) AN/SLQ-48(V) Mine Neutralisation System

Manufacturer. Alliant Techsystems Inc.

Work capabilities. Intended to neutralise bottom and moored lines. Also surveyoperatiolls.

Dimensions. Length 3.70mBreadth 1.20mHeight 1.20mWeight tn air l,247kgsConstruction GRP frame

Operating depth. 1000nr.

Propulsion. Twin 15hp. 4 x thrusters,2 horizontal, 1 lateral, I vertical.

Instrumentation and tools. Manipulator and cable cutter, 2 low light level camerasand lights. High resolution sonar and tracking system.

b) Boxer Compact

Manufacturer. Seaeye Marine Ltd.

Work capabil i t ies. Inspection and survey.

Dimensions. Length 0.725rrBreadth 0.65mHeight 0.50rnWeight in air 70kgsConstruction. POlypropylene with stainless steel f-asterlers.

Operating depth. 300nr

Propulsion. 4 x dc brushless thrusters. 2 horizontal and2 vertical.

Instrumentation and tools. 1 function manipulator optional. CP probe, FMDoptional.Cblour CCD camera,2 x 150w halogen lamps of varying intensity. Additional TVcameras optional. Fluxgate gyro with compass, depth sensor, auto pilot for depthand heading, sonar optional.

c) Diablo

Manufacturer. Hydrovision Ltd.

Work capabilities. General subsea support, drilling and construction support, surveyand inspection.

Dimensions. Length 2.10mBreadth 1.50mHeight 1 .70mWeight in air 1980kgs

326

!

Construction. HE30 aluminium channel space frilnre, speciallydesigned to give through frame lift capability of 3 tonnes.

Operating depth. l000nr

Propulsion. 75hp. 6 x HT300 Curvtech hydraulic thrusters, 2 axial,2lateral,2vertical.

Instrumentation and tools. 1 x 7 function manipulator, 1 x 5 function grabber, lowpressure water jet. Depth sensor, water alarms. I x Osprey 1323d SIT camera, 2 xOsprey 1360 colour cameras, 1 x Osprey CCD BSW low light camera, 8 x 250wlights, 2 x 400w wide flood lights. Sonar and gyrocompass.

d) Examiner

Manufacturer. SubSea Offshore Ltd.

Work capabilities. Subsea engineering, subsea completion support, pipeline support,platform inspection and drill rig support.

Dimensions. Length 2.00mBreadth 1.95mHeight l .80nrWeight in a i r I ,700kgsConstruction. Aluntiniunr frante

Operating depth. 500nrsw.

Propulsion. HPU 75 hp, 8 x hydraulic inner space thrusters. 4 x vertical, 2 x lateral,2 x horizontal.

Instrumentation and tools. 7 firnction manipulator, 5 function nranipulator, provisionfor specific tooling packages.Sensors. 2 x hydraulic pressure, 2 x hydraulic temperature, hyclraulic flow, variablebuoyancy pressure, water ingress. conrpensator vacuum, power supply voltages,cable IRs.Provision for 6 canteras rvith separate locus and on/off controls. Expandable to 12with video switching, provision for f ibre optic video mtrlt iplexing.Obstacle avoidance sonar', depth sensor, heading sensor, pitch and roll sensors.Auxil iary power supplies. Auxil iary hydraulic system. HPU 1tt.75Kw(25hp).

Additional data lspecial features. An eyeball ROV can be incorporated into thesystem and mounted within the main ROV frame.

e) Hydra 201 40

Manufacturer. Oceaneering production systents.

Work capabil i t ies. Dri l l ing and consrruction sltpport tasks.

Dimensions. Length 1.80mBreadth 1.20nrHeight l .30rnWeight in air 862kgsConstruction 6061 T6 aluminium frame. stainless steel fittinss.

Operating depth. 1000nr - 2,50011

:

-1: I

Fropulsion. 7 x thrusters (2 fore / aft,2lateral' 3 vertical)

Instrumentation and tools. 1 x 7 function manipulator, 1 x 5 function. ! -Osarey1323 SIT camera, 1 x Osprey OE 1335 colour camera, 1 x Osprey 1 352 CCD'Photosea 1000, 2000 or NDT 4000.Auto depth and heading control, fluxgate magnetic compass, digital depthmeter,high resolution sonar and acoustic tracking.

0 Hysub 5000

Manufacturer. International Submarine Engineering Ltd.

Work Capabilities. Research and salvage operations.

Dimensions. Length 2.54mBreadth 1.52mHeight 1.6[lntWeight in air 2,091kgsConstruction. Anodised alunlinium frame.

Operating depth. 5,000rn

Propulsion. 40hp hydraglic power pack, 6 x hydraulic thrusters.

Instrumentation and tools. 1 x -5 function rate am1, 1 x 7 functiott manipulator,sample skid for geophysical tools and sanrple collection. -CpSpAC compitet^sy.ttenl, depth gauge. 1x Osprey SIT 1323 video camera, I x

Osprey colour^CCD f:Ot uiOeo camera, 4 x 250-w lights, gyro corltpass andMesotech sonar.

NB Also available are Hysub 2-5, Hysub ATP 10, Hysub ATP 40, Hystrb ATP 50andHysub ATP 150.

g) Min iROVER MKI I

Manufacturer. Benthos Inc.

Work capabil i t ies. Inspection, observation and l ight work capabil i t ies.

Dimensions. Length 86cntBreadth 50cmHeight 4}ctt'tWeight in air 34kgsConitruction. Altiminium hull, PVC motor housing, rectangular keel

skids.

Operating depth. 305nr

Propulsion. Electric thruSters, I x lateral, I x vertical, 2 horizontal.

Instrumentation and tools. Low light high resolution video camera, 2 x 150w quartzhalogen lamps.

NB Also available Max ROV MK 1, MKII, MKIII and MicroVER.

328

h) MRV (Mult i Roll Vehicle)

Manufacturer. Sl ingsby Engineering Ltd.

Work Capabilities. Survey, drill support,intervention, construction, cable burialrecovery, salvage (work package available to suit customer requirements.

Dimensions. Length 1.92mBreadth 1.50mHeight 1.56mWeight in air 1,590 - 2,250kgs (basic vehicle)Construction. High strength aluminium space frame, stainless steel

fasteners.

Operating depth 600m / l,000nr / 2,000nr deeper on recluesr.

hopulsion Up to 200hp, 4 x horizontal,2 x vertical, additional thrLlsters can befitted on request.

Instrumentation and tools SEL offer a range of tooling packages. Maximum of 5cameras, mono, colour, st i l ls or SIT, 3.5kw max l ighting, spot or f lood withdimming facility.Auto alt i tude, auto depth. pitch and rol l , heading, tr im. Digicluanz depth gauge, gyro/ f luxgate compass. sonrrr to suit cr.rstonrer rerluirements, enrergency pingel andflasher.

i) Offshore Hyball

Manufacturer Hydrovision

Work capabilities Inspection and observarion.

Dimensions Length 0.575ntBreadth 0.77nrHeight 0.575nrWeight in air 60kgsConstrucrion Fibreglass, stainless steel f i t t ings.

Operating depth 300m

Propulsion 4 electric thrusters, 2 fore / aft and rotational moventent, 2 lateral andvertical movernent.

Instrumentation and tools Manipulator interface kit fitted as optional extra. Digitaldepth indicator, leak detection system, microphone to provide audio feedback to theoperator, ground fault interrupter artd circuit breakers to protect srrrf-ace equipmentand vehicle, CP interface standard.Remote focus low light CCD canrera nrounted on 360o roraring chassis. 2 x 100wquartz halogen lights, 2 x 75w lights on chassis. AC6000 super short base linetracking system optional, AC9000 sonar optional, magnetic -onrpass and rate gyrocompass.

NB Offshore Hyball is a more powertul version of Hyball having 1007a more power.

,j29

j ) Phantom Ult imate

Manufacturer. Deep Ocean Engineering

Work capabilities. lnspection

Dimensions. Length 1.81mBreadth 1. 17mHeight 0.97mWeight in air 363kgsConstruction. Full perimeter polypropylene with stainless steel crash

frame protecting all components, recessed andhardened camera Dons.

Operating depth 610m, test depth l62nt

Propulsion. Electr ic. 4x horizontalthrusters,3 xvert ical thrusters,2x lateralthrusters.

Instrumentation and tools. Compatible with almost all ntanipulator systems.Options include cable cutter, tools and santpl ing devices.Instrumentation includes audio feedback reflecting vehicle condition, CP optional.PALNTSC, colour high resolution, low light CCD canrera, built in video switch foroptional second camera. Camera / instrument platfomr with 360o tilt. 2 x 250wdimmerable tungsten halogen l ights.Fluid gimballed fluxgate c'ompa.ss, depth transducer. Options include sonar, trackingsystem and alt inteter.

NB Also available are Phantont 300, 500, Phantom DHD2, Phantonl DS4, PhantomHD2, Phantonr HVS4 attd Phantom pipeline.

k) Pioneer

Manufacturer. SubSea Offshore Ltd.

Work capabilities. Drill rig support, general survey and inspection work, guidingdri l l str ing, leak checking, bullseye checking and debris removal.

Dimensions. Length 1.65rnBreadth l .65nrWeight in a i r l ,315kgsConstruction. Polyrtrer br.royancy, aluminium frame.

Operating depth 1,525nr

Propulsion. 50hp power hydraulic power pack (pioneer plus has 75hp), 5 xproportionally controlled thrusters.

lnstrumentation and tools. I x 7 function rnanipulator with position feedback controland 1 x 5 function manipulator. Vehicle status sensors, hydraulic pressure andtemperature, water ingress alarnrs at 12 points, telemetry status panel, low oil alarms.

330

II:

I x low light camera with facility for up to 3 additional cameras. 6 x 250w lights.Depth sensor, heading sensor ( slaveable gyro), auto depth, heading and altitude,acoustic pinger, emergency flasher, obstacle avoidance sonar with hydraulictilt,vehicle turns indicator, pitch and roll sensors, optional transponder.

l) Recon MIA

Manufacturer. Perry Tritech Inc.

Work capabilities. Drill support, construction support, pipeline survey.

Dimensions. Length 2.06mBreadth 0.90nrHeight 0.85nrWeight in air 467kgs

Operating depth. 300nrsw

Propulsion. Electric. 2 x axial, 1 x lateral and 1 x vertical.

Instrumentation and tools. 2 function manipulator, cable cutter, marine growthcleaning package, 5 or 7 function Hercules manipulator, 5 or 6 firnction Schillingmanipulator. CP probe. High resolution black and white canler{r with option forcolour and SIT camera, pan ancl t i l t . 2 x 250w variable intensity l ights, sonar, autoheading and tracking s),stenr.

m) Rigworker MK 4 R3000

Manufacturer. Hydrovision Ltd.

Work capabilities. Drill suppofi plus firll range of work tasks.

Dimensions. Length 2.lOntBreadth l . .40nrHeight 1.50rrrWeight in a i r 1 , ( r5Okgs

Operating depth 1,000nr

Propulsion. Hydraulic power pack. 2 x forward / reverse, 3 lateral thrusters, 2vertical thrusters.

Instrumentation and tools. lnterface for all propriety of ntanipularors, typically I x7and 1 x 5 function. Cotrprehensive range of tooling also available. Interface for 4cameras including pan and t i l t .Auto depth, alt i tude ancl heading. Provision to f i t proprietary obstacle avoidancesonars. Optional interface for a full range of survey sensors inc:luding bathymetricsystem, dual scanning profi le and pipe / cable rracker and gyro.NB Also available, Rigrvorker 30001 / R3000S.

n) Scarab IV

Manufacturer. Oceaneering Productiolt Systenrs.

331

Work capabilities. Telecommunication cable burial and repatr.

Dimensions. Length 4.00mBreadth 2.00mHeight 2.00mWeight rn air 2,722kgs

Operating depth 1,850nr

Propulsion. Hydraulic, l50hp

Instrumentation and tools. 2 x 7 function manipulators, cable gripper and cablecutter.4 x SIT cameras, I colour CCD camera and variable intensity lighting.Cable tracking magnetometer system, acoustic positioning system, high resolutionsonar, altimeter, fluxgate compass, pitch and roll sensors, depth transducers.

o) Super Scorpio

Manufacturer. Perry Tritech

Work capabilities. Survey and inspection, including platfomr and pipeline, Preinstallation surveys and as laid surveys, diver support and sub sea lemoteintervention.

Dimensions. Length 2.-50ntBreadth 2.50nrHeight 1 .90mWeight in r t i r 2 ,100kgs

Operating depth 1,000ntsw (other depths optional)

Propuls ion. 62hp. -5 x hr ,draLr l ic thrusters,2 ax ia ls ,2 la tera l anc l 1 ver t ica l .

Instrumentation and tools. Manipulators, grabbers, suction arnrs. Standard surveyjunction box, options include CP probe, bathynretr ic sertsor.Cameras include pan and t i l t and colour with suitable l ighting. Auto heading, depth,pitch and rol l . Options Sortar, Digiquartz, responder.

Appendix K Properties Of Cable Conductors

1) Copper conductors

Diameter(mm)

0.25s0.30

0.32

0.40

0.405

0.50

0.51 1

0.60

0.644

0.70

0.80

0.90

0.91

1.00

M43

M67

M70

AWG number

30

30

28

28

26

26' ) , l

a 1L+

/ _ '

z?22

22

1 9

1 9

50

.50

7 5

-50

50

75

50

-50

1 5

-50

-50

50

50

Loop Attenuetin

resistance(Q i Km) dB i Km

680

492

433

277

270

177

170r a 1

107

90

69

5-5

-53

44

2:42..232..03r .621 . 6 11.30r .27l.0tJ1 . 0 10.920.810.120.710.65

2 . 6 1 . 3

6.s 0.68

l . t i 1 . 5

2 . 6 1 . 6

3 . 5 3 . 1 *

6 1 . 3

1 . 5 4 . 2 *

1 4.4r a ^| -1./.

1.25 0 .62

1.25 0 .76

0.450 1 .58

0.400 36.0

r&51400

13r3

1050

1036

839

822

700

652

597

524

468

460

4 1 8

Resistances are based on pure copper and do not take into accourrt cable make up

Attenuation and impedances assunle abscenceof impedance irregLrlarities

2) Coaxial cable Characterist ics

Type overafl impedance capacitanceMax dc Max RF Attenuation

diameter. (O) pF / m voltage(kVpeak dB/l0m

(mm) voltage kV @100MHz5

1 0 . 3

5.ti

I00

l(x)67

100

100

6ti

100

96

r00r0096

96

r02

2 1

401 Al +

2 1

6

4A-

5

5

r .9t .7

}/{16 5RGsSCAJ 5RG59BAJ 6.isRG174AnJ 2.8RG178B^J 1.t lRGI79Bru 2.5RG213/U 10.3RG214|U 10.8RG223N 5.sRG316 J 2.6

333

* = Attenuation dB / 10m @200MHz

Appendix L Umbil ical specif icat ions

l) MRV Tether

Electricol Propert ies : *)

Yellow TPR iocket, I 49 mmjocket thickhess: 3.4 mm opproxAromid broid, 24x10x3360 dTexDiometer: 40.5 mm oPProxYellow TPR over PUR jocket, I 38 mmTPR thickness: 3.9 mm; PUR thickness: 2 mm

(t 2) lnsuloted conductor . l .J4-mm2lon'OrCiott ploin copper 19x0.J0 mm, I 1.5insulotion: XLPE, I 4.7 mm(1) Dro inwi re 1 .J4 mmZ .^ ^ - 2 . -iohductor: ploin copper 19x0.J mm, / 1.5 mrn

Lopped copper/polYester toPeFil ler,6 4.7 mm

(O) Ooticol f ibres in qel-f i l led loose tubeStionfea oround stedl wire centre, / 2.2 mmTube size; lD : 0.85 mm; 0D = 2 mmPE jocket , I 7 .1 mm

Fil lers, f l 4.7 mm(5) Droinwires 1 mm2iohductors: p lo in copper 19x0.26 mm, I

'1 .5

(4) lnsuloted conductor 0.75 mm2ionductor : p lo in copper 7x0.37 mm, 6 1.11 mminsulotion: XLPE, I 4.7 mm

"lnterstices f i l led""The weiqht in seowoter opplies to on ossumedseowote-r density of 1026 kglm3."

*) Note : The volues ore corrected for the' ouerlength of the elements.

Current roting

Core current

1.34 mmZ Power

0.75 mm2 Power1.34 mm2 dro in

I mm2 droin

5.8 Amp4.0 Amp

5.8 Amp

4.8 Amp

condit ions:woter; ombient temPeroture 25 deg Ccontinuous operotion(5) lovers of coble on winchm6x 6onductor temperoture 85 deg C

diometer :

Opt icol Fibre Propert ies : *)

uomPonentMode Numenc0lAporture

B o n dwidthMHz*km

Attenuottonof 850 nm

dBAm

50/125 Multi 0.2 400 4

ComponentsRcond Rinsul)00 V D(

Volt.Rot ingl n l l I 1 '

HighVolt. testof 5 min.

hm/kmlvlohm*kn KV KV0. /5 mmZ 2E.J 500 '2/J.J 121.34 mmZ 1 6 . 1 E n n ?/3.5 12

rnm2 22 .0 droinwire1.34 mmZ 1 1 . O droinwire-TtToIe:

Uo is voltoqe to eorth' U is l ine- t5- l ine-vo l toqe

Mechonicol Propert ies :

Breokingstrenoth

Bendingrodius

Weight

colcr.tloted recornmended, min- calailaled

stotic dvnomic o i r seowoterKN mm m m kolkm kolkm76 1 925 - 9

-)-12+

2) MRV Umbil ical

Mechonicol Propert ies :

(2) Controhelicol loyers of greosed, preformed,ioivonised steel wir-es 2260 N/mm?iirst lover: 45 wires 6 2.3 mmsecond lover: 60 wires I 1'9 mmThe loyeri ore bolonced to minimisetorque & rototion, I 4J.6 mm

Block PUR iocket, F 35.2 mmjocket thicl iness: 2.2 mm

(26) lnsuloted conductor 2 mm?ionductor : p lo in copper 19x0.J7 mm, / 1 .85 mminsulotion: XLPE, I 4.7 mm(t2) Oot ico l f ibres in qel - f i l led loose tubeStr<inobo oround steel-wire centre' I 0'9 mmTube s ize; lD = 0.85 mm; 0D = 2 mmPE jocket , I 1 '1 .6 mm

Lopped copper/polyester toPe-

(8) Droinwires 1 mm2Lohductor : p lo in copper 19x0.26 mm, I 1 .3 mm

Lopped copper/polyester toPe.

(5) Dro inwires 1 mm2io 'nductor : p lo in copper 19x0.26 mm, 6 1.3 mm

"lnterstices f i l led"

+) Note : The volues ore corrected for theoverlenoth of the elements.

"The weioht in ,.onot.r opplies to on ossumedseowotdr density of 1026 kglmJ."

Current roting

Core current

2 mm? Power

1 mm2 droin

6.1 Amp

3.9 Amp

condit ions:sti l l oir; ombient temperoture 45 deg Ccontinuous operotion(5) lovers of coble on winchm6x ionductor temPeroture 85 deg C

Coble d iometer : 43 .6 mm.

OPticol Fibre ProPert ies : *)

uomponen(MO0e NumencolAporture

tsondwidthMHz*km

Attenuottonot 650 nm

dBlkm

50/125 Mult o.2 400 4

Electr icol Propert ies : *)

ComponentsRcond K I N S U I

r00 V DCVolt.

Rotingl ^ / 1 1 1 1

HighVolt. testof 5 min.

/ ohm*kn KV2 mm? 10.? 500 t .2 /J . t

1 mmZ 7 0 8 orornwrre

1) Note: Uo is voltoge to eorth' U is l ine- to- l ine-vo l toqe

Breokingstrenqth

Bend ingrod ius

Weight

calculated. recommended *-itt- calcttlated

stot ic dvnomic o l r seowoterKN rnm m m kolkm kolkm

594 4170 J2J5

33,5

3) Lightu'eight ROV Urnbi l ical

Ooticol Fibre Prooert ies : *)

Yellow PUR jocket, / 37 mmjocket thickness: 2.5 mm

(2) Controhelicol lovers of oromid.Non-woven tope oi eoch loyer, I 3'1.9 mm

Block PUR iocket, F 26 mmjocket thicl iness: 1.2 mm(12) lnsutoted conductor 2.4 mm?ionductors: ploin copper 19x0.4 mm, 6 2.0 mrninsulotion: PP, I 4.6 rnm

Aluminium tope screen, / ?3.5

(6) Opticol f ibres in gel-f i l led loose tubeStronded oround steel wire centre. Q 2.2 mmTube size; lD = 0.8 mm; 0D = 2 mmPE jocket , / 7 .1 mm(12) Intersticiol droinwires 0.88 mm2ionductors: ploin copper 7x0.4 mm, Q 1.2 mm

Aluminium tope screen, / 14.3

lntersticiol droinwire 2.4 mmZconductor : p lo in copper 19x0.4 mm, I 2 .0 mm

(2) lnsuloted conductors 2.4 mm?dohductor: ploin copper 19x0.4 mm, f, 2.0 mminsulot ion: PP,6 4.7 mm

Twisted shielded quod [4x0.5 mm2]conductors: ploin copper 7x0.3 mm, / 0.9 mminsulotion: PE, I 1.6 mm. Twist & polyester tope.Aluminium tope & droinwires (5x0.2 f lot) -2-poss PE jocket, fr 7.1 mm

*) Note : The volues ore corrected for theoverlength of ihe elements.

"The weight in seowoter opplies to on ossumedseowoter density of 1026 kg/m3."

Coble d iometer : 37 mm.

" lnterstices f i l led"

Electr icol Propert ies : *)

ComponentsRcond Rinsult00 v D(

Volt.Roting

HighVolt. testo f 5 m in .

)hm/kmlMohm*kn KV) . 4 mm2 8 . 9 500 I L J

2.4 mm? 8.6 500 JJOO t o7.+ mm.1 9 . 5 dro rn wrre

O.EE mm2 24 dro rnwrrel Q U . b m m z +1 500 60

ComponentMode NumericolAporture

Bondwidth

MHzrkm

Attenuotionot 850 nm

dB/km

50/125 Multi tJ. ' l 400 4

Component: power cores 2.4 mm2

Current roting: 5.5 Ampcondit ions:sti l l oir. continuous operotion.ombient oir temperoture: 45mox. conductor temperoture: 755 loyers of coble on winch.

deg Cdeg C

Voltoge drop (V/km): 83.8 48.+Supply voltoge (V): 2292 (l-ph)frequency (Hz): 60con'ductor ienip. (deq C): 70current per cohducto? (A): 5

sJsJ (J-phj6057J.5

Mechonico l Proper t ies :

Breokingstrenoth

Bendingrod ius

Weight

calailated, recqnmended min^ calculoted,s l o t i c dvnomic or r seowoter

KN mm mm ko/km kolkm1 9 5 608 1425 320

336

. f ) IvIRV Conductor idenri [ icat ion

K

I

B

c

:

:

:lI:

:l

l

Coble diomeler: 44.2 mm

"lnterstices f i l led"

"The weight in seowoter opplies to on ossumedseowoter density of 1026 kg,/m3."

*) Note : The volues ore corrected for theoverlength of the elements.

Ooticol Fibre Properties :

Component Mode NumencolAporture

uondwidth

MHzlkm

Attenuotionof 850 nm

dB,/km

50/125 Multi o.2 +

Mechonicol Propert ies :

Breokingstrenoth

Bendingrodius

Weight

colcdated, recorntnended tnill^ calculatedstot ic dvnomic o t r seowoter

KN mm mm ko/km ko/kmEE7 551 6800 5200

Electr icol Prooert ies :

ComponentsRcond Rinsuli00 v Dc

Volt.Roting

HighVolt. testof 5 min-

hm/kn /ohm*kn KV4 mm? 5.2 500 2000 I U

4 mm2 5.2 500- ( 1 E n

1 5

ITEM

A

NUMBER

24

DESCRIPTION

Fiber-optic units, eoch comprising:

Opticol f ibres in qel-f i l led loose tube.Tube size: lD = 0'.E mm, OD = 2.0 mmStronded oround o centrol steel wire / 0.9 mmPE jocket, I 5.8 mm

Power cores 4 mm2 - 2kVConductors: ploin copper 19x0.52 mm, / 2.6 mmInsulotion: PP, I J.8 mm

PE jocket, I 12.7 mmjocket thickness: 0.5 mm

Ploin copper wire / polyester yorn broid. 6 13.4 mmPloin copper 12x8x0.2 mm / Polyester 12x2x1100 dTexCoveroge of copper portl. 64 %

Loyer of non-woven tope 0.2 mm, lopped.

P o w e r c o r e s 4 m m 2 - J k VConductors: ploin copper 19x0.52 mm, / 2.6 mmInsulot ion: PP, I 4 .4 mm

Loyer of non-woven tope 0.2 mm, lopped.

Ploin copper wire / polyester yorn broid, / 24.3 mmPloin copper 24x8x0.25 mm I Polyester 24x2x1100 dTexCoveroge of copper port: 65 Z

PUR jocket, / 28.4 mmjocket thickness: 2 mm opprox

Controhelicol loyers. of preformed, greosed, golvonised steel wires 1960 N/mm2First loyer: 42 wires f, 2.0 mm

-

Second loyer : 58 wi res / 1 .0 mmThird loyei: 46 wires Q 2.5 mmFourth ioyer: 58 wires 6 2.0 mmThe loyers ore bolonced to minimise torque & rototion, 6 44.2 mm

c

12

338

5) Super Scorp io Umbi l i ca l

r) Note : The voluesoverlength

" lnterst ices f i l led."

ore corrected for theof the elements.

J x TwistedConductorlnsulotionShieldJocket

4 x 7 5 O h mCentreDielectr icScreenJocket

6 x Low PowConductorInsulotion

Tope ShieldInner JocketMoteriolThickn ess

0.5mm2 Ploin Copper [7/.3]Polyethylene to 01.65Ali-Polyester Tope & DWPolyethylene to 14.8/5.'lmm

Cooxiol Q4.8mm0.22mm2 Ploin Copper l l tO.ZlSolid Polyethylene to /3.5mmPC Broid [Cover 95%]Polyethylene to /4.8mm

er Cores 91.7mm0.5mm2 Ploin Copper l t tO.SlPolyethylene to d1.7mm

Ali-Polyester & Droin Wire

Polyethylene to l16.4mm0.8mm Rodio l

Nom Coble d iometer : 38.0mm.

"The weight in seowoter oppl ies to on ossumedseowoter density of 1026 kglm3."

15 x Power Cores l4.0mmConductor : 4 .Omm2 Plo in Copper l lStO.SZlInsulotion : Polypropylene to 64.1mm

Bedding JocketMoteriol : Polyethylene lo l26.2mmThickness : 0 .8mm Rodio l

Spirol Screen Ploin Copper Wires over Cu TopeBedding SheothMoteriol : Polyurethone to l30.6mmThickness : 1 .9mm Rodio l

Strength MemberBroid : Stondord Modulus Aromid

Outer JocketMoteriol : Polyurethone to l38mmThickness : 1 .9mm Rodio l

Cooxiol Propert ies : *)

Electr icol Propert ies : *)

ComponenisRcond Rinsul500 v D(

Volt.Roting

HighVolt. testof 5 min.

)hmlkn ilchm*kn KV)C 4.0 mm2 5 500 3000 q

'C U .5 mm 4J 500 60Coox Centre 94 500 600 3 .6

Mechonicol Prooert ies ;

Breokingstrenoth

Bend ingrod ius

Weight

calaiated" recorntnended nbt colctlaledstot ic dvnomic seowoter

KN mm m m kolkm kolkm9E 1 966 EOJ

ComponentsCopoc

r t l k H

lmped.ot

10 MHz

Attenuotion

dBl1 00moF/m 0hm 1 M H z l S M H z10 MHz

75 Ohm Coox 7 1 75 1 .45 | 2 .45 4.J

339

Appendix M Video

Commonly accepable TV camera F<lrmats in various countries

Country B&W Standard Colour Standard

Antilles Netherlands RS-1 170

Argentina

Australia

Bahamas

Belgium

Brazil

Brunei

Bulgaria

Canada

Chil ie

China

Columbia

Czechoslovakia

Denmark

Finland

France

Germany

Greece

Hong Kong

Hungary

India

Indonesia

Italy

Japan

South Korea

Malaysia

Mexico

Netherlands

New Zealand

Norway

Peru

Philippines

Poland

Portugal

Romania

CCIR

CCIR

RS-170

CCIR

CCIR

CCIR

CCIR

RS-170

RS-170

CCIR

CCIR

CCIR

CCIR

CCIR

CCIR

CCIR

CCIR

CCIR

CCIR

CCIR

CCIR

CCIR

RS- 170

RS-170

CCIR

R S - 1 7 0

CCIR

CCIR

CCIR

R S - 1 7 0

R S - 1 7 0

CCIR

CCIR

CCIR

NTSC

PAL

PAL

NTSC

PAL

PAL

PAL

SECAM

NTSC

NTSC

PAL

SECAM

SECAM

PAL

PAL

PAL

PAL

SECAM

PAL

SECAM

PAL

PAL

PAL

NTSC

NTSC

PAL

NTSC

PAL

PAL

PAL

NTSC

NTSC

SECAM

PAL

SECAM

340

Countr-v

Saudi Arabia

Singapore

South Africa

Spain

Sweden

Switzerland

Taiwan

Thailand

United Kingdom

United States

U.S .S .R .

Venezuela

Yugoslavia

B&W Standard

CCIR

CCIR

CCIR

CCIR

CCIR

CCIR

RS- 1 70

CCIR

CCIR

RS-170

CCIR

RS-170

CCIR

Specifications For Typical Underwater Video Cameras

Osprey 1382 CCD camera

i) Electr ical

Resolution

Sensit ivity

Pick up Device

Signal to noise ratio

Scan

Horizontal Frequency

Auto light con'lpen satiolr

Power

Video Output

i i) Environmental

Water depth

Temperature

Optical

Standard Lens

Iris

Focus

Angle of view

Colour Standard

SECAM

SECAM

PAL

PAL

PAL

PAL

NTSC

PAL

PAL

NTSC

SECAM

NTSC

PAL

320 l ines

0.9 Lux (faceplate)

Interline transf-er CCD (q inch format)

> ,4U dB

625 line I 50Hz PAL fbrnrat

15.625KH2

15,000 : 1

Constant Voltage 16 - 24Y dc (0.6A)

I .OV PK-PK

I (XX) rnetres (deeper ratings available)

Operating -5('C to +400C

l i .5nrm f :1 .6

Automatic

Remote via telemetr), l0nrm to infinity

600 Oiagonal (in water)

3 l l

i i i ) Mechanical

Size

Weight

Connector

Connections

Port Guard

Osprey 1323 S.I.T Canrera

i) Electr ical

Resolution

Sensit ivity

Tube type

Signal to noise ratio

Scan

Horizontal frequency

Auto l ight compensation

Power

Video output

Bandwidth

i i ) Envi ronmenta l

Water depth

Temperature

i i i) Optical

Standard lens

Iris

Angle of view

Length: 327nm

Diameter: 104mnr

Air 3.9Kg. Water 0.8Kg

Sea-Con (Branter) XSL-5-BCR

Pin 1. Ground

Pin 2. Positive Supply

Pin 3. Telemetry (+)

Pin 4. Telemetry (-)

Pin 5. Video

Removable stainless steel mesh

>600 television l ines

-5 x 10-a Lux

1 i ns . S . I .T .

40dB

625 I 50H2,525 I 60Hz available

15 .625KH2, 15 .75KH2

75 ,000 : 1

Constant voltage 16 - 24 v dc (650mA)

1.4 vo l ts PK-PK in to 75W

l2MHz (- 3dB)

1(XX)m_-50C to +400C

5.5mm f : 1 .5

Autonratic motorized

l10o d iagonal in water

342

i i i ) Mechanical

Size 298mm long, lOOmnr dianreter

Weight A i r 3 .7Kg, Water l . IKg

Connector 5 pin Sea-Con (Branter) type

XSL - 5 -BCR

Connections Pin 1. Ground

Pin2. Positive supply

Pin 3. Focus (N/A)

Pin 4. Focus (N/A)

Pin 5. Video

NB Dimensions are excludinc connector.

rl

)

-r+-)

Appendix N Dive Exerc ises

Dive Exerc ise l . Sur face Navigat ion And Contro l Fami l iar i ty

Refer to the diagranr showing the Wray Castle ROV Operational Training Area.

The objectives of this exercise is to practice communications between the Deck Officerand the Pilot, and to gain familiarity with ROV controls and their effects, particularattenrion should be given to directional orientation and field of view/scale of videocameras.

i) Pilot the ROV on the instructions of the Deck Officer to the most Easterly leg ofthe wooden .letty (Target Area A). The ROV should be on a WesterlyHeading.

ii) Pilot the ROV to rhe most Northerly leg and back again to survey the SouthEasterly side of the Jetty. Care should be taken to allow for the reduction intarget size due to the effect of the camera lens, it is inrportant to manoe^uvre thevehicle away from the target to avoid 'snagging'. A video recording of eachJetty leg should be nrade with descriptive conlnlentary.

ii) Following rhe instructions of the Deck Officer manoeuvre the ROV into themiddle of the area between the Jetty and the wet dock, then follow hisinstructions to take the ROV on the surface out on a heading of 0100 for at least50 metres thert turrt itttd return to the launch point.

NOTE: At the discretiolr of the instructor the student can be ertcouraged to use thevertical control on the.jetty, legs or on retuming fronr the last nranoeuvre by followingthe Lake bed back ro rhe launch point. This can only be encouraged where the studenthas demonstrated contpetence with the exercises on the suditce.

Dive Exerc ise 2 Tronic ROV Min i Ce Connectot ' 's tab- in '

Ref'er to the diagrant of the Operational Training Area, the connec:tor receptacle is TargetArea C.

The obiective of this cxercise is to practicc c:ontrol co-orclinittion on A typicalintervention problern.

i) Referring to the diagranrs of the Tronic ROV rrini CE Plug iind receptacle,attach the plug to the Viking ROVs manipulator ensuring that the locating lug ison the correcrt side to nratch the rec:eptacles orientation. Position the manipulatorsuch that the plug wil l be horizontal and in view of the video camera whensubmerged.

ii) Launch the vehicle ancl navigate under the instruction of the Deck Officer to therarget uea. Align the vehicle with the plate and beconre fanriliar with distance/video image relationship (Camera perspective) whilst under the instruction ofthe Deck officer and the vehicle is on the sudhce.

iii) Using the vertical thruster control, dive the vehicle to the correct depth and,allowing fbr perspective, align the plug with the receptacle. Gain full control ofthe vehicle before atten.lpting to locate the plug at this stage and set the trims tomaintain position as accurately as possible.

iv) GENTLY nrove the vehicle forward maintaining alignment and place theconnector. It is important to allow for the vehicles ntorlentul"n and apply

344

reverse ihru:ter BEFORE actuat con&rt to avtid hiuiry th urFt wift arysignitlcant torce and danragine the .-onnerncr

v) Remore the plug b1 ntainrainine the vehicle rr im and al ignnrent then applying asharp full re\erse rhrusrcr action. Return the vehicle to it stand off position atthe discretiorr of the Deck Otficer.

D ive Exe rc i se 3 . S t ruc tu ra l Su rvey

Refer to rhe Diagrants showing the Operational Training Area and the structuraldrawings. The structure is located at target area B.

The objective of this exercise is to plan, carry out, and record a full structural survey.

i) The teant shoLrld nreet and plan the operation in detail.

ii) The Safety boat shoulcl proceed to the target area rtnd drop a nrarker buoy in thevicinity of the stnrctrrre.

i i i ) The vehicle sl ioulcl be launched and under the directions of the Deck Off icer benavigated to the nrarker buoy. The vehicie should be dived fbl lowing themarker buoy l ine to within sight of the lake bed. Using the nrarker buoy as areference ancl the vehicle sonar and compass the structure is to be located andthe position with ref-erenc:e to the rrtarker buoy rec:orcled.

NOTE: During al loPerations rhe safetl ,bout is to renrain in the vicinity of the Target towarn off appnltching recreltt ional Lake Ltsers.

iv) A logicul survcv ot ' thc stnlctLlrc is to be unclert l tkett lecttrcl i t tg as ntuch detai l aspossible in rhe t inte lr l iou'ecl inclucl ing CPP u'here uppropri i t te. The instructorwil l givc guicltncc on csttbl islrecl inspection principles l t t tcl rccording nlethodsas the exerclse l)ro_grcssL's.

v) On conrpletion the vehicle shoulci lre rec:overed itncl al l clrawittgs, data, logs andvicleo tapes given to the instructor for assessll lent.

3.r5

WRAY CASTLE ROV OPERATIONAL TRAINING AREA

---+

-TargetArea C

'Stab-in' ConnectorTargetArea A(Jetty)

LaunchPoint

70m al

TargetArea B

(Structure30 'Depth)

N

tII

I

Lake Windermere- _ -'-.-.'-\\

/

346

Target B - Steel Structure

,4./ 500mm

tII

PlatformNorth

White plate welded toMA43 and MA31horizontal members

\,

Plan View(as seen from above)

'15mm

Holes

frP

347

Platform North East Face

Tubular o Estimated

". Anode. (Active)

0% Wastage

Steel Platewith 2 Holes

North West FaceVertical Diagonal

Sleeve Weldedonto MC44

4.'t\\os

Leg 2

Two WhiteBand

Bottom Node Obscurred by Mud Suspect StructureSettled into Sea Bed on Leg 3

Fine Silty BottomNo Evidence of Scour or Seabed Errosion

348

Platform North West Face

Both Leg 1 and Leg2 Bottom Nodes Buried inSi l t Suspect South East Face Sett led into Sea Bed

Fine Si l ty BottomNo Evidence of Scour or Seabed Errosion

Anode(Active)

0% Wasted

Single WhiteBand

3-19

Platform South Face

Fine Si l ty BottomNo Evidence of Scour or Seabed Errosion

t-

EEooON

350

3 5 1

l

IAppendix O Examples of Exercises

Question I

With the aid of the service manual carry out a full inspection of the Fl1 fixeddisplacment pump/motor. On completion compile a report indicating the following:-

a What components were inspected?

b What condition they were in?

c The effect of faulty components on theoperation of the unit

Question 2

Using the technical manual briefly explain the test that can be carried out in situ on theF1 1-5 pump/motor to determine its general condition of operation. Include typicalresults in your explanation.

Question 3

Briefly explain the purpose of the inlet and outlet ports and the two case drain portswith reference to the operation of the ROV

Task I

Purpose.

This particular assessment is designed to assess three main abilities:-

Firstly the students theoretical knowedge of the unit is being assessed. In orderto explain the effects of the various components on the operation of the unit theunderpinning theoretical knowledge must be present.

Secondly the students ability to apply information obtained from a technicalmanual to a practical situation is being assessed.

Lastly the students ability to inspect mechanical conlponents and appreciate theeffects mechanical wear can have on the operation of the unit.

Validity.

During the course the students have carried out inspections on various hydraulicunits. These have been carried out by refering to technical manuals as well asdiscussing the effect of wear on general performance.

This assignnrent is designed to assess all these points and is therefore valid tothe course.

The tasks carried out in the assignnrent are typical of tasks undertaken in theROV indusn'1,. This assignment is therefore valid in that some of its contentscan be applied in the workplace.

tt .

1,.-

3s2

Appendix P Task 2 Fit Co-ax Connector

Detailed notes on Co-ax connectors are given under the video section of the coursenotes. Read these carefully before attempting this exercise.Equipment required:-

1 BNC Kit

Solder Iron and Holder

Snips

Wire Strippers

Multimeter

Identify the type of connector and co-ax cable you have been provided with.

Follow the instructions given in the notes and carefully fit the connector to the co-ax

NOTIFY THE INSTRUCTOR

-1)-J

I

Appendix R Teeside Valve and Fitt ing Company Ltd

Teeside Valve and Fitting Company Ltd is a privately owned company, founded inOctober lgll as an exclusive authorised distributor, for fluid system componentsmanfactured by the Swagelok $oup of comapnies. The service territory for thecompany is the counties of Northumberland, Durham, Tyne and Wear,Cleavland,Cumbria, North Yorkshire and North and outh Humberside.

Teeside Valve and Fitting Company also provide training to customers for variousproducts in the range. As part of tnis ffain1ng, we provide installation seminars for thecorrect installation of Swagelok tube fittings. For the last 5 years we have beenassociated with Subserve al Wray Castle in this role On the ROV Pilot/Technician'sCourse.

354

!

Appendir Q Task 3 Repair of Underwater Cable

You are reguired ro make a warerproof repair/join to the cable provided to you by theinstructor. You are ro employ the following procedure:-

a Cut and stagger the conductors to prevent a large bulge at the splice

b Cut 1/4" of insulation back from each conductor

c Place the correct size heat shrink over the conductors

d Solder the conductors together ensuring each is of the same length toensure strain is equally applied

When you have completed all the necessary tasks to this stage TELLTHEINSTRUCTOR

e Apply heat to rhe heat shrink tubing

f Clean and roughen the cable insulation

g Apply self-amalgan-rating tape to each join of the conductor

h Either:-

i Apply self-amalganrating tape over the whole connection

or

ii prepare within a potting box for porring

Note: in either case i or i i ensure a r l ininrum of air is trapped in the cavit ies.

NOTIFY THE INSTRUCTOR

355

Appendix S Rigging

Cargo Handling Gear

6 x 19 Galvanised

Round Strand RopeRight-hand Ordinary Lay

Applications:Topping Ropes, Guypendants

6 x 1 9

6 x 36 &6 x 4l Galvanised

WEIGHT AND BREAKING LOAD TABLES

Fibre Core

Size WeightNominalDiameter

mm kg/100m

Steel Core

at 1tl0Grade

kg/l00m tonnef

1 82022a AL+

1 8202 122' l AL +

109134r63193

100t24r36150i78

MinimumBreakingLoadat 145tonnef

T4.417.82r .625.7

13.216.2r7.919.723.4

:!::IIfttI

I ,E " \

ar 1tt0Grade

kg/l00m tonnef

356

Round Strand RopesRight-hand Ordinary Lay

Applications:Topping Ropes, CargoPurchases for DerrickCranes and Deck Cranes.Preventer Guys, StandingRigging

1 7 x 7Multi-strand RopeRight-hand Lang's LayApplications:Cargo Purchases forDerrickCranes, Deck Cranes wherenon-rotating properties al'edesirable

Cargo Handling Gear

1 2 x 6 o v e r 3 x 2 4

1 61 8r 920222426283235363840A AAT

485256

l 61 81 920222426

94.5r20l a a- I JJ

148r792r3250289378452478533591

15.2t9.221.423.828.734.240.146.660.872.777.085.795.0

104r32146r63r972342753 1 84t6497526586650787935

l 1001 280

t6.420.723.r25.73 1 . 036.943.3s0.365.778.583.292.610.3124148174

201

9s.2r201341491801 1 4L t +

251

t + . I

1 8 . 620.722.927.833.038.8

Size Weight Mininrunr

357

Multi-Strand RopeRight-hand Lang's Lay

Applications:Cargo Purchases for DerrickCranes. Deck Cranes wherenon-rotating propertiesare desirable

NominalDiarneter

mm

1 61 81 920221 ALA

262832

kg/100m

92.6ttli 3 1t45t75208245284310

BreakingLoadar 180Gradetonnef

13 .817.519.52r .626.23 1 . 136.s42.455.3

Standing Rigging - Shrouds, Stays, Hanger Ropes

6 x 19 (lalvanised Steel Core

3sB

\

Round Strand RopeRight-hand Ordinary Lay(180 grade steel)

7 x 19 Galvanized

Round Strand RopeRight-hand Ordinary Lay(145 grade steel)

Preventer Gu-vs

Round Strand RopeRight-hand Ordinary Lay

Slewing Guy Falls

Polypropylene Ropes('Fibrefilm' or Staplespu n

Weight

Kg/100m kg/220nr

mn]

22242628

Size WeightNominalDiameter

MinimumBreakingLoadar 180Gradetonnef

3 1 . 137.043.550.4

MinimumBreakingLoadat 145Gradetonnef

53.968.284.2

102

J Z

364044

SizeNominalDianreter

nrll

20221 4: +

26

SizeDianreter

kg/100m

193229270312

3804 8 1594719

Fibre Core

Weight

kg/l00nr

I -1.11 6 31 9 3227

MininrunrBreakingLoadar 145Gradetonnef

17 . t421.625.73 0 . 1

A " l+ L

496 l- 1t - )

util l t i

l l lnt

l 6l t i20222428

1 92227a a-f -)

4053

MinimumBreakingLoadtonnef

-1. -)

4.55 .46.57 .6

1 0 . 1

3-59

Manila Ropes - Grade I

Sisal Ropes

Material

Grade 1 manilaHigh grade manil ir

PolythenePolypropylene

Polyester (Terylenet

Polyamide (Nylon)

2). Flexible Steel Wirc Rope

Material

1 61 820222428

192227a a- fJ

4053

Diameter

77rrnr - 144mnr7nr - 144nrrl

4rn - 72nrnrTntrtt - t l0rurn

4nrrn - 96nrnr

;lnrrn - 96nrnr

Dianreter

(4nrnr to 4t{nrnr)

(t lnrnr to 56nrm)

(8nrnr to -56nrnr)

2.0s2.453.253.854.556 . 1 0

1.802 . t 52.853.404.055.35

Breaking Strain Factor

2D2l3(X)

lD2/j(x)

4Dtl3tx)

5Dt/3txl

Breaking Strain Factor

15p:/ .500

211p2/-500

21D2l5(X)

1 92227334053

t 61 820222428

42496 T73881 1 8

42496 T- at )

881 1 8

METRIC FORMULAE FOR BREAKING STRESSES OF NATURAL AND SYNTHETIC

FIBRE ROPE, STEEL WIRE ROPE AND CHAIN

l). Fibre Rope 3 Strand Harvser Laid

6 x 1 2

6 x 2 4

6 x 3 7

I

t360

3). Stud Link Chain

Material

Grade IGrade 2Grade 3

4). Open Link Chain

Material.

Grade I

Grade 2

Diameter

(12.5n-rnr to(12.-5mm to(12.-5mm to

Diameter

( l 2 .5n tn r t o 50n rm)

(12.5nrnr to -50nrm)

Breaking Strain Factor

20D2160020D2150043D21600

Breaking Strain Factor

20d2t600

30D2/6fi)

l20mm)120mm)120mm)

=

=

361

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