deep rope manual

the vryhof companies

p.o. box 105

2920 ac krimpen ad yssel

the netherlands

www.vryhof.com

®

Polyester & Dyneema®

mooring ropes manual 2004

1

ACCREDITED BYTHE DUTCH COUNCILFOR CERTIFICATION

Reg. No 24

DET NORSKE VERITAS INDUSTRY B.V., THE NETHERLANDS

ISO-9001CERTIFICATED FIRM

CopyrightNo part of this book may be reproduced in any form by print, copy orany other way without written permission from Bexco.

The information disclosed herein was originated by and is the prop-erty of BEXCO n.v and its subsidiaries. BEXCO n.v reserves all intel-lectual and industrial property rights such as any and all patent,trademark, design, manufacturing, reproduction use and sales rightsthereto and to any article disclosed therein, except to the extentrights expressly granted to others.

DeepRope® is a registered trademark of Le Lis, one of the Bexco sub-sidiaries.

Bexco reserves all intellectual and industrial property rights such asany and all of their patent, trademark, design, manufacturing, repro-duction, use and sales rights thereto and to any article disclosedtherein. All information in this manual is subject to change without priornotice. Bexco or its subsidiaries are not liable and/or responsible inany way for the information provided in this manual.

N.V. - S.A.

MEMBER OF

®

DeepRope manual2004 04-03-2004 09:33 Pagina 1

3

CONTENTSSummary 5

1. Company profile 6Le Lis 6Vryhof Anchors 7

2. History 8

3. Fiber properties 10Natural fibres 10Synthetic fibres 10

Polypropylene 12Bexcoline Composite 12Polyester 13Polyamide 13Aramid 13Liquid Crystal Polyester 14Gel-Spun Polyethylene 14Fibres properties overview 14

4. ROPE CONSTRUCTIONS 16Yarn Assembly 16Strands 17Ropes 18

Parallel yarn and parallel strand 18Laid 18Stranded or wire rope construction 19Plaited 20Braided 20

Terminations 21Overview construction and rope properties 22Comparison of Fibres in Ropes 22

5. Application of synthetics in deepwater moorings 24

Taut-leg moorings 24Stevmanta VLA 24Inert Catenary mooring 25Stevpris Mk5 25

2

6. Deeprope® polyester lines 27Static loading 27Dynamic Loading 28Fatigue 28Hydrolysis 29Creep 29Creep Rupture 29Resistance against UV 30Effect of particle ingress 30Axial Compression fatigue 31Marine Finish 31

7. Specification Deeprope® polyester 32Construction 32Terminations 32Shipment & Storage 33Features 34DeepRope® Polyester mooring line; strength table 36

8. Deeprope® Dyneema® lines 38Load-elongation 38Tension-Tension fatigue 38Bending-Bending fatigue 38Creep 39Wear and tear 39UV Resistance 39Bexcoline Composite Fibre 40

9. Specification Deeprope® Dyneema® 40Construction 40Terminations 41Shipment & Storage 42Features 43DeepRope® Dyneema® mooring line; Strength table 44

Table of contentsTable of contents


Rapid developments in the field of synthetic fibreshave led to serious alternatives for the traditionalwire/chain systems in marine and offshore operations.The most important difference between fibre andwire ropes is the fact that there is extensive experience,both practical and in design, for wire rope in engi-neering applications. For fibre rope experience islargely empirical and in the marine environment.However based on the material and rope designselected an assessment of the behaviour can be made.For fibre rope the materials have a significant influ-ence on the primary characteristics of the rope, suchas elongation, weight for a given strength, fatiguelife and abrasion. Secondly the rope construction willalso affect those characteristics and determinewhether behaviour and use improves or becomesmore critical. For example within a limited rangeelongation can be increased for a rope made from agiven fibre. Certain rope designs are sensitive tokinking and others not at all.

In this manual a short overview is given of the materi-als and rope constructions available for syntheticmoorings, additionally attention is given to deepwatermooring systems and the design for deepwatermooring lines. It is written for the use of syntheticlines in offshore operations.

5

Summary

10. Hardware 46Standard terminations 46Alternative Terminations 47Reels 48

Packaging 48Shipping 48Storage 48

11. Future developments 52OSCAR (Optical SCanning Apparatus for Rope) 52

12. Installation of the Deeprope® line 54Transport 54Installation 54Safe working load 56

Temporary systems 56Permanent systems 56

Bending radius 56Abrasion resistance 57Temperature resistance 57

13. Inspection criteria 59Estimating residual strength 61

14. Repairing a braided cover 62Small Repairs 62Extensive repairs 63

15. Testing 64

16. Quality assurance 64Type approval polyester Deeprope® 64

17. Appendix 66Reference list offshore 67Textile units 67Schematic drawings of polyester Deeprope® 68Schematic drawings of Dyneema® Deeprope® 69Conversion tables 70

Table of contents

4

Here the manufacturing of a polyester deep-water mooring line is shown.


76

The first anchor, STEVIN, was followed by an ongoingseries of improvements, the HOOK, STEVMUD,STEVDIG and STEVROCK, each an optimal combina-tion of practical feedback and further research to cre-ate ideal anchor designs for specific operating condi-tions and soil types. In the 80's the specific advan-tages of the previous anchors were combined intoone new high performance anchor: STEVPRIS and itshard soil version STEVSHARK. With the Mk5 versionan anchor efficiency of 60 times its own weight isachieved and since the introduction more than 6000pieces have been sold worldwide.

With oil exploration and maritime activities goinginto deeper and deeper waters (with generally softsoils) in the 90's, Vryhof introduced the STEVMANTAVertically Loaded Anchor. This anchor type has beeninstalled successfully in several deepwater mooringprojects since then. Besides the above mentionedproducts, Vryhof Anchors is able to provide a widerange of mooring components as well as a number ofengineering services. Of the latter, assistance duringinstallation of anchors and the supply (at a rentalbase) of the special STEVTENSIONER for tensioningjobs are the most noticeable.

The company is ISO 9001-2000 certified and the abovementioned products can be supplied with certifica-tion of all major classification authorities.

Company profiles

Le LisLe Lis n.v. manufactures ropes for deepwater offshoreapplications, known as DeepRope®, and Deltaflex®

ropes. The company has been active since 1919. Thecompany is ISO 9001-2000 certified in sales, marketing,research, development and production of yarns,tapes and strapping, marine- and offshore ropes insynthetic high performance fibres. It is located some30 minutes from the Port of Antwerp and some 50minutes from Brussels.

Le Lis n.v. is a subsidiary of Bexco n.v.. Other compa-nies in the group are Vermeire n.v. and Bexco Fibresn.v. Vermeire n.v. manufactures ropes for marine andoffshore applications. The products for the marineenvironment range from polypropylene, polyester,bexcoline composites, polyamide (nylon). In offshoreapplications HMPE (Dyneema®) Aramid ropes andSingle Point Mooring hawsers are well known prod-ucts. The systems comply with OCIMF guidelines.Bexco Fibres n.v. is active in extrusion and strapping.The group has some hundred employees and in 2003a turnover of € 18 million.

Vryhof Anchors For millennia anchoring was achieved by using astone and something that looked like a rope. Overthe last twenty five years of more recent historyVryhof Anchors b.v. has brought the art to moremature status. The company has grown into a worldleader in state-of-the-art engineering and manufac-turing of total mooring systems for every kind offloating structure. From the very beginning Vryhofhas fully understood that the needs of clients are notto be satisfied by the supply of standard hardwarealone, and the exclusive specialisation and dedicationto customer's requirements have yielded remarkableresults.

Company profiles


98

affect strength, weight and other characteristics. Inthe photo the production of a four-strand rope on atraditional rope walk is shown, with a wooden dye toposition the strands.

The last big step was the introduction of braiding. Inthis process the strands are interweaved in a maypolefashion. This gives a rope that is torque free.

Today ropes are combinations of these two basicprocesses: twisting and braiding. The combination ofmaterial and construction choices allows tailoring ofthe rope characteristics to meet the requirements ofchallenging applications. Even though syntheticropes have found their way into space, the main useis still in marine and industrial applications. Choice ofmaterials ranges from polypropylene to aramid orhigh-modulus polyethylene, the latter two givingropes with comparable strengths as wire rope.Nowadays natural fibre rope is only a fraction of totalrope production.

History

The beginning of rope making is hidden in the cloudsof history. However already in pre-historic times manknew that parts of certain plants were very strongand suitable for transferring loads and fixing thingstogether. The first ropes were probably three-strandropes, with the same basic construction as still in usetoday. Ropes were made by hand and found their pri-mary use in building and ships. For example theEgyptian pyramids could not have been built withoutropes.

In the Middle Ages rope makers in Europe wereorganised in guilds and in every port rope makerscould be found. It is also around that time that theystarted to use rope walks for production. These typi-cally were narrow paths, some hundred meters long.At the beginning of the walk a wheel was placed witha hook that could be rotated. The rope maker wouldattach some fibres to the hook and someone elsewould rotate the wheel, thus forming a yarn. Thiswould then be continued until the end of the walkwas reached. When sufficient yarns were twisted,they would be laid on the rope walk again, attachedto the wheel and then a strand would be formed bytwisting the wheel in the opposite direction. Thiswould then be repeated a third time to form a rope.Needless to say this required a lot of craftsmanship.

Around 1700 people started to use horses to makeropes and later steam engines. Towards the end ofthe century register plates and dyes were introducedand this greatly improved the quality of the ropes.Around the beginning of 1800 the process was fur-ther mechanised, gradually removing the need forrope walks.

The next big step in rope making was the introduc-tion of synthetic fibres. This greatly improved thedurability of ropes as rotting was no longer an issue.Also choice between different fibres would greatly

History


determines how closely the crystalline (or sonic) mod-ulus can be approached and interaction between themolecules determines the movement or slippagewhich becomes visible as creep in the fibre. Typicallythe strength and stiffness of a molecule is significant-ly higher than that of the fibre. Overall strength isdetermined by how well the material is oriented, thecrystal size and how strong the interaction is betweenthe crystalline regions. A good example of this isDyneema: it is made from polyethylene, a materialthat normally had a low strength and stiffness. By giv-ing the material a high crystallinity and high orienta-tion the theoretical strength and stiffness isapproached where normally the low interactionbetween molecules prevents this.

Fibre MaterialsHere the different synthetic fibres mainly used in ropesand their primary characteristics are shortly discussed.The rope design can modify characteristics, but can notchange fundamental behaviour. Therefore the mate-rials have to be selected first for a given application.For polymeric materials properties (such as strength,stiffness, fatigue) are to a great extend determined bymaterial and processing conditions. With traditional synthetic fibres, such as nylon(polyamide) and polyester, the polymer is melted andthe fibre is formed by squeezing the polymer througha die. This die is rather like a shower head with a largenumber of small holes. Each thread of plastic goingthrough these holes becomes one filament. Then itsolidifies in air or liquid and is drawn. This process ofdrawing is called spinning and orients the molecules

Natural fibres are being used from the earliest timesfor ropes. They will not be discussed extensively inthis manual because they are seldom used in engi-neered applications. Natural fibre rope is used in his-toric applications or where environmental issues arecritical. For completeness they will be briefly dis-cussed in this chapter. The main focus is on the syn-thetic fibres.

Natural fibresIn principle ropes can be made from any fibrousmaterial. Examples are Cocos, Cotton. However threetypes are mainly used: Hemp, Manilla and Sisal.Hemp (Canabis sativa) originates from Central Asia.The fibres can be extracted through a rotting processor through drying and hackling. Hemp typically istarred to stop the rotting process. Manilla is the fibrefrom the leaves of Musa textilis (related to banana).They originate from the Philippines (hence its name).The lighter and thinner a Manilla fibre, the stronger itis. Sisal is also extracted leaves from the Agalvesisalana. It is less strong then Manilla and will absorbwater. The water uptake is reduced through treat-ment with oil.

Synthetic fibresAll synthetic fibres are produced from polymers; thatis to say from molecules that repeat more or less adinfinitum. Here the different fibres mainly used inropes and their primary characteristics are shortly dis-cussed. Basic behaviour of a rope is largely deter-mined by the fibre selected. The rope design canmodify characteristics, but can not change funda-mental behaviour. For polymeric materials properties(such as strength, stiffness, fatigue) are to a greatextend determined by material and processing condi-tions. Orientation of the material and interactionbetween molecules inside the fibre determine overallinteraction in the fibre, see also sketch and table.Interaction between the various crystalline regions

1110

Fiber propertiesFiber properties

Material

PETPA6AramidUHMWPE

Fibre Type

Diolen 855*Enkalon*Twaron *Dyneema+

Crystallinity

40%50%95%

>97%

Sonic modulusN/tex

13767

165

Fibre modulusN/tex

6.54.842110

DensityKg/l

1.381.141.440.97

Chain interaction

medium/high (dipolar)high (H-bridges)high (H-bridges)low (van der Waals)

extruder

spinneret

oven

filament

yarn

winding

Diolen, Enkalon and Twaron are trademarks of Acordis. Dyneema is a trademark of DSM.


PP

0

5

10

0 2,5 5 7,5 10 12,5 15elongation (%)

load

(cN

/dte

x)

PolyesterPolyester (= Dacron, Terylene, Trevira, Diolen) is a par-ticularly reliable fibre with mechanical propertiesquite close to those of nylon. The abrasion resistanceof polyester is better than that of nylon and so is thetension-tension fatigue performance. Since the costof both fibres is quite similar polyester should general-ly be preferred. In favour of nylon is its lower density(1.14 vs 1.38) and higher energy absorption.Under normal working conditions polyester is notsensitive to hydrolysis. The melting point of polyesteris around 260°C. The UV Resistance is good.

Polyamide Polyamide or Nylon was the first synthetic fibre discov-ered. It is available as a fibre as nylon 6 and nylon 6-6.Both types have virtually identical mechanical prop-erties but nylon 6-6 is thermally more stable. In ropesboth types are generally equally suitable. Since nylonwas the first fibre discovered it is better established thanpolyester but the fatigue properties of polyester are bet-ter than those of nylon. The melting point is 215°C. Innormal conditions of use nylon 6 is influenced water; ithas a softening effect. The UV resistance is acceptable.

Aramid Aramid fibres such as Kevlar and Twaron are substan-tially stronger than nylon. They derive their greatstrength by substituting the linear chain of (CH2)nwith a benzene ring. This also creates chemical andthermal stability. Aramids will not melt but start tocarbonize at temperatures above 425° C. The UV stabil-ity is medium. Aramids have excellent tension-tensionfatigue resistance and exhibit low creep. Howeverthe abrasion resistance of these fibres is not good. Anaramid co-polymer (Technora) has better bondingbetween the molecular chains and as expected theabrasion resistance and lifetime in running over pulleysis improved.

13

Fiber properties

12

developing high tensile strength; see also sketch. Forexample the tensile strength of nylon plastic is 30 – 90N/mm2. When drawn into a fibre this same plasticdevelops 900 N/mm2. In the case of the aramids andaromatic polyesters there is no melting point and thefibres have to be spun by chemically dissolving thepolymer. This is a much more expensive process.

PolypropyleneFor ropes polypropylene is most often produced assplit film. This means a film is extruded and is splitusing knifes before drawing. The strength is obtainedin this drawing process. Other fibres are mostly pro-duced as multi-filament. Polypropylene is chemicallyinert, has a low density (it floats), but has a somewhatlower melting point (160°C) and lower strength.Standard PP has a low UV resistance; however withUV stabilisation the resistance can be good.

Bexcoline CompositeBexcoline composite is a mixed or composite fibrebased on polyester and our proprietary bexcord yarn.It combines the abrasion resistance and fatigue life ofpolyester with the lower density of nylon (1.1 –1.14).Because of its lower weight it has excellent handlingcharacteristics. The UV resistance is good. Wet anddry strength is identical. A special marine finish isapplied to further increase the wear resistance in amarine environment. This finish has been tested con-form ASTM D6611-00 and is water repellent.

Fiber properties

Polyester

0

5

10

0 5 10 15elongation (%)

load

(cN

/dte

x)

Secondary FibreProperties

Aramid HTAramid copolymerAramid SMGel-spun PELC polyesterSteel wirePolypropyleneBexcoline CompositePolyesterNylon

Abrasion

poormediumpoorvery goodmediumvery goodpoorgoodgoodgood

Creep

lowlowlowhighlowvery lowmediumlow/mediumlow/mediumh. medium

Kinking

susceptiblesusceptiblesusceptibleresistantsusceptiblevery resistantresistantresistantresistantresistant

Bexcoline Composite

0

5

10

0 5 10 15 20elongation (%)

load

(cN

/dte

x)

aramids

0

10

20

0 1 2 3 4 5

elongation (%)

load

(cN

/dte

x)

Polyester

0

5

10

0 5 10 15elongation (%)

load

(cN

/dte

x)

Polyamide

0

5

10

0 5 10 15 20 25

elongation (%)

load

(cN

/dte

x)


1514

Fiber properties

Liquid Crystal Polyester The hope was that liquid crystal polyesters (= Vectran)would have higher strengths than the aramids with amuch improved abrasion performance. The reportedresults have been mixed, breaking strength and elon-gation are very similar and abrasion is higher. Theactual strengths in ropes are no higher than witharamid and the lifetime in tension-tension fatigue isabout equivalent. However it has a good perfor-mance in cycling over sheaves.

Gel-Spun PolyethylenePolyethylene is an amorphous plastic with relatively lowtensile strength compared to what would be possible ifit was aligned and crystalline. With a ultra-high mole-cular weight polyethylene and a special process calledgel spinning this alignment and cristallinity can beachieved. The polymer is dissolved in a solvent whichresults in a gel like solution and under these circum-stances it is possible to spin a highly drawn fibre. It iscommonly known as High Modulus PolyEthylene (=Dyneema, Spectra). The fibre has a very high tensilestrength. The fibre density is only 0.97 and consequent-ly the strength to weight ratio is also very high. Thefibre has an extremely low coefficient of friction and isextremely resistant to internal and external abrasion.The lifetime in cycling over sheaves is extraordinary. Thethermal properties of HMPE are no better than ordi-nary polyethylene and it melts at around 150° C. HMPEis also prone to cold flow and therefore has a highcreep rate.

Fibres properties overviewOn the next page, the fibre properties are shown inthe top table and graphically represented below that.

Fiber properties

Aramid HTAramid copolymerAramid SMGel-spun PELC polyesterSteel wirePolypropyleneBexcolineCompositePolyesterNylon

TensilestrengthN/mm2

3 6003 5002 7603 3003 0002 160500650

1050850

Modulus ofelasticityN/mm2

60 00073 00060 00085 00080 000

200 0004 200 4 300

9 0005 500

Elongationto break(yield) %

4.04.03.73.53.81.11215

12.518.0

short

20020020080

180

100120

180140

continuous

16016016060

120

7080

12080

MeltingPoint ° C

480480480145330

1600165

165/260

260215

Densitykg/l

1.441.391.440.971.417.860,911.14

1.381.14

Max Use Temperature °C

UHMWPE

0

10

20

30

40

0 1 2 3 4 5

elongation (%)

Loa

d (c

N/d

tex)

Strength

0

500

1000

1500

2000

2500

3000

3500

4000

AR HT AR HM AR SM AR C HMPE LCP ST PET PA

Unit:Unit:

N/mmN/mm2

Strength versus weight

0,00

5,00

10,00

15,00

20,00

25,00

30,00

35,00

40,00

45,00


Unit:Unit: g/deng/den

Elongation

0,0

5,0

10,0

15,0

20,0


Elasticity

0

200

400

600

800

1000

1200

1400


Unit:Unit: g/den g/den


With high modulus yarns it is important that theyarns are twisted with even tensions and that theyshare load evenly in the resultant construction. Thislimits the methods that can be used and generallyinvolves more production steps than with traditionalropes.

An alternative method for assembling yarns is bind-ing them together in an outer jacket or encapsulatingin a resin. Since these jackets have a relatively largecross-sectional area they result in ropes of large diam-eter and weight. Consequently this technique israrely used.

StrandsThe basic geometry of a strand is similar to that of ayarn, assembled yarns are twisted together to make astrand, this causes length differences between thoseyarns. The number of layers and the lay length in thestrand are the key parameter that determines this. Bycarefully separating the yarns in layers the variationbetween yarns in a layer can be further minimised.This is done using dyes, tensioning and separatorplates. There are three fundamental methods formaking strands; here a two-for-one strander isshown.

17

Various techniques are used to convert fibres intoropes. Unlike steel wire, fibres can tolerate substan-tial twist during manufacture and this allows a widerange of possibilities for a rope construction. Mostropes constructions use twisting during one or moreproduction steps to obtain load sharing, handling sta-bility and other characteristics.

Here the production steps in rope making, their ter-minology and the constructions possible are shortlydiscussed. In the next chapter the characteristics ofpolyester deepwater mooring lines are discussed.

Yarn AssemblyA yarn is made up of a large number of fine filaments.In the case of the high modulus yarns which are high-ly drawn the filament diameter is around 12 microns.In a yarn there are typically 1000 or more filaments.Yarn diameters are extremely small and they areassembled together by one of several possibleprocesses. The main assembly method is twisting, forthis process strength of the assembled yarn is a func-tion of the material, twist level and processing con-trol. Once the twist level is known for which thestrength is optimal it can easily be translated to othersizes of yarn. If the twist angle is similar the twist losswill also be similar, see sketch.

Twist direction is expressed as Z (right-hand lay) and S(left-hand lay), see sketch. Normally twist directions arealternated each production step to obtain a stable con-struction with minimal torque, see sketch. The choicefor a singly ply or a double yarn typically is determinedby the machinery available and/or the required stabili-ty. A doubled yarn requires an extra production step,however it also has more shape stability. This gives thedoubled yarn a better wear and abrasion resistancethan a single ply. Traditional yarns have high elonga-tion and then twisting this is not a critical operation,assuming good manufacturing and QC practices.

16

Rope constructionsRope constructions

Z-twist S-twist

SZ

laystrand

dstrand


below. For a typical design a good fibre strength andfatigue life will translate into acceptable propertiesin the rope. A laid rope will rotate under load, but theeffect on the strength is limited.

The high modulus fibres do not tolerate these highlevels of twist in large ropes without catastrophic lossof tenacity. This is due to the fact that these yarns areprone to squeeze breaks and cannot withstand highinternal compression. Consequently the use of laidconstructions is limited to cords and small ropes. Itshould be noted that 3 and 4 strand ropes can bemade with low helix angles but they then need anexternal jacket or resin to provide structural integrity.In this form they can be treated as a wire rope.

Stranded or wire rope constructionsIn this construction, twisted strands are arranged inone or more concentric rings around a central corestrand as in constructing wire rope. The core strandmay not be designed to carry load. Common con-structions are:• 6 + 1 (six strands around the core)• 12 + 6 + 1 (twelve strands around six strands)• 18 + 12 + 6 + 1Most wire rope constructions are supplied with abraided polyester or nylon jacket. Extrusions andpolyurethane coatings have also been used. A combi-nation of both a braid and an extrusion or coatingmakes an extremely tough jacket. A six-strand rope isshown here. Also a stranded rope will have a goodstrength and fatigue translation from the fibre. It willrotate under load with a limited effect on thestrength.

Torque balance can be achieved by designing therope in two concentric layers. The inner layer isstranded in one direction and the outer layer in theopposite direction. The rope is designed so that thetorques produced in each layer is equal in magnitudebut opposite in direction. The individual strands are

19

RopesLay length or plaiting period for the rope not onlyinfluences strength, but also other characteristics likeelongation and shape stability. In a design these char-acteristics have to be weighed against each other foreach application. For the same material a highstrength design will have a low elongation and a sta-ble, firm rope will have a lower strength for the sameamount of material.

Rope constructions are divided in 4 broad categoriesas listed below:1. parallel lay2. stranded (wire rope construction)3. laid4. plaited & braided

Parallel yarn and parallel strandMost parallel lay ropes are actually made using paral-lel yarns and an extruded plastic jacket usually poly-ethylene. An intermediate step between parallelropes and wire ropes is the parallel strand rope. In thiscase the yarns are twisted to form strands which are flexible and thenassembled together under an outer jacket. This hasoften been braided. These two types of parallel ropesare illustrated here.

Fibre properties are translated into rope with highefficiencies. It will not rotate under load and is insen-sitive to twisting.

LaidLaid constructions are extremely old and were origi-nally made by hand from natural fibres. The pointabout them is that they are made with a substantialamount of twist, 30° or more. This gives them struc-tural integrity and they do not need external jacketsto hold them together. The most common laid con-structions are 3 and 4 strand and an example is shown

18

Rope constructionsRope constructions

plaiting period


TerminationsTerminations are normally critical in the rope design.Most of the handling and abrasion occurs on the ter-minations, load is transferred into the rope. Fourtypes of rope terminations are mostly used:

KnotsDepending on the rope design and the type of knotused the knot strength will vary. For plaited ropes theknot strength typically will vary between 25 and 35%of the new strength. Also the life of rope is signifi-cantly reduced by a knot. Because of this knots shouldbe removed at the earliest possible moment.

ClampsClamps are mostly used in leisure applications. Forexample in yachting rope special rope designs areused that can withstand the local compression fromthis termination. Efficiencies are very material andconstruction specific.

SocketsSockets are widely used for wire rope. However forsynthetic ropes sockets are seldom used, because theyare difficult to inspect and have a negative effect onthe fatigue life of the rope. An exception is aramidrope, where sockets are well accepted. Strength effi-ciencies of 100 % are possible, depending on thediameter, design of the rope and termination.

SplicesThis is the most widely used termination for syntheticropes. For a professional splice the reduction inbreaking strength is minimal (10%). Typically thereduction in the fatigue life is also very small. Manydifferent types of thimbles are available for insertionin the eye. They can be optimised for handling, life orother criteria.

21

Rope constructions

20

often jacketed with a thin cover. This holds the fibreyarns together during production but can also be afactor in providing optimum performance whencycling over pulleys particularly for aramids.

PlaitedPlaited ropes are sometimes described as squarebraids. They are produced on a plaiting machine con-taining eight reels, each containing one strand.Groups of two reels interweave as a pair around theother pairs of reels to produce an eight strands ropeof a somewhat square cross section. No twist is takenout of the strand during manufacturing, which isimportant for large size ropes.As previously observed the high modulus fibres areunsuitable for high twist constructions and are notcommon in plaited ropes. However it is possible toproduce this construction with low levels of twistwithout losing all structural integrity.

BraidedBraids can either be solid or circular. Single circularbraids are hollow. The braid consists of an equal num-ber of interwoven clockwise and anti-clockwisestrands. The braid pattern is normally over 1 under 1or under 2 over 2. The individual strands are general-ly made up of 1 or more parallel twisted textile orrope yarns. In many good designs the yarns on theoutside of the braid are aligned with the axis of therope. The rope does not rotate under load, howeverif twist is introduced the strength will be affected.Here a twelve-strand rope is shown. It is very stable onthe winch, because of its round shapeDouble braid or braid on braid consists of an outerbraid over an inner braid. These are more compactthan single braids and are the only realistic braidedalternative in large ropes. The comments made abouthigh levels of twist in laid and plaited ropes applyequally to braided ropes and consequently these arenot practical alternatives for high modulus fibresunless the helix angles are kept extremely low.

Rope constructions

crotch of eye

eyefull spliceclear rope taper


All Ultraline® ropes have a Bexcoline Composite cover.2322

Rope constructions

Construction and rope propertiesThe information given her is only a small part of thedata that is available. Often it is difficult to determinebeforehand what data is needed to estimate thebehaviour in the application. Also in answering ques-tions from users, often more questions are generat-ed. To address this efficiently the documentation atBexco has been structured per product:

Comparison of Fibres in RopesHere the most widely used materials for ropes in amarine environment are compared, both 8-strandplaited and the parallel-strand design. BexcolineComposite 099 (BC 099) and Bexcoline Composite 110(BC 110) are our composite materials, with a densityof resp. 0.99 kg/l and 1.1 kg/l.

Rope constructions

Rope construction

Parallel strand ropesParallel yarn ropeslaid 3- and 4-strandWire-rope constructionsTorque-balanced8 plait12 braidBraid on braid

Tension-tension

v. goodv. goodgoodv. goodv. goodgoodgoodgood

Cycling oversheaves

moderatepoorhighexcellentgoodpoorgoodpoor

Strength to dia.

highexcellentmediumhighhighmediummediummedium

Toughness

moderatepoorgoodgoodmoderateexcellentexcellentv. high

HMPELINE Bexcolon Bexcord 091 BC 099 BC 110 BexcoFlex BexcoPET138

Diammm

l3236404448

5256606468

7276808896

Circ.“

44,55

5,56

6,57

7,58

8,5

99,5101112

MBLkN

8831025121814561687

19632230254128453142

34813815418949275649

weightkg/100m

47,660,274,389,9107

126146167190215

241268297360428

MBLkN

224282347417490

569658749850954

10661182130615691856

weightkg/100m

56,872,189,2108128

150174199227256

287320355430512

MBLkN

181238295351406

480535627699790

880988

107812751489

weightkg/100m

48,458,072,687,1102

121136160179204

228252286358430

MBLkN

162204296358422

495569647736829

9271015113713631618

weightkg/100m

43,352,972,291,5106

126145164188213

237261295352417

MBLkN

196243336400465

545620710801901

10011101122414561711

weightkg/100m

48,660,087,5104120

141157183206232

258283319380447

MBLkN

300346417481544

627709790879

1016

10971302143316981988

weightkg/100m

68,579,596,6112128

149169190211246

267315348415489

MBLkN

179230280336396

460529603681763

850941

103712431467

weightkg/100m

66,884,5104126150

176204235267301

338377417505601

8-strand rope strengths vs diameter and weight.

Parallel-strand rope streghts vs diameter and weight.

HMPELINE Nylon Polyester Bexcord 091

Diammm

3236404448

5256606468

7276808896

104

Circ.“

44,55

5,56

6,57

7,58

8,5

99,5101112

13

MBLkN

737957110313981692

19852354272130873528

39694190463157336615

7938

Weightkg/100m

587388

108127

146170194225253

281309337408486

571

MBLkN

219284331402497

5917098038981040

11341229137017011985

2315

Weightkg/100m

648198117140

164192216247281

305340375455545

627

MBLkN

259338394479591

70484495610691238

13501463163120252363

2756

Weightkg/100m

7392112133161

188222249284325

353392433528630

726

MBLkN

201260302378463

533633742812935

10511154129815931813

2128

Weightkg/100m

53668198117

132154177200226

254288319386456

535


Inert Catenary mooringFor temporary systems either a polyester taut-leg or acatenary mooring with Dyneema insert lines are a cost-effective alternative for dynamically positioned rigs.The choice between these two alternatives is driven bycost of the mooring versus operational limitations.

A DeepRope® Dyneema® insert will transfer mooringforces without changing the catenary. In shallowwaters, an all chains system works well but as thewater depth increases the weight of the chainbecomes excessive and it tends to hang directly downfrom the rig. By inserting a Dyneema® line the moor-ing stiffness increases, without a weight penalty. Thusno modifications to the riser system are necessarywhen going to deeper water. Depending on the exactdesign it is even possible to improve the restoringcharacteristics. This will extend the weather windowfor drilling time. As the DeepRope® Dyneema® linesare neutrally buoyant they can be pre-installed withonly a small surface buoy, thus reducing hook-up time.Depending on the soil conditions and anchor designused a small up-lift may be allowable at the anchorpoint. This will simplify installation considerably.

Stevpris Mk5The Stevpris/Stevshark anchor exists since 1980 andsupersedes older Vryhof models like Stevin, Stevmudand Hook. The development of the anchor was basedon two philosophies;a) Reduce resistance to the anchor during penetra-tion and consequently deep embedment to obtain ahigh holding capacity.b) Enlarge flukes as much as possible to mobilise amaximum of soil resistance. This resulted in an anchor with wide flukes. To reducethe bending moment in the flukes, the shank wasmade out of two parts, widely spaced at the flukesand joining each other at the anchor shackle.

25

Below, two basic systems that are used in deepwatermooring today and the characteristics are discussed.

Taut-leg mooringsAs water depth increases conventional, catenary sys-tems become less and less economical. For permanentsystems a cost-effective, synthetic alternative has beendeveloped: Taut Leg Mooring.

In this system each line is strung out directly to theseabed typically at an angle of 45°. As the platformdrifts horizontally with wind or current, the linesstretch and this sets up an opposing force. Polyestermooring lines have the right restoring characteristicsand thus are the preferred choice for this application.Because of the angle at which the rope arrives at theseabed the anchor will be loaded vertically. Suctionpiles or special anchors, so-called VLA’s have to be used.

Stevmanta VLAThe Stevmanta VLA (Vertically Loaded Anchor) is a newdesign anchor whereby a traditionally rigid shank hasbeen replaced by a system of wires connected to aplate. The anchor is designed to accept vertical (or nor-mal) loads and is installed as a conventional dragembedment anchor with a horizontal load to the mud-line to obtain the deepest penetration possible. Bychanging the point of pulling at the anchor, vertical (ornormal) loading of the fluke is obtained thus mobilisingthe maximum possible soil resistance. Thus it is ideallysuited for taut-leg moorings.

As a VLA is deeply embedded and always loaded in adirection normal to the fluke, the load can be applied inany direction. Consequently the anchor is ideal for taut-leg mooring systems, where generally the load anglevaries from 25 to 45 degrees. The angle adjusterchanges the mode of the anchor from pull-in mode tovertical (or normal) mode.For more details consult the Vryhof anchor manual.

24

Application of synthetics in deepwater mooringApplication of synthetics in deepwater mooring


The V-shape of the shank added another advantageto the anchor, soil resistance is not only mobilised inthe cable pulling direction, but also perpendicular tothe large surfaces of the shank. The soil is compressedin forward and sideways direction. The shank mobilis-es more soil resistance and adds a downward directedload component to the anchor, improving the pene-tration. Thus this anchor has a very high ratio of ulti-mate holding capacity (UHC) versus anchor weightand a very quick and deep penetration, i.e. a veryshort drag length. The deep penetration of theStevpris anchor makes it very suitable to resist upliftforces that might occur in deep water. The latestmodels, the Stevpris Mk5 and Stevshark Mk5, are theimproved versions of the Stevpris, and have beeninstalled all over the world since 1990.

For more details on this anchor and its design pleaseconsult the Vryhof anchor manual.

Application of synthetics in deepwater mooring

26

The DeepRope® line for mooring applications is a so-called parallel core construction. It consists of threeparts, namely core elements, sand and mud barrier andthe cover (see figure). However the general character-istics, like elongation, elasticity and fatigue are deter-mined by the polyester fibre and the three-strand core.In the next chapter the specification of the rope willbe discussed.

Static loading Elongation of ropes typically is non-linear, further-more it is a parameter describing different mecha-nisms, such as elongation from initial load or thatfrom the fibre itself or elongation from the ropeitself versus that from the splices. These differentcauses for the same phenomenon can lead to con-fusion and thus errors. Here we try to differentiateand clarify when what type of elongation can beexpected in the use of a Deepwater mooring rope.

The constructional or initial elongation under load isa function of the rope construction and manufactur-ing conditions. It is non-reversible and occurs on afirst loading (see graph), manufacturing conditions,construction and splicing all play a role. Typicallythere will be more free space in a braided rope thanin a laid rope. The underlying cause is the free-spacebetween filaments in a yarn. This free-space isreduced when the fibres start bedding in (see sketch).This causes a reduction in diameter of the yarns whilethe length of the filaments does not chance. Becauseof the helical structure this results in an overalllengthening. This lengthening is a function of therope construction (3-strand laid, 8-strand braided,etc.) and initial free-space between the filaments.

For a given rope the amount of constructional elon-gation found in the field is mainly determined by themaximum load level achieved. This is clearly visible inthe above graph.

27

Deeprope® polyester lines


The elongation to break is measured from pin to pin,here the terminations (= splice) is included with themeasurement. This typically gives a slightly lowerelongation (0.1-0.3%) than when measured mid-spanwith an extensiometer. This can be expected as splicesare included in this measurement. In the splice elon-gation will be lower.

An average test result is slightly higher than theMinimum Breaking Load.

Dynamic LoadingUnder dynamic loading conditions polyester quicklystiffens and shows a lower elongation. This effect hasbeen extensively studied. For example in DeepwaterFibre Moorings, an Engineers Design Guide (OPL pub-lication) tests are published on polyester fibres andropes (for the ropes Acordis Diolen is mostly used).The dynamic stiffness of polyester ropes is deter-mined to a great extent by the mean load and load amplitude, the frequencyhas a minor negligible influence over the frequencyranges normal for offshore mooring systems (6-600sec). For a well designed rope with only minor imbal-ances the stiffness stabilises within a hundred cycles.

More additional data are available, here only anoverview is given.

FatigueBased on Deepwater Fibre Moorings, an EngineersDesign Guide (OPL publication) the fatigue life ofpolyester is superior to that of other mooring compo-nents below load ranges of 60 % of the MBL.

The Best-Fit curve is taken from Engineers DesignGuide.


28

HydrolysisFor polyester, water will penetrate into the materialwhen it is submerged over long periods. More specif-ically it penetrates into the amorphous zones, whereit causes a slight swelling. Strength reductionthrough hydrolysis can be characterised from fibredata as this mechanisms works on the fibre level.

Based on tests conducted by Acordis and extrapola-tion a conservative estimate of the strength reduc-tion can be made, see graph.

For a Deepwater mooring line at a temperature of20° C the strength reduction will be some 6% of theMBL after 20 years.

CreepThe creep behaviour of polyester rope can be accu-rately predicted from fibre data, see curve.Initially there is a small difference between yarn andrope. This is probably caused by construction effects.

First elongation under constant load for the rope isbest estimated from the initial load elongation curve.After a short time (10 minutes), the creep of individ-ual yarns in the rope has stabilised and differences inlength from rope making do not have a significanteffect on the lengthening or creep.

Creep RuptureThe time-dependent elongation of polyester can beseparated in several categories. There is an effectiveand instantaneous extension, this extension is mea-sured under a single loading. Secondly there is a time-dependent, recoverable extension. This shows as ahysteresis loop in cyclic loading. Thirdly there is thenon-recoverable elongation which occurs under longcontinuous load. Given enough time the yarns willfail under high continuous loads and this phenome-non is known as stress rupture.

29


Creep ruptureDiolen 855 TN

50

60

70

80

90

0,01 0,1 1 10 100 1000

time (yrs)

25 yrs


To prevent this particle ingress a filter material hasbeen wrapped between the cover and the innercores, see sketch. This was necessary, because the mudparticles are so fine that only in depth filtration willprevent them from getting into the inner strengthmembers. Also the stability of the filter system ishigher. In the test this also showed. The polyestercover filters out most of the sand. The filter stops thesand that did get through the cover. The mud passedthrough the cover and is stopped by the filter.

Axial Compression fatigueThis can occur when a rope experiences an excessivenumber of cycles at low tension or when it goes slack.Under these conditions the repeated sharp kinkingwill have an adverse effect. Based on the data forpolyester from the Engineers Design Guide a safelimit is 100 000 cycles (severe strength loss starts tooccur above 1 000 000 cycles). Thus under normal installation and operational con-ditions axial compression fatigue will not occur.

Marine FinishNylon was one of the first fibres used for single pointmooring hawsers. Here it was found that under nor-mal conditions of use cycling caused movementbetween fibres. This movement caused abrasion, giv-ing an unacceptable reduction in strength of the rope.

Marine Finish has first been developed for nylon toimprove the abrasion resistance between yarns. It istested conform ASTMD 6611-00. With the introduc-tion of other materials in marine applications finishesalso have been developed to improve the material’sinternal abrasion resistance. Here a typical curve isshown for a polyester yarn. Even though polyester isnot sensitive to hydrolysis, a marine finish is standardfor fibres used in permanent mooring systems. Withthe marine finish the life of the fibre is significantlyimproved under higher loads (e.g. in storm conditions).

31


In the Engineers Design Guide a conservative esti-mate is given for creep rupture, see curve.

Because of the non-linear behaviour of polyester esti-mates below 60% of the MBL are too conservative.However even with these numbers it can be conclud-ed that under normal conditions creep rupture is nota critical factor for the life of the mooring line.

For a Deepwater mooring line the time to rupture ata continuous load of 60% of the MBL is some 160 years.

Resistance against UVTypical penetration depth of UV light into a materialis 1-4mm, depending on the colour of the yarn.

The polyester fibres used for the DeepRope® mooringlines have an excellent intrinsic UV stability. Based ontests the cover yarns will have some 80% of their orig-inal strength after one year of direct exposure inEurope (worst case is Australia were this will be 80%after half a year).

As the cover for Deeprope® mooring lines is some 7 mm thick the inner strength members will not beexposed to direct sunlight under normal conditions.Thus no strength degradation is foreseen.

To what extent the seawater filters the UV light is notevaluated.

Effect of particle ingressThere is a relative high risk of sand and mud gettingin the rope if it accidentally is dropped on the seabedduring installation. Alone these particles have little tono effect; however in combination with cyclic loadingparticles will abrade the fibres. This will affect thestrength and can considerably shorten the life of therope as fibres abrasion progresses.


30

Yarn On Yarn Abrasion

1

10

100

1000

10000

100000

0 5 10 15 20tension (mN/tex)

conv. finish

Improved finish


33

quence on the rope strength. If that core is splicedinto another core, then this second core may slip as aresult of the damage to the first core. Thus this sec-ond core also no longer bears load. This way slippagemay migrate through the rope causing imbalancesbetween the subropes, resulting in a severe reductionin overall rope strength. This problem is overcome bysplicing every single sub-rope back into itself. Nowthe rope is more damage tolerant; if a subrope isdamaged, then only that part is affected. Damageassessment can focus on that section, overall integrityis not affected.

For DeepRope® mooring lines every subrope isspliced into itself, making the design more damagetolerant, for this purpose every sub-rope has a specialmarker tape allowing easy identification (see photo).Also the technique has been developed to splice withminimal tools. This allows splicing on site, requiringonly a few tools and a clean, dry workspace. With themore accurate splicing technique variation hasreduced, giving a higher reproducibility in strengthand stiffness when the ropes are used.

To further improve the life of the splice the eye andthe splice are protected using DeltaWeb plus a 2-com-ponent polyurethane.

Detailed installation procedures for mounting thethimble in the eye are available on request.

Shipment & StorageTypically the DeepRope® Polyester are shipped on areel. Only short lengths are shipped in a box.


32

Construction The DeepRope® line for mooring applications is a so-called parallel core construction. This constructionconsists of three parts, namely the core elements,sand and mud barrier and the cover (see figure).

The core elements are three-strand ropes that are ori-ented parallel to the longitudinal axis of the rope.The three-strand core design is used because of itsstrength efficiency and splice ability.

Depending on the installation procedure there maybe a potential risk that the rope is dropped on theseabed. Although this in itself has no effect on therope it is possible that seabed particles may diffuseinto the rope. These particles will have a deteriorat-ing effect on the strength over the life of the ropedue to their abrasive nature. To avoid this a filtermaterial is inserted between the cover and the core.Initially operators required the filter to stop particlesof 20 µm or bigger and a filter was approved for thatpurpose. However requirements have gone down toparticles of 5 µm. For this a new filter material hasbeen approved that exceeds the requirements and fil-ters down to 2 µm.

Typically the cover will be some seven millimetresthick. A standard marking will be included in thecover. For special applications alternative materialsand different thickness are also possible.Here the manufacturing process of DeepRope® isshown.

TerminationsThe DeepRope® Polyester line has a splice plus roundthimble as standard termination. The splice proce-dure used here has been specially developed for theseapplications. Operators and certifying authoritieshave raised a concern for the parallel-strand design:by random splicing of the sub-ropes the consequenceof a single core damage can have catastrophic conse-


sand barrier

strength membersouter cover

spool

whipping twine


35


34

Deeprope® features


MaterialConstructionColour of RopeSpecific GravityMelting PointAbrasion ResistanceU.V. resistanceTemperature resistanceChemical resistanceWater absorption/ FibresWater uptakeDry & wet conditions

PolyesterLoad-bearing cores with a protective cover of polyesterWhite with marker yarns1,38251° CExcellent Excellent Workable in sub-zero temperatures Good< 0,05% ± 30 %Resistant to corrosion and seawater; can be stowed wet


Material: Acordis Polyester 855TNMinimum Breaking Load in spliced condition Total weight is in air: Submerged weight is in seawater (_ = 1,05 kg/l)conform ISO (@1- 2% MBL) conform PetroBras spec. (@20% MBL)

Modulus based on type approval tests for BV and PetroBras:1 cycling between 10-30% MBL, 2 cycling between 20-30%MBL, 3 cycling between 40-50% MBL

37


36

DeepRope® Polyester strength tableMaterial: Acordis Polyester 855TNMinimum Breaking Load in spliced condition Total weight is in air: Submerged weight is in seawater (_ = 1,05 kg/l)conform ISO (@1- 2% MBL) conform PetroBras spec. (@20% MBL)

Dynamic Modulus based on type approval tests for BV andPetroBras: 1 cycling between 10-30% MBL, 2 cyclingbetween 20-30% MBL, 3 cycling between 40-50% MBL


Diam

mm

113117126130133

137141144147151

154157160163166

169172175177180

183185188190193

195198200203205

207210212214221

227233239245

tf

380414467518552

587621656690725

759794828863897

932966

100110351070

11041139117312081242

12771311134613801415

14491484151815531656

1760186319672070

kN

37234061473850775415

57546092643067697107

74467784812384618800

9138947698151015310492

1083011169115071184612184

1252212861131991353813876

1421514553148921523016245

1726118276192920307

MBL

@2% MBL

8,809,4910,911,512,2

12,913,614,214,915,6

16,216,917,518,218,9

19,520,220,821,522,1

22,823,424,124,725,4

26,026,727,328,028,6

29,229,930,531,233,1

35,036,938,840,7

@20%MBL

8,248,8810,210,811,4

12,012,713,313,914,5

15,115,816,417,017,6

18,218,819,420,020,6

21,221,822,423,023,6

24,224,825,426,026,6

27,227,828,429,030,8

32,634,436,137,9

@2%MBL

2,112,272,602,762,92

3,083,243,403,563,72

3,884,044,194,354,51

4,674,824,985,135,29

5,455,605,765,916,07

6,226,386,536,696,84

6,997,157,307,457,91

8,378,839,299,74

@20%MBL

37234061473850775415

57546092643067697107

74467784812384618800

9138947698151015310492

1083011169115071184612184

1252212861131991353813876

1421514553148921523016245

1726118276192920307

EA1

7,19E+047,84E+049,15E+049,80E+041,05E+05

1,11E+051,18E+051,24E+051,31E+051,37E+05

1,44E+051,50E+051,57E+051,63E+051,70E+05

1,76E+051,83E+051,89E+051,96E+052,03E+05

2,09E+052,16E+052,22E+052,29E+052,35E+05

2,42E+052,48E+052,55E+052,61E+052,68E+05

2,74E+052,81E+052,87E+052,94E+053,14E+05

3,33E+053,53E+053,72E+053,92E+05

EA2

8,43E+049,20E+041,07E+051,15E+051,23E+05

1,30E+051,38E+051,46E+051,53E+051,61E+05

1,69E+051,76E+051,84E+051,92E+051,99E+05

2,07E+052,15E+052,22E+052,30E+052,38E+05

2,45E+052,53E+052,61E+052,68E+052,76E+05

2,84E+052,91E+052,99E+053,07E+053,14E+05

3,22E+053,29E+053,37E+053,45E+053,68E+05

3,91E+054,14E+054,37E+054,60E+05

EA3

1,10E+051,20E+051,40E+051,50E+051,60E+05

1,70E+051,80E+051,90E+052,00E+052,10E+05

2,20E+052,30E+052,40E+052,49E+052,59E+05

2,69E+052,79E+052,89E+052,99E+053,09E+05

3,19E+053,29E+053,39E+053,49E+053,59E+05

3,69E+053,79E+053,89E+053,99E+054,09E+05

4,19E+054,29E+054,39E+054,49E+054,79E+05

5,09E+055,39E+055,69E+055,99E+05

Total weight [kg/m] Submerged weight Stiffness [kN] Diam

inch

4,454,624,955,105,25

5,405,545,675,805,93

6,066,186,316,426,54

6,656,776,886,987,09

7,197,307,407,507,60

7,697,797,887,988,07

8,168,258,348,438,68

8,939,189,419,64

tf

380414467518552

587621656690725

759794828863897

932966100110351070

11041139117312081242

12771311134613801415

14491484151815531656

1760186319672070

kips

837913103011411217

12931369144515211597

16731749182519011978

20542130220622822358

24342510258626622738

28142890296630423118

31943271334734233651

3879410743354563

MBL

@2% MBL

5,926,387,307,758,21

8,669,119,5610,0110,45

10,9011,3411,7912,2312,67

13,1113,5513,9914,4314,87

15,3015,7416,1816,6117,05

17,4817,9218,3518,7919,22

19,6520,0820,5120,9522,24

23,5324,8126,1027,38

@20%MBL

5,545,976,827,257,67

8,098,518,929,349,76

10,1710,5811,0011,4111,82

12,2312,6413,0513,4513,86

14,2714,6715,0815,4815,89

16,2916,6917,1017,5017,90

18,3018,7119,1119,5120,71

21,9023,1024,2925,48

@2%MBL

1,411,531,741,851,96

2,072,182,292,392,50

2,612,712,822,923,03

3,143,243,353,453,56

3,663,763,873,974,08

4,184,284,394,494,60

4,704,804,915,015,32

5,635,936,246,55

@20%MBL

1,321,431,631,731,83

1,932,032,132,232,33

2,432,532,632,732,83

2,923,023,123,223,31

3,413,513,613,703,80

3,903,994,094,184,28

4,384,474,574,664,95

5,245,525,816,09

EA1

1,62E+041,76E+042,06E+042,20E+042,35E+04

2,50E+042,64E+042,79E+042,94E+043,08E+04

3,23E+043,38E+043,52E+043,67E+043,82E+04

3,96E+044,11E+044,26E+044,41E+044,55E+04

4,70E+044,85E+044,99E+045,14E+045,29E+04

5,43E+045,58E+045,73E+045,87E+046,02E+04

6,17E+046,31E+046,46E+046,61E+047,05E+04

7,49E+047,93E+048,37E+048,81E+04

EA2

1,89E+042,07E+042,41E+042,58E+042,76E+04

2,93E+043,10E+043,27E+043,44E+043,62E+04

3,79E+043,96E+044,13E+044,31E+044,48E+04

4,65E+044,82E+044,99E+045,17E+045,34E+04

5,51E+045,68E+045,85E+046,03E+046,20E+04

6,37E+046,54E+046,72E+046,89E+047,06E+04

7,23E+047,40E+047,58E+047,75E+048,27E+04

8,78E+049,30E+049,82E+041,03E+05

EA3

2,47E+042,69E+043,14E+043,36E+043,59E+04

3,81E+044,04E+044,26E+044,49E+044,71E+04

4,93E+045,16E+045,38E+045,61E+045,83E+04

6,06E+046,28E+046,50E+046,73E+046,95E+04

7,18E+047,40E+047,62E+047,85E+048,07E+04

8,30E+048,52E+048,75E+048,97E+049,19E+04

9,42E+049,64E+049,87E+041,01E+051,08E+05

1,14E+051,21E+051,28E+051,35E+05

Total weight [lb/ft] Submerged weight Stiffness [kips]

Deeprope® Polyester strength table (ASTM)


39

CreepCreep is defined as the non-recoverable plastic defor-mation of the fibre. In ropes creep has two importanteffects. Firstly, as individual fibres creep under ten-sion loads will equalise between the different yarns,thereby optimising rope strength. Secondly, as dis-cussed below creep can be used to estimate the safeworking life of a rope. Because creep is strongly influ-enced by load and temperature, high, continuousloads should be considered for a first estimate of thecreep behaviour. Special grades for mooring lines areavailable, that have a lower creep.For a detailed estimate consult our technical staff.

Wear and tearDyneema® has very high abrasion resistance com-pared with other synthetic fibres, as can be seen inthis table. Both the cut resistance and the wet abra-sion resistance are excellent, which makes Dyneema®very suitable for marine applications. However, anysynthetic fibre in direct contact with unpolished orcorroded steel can be damaged. Thus it is recom-mended that smooth, clean contact points should beused. A non-load bearing nylon jacket braid has beenused to provide additional abrasion protection forthe strength member cores.

UV ResistanceThe UV Resistance of Dyneema is excellent and nor-mally no special protection against UV is necessary. Asdiscussed with the UV Resistance for the DeepRope®Polyester (page 25), here the cover also provides addi-tional protection.

Deeprope® Dyneema® lines

The DeepRope® Dyneema® line for mooring applica-tions is also a parallel core construction. It consists oftwo parts, namely core elements and the cover (seefigure). Unlike for polyester lines, here a differentcover is used, namely based on our BexcolineComposite fibre. Also here the Dyneema fibre andthe three-strand core determine the general charac-teristics, like elongation, elasticity and fatigue.In the next chapter the specification of the rope willbe discussed.

Load-elongation DeepRope® Dyneema ropes in new condition typical-ly have a higher elongation than when they are used.Here the elongation is shown when the rope isloaded a first time (3-4% elongation @ 50% MBL) andthe elongation when the rope is broken in (after 10cycles to 50% MBL, conform ISO).

Tension-Tension fatigueThe fatigue resistance of Dyneema is excellent, asshown in this figure. Especially at high loads (i.e.shock loading) the number of cycles to failure is rea-sonable to good. This makes DeepRope® Dyneema®

ropes very suitable for dynamic applications. Alsobecause of the low fibre to fibre friction little to nointernal abrasion occurs. Thus under fatigue loadingthe breaking strength does not deteriorate until therope is close to failure.

Bending-Bending fatigueThe figure shows the results of tests carried out atStuttgart University on Dyneema ropes, wire ropesand Aramid ropes. From these tests it can be seen thatthe bending fatigue of Dyneema is as good as, or bet-ter than, steel wire rope. The standard DeepRope® line design normally willhave a lower bending fatigue, although local bend-ing will not have a strong effect. If the bendingfatigue is critical modified designs are recommended.


38

Yarn type

DyneemaBexcoline Comp.Polyester Nylon PP Aramid

Dry

++ ++ ++ +++ + +

Wet

++++++ ++ + 0-

Cutresistance

+++ ++ ++ ++ + +++

Abrasion resistance

DeepRope�

Dyneema

0

20

40

60

80

100

0 1 2 3 4 5elongation [%]

first load

return

used

% M

BL

TensionFatigue

100

1000

10000

100000

1000000

20% 40% 60% 80% 100%peak load (% of MBL)

Dyneema PET aramid nylon wire

cycl

es to

faill

ure

Bending Fatigue

100

1000

10000

100000

1000000

0% 20% 40% 60%peak load (% of MBL)

Dyneema PET aramid wire

cycl

es to

faill

ure


40

Because of it's low weight and small diameter aDeepRope® Dyneema® line can be transported with-out special measures. In most cases length is dictat-ed by the use and not by shipping limitations.

TerminationsThe DeepRope® Dyneema® line typically has a spliceplus thimble as termination. The splice procedureused here has been especially developed for theseapplications. Operators and certifying authoritieshave raised a concern for the parallel-strand design:by random splicing of the sub-ropes the conse-quence of a single core damage can have cata-strophic consequence on the rope strength. If thatcore is spliced into another core, then this secondcore may slip as a result of the damage to the firstcore. Thus this second core also no longer bearsload. This way slippage may migrate through therope causing imbalances between the subropes,resulting in a severe reduction in overall ropestrength and all as a result of a single core failing.This problem is overcome by splicing every singlesub-rope back into itself. Now the rope is moredamage tolerant; if a subrope is damaged, thenonly that part is affected. Damage assessment canfocus on that section, overall integrity need not beconsidered.

For DeepRope® mooring lines every subrope isspliced into itself, making the design more damagetolerant. Also the technique has been developed tosplice with minimal tools. This allows splicing onsite, requiring only a few tools and a clean, dryworkspace. With the more accurate splicing tech-nique variation has reduced, giving a higher repro-ducibility when the ropes are tested. The main dif-ference between a polyester and Dyneema® spliceit the low friction of the Dyneema® fibre. To com-pensate for this, special coatings in the splice andmore tucks are used.

41


Bexcoline Composite FibreBexcoline is a composite fibre with polyester asstrength member, with excellent fatigue characteris-tics and abrasion resistance. The fatigue life is compa-rable to pure polyester, but the weight for a givenstrength is comparable to that of nylon. The behav-iour of the rope is not influenced by water, thus wetand dry strength are identical. Because of materialand its life cycle under normal use its most importantapplication is a cost-effective solution for SPMHawsers.

Here the Bexcoline Compostite fibre is used for thecover. It has a lower friction than polyester, thus lessfriction is generated on bollards and capstans. Alsothe cover is less likely to catch. Also the abrasion inthe YOY test (ASTM 6611-00) is comparable. For thisdesign a Marine Finish is applied to further improvethe abrasion resistance.

ConstructionThe DeepRope® line for mooring applications is a so-called parallel core construction. This constructionconsists of two parts, namely the core elements andthe cover (see figure).

The core elements are three-strand ropes that areoriented parallel to the longitudinal axis of therope. The cover is a Bexcoline Composite braid thatprovides dimensional stability to the rope structureand protects the cores from external damage. It istreated with a Marine Finish to further enhance thelife of the cover under abrasion loads. The coverbraid does not contribute to the strength of therope. The three-strand core design is used becauseof the good stretch characteristics and excellentsplice strength efficiency exhibited by this type ofcore design.


Yarn-on-Yarn Abrasion

10

100

1000

10000

100000

0% 2% 4% 6%

Applied Tension (N/ tex)

MarineFinishstandardcy

cles

to f

aill

ure

Tubular thimble

K2B thimble for deepwater mooring


43

Deeprope® Dyneema® linesDeeprope® Dyneema® lines

42

Deeprope® features

To further improve the life of the splice the eye andthe splice are protected using DeltaWeb® plus a 2-component polyurethane.

The end termination may also consist of a standardremovable spool (as for the polyester). However,because handling is very important for this type ofmooring line typically an alternate termination isused, such as: • Tubular thimble for use with a standard shackle• K2B Thimble for use with standard Kenter Shackle

Shipment & StorageTypically the DeepRope® Dyneema® lines areshipped on a reel, see also page 41. Only short lengthsare shipped in a box

MaterialConstructionColour of RopeSpecific GravityMelting PointAbrasion ResistanceU.V. resistanceTemperature resistanceChemical resistanceWater absorption/ FibresWater uptakeDry & wet conditionsRange of use

High Modulus PolyEthyleneload-bearing cores with a protective cover of composite yarn (other covers on request)White (other colours on request)0,975 floating145° C Excellent GoodMediumExcellent< 0,05% n.a.Strength & fatigue do not change in waterOff-shore installation, mooring


45

Deeprope® Dyneema® linesDeeprope® Dyneema® lines

44

DeepRope® Dyneema® mooring line; Strength table

All measurements conform ISO

Dia

mm

81879398

103

108113117121125

129133137140144

147150154157160

163166169171174

177180182185187

tf

372447521596670

745819894968

1043

11171191126613401415

14891564163817131787

18621936201120852159

22342308238324572532

kN

36494379510858386568

7298802787579487

10217

1094611676124061313613865

1459515325160551678417514

1824418974197032043321163

2189322622233522408224812

Weight

kg/m

3,303,834,344,855,35

5,856,346,837,327,80

8,288,769,249,7210,2

10,711,111,612,112,5

13,013,513,914,414,9

15,315,816,316,717,2

EA [tf]

2,07E+042,48E+042,89E+043,31E+043,72E+04

4,13E+044,55E+044,96E+045,37E+045,79E+04

6,20E+046,61E+047,03E+047,44E+047,85E+04

8,27E+048,68E+049,09E+049,51E+049,92E+04

1,03E+051,07E+051,12E+051,16E+051,20E+05

1,24E+051,28E+051,32E+051,36E+051,41E+05

EA [kN]

2,03E+052,43E+052,84E+053,24E+053,65E+05

4,05E+054,46E+054,87E+055,27E+055,68E+05

6,08E+056,49E+056,89E+057,30E+057,70E+05

8,11E+058,51E+058,92E+059,32E+059,73E+05

1,01E+061,05E+061,09E+061,14E+061,18E+06

1,22E+061,26E+061,30E+061,34E+061,38E+06

Min Break Load Stiffness

Dyneema® DeepRope® Strength table (ASTM)

Dia

inch

3,173,423,653,864,07

4,264,444,614,774,93

5,095,245,385,525,66

5,795,926,056,176,29

6,416,526,646,756,86

6,977,077,187,28

7

tf

372447521596670

745819894968

1043

11171191126613401415

14891564163817131787

18621936201120852159

22342308238324572532

kips

821985

114913131477

16421806197021342298

24622627279129553119

32833447361237763940

41044268443245974761

49255089525354175582

Weight

[lb/ft]

2,222,572,923,263,59

3,934,264,594,925,24

5,565,896,216,536,85

7,167,487,808,118,43

8,749,059,379,689,99

10,310,610,911,211,5

EA [tf]

2,07E+042,48E+042,89E+043,31E+043,72E+04

4,13E+044,55E+044,96E+045,37E+045,79E+04

6,20E+046,61E+047,03E+047,44E+047,85E+04

8,27E+048,68E+049,09E+049,51E+049,92E+04

1,03E+051,07E+051,12E+051,16E+051,20E+05

1,24E+051,28E+051,32E+051,36E+051,41E+05

EA [kips]

4,56E+045,47E+046,38E+047,29E+048,20E+04

9,11E+041,00E+051,09E+051,18E+051,28E+05

1,37E+051,46E+051,55E+051,64E+051,73E+05

1,82E+051,91E+052,00E+052,10E+052,19E+05

2,28E+052,37E+052,46E+052,55E+052,64E+05

2,73E+052,82E+052,92E+053,01E+053,10E+05

Min Break Load Stiffness


47

Hardware

46

GN ThimbleThis thimble is an improvement of the standardthimble plus shackle from the previous paragraph.It has the same basic geometry on the rope side,however now a pin can be inserted for easy connec-tion to a link. This simplifies handling considerably.

K2B Thimble with or without linkThis shackle is mostly used for direct connection to aStandard or Kenter shackle. Basically the rope is laid ina U-groove, that has been bent. The K2B allows forquick and easy connections. It gives no protection if therope is dragged over the deck of a vessel.

Tubular Thimble with or without linkThis thimble is widely used for SPM Hawsers. Here therope is put in a bent tube. It gives excellent protectionand can be easily connected to a shackle.

Cast ThimbleThis thimble is used for SPM Hawsers. It is very durableand gives excellent protection. Also it allows inspectionof the eye. It can be easily connected to a shackle.

Bell mouth thimbleThis thimble allows changing out the rope, whilst keep-ing the thimble. For SPM Hawsers this termination istypically used if it can be exchanged easily.

See termination table on page 50.

Hardware

Standard terminationsThe DeepRope® line has a splice plus a round thim-ble as standard termination. To further improve thelife of the splice the eye and the splice are protect-ed us ing De l taWeb p lus a 2 - componentpolyurethane.

The removable spools should be inserted in the eyeduring installation. The two legs of the eye shouldbe compressed together with the whipping twineto hold the spool in place (see figure). In addition,the spool should be secured in place with a twinewhich passes through a special hole in the flange ofthe spool and around the line.

Here the termination design is given for polyesterropes. Alternative terminations are also availableboth for polyester and Dyneema®, see also page 38.

Alternative TerminationsThe standard termination for DeepRope® Polyestermooring lines has been optimised for maximumlife. The round thimble gives an optimal contactpressure on the rope in the eye. If installed correct-ly, there are no sharp edges for the rope to chafeagainst. However it is also a relative heavy design.

Many alternative thimble designs are available thatare easier to handle or better lock the rope in posi-tion. Here a short overview is given of possible eyeterminations. The splice itself is identical; all sub-ropes are spliced back into themselves.

Winw

Hin

wDinw

winw

R

spool

whipping twine

≤≤


49

Hardware

48

Unprotected ropes can lose strength in outer coverfibres caused by U.V. degradation. Under normal con-ditions of use this will not influence the performanceof the rope. However, it may affect the abrasion resis-tance of the cover.A visual inspection of the splice and the cover isalways recommended when retrieving the rope fromstorage. When in doubt BEXCOropes should be con-tacted.

TemperatureA Polyester Deeprope should not be exposed toextreme heat the storage temperature should be lessthan 80°C continuously or peak temperatures of100°C over a period of 5 years.

A Dyneema Deeprope should not be exposed toextreme heat the storage temperature should be lessthan 40°C continuously or peak temperatures of 60°Cover a period of 5 years.

ChemicalsSeawater chemicals and pollutants in normal concen-trations are not known to adversely affect Deepropelines, both Polyester and Dyneema. Bases and sol-vents may have a mild effect.

Note: Never store base chemicals or solvents closeto the DeepRope line. Base chemicals and solventscan degrade the rope.

Biological attackNo effects are known to be significant on syntheticDeepRope lines.

MoistureNo effect on Deeprope lines in function of time.

ReelsDeepRope mooring lines are spooled on steel reels. Seesketch.

PackagingThe mooring line is connected to the reel using a smallsynthetic forerunner. As a first protection a polyethyl-ene foil is wrapped around the rope. Then a protectivesheet with a high compressive strength is wrappedaround the rope. Lastly a second PE foil is wrappedaround the rope onto the flange; this keeps the ropesafe from dirt or rain. See also sketch and photos.

ShippingOnly trained and experienced personnel should han-dle the steel reels. A special lifting beam is providedwith the reels, with the Safe Working Load (SWL)indicated on the beam.

The reel should be connected to the beam with spe-cial wires and a shackle, matching the SWL. See sideview and photos.

The SWL should not be exceeded, or the wires riggeddifferently than indicated here. Before lifting the rig-ging should be inspected to ensure that wires can notslip loose. Lifting should be done controlled; the reelshould never be dropped. The (un)loading surfaceshould be even, otherwise the reel may roll once thebeam is lowered. Any motion should be blockedusing kegs or similar devices. The reel should not berestrained manually.

StorageStorage of the ropes should be done with the utmostcare. A Deeprope line should be stored in closed pack-aging. Well-protected ropes will not lose strengthduring storage. Unprotected rope parts may beaffected by exposure to direct sunlight as this causesU.V. degradation.

Hardware

PE foil

protective sheet

PE foil

rope

steel strap

mutiplex sheet

flange


Reel design and dimensions

There are various reel designs available, depending on theinstallation requirements. Here a typical design and its dimen-sions are shown. For other designs please contact our staff.

51

HardwareHardware

50

Thimble and shackle table (Polyester)

Rope

diamm

113117126130133

137141144147151

154157160163166

169172175177180

183185188190193

195198200203205

Rope

MBLtf

367400467500533

567600633667700

733767800833867

900933967

10001033

10671100113311671200

12331267130013331367

Dtotmm

441456491507519

534550562573589

601612624636647

659671683690702

714722733741753

761772780792800

Dinwmm

283293315325333

343353360368378

385393400408415

423430438443450

458463470475483

488495500508513

wtotmm

191196208213216

221226230234239

243246250254258

261265269271275

279281285288291

294298300304306

winwmm

141146158163166

171176180184189

193196200204208

211215219221225

229231235238241

244248250254256

W totmm

403416443455464

476488498507519

528537546555564

574583592598607

616622631637646

653662668677683

Winwmm

201206218223226

231236240244249

253256260264268

271275279281285

289291295298301

304308310314316

Hinwmm

541556591607619

634650662673689

701712724736747

759771783790802

814822833841853

861872880892900

Thimble Shackle Flange DiameterCore diameter (cm)Inner width (cm)

Weight incl. PES Rope (mt)

Rope dia (mm)

113117126130133

137141144147151

154157160163166

169175180185190

195200205210214

221227233239245

350102150

10,4

931868749703672

633598573550521

501482464447431

416388367347329

313297283270260

243231219208198

350102200

13,3

1.2411.158998938896

845797764734695

668643619597575

555518489463439

417396377359346

325308292277264

350102250

16,1

1.5521.4471.2481.1721.120

1.056997956917869

835804774746719

694647612579549

521495471449433

406385365347330

350102300

19,0

1.8621.7371.4981.4071.344

1.2671.1961.1471.1001.043

1.003965929895863

832776734695659

625594566539519

487461438416396

350102350

21,9

2.1722.0261.7471.6411.568

1.4781.3951.3381.2841.217

1.1701.1251.0841.0441.007

971906856810768

729693660629606

568538511486462

350102400

24,7

2.4832.3161.9971.8761.792

1.6891.5951.5291.4671.390

1.3371.2861.2381.1931.150

1.1101.035978926878

834793754719692

649615584555528

350102450

27,5

2.7932.6052.2462.1102.016

1.9001.7941.7201.6501.564

1.5041.4471.3931.3421.294

1.2491.1651.1011.042988

938892849809779

730692657624594

350102480

29,1

2.9792.7792.3962.2512.151

2.0271.9131.8351.7601.668

1.6041.5431.4861.4321.381

1.3321.2421.1741.1121.054

1.000951905863831

779738701666634

m rope/reel


53

Future developmentsFuture developments

52

ner. By using multiple optical fibres two things areachieved. Firstly the system has built-in redundancy,ensuring that even if one of the optical fibres is dam-aged signal can still be measured. Secondly the fibrescan be configured to have a different gain, optimis-ing measurements over a wide range of elongations.

ResultsA scaled-down polyester DeepWater mooring linewith variable strength along its length has been mon-itored by a purpose designed, built-in optical fibrestrain transducer incorporating standard, unmodifiedoptical fibre. Brillouin analysis of the transducer sig-nal has been used to unambiguously identify theweaker and stronger zones of the rope in a blind test,by determination of local fibre strain. Resolution ofthe technique used was around 2 metres, but this canbe improved with next generation equipment. In thegraph the strain of three different fibres is shown,each with a different gain. A, B, C represent the fibresof different gain all simultaneously measured. In eachof the readings A, B and C from the three fibres, thevalley between the two adjacent peaks clearly identi-fies the location of low strain, and this correspondsvery well with the location of local strengthening.

The partners in the OSCAR project- Selantic- TTI- BexcoRopes- University of Strathclyde- BPP Technical Services Ltd.

OSCAR (Optical SCanning Apparatus for Rope)

Deepwater mooring Ropes are intended to be in ser-vice for long periods, up to twenty-five years. Oversuch a period all kinds of unforeseen events, likeoverloading, particle ingress, combination of fatigueand abrasion damage and others can influence ropesproperties. To date no practical Non-Destructive Testtechniques (NDT) have been developed for polyesterlines. Visual inspection of the rope, for example witha ROV, will only show external damage. However,ropes can fail from various causes that can not bedetected in a visual inspection of the exterior of therope. To monitor property changes of the mooringsystem test legs must be inserted and removed at spe-cific intervals for testing. This is expensive and time-consuming.

In the OSCAR project a first NDT method has beendeveloped for ropes. It works by measuring localchanges in tensile properties for a long length ofrope. The basis for this NDT method is the assumptionthat a change in rope properties will be accompaniedby a change in modulus. Consequently local strain willvary along the length of a rope. If this local strain dis-tribution can be measured, it is possible to identifythe location of local modulus changes.

BrillouinStrain may be determined continuously along thelength of a single mode optical fibre by utilising thestrain dependence of the Brillouin gain coefficient.This method allows local strain measurements overlong ranges of optical fibre.

A special transducer cable has been developed incor-porating multiple optical fibres for strain sensing. Themechanical design of the cable ensures that it will fol-low the elongation of the rope with strain beingtransferred to the optical fibre in a controlled man-


55

Installation of the Deeprope® lineInstallation of the Deeprope® line

54

The cover is designed to withstand normal handlingbut not the heavy shearing forces that could resultfrom using a stopper chain. Thus stopper chain orother types of choking devices should not be used.

This also applies to the use of the forkstopper.Typically a few chain links are used between thePolyester and the rest of the system, these links aremeant to stop the line. The stopper should not beused on the line itself.

Do not drag the rope along the deck. If this isunavoidable ensure that the rope passes clear ofsharp edges or rough surfaces to prevent snagging ortearing of the cover braid. The rope should not comeinto contact with any abrasive surfaces such as welds,rust, etc. All potential contact surfaces on the vesselshould be checked prior to the installation process toensure that there are no areas that may damage therope. All rolling surfaces should be free-turning andsmooth. If damage to the cover occurs, it should berepaired as described elsewhere in this manual priorto proceeding with the installation.

When deploying each section over the stern, the eyesof the rope should be kept in the horizontal plane toavoid damaging the rope and spool on the sternroller. The fleet angle between the installation winchand the stern of the vessel should be kept to a mini-mum to avoid side contact between the rope and theflanges of the winch. Otherwise the rope is liable tochafe against the sides.

Typically the terminations for DeepRope® Polyesterlines are roll thimbles. These are shipped separatelyand mounted during installation. They are fixed tothe splice by a seizing; a separate installation proce-dure is available. For Dyneema® alternate termina-tions are used (e.g. K2B).

Synthetic ropes are fundamentally different fromsteel wire ropes in many aspects. In the following sec-tions the main influences on the installation of theselines are discussed.

TransportTransportation of the ropes should be done with theutmost care. General recommendations for storageshould be adhered also during transport (see page 40).The reels should not be allowed to shift position duringtransport. Depending on the weight of the reel plusrope either slings or a lifting beam should be used, seesketch.

InstallationHere the main influences on the installation of theselines are discussed. These are by no means complete,detailed installation procedures can only be made in co-operation with the installation crew. It is recommended that the lines are installed from awinch. To prevent burying of the ropes on the winchthey should always be spooled with a minimum ten-sion. As a guideline the spooling tension should beequal to or higher than the weight of the hardware onthe bottom end of the mooring line. This is especiallyimportant when the ropes are new, because they willstill have their constructional elongation. Thus it is rec-ommended to use a bollard or capstan to tension therope as it is spooled.

Synthetic stoppers should be utilised if the spools haveto be inserted during the rope installation process.These stoppers should only be used to secure the ropewhile disconnecting from the winch and during inser-tion of the spool, see also sketch. The lashing at the footof the splice has been strengthened to take normalinstallation loads and the sling should be mountedbehind it as shown here. Other connections (shackles,chain) should only be attached to the spools. After thisthe stopper should be removed.

max 2 tf

synthetic sling

fork stopper

rope withround thimble

shackle

3 chain links


57

Installation of the Deeprope® lineInstallation of the Deeprope® line

56

Abrasion resistanceThe cover of this rope has not been designed to with-stand excessive external abrasion, caused by burrsand grooves in older fairleads. Thus it is recommend-ed to use smooth, clean fairleads, bitts, etc. duringinstallation. If abrasion does occur initially the coverbecomes fuzzy and if measures are not taken imme-diately the fibres in the cover will fail. This exposesthe inner cores and they, in turn, will also start toabrade. As a result the breaking strength will reduce. Upon request special epoxy coatings are available tosmoothen damaged fairleads for synthetics.

Temperature resistanceThe melting temperature of Polyester is ± 250°C,although, under prolonged exposure, the mechanicalproperties start to change above 100°C. It is impor-tant to keep a Polyester rope away from any heatsource like an open fire, exhaust pipes, welding, etc.Do not store these ropes in the vicinity of a boiler orheater or against bulkheads or on decks which mayreach high temperatures.

The melting temperature of HMPE (Dyneema®) is ±150°C, although, under prolonged exposure, themechanical properties start to change above 70°C. Itis important to keep a Dyneema® rope away fromany heat source like an open fire, exhaust pipes,welding, etc. Do not store these ropes in the vicinityof a boiler or heater or against bulkheads or on deckswhich may reach high temperatures.

Safe Working LoadTemporary systemsThe fatigue life of both Polyester and Dyneema® isbetter than that of wire ropes under normal loadingconditions. Depending on the certification rules acomparable safety factor can be used as for the othermooring components.

Permanent systemsBecause of the excellent fatigue life of Polyester,(compared to wire under normal loading conditions)a comparable or slightly higher safety factor is usedfor polyester than for the other mooring compo-nents. This is dependent on the certification rules.Here a limited, quick comparison is made.

Bending radiusThese ropes can be bent over relative small sheaves orguides under low tensions (less than 5% of the MBL).For the main part the minimum bend radius is equalto one and a half (1,5) times the rope diameter (orthree times the rope radius). This does not apply tothe terminations. For the terminations the size of the round spool andthe stiffness of the protective cover (impregnatedwith the orange, 2-component polyurethane) limitthe minimum bending radius. Here the typical bend-ing radius is six (6) times the rope diameter. These measures will reduce the risk of installationdamage, thus ensuring a very long service life.

Norm

API RP2SMABSBVDNV

S.F.

1.671.8221.82

Condition

Intact dynamicMax intact tensionAPI rules +20%Posmoor


59

Inspection criteriaInspection criteria

58

InspectionThe lifetime of a rope is strongly influenced by its con-struction, the environment it is used in and the typeof application. The inspection interval is dependenton the type of application.

The DeepRope® design uses a special splice, with theessential characteristic that individual sub-ropes arespliced back into themselves. As a consequence dam-age is only limited to the affected sub rope(s).

The residual breaking strength of the rope should bequantified using the procedures described below toobtain a clear view of the strength decay and life-time.

Discard criteriaThe following factors may warrant removing a ropefrom service:• wear and abrasion• friction burns• creep• crushing/pinching• local damageIf local damage is observed then a length of 50 timesthe diameter before and after that position should beclosely inspected and all reductions in strengthshould be added together.

Wear and AbrasionWear and abrasion are the most common causes ofrope failure. Rough surfaces, sharp edges, burrs, rustand dirt can cause serious damage to a rope. Winches,pulleys, chocks, bitts, etc. should be clean and in goodcondition. Wear and abrasion can occur over greater lengths orlocally. Particular attention should be paid to thesplice area and the eye. Frayed and broken yarns should be removed and thedamaged area should be estimated.

The decision to discard, repair or continue using aPolyester rope can never be taken on the grounds ofexact standards. For correct use of the criteria givenhere general knowledge of, and experience with,fibre ropes in general and Polyester ropes in particu-lar is essential. In case of doubt the rope manufactur-er should be consulted. Here only a rough guide ondamage and its assessment is given.

Damage to the mooring line is most likely to occurduring installation or maintenance of the mooringsystem. For permanent mooring lines damage can notbe accepted as the consequences on the safe workinglife over a period of twenty years are difficult to asses.Here one needs to decide whether a rope should bereplaced immediately or if the replacement can bescheduled.

For temporary moorings, for example drilling, somedamage can be accepted as repair or replacement canbe done off location. As a guideline the ResidualBreaking Strength of the damaged rope should notbe less than 75 % of the New Breaking Strength.However this should be agreed by all parties con-cerned. As previously mentioned, the cover braid ofthe mooring rope does not contribute to the rope'sstrength. Therefore, any damage that is confinedsolely to the cover will not cause a reduction instrength; however, the cover does play an importantrole in the overall integrity of the rope. Therefore,any damage to the cover should be addressed asquickly as possible. Even if damage appears to be lim-ited to the cover the rope should be inspected thor-oughly to ensure that the core strength membershave not been affected.To date an damage JIP is underway to establish anindustry acceptable standard for damage assessmentof deepwater mooring systems. Bexco is participatingin this JIP. Co-ordination is done by DnV. The method-ology presented there is an acceptable alternative.


61

Inspection criteriaInspection criteria

60

Pulled cover braid yarns or strandsIndividual yarns or strands can be caught behindobjects (nails, burrs, etc.) and be pulled out of therope. This damage makes the rope very unsafe,because the pulled yarns can easily snag behind anobject. Thus care should be taken to work the yarn orstrand back into the rope. If a cover yarn pull is toosevere the yarn can be cut and the ends worked backinto the rope. A pulled core yarn or strand should notbe cut. Rather, the pull should be buried back intothe interior of the rope.The number of pulled yarns or strands should becounted and noted in the inspection card. The causeshould be traced and alleviated.

Cut yarns or strandsIndividual yarns or strands can be cut through chafingagainst sharp objects (e.g. the side of a steel plate).The number of cut yarns or strands should be countedand the damaged area per strand estimated.

OthersNo attempt is made here to list a complete catalogueof discard criteria. Many different types of damage toa rope are possible. Thus common sense during inspec-tion to assess the Residual Strength is paramount.

Estimating residual strengthThe Breaking Strength of a rope is reduced by dam-age to the yarns. Through inspection the reduction instrength is estimated per damaged spot. All damagesover the inspected length of the rope should then beadded together. Only the damage on the three-strand cores should be evaluated.

The cover braid does not contribute to the strengthof the rope. On the basis of that total estimate the rope is down-graded or removed from service.

Friction BurnsFriction burns can occur over greater lengths or local-ly. Direct contact with hot objects should always beavoided (eg. exhaust pipes). Also when using the ropeon a winch, capstan, sheave, etc. care should be takento avoid surging the rope while it is under load. Whenthe rope slips a lot of heat can be generated throughfriction.When friction burns are detected, the rope should beopened and it should be estimated how much of therope is fused. The damaged area should be consid-ered to be about twice the fused area.

CreepFor polyester ropes creep does not play a role fordynamic applications.

Crushing/pinchingWhen a rope has been crushed or pinched it shouldbe removed from service. Typically with this type ofproblem the resulting damage in the rope is a combi-nation of broken/cut yarns and pulled yarns orstrands, the assessment of this type of damage isextremely difficult. Thus this gives very unreliableestimates of the resulting reduction in strength. Aknot has a similar effect.

Local DamageDepending on the extent of localised damage it maybe possible to repair the rope rather than remove itfrom service. Options include local repair plus down-grading or removal of the damaged section andresplicing. A second, independent evaluation by a competentperson (e.g. the ropemaker) is strongly recommendedbefore resplicing.


63

Repairing a braided cover

62

Extensive repairsFor extensive repairs the following tools are needed:Deltaweb, some sewing twine and a large sewingneedle. Optionally additional protection can beobtained by a two-component polyurethane.

Remove all the damaged yarns and inspect the rope.After inspection coat the free yarn ends with theglue, in order to prevent further unraveling of thecover. Wrap the damaged part in Deltaweb. Pleasenote that the sides should be folded back, see sketchand photo. Stitch the web together, with a specialknot that will prevent the stitching yarn from loosen-ing when it is torn.

Protect the beginning and the end of the Deltawebwith whipping. Start whipping at least three cen-timeters away from the edge, as shown in the draw-ing. Lay a loop of twine across the rope, leaving a freetail after the damage zone of about ten centimeters.This tail has to be grasped later, so avoid covering itcompletely.

With the working end of the twine, make multiplewraps around the rope from the tail end toward theapex of the loop, covering the loop until the whip-ping is at least three centimeters beyond the damage.

To finish the whipping, insert the working end of thetwine through the loop. Pull on the very end or tail ofthe twine until the loop slides completely out ofsight. Clip the ends close to the whipping.

Repairing a braided cover

When the cover is damaged we recommend inspec-tion of the inner strength member. If the innerstrength member is damaged then it may be neces-sary to downgrade the rope. The cause of the dam-age should be determined and if possible removed.

Depending on the extent of the damage either asmall repair or an extensive repair is recommended.

Small RepairsThe most durable method to make small repairs onthe jacket braid requires the use of nylon whippingtwine and polyurethane glue.

Remove all the damaged yarns and coat the free yarnends with the glue, in order to prevent further unrav-eling of the cover. Start whipping at least three cen-timeters away from the damage, as shown in thedrawing. Lay a loop of twine across the rope, leavinga free tail after the damage zone of about ten cen-timeters. This tail has to be grasped later, so avoidcovering it completely with whipping.With the working end of the twine, make multiplewraps around the rope from the tail end toward theapex of the loop, covering the loop until the whip-ping is at least three centimeters beyond the damage.

To finish the whipping, insert the working end of thesmall twine through the loop. Pull on the very end ortail of the small twine until the loop slides complete-ly out of sight. Clip the ends close to the whipping.

If necessary, a temporary cover repair can be madeusing high quality adhesive tapes such as vinyl electri-cal tape, etc. A more permanent repair, as describedabove, should replace the tape as soon as possible.


65

Quality assurance

64

TestingDuring production, sample tests will be carried out onyarns and strands and sub-ropes. An external survey-or will witness and certify all tests. Testing shall be inaccordance with Le Lis QA Procedures for these tests,see also flow chart.

Quality assuranceThe Group Bexco N.V. and his subsidiaries has a TotalQuality Management System (TQM) and is certifiedaccording to ISO 9001-2000.

A copy of the Quality Assurance Manual is availableon request.

Other sizes with official Type Approval: 400 mT, 450mT, 630 mT, 710 mT and 750 mtT.

Quality assurance


67

Textile unitsReference list offshore

66

StrengthWeightSpecific strength

StrengthWeightSpecific strengthDiameter

Example

RunnageYarn count

Conversion

Example

Textile units according to ISO:

Prefixes according to ISO:

Newton (N), kilogram (kgf)tex, dtex, denier (den), g/mN/tex, cN/dtex of g/den

kilo Newton (kN), ton (tf)g/m, kg/100mkN/ (g/m) of N/texmm, Size (=circumference in inches; size = diameter / 8)

A rope with a diameter of 48 mm = 48 / 8 = 6 inch circumference

meter / kilogram (m/kg)tex = gram / 1000 meterdtex =gram / 10 000 meterden = gram / 9000 meter

tex = 1 000 000 / runnagedtex = 0,1 tex = 10 000 000 / runnageden = 0,9 dtex = 9 000 000 / runnage

A yarn with a runnage of 420 m/kg has a yarn count of 1 000 000/ 420 = 2381 tex or 23810 dtex and this gives a denier of 21430 den.

Fibre: Newton & tex (dtex)Rope: Newton (kN) & kg/m

mili = 1/1000 ...deci = 1/10 1dtex = 1 decitex = 1 g /10 000 m = 0,1 texkilo = 1000 ...

Yarns

Rope

Units

ELF, FRANCEELF, FRANCE

COSALT, UKCOSALT, UKCOSALT, UKCOSALT, UK

FYNS KRAN, DENMARKFYNS KRAN, DENMARKFYNS KRAN, DENMARK

DREYFUS, FRANCE

KOS, NORWAY

SAGA, NORWAY

PETROBRAS, BRAZILPETROBRAS, BRAZILPETROBRAS, BRAZILPETROBRAS, BRAZIL

COFLEXIP STENA, UK

SBM, MONACO (Shell Bonga)

FMC Technologies (Enterprise Oil –Bijupirà & Salema)

SPECIAL VESSELSCONSUS LLC – BRAZIL

FRANKLIN OFFSHORE: SUPPLY & ENGINEERINGPTE LTD, SINGAPORE(TotalFinaElf)

SAIBOS, USA

1 x 500 m Polyester, DeepRope® mooring line, 500 Tf, (Congo)2 x 1450 m, 113 Tf, Deepwater Anchorline, Dyneema (HMPE, Angola)

4000 m one length Polyester rope, 30 Tf for pipe laying1000 m Polyester rope cable laying 26,4 Tf.1000 m Polyester rope cable laying 50,0 Tf.1000 m Dyneema rope cable laying 20,0 Tf.

10 x 2000 m Polyester rope cable laying 36,4 Tf.10 x 2000 m Polyester rope cable laying 52,5 Tf.25 x 1000 m Polyester rope cable laying 52,5 Tf.

20 x 1000 m Polyester rope cable laying 30 Tf

Dyneema ropes with special terminations, 90 Tf, for ROV use

1 x 500 m Polyester, DeepRope® mooring line, 500 Tf.

3 x 600 m Polyester, DeepRope® mooring lines, 1000 Tf, DW P36. 1 x 300 m Polyester, DeepRope® mooring line, 710 Tf.1 x 500 m, 1 x 600 m, 1 x 700 m, DeepRope® mooring lines, 1000 Tf. 2 x 200 m, 1 x 970 m Polyester, DeepRope® mooring lines, 710 Tf.

200 m Dyneema, 900 Tf for trenching plough 2 x 50 m Deltaflex stretcher.

6280 m Polyester, DeepRope® mooring lines, 400 Tf5028 m Polyester, DeepRope® mooring lines, 450 Tf

8235 m Polyester, DeepRope® mooring lines, 750 Tf

2 x 300 m Polyester, DeepRope® towing pennants, 431 Tf

9 x 610 m, Polyester, DeepRope® mooring lines, 425 Tf2 X 1220 M Polyester, DeepRope® mooring lines, 525 Tf

2 x 130 m Grommet Ultraline Nylon mooring hawser 515 Tf (Elf Canyon Express)


Schematic drawings of Deeprope®

68

Polyester Dyneema®

69

Schematic drawings of Deeprope®


Other conversions

71

Conversion tables

Conversion to and from ISO can be done using thetables on following pages. Please note that total cross-sectional surface of a yarn is a function not only of thematerial surface, but also of the packing factor. In theconversion only the material surface is considered.

The total surface can only be correlated to the mater-ial surface using experimental data, as this relation isinfluenced by construction and manufacturing.

Approximate densities g/cm3

Polypropylene 0.91Polyethylene 0.97Nylon 6 1.18Nylon 6.6 1.17Polyester 1.38Steel 7.8Polyaramide 1.44

Conversion: from A to BExample: 1 g/den = 0.883 cN/dtex

Conversion tables

70

A \ B

GPAN/m2

N/mm2

g/deng/tex

G/dtexN/tex

CN/texCN/dtexKgf/cm2

Ton/cm2

PSI

GPA

110-9

0.0010.0883x9.80x0-3x0.098x

0.01x0.1x

9.81x10-5

0.09816.90x10-6

N/m2

109

1106

8.83x10-9.80x106x9.80x10-

109x107x108x

981009.81x107

6900

N/mm2

103

10-6

188.3x9.8x98x

1000x10x100x

0.098198.1

0.0069

g/den

11.33/1.13x10-8/1.13x10-2/

10.1111.1111.33

0.11331.1331110/1.11/

7.82x10-5/

g/tex

102x-1

1.02x10-

0.102/9.01

1101021.0210.20.01/10/

7.04x10-

g/dtex

102x-1

1.02x10-

1.02x10-

0.9010.11

10.20.1021.02

0.001/1/_

7.04x10-

N/tex

-1

10-9/10-3/

8.83x10-2

9.80x10-3

9.80x10-2

10.010.1

9.81x10-5/0.0981/

6.90x10-6/

cN/tex

100x-1

10-7/0.1/8.830.9809.80100110

0.00981/9.81/

6.90x10-4/

cN/dtex

10x-1

10-8/0.01/0.883

0.09800.98100.11

9.81x10-4/0.981/

6.9x10-5/

kgf/cm2

1.02x104

1.02x10-5

10.2901x100x

1000x10 200x

102x1020x

11000

0.0704

ton/cm2

10.21.02x10-8

0.01020.901x0.1x

10.2x0.102x_1.02x0.001

17.04x10-5

PSI

1.45x105

1.45x10-4

1451.28x104x1420x

1.42x10-4x1.45x105x1450x_1.45x104x

14.201.42x104

1

Length Area

1 millimeter (mm) = 0.0394 in 1 sq cm (cm2) = 100 mm2) = 0.1550 in2

1 centimeter (cm) = 10 mm = 0.3937 in 1 sq meter (m2) = 10 000 cm2 = 1.1960 yd2

1 meter (m) = 100 cm = 1.0936 yd 1 hectare (ha) = 10 000 m2) = 2.4711 acres1 kilometer (km) = 1000 m = 0.6214 mile 1 sq km (km2) = 100 ha = 0.3861 mile2

1 inch (in) = 25.4 mm 1 sq inch (in2) = 645.16 mm2

1 foot (ft) = 12 in = 0.3048 m 1 sq yard (yd2) = 9ft2 = 0.8361 m2

1 yard (yd) = 3 ft = 0.9144 m 1 acre = 4840 yd2 = 4046.86 m2

1 mile = 1760 yd = 1.6093 km 1 sq mile (mile2) = 640 acres = 2.59 km2

Volume / capacity Mass (weight)

1 cu cm (cm3) = 0.0610 in3 1 gram (g) = 1000 mg = 0.0353 oz1 cu decimeter (dm3) = 1000 cm3 = 0.353 ft3 1 kilogram (kg) = 1000 g = 2.2046 lb1 cu meter (m3) = 1 dm3 = 1.3080 yd3 1 tonne (t) = 1000 kg = 1.1023 short tons1 liter (l) = 1 dm3 = 0.2642 US gal 1 tonne (t) = 1000 kg = 0.9842 long tons1 liter (l) = 1 dm3 = 0.2200 Imp gal 1 ounce (oz) = 437.5 grains = 28.350 g1 hectoliter (hl) = 100 l = 2.8378 US bu 1 pound (lb) = 16 oz = 0.4536 kg1 cu foot (ft3) = 0.0283 m3 1 short cwt = 100 lb = 45.359 kg1 cu yard (yd3) = 27 ft3 = 0.7646 m3 1 long cwt = 112 lb = 50.802 kg1 US dry pint = 0.9689 Imp pt = 0.5506 l 1 short ton = 2000 lb = 0.9072 t1 US bushel = 64 US dry pt = 35.239 l 1 long ton = 2240 lb = 1.0161 t1 US liquid pint = 0.8327 Imp pt = 0.4732 l1 US gallon = 8 US liquid pt = 3.7854 l


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