DeepRope_manual.pdf

7/30/2019 DeepRope_manual.pdf

1/8

Deepwater Mooring Lines 2007


2/8

Experience in Depth

Vryhof Anchors has been active in the offshore mooring system market for 35 years

giving it an unrivalled level of experience and knowledge in the requirements of

its selected clients and markets. An ISO 9001-2000 certified company; Vryhof is

committed to the development of cutting edge, market leading products and

works with its partners to ensure this philosophy is replicated across the

whole product range. Vryhofs partner, Bexco Ropes, was one of the pioneering

companies in the development of deep water polyester mooring lines introducing

the DeepRope product in the early 1990s.

Innovation, Research & Development

Vryhof Anchors has grown into a world

leader in state of the art engineering and

manufacturing of total mooring systems.

Fully understanding its clients needs are

not to be met with standard products alone

Vryhof focuses on specialisation and a

dedication to customer needs ensuringthe client reaps the benefit of innovative

product developments and the competitive

advantage it affords. The research teams are

constantly investing time and effort into the

continuous improvement of the established

product lines.

Quality, Health & Safety

ISO 9001-2000 certified the constant need forthe highest quality products and services is

fully recognised. Quality Assurance is a key

business driver and quality controls are in

place for all processes and procedures of

polyester rope manufacturing, splicing and

testing. The industry focus on constantly

improving health and safety performance is

also recognised with QHSE policies, procedures

and practices implemented and maintained.

DEEP ROPE MOORING LINES


3/8

DEEPWATER MOORING LINES

Polyester Tether Manufacturing

Base Yarns

The fundamental building block of any

polyester tether is the high tenacity yarn

obtained from the premier manufacturing

companies in the world. The yarn is made up

of a large number of fine filaments twisted

together. Each is individually treated with a

specialist marine finish during the extrusion

process to provide improved performance.

Yarn material is specially selected according

to specific performance requirements such

as yarn on yarn abrasion and tenacity.

Subropes

Polyester tethers are manufactured from

a defined number of high efficiency sub

ropes. The subropes consist of a number of

assembled yarns twisted together in either

a right or left hand direction.

During manufacturing the yarn position and lay length is carefully

managed to ensure equal tension between yarns within the subrope.

Each subrope also has a unique marker ribbon enclosed within the

construction which will be later used to aid splicing operations.


4/8

Full Rope Assembly

A defined number of subropes in a

combination of right and left hand lay to

meet the required project torque

considerations are laid parallel together

and overbraided with a high efficiency

polyester jacket. The diameter and strength

of the rope is determined by the number of

subropes used whereas the torque

properties, whether torque balanced or

torque matched to a wire rope, will be

determined by the lay directions of the

assembled subropes. Between the subropes

and the braided jacket a multiple layer sand

filter is installed to prevent the migration

of particles into the rope; the filter has a

capability to filter out particles of down

to 2m.


5/8


Termination Techniques

Polyester tethers are terminated with

a specialist splice which maintains the

efficiency of the rope construction.

Each subrope is identified by its unique

marker ribbon and spliced back into itself

to minimise performance loss in the event of

a damaged subrope and thereby making the

rope more damage tolerant. The completed

splice is further protected with the use of

DeltaWeb plus a two component

polyurethane. The standard connection

device to adjoining mooring components

is the steel thimble spool with a hole

dimensioned to suit a round pin shackle

however alternate more complex designs

may be considered.

Thimble spool and shackle dimensions areto a great degree project specific being

calculated from the minimum dimension

requirement from a rope design perspective

then adapted to suit project specific

requirements such as design life and

corrosion allowance. The table shows

typical dimensions considering a

10 year design life assuming a 0.4mm

per annum corrosion allowance.

Termination Hardware Dimensions

Diameter Minimum Thimble Dimensions Shackle Dimensions

Breaking Load

(mm) (tf) (kN) Flange Barrel Overall Internal Overall Internal Internal

Diameter Diameter Width Width Width Width Height

mm Dtot mm Dinw mm Wtot mm Winw mm Wtot mm Winw mm Hinw

151 700 6867 430 270 255 190 544 265 530

160 800 7848 460 290 265 200 570 275 560

175 1000 9810 510 320 285 220 620 295 610

190 1200 11772 550 350 305 240 670 315 650

219 1400 13734 625 395 335 270 735 345 725

233 1600 15696 670 420 360 295 805 370 770

246 1800 17658 705 445 385 315 850 395 805

258 2000 19620 735 465 405 335 870 415 835

WinwHinw

Dinw Winw

R


6/8

Performance Characteristics

Diameter, Weight & MBL

Polyester tethers may be designed within

reason to any diameter or minimum breaking

load requirement as required by a given

project. For information purposes a range of

standard designs are presented in the table.

Diameter Minimum Breaking Load

Extension

Polyester tethers display a combination of

permanent and visco-elastic extension when

loaded. The various elements of extension

may be detailed as follows:

Constructional Elongation is the extension

exhibited due to the bedding down of the

rope when first loaded. This extension ispermanent and is fully accounted for after

5-10 loading cycles. Constructional extension

is load dependent with extensions between

1.6% and 3.6% of rope length expected at

load ranges between 20% and 50% of MBL.

Creep is the elongation of the polyester

material at a constant tension over time.

Creep is caused by molecular realignment

within the yarn structure plus physicaldamage to the rope structure which allows

further yarn realignment. Creep is for all

practical purposes permanent but is

relatively minor with creep elongation over

a typical project design life expected to be in

the region of 1% to 2% of the rope length.

Elastic elongation is the extension of the

rope when a load is applied which will

fully recover immediately once the load is

removed. Elastic elongation is highly load

dependent with extension of 2.5% to 7.5%

of the rope length expected at load ranges

between 20% and 50% of MBL.

Thus the elongation characteristic of the

polyester tether needs to be carefully

considered in conjunction with the predicted

load cycle range to establish the required

installed length of the tether.

Stiffness

An important consideration in the design

of a mooring system is the stiffness of thepolyester mooring line itself. The visco-elastic

behaviour exhibited by polyester tethers must

be understood to establish tether performance

with regard to stiffness. The offshore industry

looks at a number of load cases and the

associated polyester stiffness when determining

mooring line behaviour.

The graph (right above) depicts the stiffness

performance of a polyester tether in a scenariosimilar to that expected of a drift stiffness

condition. The graph demonstrates that

stiffness is predictable and stabilises between

Diameter Minimum Total Weight Submerged Weight Stiffness EA

Breaking Load (kg/m) (kg/m) (kN)

(mm) (tf) (kN) @2% @20% @2% @20% Cycling Cycling Cycling

MBL MBL MBL MBL 10-30% 20-30% 40-50%

MBL MBL MBL

151 700 6867 15.5 15.2 3.7 3.6 1.37E+05 1.61E+05 2.10E+05

160 800 7848 17.5 17.2 4.2 4.1 1.57E+05 1.84E+05 2.40E+05

175 1000 9810 20.8 20.4 5.0 4.9 1.89E+05 2.22E+05 2.89E+05

190 1200 11772 24.7 24.2 5.9 5.8 2.29E+05 2.68E+05 3.49E+05

219 1400 13734 30.6 29.9 7.3 7.2 2.74E+05 3.22E+05 4.19E+05

233 1600 15696 34.5 33.8 8.1 7.9 3.14E+05 3.68E+05 4.79E+05

246 1800 17658 38.4 35.7 8.6 8.4 3.53E+05 4.14E+05 5.39E+05

258 2000 19620 42.3 41.4 10.0 9.8 3.92E+05 4.60E+05 5.99E+05


7/8


80 and 100 cycles. In this load case the stiffness

approximates to 22xMBL, however stiffness

will increase with load to nominally 30xMBL

for loadings between 30-50% MBL.

Handling & Packing

Reels

An important aspect of the polyester rope is

its delivery package to ensure it arrives on sitein sound condition. The main rope carrier is a

specially designed steel transport reel

engineered to accommodate the package

weight and any loadings imposed during

shipment and respooling. Storage reels may

be painted with long life paint coating systems

designed to last the project lifetime. Each reel

will be subject to multi layer packaging to

protect the rope from the elements during

transit and storage as depicted in the diagram.

Spreader Beams

Lifting beams may be provided with any project with reels specifically

designed for each project reel package. The reels may be lifted from

either a flange arrangement at the reel barrel or by adding lifting

pad-eyes at the outer rim of the reel flange. Both onshore and offshorerated lifting beam in accordance with VMO Maritime Regulations can

be provided.

Installation Aids

Installation aids such as buoyancy lashings of tie-off lashings may be

applied to the polyester tether. Buoyancy lashings with a significant

holding capacity have been successfully supplied to projects such as

Shell Bonga.


8/8

DeepRope is exclusively

marketed worldwide by Vryhof,

the worlds leading anchor manufacturer.

Vryhof Anchors BVP.O. Box 109

2900 AC Capelle a/d Yssel

The Netherlands

Phone: +31 10 266 8900

Fax: +31 10 266 8999

e-mail: [email protected]

www.vryhof.com

Copyright Vryhof Anchors 2007. DeepRope is a registered trademark

of Le Lis, a Bexco subsidiary. All information in this brochure is subject

to change without prior notice. Vryhof Anchors, Bexco or one of its

subsidiaries is not liable and/or responsible in any way for the information

provided in this brochure.

D e e p w a t e r M o o r i n g L i n e s

Documents

DeepRope_manual.pdf