1 - Stability of Passengers Ships

7/27/2019 1 - Stability of Passengers Ships

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ASM COMPLIED NOTES

CONTENTS

STABILITY OF PASSENGER SHIPS

BACKGROUNDREVISED GUIIDANCE TO THE MASTER


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STABILITY OF PASSENGER SHIPS

IN DAMAGED CONDITION

STANDARD OF SUBDIVISION :

SUFFICIENT INTACT STABILITY, IN ALL SERVICE

CONDITIONS , SO AS TO WITHSTAND THE FINALSTAGE OF FLOODING , OF ANY :

A) ONE MAIN COMPT., WHERE F.O.S. IS BETWEEN

0.50 & 1.00 .

B) TWO ADJ. MAIN COMPTS., WHERE F.O.S. IS

BETWEEN 0.33 & 0.50.

C) THREE ADJACENT MAIN COMPTS., WHERE F.O.S.

IS


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CONDITION OF FLOODING

A) FOR SYMMETRICAL FLOODING :AFTER EQUALISATION MEASURES HAVE BEEN TAKE, APOSITIVE RESIDUAL GMT IS TO BE AT LEAST 50 mm ASCALCULATED BY CONSTANT DISPLACEMENT METHOD .

B) FOR UNSYMMETRICAL FLOODING :

i) THE ANGLE OF HEEL NOT TO EXCEED :

a) 70 FOR ONE COMPT. FLOODING ;

b) 120 FOR TWO OR MORE ADJACENT COMPTS.

FLOOODING ;

ii) IN NO CASE THE MARGIN LINE TO BE SUBMERGED ;

iii) THE MINIMUM RANGE OF THE POSITIVE RESIDUALRIGHTING LEVER CURVE IS TO BE AT LEAST 150BEYOND THE ANGLE OF EQUILIBRIUM .

(THIS RANGE MAY BE REDUCED TO A MINIMUM OF 10 0 ,

IN THE CASE WHERE THE AREA UNDER THE CURVE ISAS MENTIONED IN SUB PARA (14) BELOW , INCREASEDBY THE RATIO :

1500

______________

RANGE IN DEGREES)


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iv) THE AREA UNDER THE R.L. CURVE IS TO BE AT

LEAST 0.015 M. RADIANS , MEASURED FROM THE

ANGLE OF EQUILIBRIUM TO THE LESSER OF :

a) 220 IN THE CASE OF 1 COMPT. FLOODING ;

b) 270 IN TWO OR MORE ADJ. COMPTS. FLOODING.

c) ANGLE OF PROGRESSIVE FLOODING.

iv) A RESIDUAL RIGHTING LEVER IS TO BE OBTAINED

FROM THE FORMULA :

GZ(m) = HEELING MOMENT + 0. 04

DISPLACEMENT

WHERE , THE ABOVE HEELING MOMENT IS TO BE THE

GREATEST OF ANY OF THE FOLLOWING , CREATED BY :


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a) THE CROWDING OF ALL PASSENGERS

TOWARDS ONE SIDE ;

b) THE LAUNCHING OF ALL FULLY LOADED

DAVIT LAUNCHED SURVIVAL CRAFT ON ONE

SIDE ;

c) THE WIND PRESSURE.

IN NO CASE SHALL THE GZ VALUE , SO

DETERMINED , BE LESS THAN 0.10 Metres.


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Heeling moments

1. FOLLOWING ASSUMPTIONS TO BE MADE FOR THE

CROWDING OF PASSENGERS :

a) FOUR PERSONS PER m2.

b) A MASS OF 75 kg PER PERSON (MAY BE REDUCED TO AMINIMUM OF 60 kg).

c) PASSENGERS TO BE DISTRIBUTED ON ONE SIDE ATMUSTER STATIONS , SO THAT THEY PRODUCE

THE MOST ADVERSE HEELING MOMENT .

d) C.o.g. , ABOVE DECK , OF EACH PASSENGER :

STANDING......1.0 m ; SITTING.......0.30 m.


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2. MOMENT DUE TO LAUNCHING OF ALL

FULLY LOADED DAVIT LAUNCHEDSURVIVAL CRAFT :

a) ALL LIFE BOATS , RESCUE BOATS & DAVIT-LAUNCHED LIFE RAFTS ARE ASSUMED TO BESWUNG OUT ,READY FOR LOWERING , & FULLY

LOADED.

b) PERSONS NOT IN THE L.S.A. WHICH ARE SWUNGOUT ARE NOT TO PROVIDE ANY ADDITIONALHEELING OR RIGHTING MOMENTS.

c) L.S.A. ON THE SIDE OPPOSITE TO THE SIDE TOWHICH THE SHIP HAS HEALED ARE ASSUMED TOBE IN STOWED1 CONDITION.


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3) MOMENT DUE TO WIND PRESSURE :

a) A WIND PRESSURE OF 120 N/m2 IS TO BE APPLIED.

b) AREA APPLICABLE IS THE PROJECTED LATERAL

AREA OF THE SHIP ABOVE WATER LEVELCORRESPONDING TO THE INTACT CONDITION.

c) THE MOMENT ARM IS THE VERTICAL DISTANCEFROM A POINT AT ONE HALF OF THE MEANDRAUGHT CORRESPONDING TO THE INTACT

CONDITION TO THE CENTROID OF THE LATERALAREA.


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2) The Permeability Of CARGO COMPARTMENT :

Spaces Permeability

At Draft

ds dp dl

Dry Cargo Spaces 0.70 0.80 0.95

Container Spaces 0.70 0.80 0. 95

Ro - Ro Spaces 0.90 0.90 0.95

Cargo Liquids 0.70 0.80 0.95

Where, ds: Deepest Sub Division Draft.

dp: Partial Sub Division Draft .

dl: Light Service Draft.


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DAMAGE STABILITY OF ALL PASSENGER SHIPS, AND CARGO

SHIPS OF 80 m Or > 80m In LENGTH

PERMEABILITY

As Per Solas 2009, Ships, the Keel of which are laid or which are at asimilar stage of construction, on or after 1st jan. 2009, permeability to beassumed as follows :

1) The permeability of each GENERAL COMPARTMENT :

SPACES PERMEABILITY

Appropriated to stores 0.60

Occupied by accommodation 0.95

Accupied by machinery 0.85

Void spaces 0.95

Intended for liquids 0 or 0.95*

*which ever resulys in more severe requirements.


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MARPOL CONSOLIDATED EDITION 2006

3.1 for wing cargo tanks : 0.2L

3.2 for centre cargo tanks:

3.2.1 if bi/B is equal to or greater than one fifth: 0.2L

3.2.2 if bi/B is less than one fifth:

3.2.2.1 where mo centreline longitudinal bulkhead is provided:

(0.5bi/B+0.1)L

3.2.2.2 where a centreline longitudinal bulkhead is provided:

(0.25bi/B+0.15)L

bi is the minimum distance from the ships side to the outerlongitudinal bulkhead of the tank in question measured inboard at right

angles to the centreline at the level corresponding to the assignedsummer freeboard.

5. In order not to exceed the volume limits established by paragraphs 2,3 and 4 of this regulation and irrespective of the accepted type of cargotransfer system installed, when such system interconnects two or morecargo tanks, valves or other similar closing devices shall be closed whenthe tanker is at sea.

6. Lines of piping which run through cargo tanks in a position less thantc from the ships side or less than Vc from the ships bottom shall befitted with valves or similar closing devices at tha point at which theyopen into any cargo tank. These valves shall be kept closed at sea atany time when the tanks contain cargo oil, except that they may beopened only for cargo transfer needed for the purpose of trimming of the

ship.


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7. This regulation does not apply to oil tankers delivered on or after 1January 2010, as defined in regulation 1.28.8.

Regulation 27

Intact stability

See interpretation 45

1). Every oil tanker of 5,000 tonnes deadweight and above delivered

on or after 1 February 2002, as defined in regulation 1.28.7, shallcomply with the intact stability criteria specified in paragraphs 1.1 and1.2 on this regulation, as appropriate, for any operating draught underthe worst possible conditions of cargo and ballast loading, consistentwith good operational practice, including intermediate stages of liquidtransfer operations. Under all conditions the ballast tanks shall beassumed slack.

1. In port, the initial metacentric height GMo, corrected for the free

surface measured at 00 heel, shall be not less than 0.15m:

2. At sea, the following criteria shall be applicable :

2.1 the area under the righting lever curve (GZ curve) shallbe not less than 0.055 m.rad up tp 0= 30o angle ofheel and not less than 0.09 m.rad up to 0= 40o or otherangle of flooding 0.0 if this angle is less than 40o.

Additionally, the area under the righting lever curve

(GZ curve) between the angles of heel of 30o and 40oor between 30o and 0o if this angle is less than 40o ,shall be not less than 0.03 m.rad;

2.2 the righting lever GZ shall be at least 0.20 m at anangle of heel equal to or greater than 30o ;

2.3 the maximum righting arm shall occur at an angle ofheel preferably exceeding 30o but not less than 25o ;

and


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2.4 the initial metacentric height GMo, corrected for freesurface measured at 0o heel, shall be not less than0.15 m.

2). The requirements of paragraph 1 of this regulation shall be metthrough design measures. For combination carriers simplesupplementary operational procedures may be allowed.

3). Simple supplementary operational procedures for liquid transferoperations referred to in paragraph 2 of this regulation shall mean writtenprocedures made available to the master which:

1 Are approved by the Administration;

2 Indicate those cargo and ballast tanks which may,under any specific condition of liquid transfer and possible range ofcargo densities, be slack tanks may vary during the liquid transferoperation and be of any combination provided they satisfy thecriteria;

3 Will be readily understandable to the officer-in-charge of liquidtransfer operations;

4 Provide for planned sequences of cargo/ballast transferoperations;

5 Allow comparisons of attained and required stability using stabilityperformance criteria in graphical or tabular form;

6 Require no extensive mathematical calculations by the officer-in-charge;

7 Provide for corrective actions to be taken by the officer-in-chargein case of departure from recommended values and in case ofemergency situations; and

8 are prominently displayed in the approved trim and stability bookletand at the cargo/ballast transfer control station and in anycomputer software by which stability calculations are performed.

Regulation 28


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Subdivision and damage stability

1) Every oil tanker delivered after 31 december 1979, as defined inregulation 1.28.2, of 150 gross tonnage and above, shall comply

with the subdivision and damage stability criteria as specified inparagraph 3 of this regulation, after the assumed side or bottomdamage as specified in paragraph 2 of this regulation, for anyoperating draught reflecting actual partial or full load conditionsconsistent with trim and strength of the ship as well as relativedensities of the cargo. Such damage shall be applied to allconceivable locations along the length of the ship as follows;

1. In tankers of more than 150 m, but not exceeding 225 m inlength, anywhere in the ships length;

2. In tankers of more than 150 m, but not exceeding 225 m inlength, anywhere in the ships length except involving eitherafter or forward bulkhead bounding the machinery spaceshall be treated as a single floodable compartment; and

3. In tankers not exceeding 150 m in length, anywhere in theships length between adjacent transverse bulkheads withthe exception of the machinery space, for tankers of 100 mor less in length where all requirements of paragraph 3 ofthis regulation cannot be fulfilled without materially impairingthe operational qualities of the ship, Administrations mayallow relaxations from these requirements.

Ballast conditions where the tanker is not carrying oil in cargo tanks,excluding any oil residues, shall not be considered.

SEE INTERPRETATION 46

2) The following provisions regarding the extent and the character ofthe assumed damage shall apply:

1. Side damage:

1.1 Longitudinal extent: 1/3(L2/3) or 14.5m, whichever is less


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1.2 Tramsverse extent (inboard B/5 or11.5 m,

from the ships whichever is less

Side at right angles to the centreline

at the level of the summer load line):

1.3 vertical extent: from the module line of thebottom shell plating atcentre line, upwards withoutlimit.

2 Bottom damage:

For 0.31 from the forwardany other part

perpendicular of the ship of the ship

2.1 longitudinal extent: 1/3(L2/3) or 14.5 m, whichever1/3 (L2/3) or 5 m,

Is less whichever isless

2.2 transverse extent: B/6 or 10 m, whichever is less B/6 or 5

m,whichever is

less

2.3 vertical extent: B/15 or 6 m, whichever is less, B/15 or6 m, which-

Measured from the moulded lineever is less, measur


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Of the bottom shell plating at ed fromthe

Moulded line

of theBottom shell

plating atcentreline

3. If any damage of a lesser extent than the maximum extent ofdamage specified in subparagraphs 2.1 and 2.2 of this paragraphwould result in a more severe condition, such damage shall be

considered.

4. Where the damage involving transverse bulkheads is envisagedas specified in subparagraphs 1.1 and 1.2 of this regulation,transverse watertight bulkheads shall be spaced at least at adistance equal to the longitudinal extent of assumed damagespecified in subparagraph 2.1 of this paragraph in order to be

considered effective. Where transverse bulkheads are spaced at alesser distance, one or more of these bulkheads within suchextent of damage shall be assumed as non-existent for thepurpose of determining flooded compartments.

5. Where the damage between adjacent transverse watertightbulkheads is envisaged as specified in subparagraph 1.3 of this

regulation, no main transverse bulkhead or a transverse bulkheadbounding side tanks or double bottom tanks shall be assumeddamaged, unless:

5.1 tha spacing of the adjacent bulkheads is less than thelongitudinal extent of assumed damage specified insubparagraph 2.1 of this paragraph; or


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5.2 there is a step or recess in a transverse bulkhead ofmore than 3.05 m in length, located within the extent ofpenetration of assumed damage. The step formed bythe after peak bulkhead and after peak top shall not be

regarded as a step for the purpose of this regulation.

6. If pipes, ducts or tunnels are situated within the assumed extentof damage, arrangements shall be made so that progressiveflooding cannot thereby extend to compartments other than thoseassumed to be floodable for each case of damage.


3. Oil tankers shall be regarded as complying with the damage stabilitycriteria if the following requirements are met:

1. The final waterline, taking into account sinkage, heel andtrim, shall be below the lower edge of any opening throughwhich progressive flooding may take place. Such openingsshall include air-pipes and those which are closed by meansof watertight doors of hatch covers and may exclude thoseopenings closed by means of watertight manhole covers andflush scuttles, small watertight cargo tank hatch covers whichmaintain the high integrity of the deck, remotely operatedwatertight sliding doors, and sidescuttles of the non-openingtype.

2. In the final stage of flooding, the angle of heel due tounsymmetrical flooding shall not exceed 25o, provided thatthis angle may be increased upto 30o if no deck edge

immersion occurs.


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3. The stability in the final stage of flooding shall beinvestigated and may be regarded as sufficient if the righting

lever curve has at least a range of 20o

beyond the position ofequilibrium in association with a maximum residual rightinglever of at least 0.1 m within the 20o range; the area underthe curve within this range shall not be less than 0.0175 m-rad. Unprotected openings shall not be immersed within thisrange unless the space concerned is assumed to be flooded.Within this range, the immersion of any of the openings listedin subparagraph 3.1 of this paragraph and other openings

capable of being dosed watertight may be permitted.

4. The administration shall be satisfied that the stability issufficient during intermediate stages of flooding.

5. Equalization arrangements requiring mechanical aids such

AS valves of cross-levelling pipes, if fitted, shall not beconsidered for the purpose of reducing an angle of heelattaining the minimum range of residual stability to meet therequirements of subparagraphs 3.1, 3.2 and 3.3 of thisparagraph and sufficient residual stability shall be maintainedduring all stages where equalization is used. Spaces whichare linked by ducts of a large cross-sectional area may beconsidered to be common.

4. The requirements of paragraph 1 of this regulation shall be confirmedby calculations which take into consideration the design duraetcmlintol the ship, the arrangements, configuration and contents ol tin*IIUIK...it compartments; and the distribution, relative densities and thefree MW.NC effect of liquids. The calculations shall be based on thefollowing:


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1. Account shall be taken of any empty or partially filled tank,the relative density of cargoes carried, as well as any outflowof liquids from damaged compartments.

2. The permabilities assumed for spaces flooded as a result ofdamage shall be as follow:

Spaces Permeabilities

Appropriated to stores 0.60

Occupied by accommodation 0.95

Occupied by machinery 0.S5

Voids OM

Intended for consumable liquids 0 to OM*

Intended for other liquids 0 to OM*

3. The buoyancy of any superstructure directly above the sidedamage shall be disregarded. The unflooded parts ofsuperstructures beyond the extent of damage, however, maybe taken into consideration provided that they are separatedfrom the damaged space by watertight bulkheads and therequirements of subparagraph 3.1 of this regulation in respectof these intact spaces are complied with. Hinged watertightdoors may be acceptable in watertight bulkheads in the

superstructure.

The permeability of partially filled compartments shall be consistent with

the amount of this assumed that the contents are completely lost from

that compartment and replaced by salt was up to the final plane of

ecliilibrium.


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4. The free surface effect shall be calculated at an angle of heelof 5o for each individual compartment. The administration mayrequire or allow the free surface corrections to be calculated atan angle of heel greater than 5o for partially filled tanks.

5. In calculating the effect of free surfaces of consumableliquids it shall be assumed that, for each type of liquid, at leastone transverse pair or a single centreline tank has a freesurface and the tanks or combination of tanks to be taken intoaccount shall be those where the effect of free surface is thegreatest.

5. The master of every oil tanker to which this regulation applies andthe person in charge of a non-self-propelled oil tanked to whichthis regulation applies shall be supplied in a approved form with:

1. Information relative to loading and distribution of cargonecessary to ensure compliance with the provisions of thisregulation; and

2. Data on the ability of the ship to comply with damage stabilitycriteria as determined by this regulation, including the effect ofrelaxations that may have been allowed under subparagraph 1.3 ofthis regulation.

6. For oil tankers of 20,000 tonnes deadweight and above deliveredon or after 6 July 1996, as defined in regulation 1.28.6, thedamage assumptions prescribed in paragraph 2.2 of this regulationshall be supplemented by the following assumed bottom rakingdamage;

1. longitudinal extent:

1.1 Ships of 75,000 tonnes deadweight and above:

0.6L measured from the forward perpendicular;

1.2 Ships of less than 75,000 tonnes deadweight;

0.4L measured from the forward perpendicular;


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2. transverse extent : B/3 anywhere in the bottom;

3. vertical extent : breach of the outer hull.

Regulation 29

Slop tanks

1. Subject to the provisions of paragraph 4 of regulation 3 of this Annex,oil tankers of 150 gross tonnage and above shall be provided withslop tank arrangements in accordance with the requirements ofparagraphs 2.1 to 2.3 of this regulation. In oil tankers delivered on orbefore 31 december 1979, as defined in regulation 1.28.1, any cargotank may be designated as a slop tank.

2.1 Adequate means shall be provided for cleaning the cargo tanksanil transferring the dirty ballast residue and tank washings fromthe cargo tanks into a slop tank approved by the Administration.

2.2 In this system arrangements shall be provided to transfer the oilywaste into a slop tank or combination of slop tanks in such a way

that any effluent discharged into the sea will be such as to complywith the provisions of regulation 34 of this Annex.

2.3 The arrangements of the slop tank or combination of slop tanksshall have a capacity necessary to retain the slop generated bytank washings, oil residues and dirty ballast residues. The totalcapacity of the slop tank or tanks shall not be less than 3 per cent

of the oil-carrying capacity of the ship, except that theAdministration may accept:


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1. 2% for such oil tankers where the tank washingarrangements are such that once the slop tank or tanks

charged with washing water, this water is sufficient fortank washing and, when applicable, for providing thedriving fluid for ediutors, without the introduction ofadditional water into the system;

2. 2% where segregated ballast tanks or dedicated cleanluiiaM tanks are provided in accordance with regulation

IK of (Im Annex, or where a cargo tank cleaningsystem using crude oil washing is fitted in accordancewith regulation 33 of this Annex. This capacity may befurther reduced to 1.5% for such oil tankers where thetank washing arrangements are such that once theslop tank or tanks are charged with washing water, thiswater is sufficient for tank washing and, whereapplicable for providing the driving fluid for educators,

without the introduction of additional water into thesystem; and

3. 1% for combination carriers where oil cargo is onlycarried in tanks with smooth walls. This capacity maybe further reduced to 0.8% where the tank washingarrangements are such that once the slop tank or tanks

are charged with washing water, i hi>> water issufficient for tank washing and, where applicable, forproviding the driving fluid for educators, without theintroduction of additional water into the system.


2.4 Slop tanks shall be so designed, particularly in respect of theposition of inlets, outlets, baffles or weirs where fitted, so as to


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avoid excessive turbulence and entrainment of oil or emulsion withthe water.

3. Oil tankers of 70,000 tonnes deadweight and above delivered after31 December 1979, as defined in regulation 1.28.2, shall beprovided with at least two slop tanks.

ALLOWABLE KG (AFTER CORRN. FOR F.SE) DSB8 DIAGRAM


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F.S.E. CURVE FOR LIQUIDS DUE TO HEEL NO. 4 CARGO TANK (S)


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MEMO TO: MEMO NO.: NACNO845-01.3

ALL CSM STATIONS FROM:DATE: 2010-08-19

PREP. BY: EIRIK LINDSETH

Support to owners in connection with Concentrated Inspection

Campaign by paris MoU towards damage stability for Tankers

BACKGROUNG

As of 1st September to end of November 2010 Paris MoU will run a

concentrated campaign towards compliance with flag administrationsrequirements for control of damage stability on tankers.

Ships that

- are not equipped with a loading instrument that is approved to calculatedamages stability and

- do not have or fail to demonstrate that they are able to use damagestability limit curves and

- are not loaded according to the approved loading conditions in thestability book may be subject to PSC detentions.

DNV want to assist owners to avoid ending up in this situation and haveprepared a service to carry out examination of damage stability requirementsfor loading conditions in case this cannot be demonstrated to the PSCOssatisfaction.

Loading instrument

The preferred solution may be to furnish the ship with a loading instrumentcapable to do the necessary calculations. DNV will assist with top priority tothe approval work to be carried out.

Acceptance of additional loading conditions

If the planned loading conditions differ significantly from the conditions in the

approved loading manual and the master is unable to prove damage stabilitycompliance by other means, DNV may assist you with calculating and


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verifying damage stability for of such loading conditions. On ships enrolledwith ERS and other ships where we are in possession of a verifiedcomputerised stability model we will be able to deliver the results within theestimates below.

In order to be able to provide this service, the planned loading conditions(departure and arrival) must be run on the vessels loading computer and theprintouts must be submitted to DNV.

Fixed fee for one pair of conditions (departure and arrival) NOK 8 500,-

Additional loading conditions received in same package:NOK 2 000,- per pair.

Subsequent submittals, one pair of conditions: NOK 5 000,-

Estimated normal handling time is 24 hours from receipt of documentationduring working days (8.00-16.00 Norwegian hours). The fees do not cover anyrevisions.

If computerised model is unavailable we will attempt to carry out verificationon other basis. In this case, neither the estimated handling time nor the fixedfee will be applicable. Additional work will be invoiced on an hourly basis.

If you require assistance for examination of loading conditions, please contact

us as soon as possible in order that we may help you in good time prior to thecommencement of the CIC.

Emergency assistance.

Outside normal working hours

If emergency need for such assistance arises outside normal working hours

DNV will assist with a 27/7 response service similar to our ERS duty service.This will give you access to direct response for immediate mobilisation ofresources to do necessary support. On ships enrolled with ERS and otherships where we are in possession of a verified computerised stability modelwe will be able to deliver the results within the estimates below.

In order to be able to provide this service, the planned loading conditions(departure and arrival) must be run on the vessels loading computer and theprintouts must be submitted to DNV.

Fixed fee for one pair of conditions (departure and arrival) NOK 30 000,-


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Additional loading conditions received in same package : NOK 4 000,- perpair.

Estimated reply time will in this case be 8 hours. The fees do not cover any

revisions of the documentation.If computerised model is unavailable we will attempt to carry out verificationon other basis. In this case neither the estimated handling time nor the fixedfee will be applicable. Additional work will be invoiced on an hourly basis.

Contact information

Contact through your local customer service Manager or directly to directly to

stability Approval Section:

E-mail : [email protected]

Phone : +47 67 57 70 80

Emergency assistance : +47 91 84 97 15

Additional information

Our delivery will be a letter stating our stability acceptance and the relevantdamage stability requirements, and returned loading conditions withExamined stamp. Letter and loading conditions will be scanned and returnedby email to sender as well as other recipients specified.

DNV can provide the above service for vessels where we are authorised toapprove stability on behalf of the administration. We may also provide this asan advisory service for vessels where the administration is handling stability

themselves, and for vessels not in DNV class but enrolled in our ERS service.Our acceptance letter will then clearly state the basis for our evaluation.
mailto:[email protected]:[email protected]


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ALLOWABLE KG (after corn. For FSE) DSB8 DIAGRAM


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DAMAGE CONDITION NO.9

DIAGRAM


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F.S.E. CURVE FOR LIQUIDS DUE TO HEEL NO.4 CARGO TANK (S)

DIAGRAM


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FLOW CHART (DAMAGE STABILITY)

DIAGRAM


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REVISED GUIDANCE TO THE MASTER FOR AVOIDING

DANGEROUS SITUATIONS IN ADVERSE WEATHER AND SEA

CONDITIONS

1. The maritime safety committee, at its eighty-second session (29 Novemberto 8 December 2006), approved the revised guidance to the master foravoiding dangerous situations in adverse weather and sea conditions, setout in the annex, with a view to providing masters with a basis for decisionmaking on ship handling in adverse weather and sea conditions, thusassisting them to avoid dangerous phenomena that they may encounter insuch circumstances.

2. Member governments are invited to bring the annexed revised guidance tothe attention of interested parties as they deem appropriate.

3. This revised guidance supersedes the guidance to the master for avoidingdangerous situations in following and quartering seas (MSC/Circ.707).


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REVISED GUIDANCE TO THE MASTER FOR AVOIDING

DANGEROUS SITUATIONS IN ADVERSE WEATHER AND SEA

CONDITIONS

1 General

1.1 Adverse weather conditions, for the purpose of the following guidelines,include wind induced waves or heavy swell. Some combinations ofwave length and wave height under certain operation conditions maylead to dangerous situations for ships complying with the IS code.However, description of adverse weather conditions below shall notpreclude a ship master from taking reasonable action in less severeconditions if it appears necessary.

1.2 when sailing in adverse weather conditions, a ship is likely to encountervarious kinds of dangerous phenomena, which may lead to capsizing orsevere roll motions causing damage to cargo, equipment and personson board. The sensitivity of a ship size and ship speed. This impliesthat the vulnerability to dangerous responses, including capsizing, andits probability of occurrence in a particular sea state may differ for eachship.

1.3 on ships which are equipped with an on-board computer for stabilityevaluations, and which use specially developed software which takesinto account the main particulars, actual stability and dynamiccharacteristics of the individual ship in the real voyage conditions, suchsoftware should be approved by the Administration. Results derivedfrom such calculations should only be regarded as a supporting toolduring the decision making process.

1.4 waves should be observed regularly. In particular, the wave period Twshould be measured by means of a stop watch as the time spanbetween the generation of a foam patch by a breaking wave and itsreappearance after passing the wave trough. The wave length isdetermined either by visual observation in comparison with the shiplength or by reading the mean distance between successive wavecrests on the radar images of waves.

1.5 The wave period and the wave length are related as follows :

=1.56 . Tw2 [m] or Tw = 0.8 [s]


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1.6 The period of encounter and TE could be either measured as the periodof pitching by using stop watch or calculated by the formula:

Where V = ships speed [knots]; and

= angle between keel direction and wave direction (=0 o means headsea)

1.7 The diagram in figure 1 may as well be used for the determination ofthe period of encounter.

1.8 The height of significant waves should also be estimated.

DIAGRAM


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2 Cautions

2.1 It should be noted that this guidance to the master has been designed

to accommodate for all types of merchant ships. Therefore, being of ageneral nature, the guidance may be too restrictive for certain ships withmore favourable dynamic properties, or too generous for certain otherships. A ship could be unsafe even outside the dangerous zonesdefined in this guidance if the stability of the ship is insufficient. Mastersare requested to use this guidance with fair observation of the particularfeatures of the ship and her behaviour in heavy weather.

2.2 It should further be noted that this guidance is restricted to hazards inadverse weather conditions that may cause capsizing of the vessel orheavy rolling with risk of damage. Other hazards and risks in adverseweather conditions, like damage through slamming, longitudinal ortorsional stresses, special effects of waves in shallow water or current,risk of collision or stranding, are not addressed in this guidance andmust be additionally considered when deciding on an appropriatecourse and speed in adverse weather conditions.

2.3 The master should ascertain that his ship complies with the stabilitycriteria specified in the IS Code or an equivalent thereto. Appropriatemeasures should be taken to assure the ships watertight integrity.Securing of cargo and equipment should be re-checked. The shipsnatural period of roll TR should be estimated by observing roll motions incalm sea.


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3 Dangerous Phenomena

3.1 Phenomena occurring in following and quartering seas

A ship sailing in following or stern quartering seas encounters the waveswith a longer period than in beam, head or bow waves, and principaldangers caused in such situation are as follows :

3.1.1 Surf-riding and broaching-to

When a ship is situated on the steep forefront of a high wave infollowing or quartering sea conditions, the ship can beaccelerated to ride on the wave. This is known as surf-riding. Inthis situation the so-called broaching-to phenomenon may occur,which endangers the ship to capsizing as a result of a suddenchange of the ships heading and unexpected large heeling.

3.1.2 Reduction of intact stability when riding a wave crestamidships

When a ship is riding on the wave crest , the intact stability canbe decreased substantially according to changes of thesubmerged hull form. This stability reduction may become criticalfor wave lengths within the range of 0.6 L up to 2.3 L, where L isthe ships length in metres. Within this range the amount of

stability reduction is nearly proportional to the wave height. This


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situation is particularly dangerous in following and quarteringseas, because the duration of riding on the wave crest, whichcorresponds to the time interval of reduced stability, becomeslonger.

3.2 Synchronous rolling motion

Large rolling motions may be excited when the natural rollingperiod of a ship coincides with the encounter wave period. Incase of navigation in following and quartering seas this mayhappen when the transverse stability of the ship is marginal andtherefore the natural roll period becomes longer.

3.3 Parametric roll motions

3.3.1 Parametric roll motions with large and dangerous roll amplitudesin waves are due to the variation of stability between the positionon the wave crest and the position in the wave trough. Parametricrolling may occur in two different situations:

1. The stability varies with an encounter period TE that isabout equal to the roll period TR of the ship (encounter ratio1:1). The stability attains a minimum once during each rollperiod. This situation is characterized by asymmetricrolling, i.e. the amplitude with the wave crest amidships ismuch greater than the amplitude to the other side. Due tothe tendency of retarded up-righting from the largeamplitude, the roll period TR may adapt to the encounterperiod to a certain extent , so that this kind of parametric

rolling may occur with a wide bandwidth of encounterperiods. In quartering seas a transition to harmonicresonance may become noticeable.

2. The stability varies with an encounter period TE that isapproximately equal to half the roll period TR of the ship(encounter ratio 1:0.5). the stability attains a minimum twice

during each roll period. In following or quartering seas,where the encounter period becomes larger than the wave


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period, this may only occur with very large roll periods TR,indication a marginal intact stability. The result is symmetricrolling with large amplitudes, again with the tendency ofadapting the ship response to the period of encounter due

to reduction of stability on the wave crest. Parametric rollingwith encounter ratio 1:0.5 may also occur in head and bowseas.

3.3.2. Other than in following or quartering seas, where the variation ofstability is solely effected by the waves passing along the vessel,the frequently heavy heaving and/ or pitching in head or bow seasmay contribute to the magnitude of the stability variation, inparticular due to the periodical immersion and emersion of theflared stern frames and bow flare of modern ships. This may leadto severe parametric roll motions even with small wave inducedstability variations.

3.3.3. The ships pitching and heaving periods usually equals theencounter period with the waves. How much the pitching motion

contributes to the parametric roll motion depends on the timing(coupling) between the pitching and rolling motion.

3.4 Combination of various dangerous phenomena

The dynamic behaviour of a ship in following and quartering seas is very

complex. Ship motion is three-dimensional and various detrimental factorsor dangerous phenomena like additional heeling moments due to deck-edge submerging, water shipping and trapping on deck or cargosimultaneously or consecutively. This may create extremely dangerouscombinations, which may cause ship capsize.

4 Operational Guidance


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The shipmaster is recommended to take the following procedures of shiphandling to avoid the dangerous situations when navigating in severeweather conditions.

4.1 Ship condition

This guidance is applicable to all types of conventional ships navigating inrough seas, provided the stability criteria specified in resolution A.749(18),as amended by resolution MSC. 75(69), are satisfied.

4.2 How to avoid dangerous conditions

4.3 For surf-riding and broaching-to

Surf-riding and broaching-to may occur when the angle of encounter is in therange 135o<


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1.1.1 For successive high wave attack

1.1.1.1 when the average wave length is larger than 0.8 L andthe significant wave height is larger than 0.04 L, and at

the same time some indices of dangerous behaviour ofthe ship can be clearly seen, the master should payattention not to enter in the dangerous zone as indicatedin figure 3. When the ship is situated on this dangerouszone, the ship speed should be reduced or the shipcourse should be changed to prevent successive attack ofhigh waves, which could induce the danger due to thereduction of intact stability, synchronous rolling motions,

parametric rolling motions or combination of variousphenomena.

1.1.1.2 The dangerous zone indicated in figure 3 correspondsto such conditions for which the encounter wave period(TE) is nearly equal to double (i.e., about 1.8-3.0 times) ofthe wave period (TW) (according to figure 1 or paragraph1.4).

1.1.2 for synchronous rolling and parametric rolling motions

1.1.2.1 the master should prevent a synchronous rollingmotion which will occur when the encounter wave periodTE is nearly equal to the natural rolling period of ship TR.

1.1.2.2 For avoding parametric rolling in following quartering,head, bow seas the

course and speed of the ship should be selected in a wayto avoid condition for which the encounter period is closeto the ship roll period (TE ~ TR) or the encounter period isclose to one half of the ship roll period (TE ~ 0.5.TR)

1.1.2.3 The preiod of encounter TE may be determined fromfigure by 1 by entering with the ships speed in knots, theencounter angle and the wave period TW.


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DIAGRAM


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Abbreviations and symbols

Symbols explanation

units

TW wave periods

wave lengthm

TE encounter period with waves

s

angle of encounter (=0o in head sea, =90o for sea from

starboard side)degrees

V ships speedknots

TR natural period of roll of ships

L length of ship (between perpendiculars)m

DIAGRAM


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THE WEATHER CRITERION & MINIMUM STABILITY REQUIREMENTSHOULD GOVERN THE MINIMUM REQUIREMENTS FOR

RASSENGER OR CARGO SHIPS OF 24 m IN LENGTH AND OVER.AREA B SHOULD BE EQUAL TO OR > AREA A

IW1 =P.A.Z/ 1000G (METRES),

WHERE :

P= 504 N/M2

A= PROJECT LATERAL AREA ABOVE WATER LINE.

Z= VERT. DIST. BET CENTRE OF H AND APPROX OF DRAUGHT

G= 9.81 M/S2 ;

= DISPL.

IW2 = 1.5 Iw1 (METRES)

O : ANGLE OF HEEL UNDER ACTION OF STEADY WIND. (SHOULDBE LIMITED TO 16O OR 80% OF THE ANGLE OF DECK EDGEIMMERSION, WHICH EVER IS LESS).

1: ANGLE OF ROLL TO WINDWARD DUE TO WAVE ACTION

1 = 109 k.X1. X2 rs DEGRES

2: ANGLE OF FLOODING OR 50O WHICH EVER IS LEAST

WEATHER CRITERION

WHERE,

K : BILGE/BAR KEEL FACTOR (BETWEEN 0.7& 1)

X1: BREADTH/DRAFT, RATIO FACTOR (BETWEEN 0.84 & 1)

X2: CO COEFFICIENT (BETWEEN 0.75 & 1.0)


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R : 0.73+0.6 OG/d, WHERE OG IS DISTANCE BETWEEN COG &W/L(OG=KG-D)

S : ROLLING PERIOD FACTOR (0.035-1.0)

T : ROLLING PERIOD = 2CxB/GM, SECONDS

WHERE,

C=0.373+0.023(B/D) 0.043 (LW2/100)

B= MOULDED BREADTH

d= MEAN MOULDED DRAFT

LW2= WATER LINE LENGTH OF SHIP

GM= GM (FLUID)

Ak = TOTAL OVERALL AREA OF BILEAGE KEELS OR BARKEEL ORSUM OF THEIR AREAS (M2)

Documents

1 - Stability of Passengers Ships