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25/11/2013 Techniek van het schip - 1stekan. N.W. - kapt. K. de Baere 1

Cables and ropes

Ships techniqueKapt. K. De Baere


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25/11/2013Techniek van het schip - 1stekan. N.W. - kapt. K. de Baere 2

Cables and ropes

1. Head lines

(amarre delavant)

2. Spring(garde

montante)3. Breast line

(traversire)


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Terminology

1. Working part Tambour actif

2. Storage part Tambour destockage

3. Warping head

la Poupe4. Gipsy - Barbotin


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Capstan


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Foredeck (gaillard) of atanker

1. Warping head Lapoupe

2. Drum Tambour

3. Bollard Bollard oubite damarrage

4. Eyes to connect thestoppers oeillet

pour attacher labosse


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Foredeck (gallaird) of atanker

5. Fairlead guideroller le guidage

6. Centre lead

lcubier de Panama

7. Leadway chaumard

8. Head line lignedavant

9. Foreward spring lagarde montante


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Roller fairlead chaumard rouleaux

Fairlead - Chaumard galoches

Panama chock cubier de Panama

Chaumard bittard rouleaux


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Chocks and fairleads

Panama chock androller fairlead Lcubier de Panama

et chaumard rouleaux


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Bollard

1. Guide roller guidage rouleau

2. Nose - nez3. Stopper eye

illet por labosse


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Cables and ropes

Springs (gardesmontantes)

Stored on a whinchdrum


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Forerunner (stretcher Allongement de la touline)


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8 strands (torons) on adrum (tambour)


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Primary and secondary lines


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Ropes in the off-shoreworld


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Application

Cables and ropes are used for:

a. to moor the ship and maintain itsposition and for towing.

b. for the cargo gear

c. in fishing and dredging

The cables mentioned in a. are usually

made of rope and called hawsers((h)aussires) or lines. The cables used inb. and c. generally are steel cables.


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French Terminology

Hawser = amarre ou (h)aussire

Rope Filin ou corde

Grelin: Gros cordage pour l'amarrage oule touage (remorquage) d'un navire. Legrelin est compos de plusieurs (3)aussires commises ensemble. Il est doncplus gros et plus rigide l'aussire. Audessus de onze pouces de circonfrence,il prend le nom de cble

Stopper La Bosse (stoppeur)


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Material - ropes

Natural

Synthetic fibres.

Nowadays, with a few exceptions, mostropes are made from synthetic fibres. Thesynthetic fibres are manufactured frommineral oil products that have undergone

a chemical process.


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Ropes - construction

The rotation of thethreads is oppositeto the strands,preventing therope to unlay.


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French Terminology

Fibre - fibre

Thread fil de caret

Rope yarn- tortis

Strand - toron

3-strand rope aussire troistorons


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Ropeconstruction


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Rope types

Stranded or wire rope construction(in strengen verdeeld)

Parallel lay Plaited (gevlochten) (tress)

Braided (geweven) (tiss)

Laid (geslagen)(toronn)(commett) (commettre commettage)


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1. Stranded or wirerope construction

2. Parallel strandstrand withmantle

3. Parallel yarn with

mantle(Strand >yarn)

1

2

3


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3. 4x2 strand plaited(tress)

4. Braided (tiss)

3

4


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Purpose of the mantle(chemise ou gaine)

To keep the strands in the core together.

The strands in the core can be arranged in aparallel fashion: this gives the maximum

tensile strength (rsistance la traction).The mantle itself rarely contributes to thetensile strength.

The threads in the core need not be

resistant to wear (friction) as the mantleprovides the wear resistance. Therefore itis important that the wear resistance of themantle is higher than the wear resistanceof the core (noyau fil conducteur).


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Purpose of the mantle

A mantle keeps the cable round andcompact, which reduces sensitivity to wear.

Some core-types that can be present in

core-with-a-mantle-cables: Braided

Stranded

Parallel strands

Parallel threads


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Construction 3-strand

Example polyester

6 72mm

Minimum strength862 -> 94.000 kg

Specific gravity 1.38


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Example polyester

48 80mm

Minimum strength40.000 -> 104.000 kg



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Example nylon

40 144mm



Octopus


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Example ultra bluefibre

60 72mm




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Construction braided

Example ultra bluefibre

16 72mm




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Construction double braid

Example polyester

6 120 mm

Minimum strength887 -> 270.000 kg



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Braided ropes

Kevlar Polyester


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Important Characteristics MBL. (minimum break load)(charge

minimale la rupture) This is theminimum force in kN needed to break therope.

Elasticity. Density. The larger the density, the

heavier the rope. It is important to knowwhether the density is smaller or larger

than 1.000 t/m3, in other words: doesthe rope sink or float.

UV-resistance. After several years,sunlight can degrade the rope.


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Important Characteristics

Wear resistance.

Construction. The number of strands andthe way that the rope is plaited, the

presence of a mantle. Water-absorption, expressed as a weight

percentage of the rope.

Backlash or snapback. This indicates if, incase of breaking, the rope falls "dead" onthe deck, or snaps back. Rubber has alarge backlash (contrecoup).


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Creep (kruip grimpement) limit. This isthe lengthening of the cable in time underconstant tension

Chemical durability. This indicates howwell the rope can resist (the action of)chemicals.

A knot or splice in a cable can reduce thestrength by as much as 50%.


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TCLL-value (thousand cycle load level(rsistance la rupture)). This is thecyclic load level as a percentage and as

an absolute value of the maximum loadunder wet conditions. This is the load atwhich a cable will break when it hasundergone the load a 1000 times. For

example, if the TCLL-value of a 100 ton.cable is 50%, or 50 tonf, then the cablewill break if subjected to a 50 ton load a1000 times


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SWL = Safe Working Load

The termsafe working load, (SWL)(charge de

scurit) was the cornerstone of engineering,

particularly with regard to load carryingequipment, for many years.It was generally

considered to be the breaking load of a

component divided by an appropriatefactor of

safety giving a safe load that could be lifted

or be carried.


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SWL = Safe working Load

About 20 years ago, however, the USA ceased usingthis term, because of legal implications. TheEuropean and ISO Standards followed suit a few

years later. However, while this was a clean-cutmove, for some time there has been indecision as toexactly what replacement terms could be used.

Over the past two or three years, both the Americans

and Europeans have agreed that working load limit(WLL) should replacesafe working load (SWL) indescribing the capacity of items such as hooks, slings(sangles) and shackles (manilles) etc.


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A general definition of WLL is:

the maximum mass or force which a product

is authorized to support in general servicewhen the pull is applied in-line, unless noted

otherwise, with respect to the centreline of the

product


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At sea SWL is still used every dayand is clearly indicated on all lifting

gear, hooks, shackles, slings etc. Rules of thumb:

New ropes SWL = MBL/4.

Common safety factors are 6 & 8. Old ropes SWL = MBL/10.


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Safety factors Bureau Vritas

New ropes

Standing rigging (manuvresdormantes): SWL = MBL/8

Moving rigging(manuvres courantes)

: SWL = MBL/10 Intermittent load (shock loads): SWL =

0.06 MBL

f


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MBLs according Board ofTrade (B.O.T.)

Manilla : BL = 2 D2/300

Polyprop : BL = 3 D2/300

Polyester : BL = 4 D2/300 Nylon : BL = 5 D2/300

Viking : BL = 6 D2/300


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MBL Polyprop mooring ropes accordingLloyds Register


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Comparison

Mooring rope 64mm TableLloyds Register MBL = 457 kN

System B.O.T. 3 x (64)2/300 = 402kN

SWL basis safety factor 8 = 457/8 =

57 kN (+/- 6 ton)


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The following figures and formulae arebased on information in the Admiralty"Manual of Seamanship" volumes 2 & 3,

and a data sheet from Marlow Ropes. A minimum safety margin of 6 is used.

The figures assume that gear is wellmaintained and in good condition, but the

approximations and simplifications are onthe safe side..


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1) Natural Fibre

SWL in kilogram's is 3/4 x D2, where D is

diameter of rope in millimetres.2) Polypropylene, nylon, polyester,aramide & HMPE

Double the SWL of natural fibre - 3/2 x D2 -ofthe same size, or, for new rope, one sixth of thenominal breaking strain as shown in themanufacturer's data sheet.


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SWL of wire rope

How to measure arope or wire ?

The read out =NOM or Nominalvalue ISO value

SWL (ton)=

(Diameter inch)2x 8

TCLL l f b


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TCLL-values for a numberof ropes

Polyprop will breakif submitted 1000times at a fore =52% of his MBL

Dyneema will NOTbreak if submitted

1000 time at100% of his MBL


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Common cables

Natural fibres

Synthetic fibres

Steel cables

N t l fib H


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Natural fibres Hemp(Chanvre)

General Properties UseHempplant

(Cannabis sativa)Strongest naturalfibre

Does nor resist

water => oftentarred .

Heaving lines

Sounding linesLog line

N t l fib M il(l)


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Natural fibres Manil(l)a(manille)

General Properties UseAbaca or wild

banana (Musa textilis)Most suitablenatural fibre

The surface of the

rope is rough andoiled. The colour ofthis rope is darkerwhen you compareit with the sisal-rope

Floats when dryVery flexible andsupple

Mooring ropes

HayliardsHeaving lines andmessengers

Clew lines


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Manila rope


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Natural fibres Sisal (sisal)

General Properties UseThis rope is made of

Agaves-plantCheap

The surface of the

rope is rough andthe rope is almostinelastic

Does not resistwater

Not as strong asmanilla

Sounding line


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Techniek van het schip - 1ste

kan. N.W. - kapt. K. de Baere 57

Sisal rope

N t l fib e Coi (fib e


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Natural fibres Coir (fibrede coco)

General Properties Usefibres from the

fruits of the coconutpalm, (Cocos nucifera)

Very light, floats

even when wetVery elastic

Weakest naturalfibre

Used to fabricate a

fender or pudding


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Coir


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Natural fibres Cotton

General Properties UseCottonplant Very white

Absorbs a lot ofwater

Supple even whenwet

Decoration

Signal halyardSounding lines


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Cotton

S th ti fib N l


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Synthetic fibres Nylon =polyamide

Properties UseHigh strength, ShockabsorbentLose 10% of their strength whenwet

Torque free => Easy to handleHighly elastic and will elongate10% to 40%

Excellent abrasion resistanceDoes not float

Susceptible to heat and sunlightVery slippery when wet

Attacked by acids and paints

Multifilament = number of fibres isendless

Deep water buoy lines

Dangerous when it snaps underload

Nylon is the preferred line fortowing and dock lines since itstretches sufficiently to dampenthe shock of wave action andwind danger of breakingout


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Nylon ropes


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Synthetic fibres Polypropylene

Properties UsePolypropylene line is the leastexpensiveof the synthetic lines,It deteriorates quickly from

ultra-violet rays and wear.It floats

Resistant to alkalies, fat andacids but not to solvents andbleaching agents

Weakest synthetic fibre

Equal strength wet or dry

Transition between mono &multifilament

General use

Ideal as fore- or aftline since itfloats

Appropriate for dinghypainters, short mooringpendants or other applicationswhere you want to be able tosee the line on top of thewater.

Rescue line


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Synthetic fibres Polyester

Properties UsePolyester rope wears betterthan polypropylene, is almostas strong as Nylon, and retains

its strength when wet. It doesnot stretch as much as Nylonand does not float.

Better resistance to acids, oiland organic sollutions than

nylon.Multifilament

Mooring ropes

Polyester (such as Dacron) isused for running rigging,towing lines and otherapplications where you don'twant line stretch to interfere.It will, however, chafe easilyso check it often and protect

as necessary.


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Synthetic fibres Polyethylene

Properties UseSoftens with rising temperatures

Monofilament composition

FloatingExpensive

Resistant to acids and alkalis

Basis for many modern synthetic

fibres.

HMPE = High ModulusPolyethylene

Dyneema & Spectra

Fore- and aft line

ARAMID ( KEVLAR TWARON


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ARAMID (= KEVLAR, TWARON,TECHNORA)

Aramid fibressuch as Kevlarand Twaron are substantiallystronger than nylon.

They are chemical and thermal stable

Aramids will not melt but start to carbonise at

temperatures above 425 C. Aramids have excellent tension-tension fatigue resistance

and exhibit low creep.

The abrasion resistance of these fibres is not good.

Since these ropes are nearly always jacketed it is not

possible to observe the wear due to abrasion and failurecan occur without warning.

Technora (Aramid co-polymer) has an improved lifetime inrunning over pulleys (better abrasian resistance)


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General Features of Kevlar


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General Features of Kevlar

Aramid Fibre

High Tensile Strength at Low Weight

Low Elongation to Break High Modulus (Structural Rigidity) Low Electrical Conductivity

High Chemical Resistance

Low Thermal Shrinkage High Toughness (Work-To-Break) Excellent Dimensional Stability High Cut Resistance Flame Resistant, Self-Extinguishing


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Commercial Products of Kevlar Aramid Fibre

Filament form-KEVLAR 29,49,68,100, 119, 129, 149.

Kevlar 29 -Representative, Rubber Reinforcing, Personal protection vests,

Reinforcement for hard armor, helmets, Spall Panels, electronic housing

protection

Kevlar 49 - High modulus type, Composite, marine sporting goods, and aerospaceapplications

Kevlar 68 - Medium type between 29 and 49

Kevlar 100 - Colored Kevlar, Gloves, Protective Apparel

Kevlar 119 - High durable, Tire, V-belt, Hose, C-belt

Kevlar 129 - High tenacity type, Ballistic vest, Rope, Tire Kevlar 149 - Ultra high modulus type, Composite, Rope


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New materials

Vectran = Liquid crystal polyester

The actual strength in ropes are no

higher than with aramid and thelifetime in tension-tension fatigue isabout equivalent. However there areclaims of a good performance in cycling

over sheaves.


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New materials

Steelite Dyneema High Modulus Polyethylene

Stronger than steel wire

Alternative for steel wire MBL 64mm 276t

Flexline Polyester multifilament

MBL 64mm 89t Atlas

Nylon multifilament

MBL 64mm 81t


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Ropes construction


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Ropes construction


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Ropes overview - fibres


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Ropes breaking strength

New synthetic fibres -


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New synthetic fibres overview

The very classic wire rope construction is apparantly stillthe best for pulley-block work (cycling over sheaves)

Parallel yarn ropes have the best strength-diameterrelation.

HMPE & steel resist best to abrasian

Many modern fibres are suspectible to kinking

Many modern fibres are stronger than steel

Many modern fibres are heavy

Steel is still the least elastic material Nylon is very strong but the more modern fibres are

lighter


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Wire ropes

Steel cables or wire ropes have advantages anddisadvantages. They are strong, cheap, havelittle elongation under tension, have a highwear resistance, but they are heavy, and they

rust. They are used where the circumstances allow

or demand it, for instance for hoisting andlifting wires in cranes, mooring wires for

tankers and bulk carriers, anchor wires indredging and offshore, towing wires for fishingand tugboats. In case of fire they are notimmediately destroyed.


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Wire ropes Steel wires are available in numerous constructions,

depending on the requirements.

The basic element of wire rope is the wire - usually round,but sometimes shaped. Most wire is made out of one of

three grades - Improved Plow Steel (IPS), ExtraImproved Plow Steel (XIP) with 15% greater tensilestrength than (IPS) and Extra, Extra Improved Plow Steel(XXIP) which has a 10% greater tensile strength than(XIP).

When the wire has a natural finish, it is called bright.Otherwise, it is plated, galvanized, or may have someother surface treatment for special applications.


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Strands

Strands (torons) are composed out ofsteel wires (fils) layed around a centralcore (ame)(rope(textile) or wire(acier))

2 ways laying: cross lay (commettagecrois) and equal lay (commettagegale) MBL of equal lay is 14% > MBL of cross lay

Equal lay has less internal friction because thewires do not cross each other

Cross lay is less popular


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Cross lay and equal lay

Cross layCommettage crois

Equal layCommetage gale


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Strands

It is possible that all of the wires donot have the same diameter

Seale (S) Filler (FS)

Warrington (W) & Warrington Seal


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Seale (S)

2 or more layers ofdifferent diameterslaid around a

central core 6 stands of 19

wires (6 torons de19 fils)


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Filler (FS)

Space between thewires is filled withwires of a smaller

diameter FillerSeal

6 strands of 19

wires (6 torons de19 fils)

Warrington (W) +


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Warrington (W) +Warrington Seal (WS)

The outer layers arecomposed out of 2kinds of wire with

different diameters The small diameter

wire falls between thelays of the wiresunderneath the bigdiameter wire comeson top of this layer


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Cores (mes)

Wire rope cores are usually one of three types:

1. Fibre rope core - either natural sisal fibre(FC), or man made fibre such as

polypropylene (PPC). This core, though notas strong allows for better bendingcharacteristics of the wire rope.

2. Wire rope core (IWRC) (Independent WireRope Core)- This is basically an independent

wire rope made up of numerous strands.3. Strand Core (SC) - This core is made up of a

single strand with several wires.


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Construction of a steel wire

3 different types can be distinguished Ordinary or Cross lay (kruisslag)(commettage

crois)

Wires in the strands and the strands are laid in theopposite direction

Lang lay (Langs slag)(commettage de lang) Wires in the strands and the strands are laid in the

same direction

Mixed lay & non-rotating lay


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Direction of the strands

Only outer layer isconsidered

Z or right handedlaid wire rope

S or left handedlaid wire rope


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Wire rope construction

A wire rope isconstructed out ofdifferent layers

The direction ofthe outer layer isdecisive to call the

wire rope left orright handed


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Ordinary or cross lay

Like ordinary rope, there are right hand and lefthand laid cables. Analogue to synthetic rope, thedirection of rotation of strands and wires is

opposite, called 'ordinary lay or cross lay

Z = right

S = left


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Cross lay cblage croix

zS =cross lay left

sZ = cross lay right

z or s laying of the

wire in the strands Z or S is the laying

of the strands

Cross because

stands and wiresare laid in theopposite direction


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Cross Lay or Ordinary lay

Combination of innerand outer layer

On the left sideRHOL Right handedordinary lay

On the right sideLHOL Left handedordinary lay

RHLL Right handedlang lay

LHLL left handedlang lay


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Langs lay

Wire and strands are twisted in thesame way

Wire is more flexible and has betterwear and tear properties

Disadvantage: the wire kinks faster

Limited applications


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Mixed lay & non-rotating


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y glay

Combination of ordinary and Langslay

Non-rotating lay f.i. elevator cablesor hoisting cables of a crane

4 important steel wire


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pconstructions

Round strands

Multi strands

Flattened strands Rotation free constructions


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Round strands

Example 6x37+1

6 strands of 37wires each

1 = rope core

37 = 1+6+12+18

All wires have the

same diameter


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Multi-strands

18x7+1 steel core

18 x 19 + 1 steelcore

Multiple layers ofstrands to obtain aminimal tendency

to twist


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Flattened strands

Strands have atriangular shape

Outer surface

becomes smootherand betterresistant to wear

6x25WS+1 (ropecore)


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Examples Wire Ropes


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p pSteel core


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Examples Wire Ropes

Examples Wire Ropes


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p pFibre Core

Examples Wire RopesRotation Resistant Wire Used As Hoisting


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Rotation Resistant Wire Used As HoistingRope

Handling of a wire rope on


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board

Most important is to avoid kinking of thecable

When unwiding a coil Use a turning table Or unwind on the floor (see to it that the

ground is clean)

When unwinding from a drum Use a turning table Unwind on the floor

Reel block


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Winding of a wire rope on


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the drum of the winch

Basis principle is that a wire rope has thetendency to open under tension.

The direction of the wire on the drum

must be choosen to oppose this tendency

On a drum with one single layer thedirection of the wire rope has to be

opposite to the direction of winding onthe drum

Winding of a wire rope on


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the drum of the winch

On a reel with multiple layers thepitch changes per layer

The direction of laying of the wirerope has to be selected in functionof the direction of of the mostfrequent used layer on the drum

How to determine the


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direction of a cable reel

Start at the point of securing thewire rope on the reel

Follow the cable windings with yourfinger

If your finger turns clockwise wehave a right-handed reel

consequently we need a left layedwire rope

Fig a: right drums with left wireropes


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ropesFig b: left drums with right wire

ropes


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Inspection of a wire rope

5 criteria

1. Damaged fibres

2. Reduction of diameter3. Wear and tear

4. Corrosion

5. Deformations


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Damaged fibres

Standards are laid down in DIN 15020 2ndsheet

Number of damaged wires has to be

counted over a length of 6 x and 30 x Maximum number of broken is wires is

function of the classification of the

installation, number of external strandsand direction of construction of the wirerope


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Breaking of a wire rope

a) Overloadingb) Combination of axial and diagonal loads

c) & d) Fatigue phenomena

Reduction of diameter &


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wear

If the reduction is > 15% due tostructural changes the wire rope hasto be changed

A steel wire rope subjected to wear,internal and external. If thereduction in diameter is > 10% dueto wear the wire has to be changed


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Corrosion & deformations

Corrosion Standardfor changing the wireis also 10% reductionin diameter

Corkscrew Does notnecessarily result in aweakening of the wirerope.

Increased friction. If the deformation is

> 1/3 wire ropeshould be changed


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Deformations

Cages and loops

Entail both achanging of the

wire rope


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Deformations

Flattening, kinking and twisting

If pronounced change wire

Wire exposed to high temperatures (>300C)

have to be changed

d


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Load testing equipment

All equipment intended to be used in liftinggear needs to be certified. Regulations forlifting equipment and testing are

internationally harmonized. This means thatmaterial qualities are cheched,workmanship is judged and that a load testhas to be carried out under the supervisionof a regulating body. For ships this is

normally the Classification Bureau.


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All the items in hoisting gear must becovered by a certificate, stating an

identification and a test. The load test iscarried out to guarantee a Safe WorkingLoad (SWL) or the Working Load Limit(WLL). A crane as a complete unit is testedby lifting a weight, and carrying out the

normal movements like hoisting, lowering,slewing and topping. When the power tothe crane is interrupted, the brake has tohold the load. The weight for testing isheavier than the WLL. For the smallestcranes this means 25 % overweight, for thebiggest cranes it is 5 tons more than theWLL.

L d i i


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L d i i


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Individual small items belonging tothe crane, such as the hook,shackles, etc. are normally tested attwice the WLL.

L d t ti i t


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Test weights can be steel weightswith a known mass, the modemvariant is a water bag, which can befilled with water till the requiredmass is reached. A certified load cellindicates the weight. Water bags are

available up to 35tons.

V i t


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Various parts

Various parts explained on thesepages:

End connections

Shackles

Turnbuckles or Bottle screws

Thimbles

Sockets

EndC ti 1) Gaff socket with


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Connections 1) Gaff socket withrolled connection2) Cast spelter socket3) Rolled eye terminal

4) Thimbled taluriteye

5) Spliced eye withthimble

6) Thimbled flamisheye, swaged

7) Wedge socket (notallowed inhoisting).

T l it l


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Talurit clamps

A Talurit clamp, is an aluminium bush,which is pressed under high pressure atthe position where normally a splice

would be, replacing the time-consumingsplicing. The pressing makes the originaloval shaped bush into a cylindrical clamp,with the strength of the replaced splice. A

Talurit clamp is not to be used in bendingsituations

T l it li


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Talurit-clips

The loop is made bymeans of analuminium ferrulestandard or conical.

Slings are madeashore anddelivered to theship together witha certificate stating

testing- andnominal breakingload.

S li i b h d


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Splicing by hand

Time consuming

Require great skill

Will reduce the strength of the wire till80% of its nominal breaking strength

If formed with less skill the wire willbreak at 50% of the N.B.L.

B lld li


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Bulldog-clips

Allow eyes to beformed by unskilledpersons

A perfect eyearound a thimblewill hold at 90 ->100% of the N.B.L.Of the wire

B lld i li ti


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Bulldog-grips applications

Ri ht d


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Right and wrong

Bulldog-grips -ecommendations


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recommendations

Not less than 3 grips at each eye (4 forwires 20mm ->32mm & 5 for wires 32 >38mm a.s.o.)

Bulldog grips have a grooved surface and

are suitable for a standard wire RH 6strands.

Before cutting the wire to length whip ortape both ends

The first grip must be close to the thimle.The other grips must be 6 rope diametersapart (f.i. 96mm on a 16mm diameter wire)


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Wrong bulldog eyes


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Wrong bulldog eyes

2 grips appliedwrongly the thirdone is positionedcorrectly

Distance betweenthe grips is notcorrect

The cut end is notwhipped

Slippage is likely tooccur at 0.4 NBL

Wrong bulldog eyes


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Wrong bulldog eyes

All 3 grips appliedin the wrongdirection

End is not taped orwhipped

The cut end is notwhipped

Slippage is likelyto occur at 0.5NBL

Steel wire clamps


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Steel wire clamps

A steel wire clamp can be used to quicklymake an eye in a cable. The U-bolt of theclamps should be attached to the part ofthe cable that is free from pulling forces.The bolts should be attached to the

dead part, where no pulling forces areacting on the cable.

Steel wire clamps may not be used forlifting purposes, with an exception forguys and keg sockets to make sure thatthe cable does not slip.

Kegsockets


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Kegsockets

Shacles


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Shacles

Shackles can be divided into bowshackles and D-shackles. These canboth come with or without a lockingpin. Their general purpose is toconnect certain parts to each otheror to the ship. The Safe Working

Load (SWL) can vary from 0.5 to1000 tons

D and Bow shackles


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D- and Bow shackles

Shackles come in several shapes,sizes and strengths of material.

Two shapes commonly used for

general cargo lashing purposes areD-shackles and bow-shackles

Bow shackle


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Bow-shackle

Dee shackle


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Dee-shackle


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Shackles

Safety Hooks


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Safety Hooks

A safety hookprevents the loadfrom falling out of

the hook, even ifthe load is resting.The hook can onlybe opened by

pressing the safetypin.

Turnbuckles


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Turnbuckles

Turnbuckles are usedto connect andtension steel wire orlashing bars. The

bottle screw consistsof two screws, onewith a left screwthread, and the otherwith a right screw

thread. These areconnected by ahouse.

1. House2. Thread

3. Gaff

4. Eye

Timbles


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Timbles

A timble is madeout of galvanisedsteel. Its function

is to protect theeye of the cablefrom wear anddamage

When lifting objects, often slings areneeded. A sling is a wire with at each end


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gan eye spliced or clamped. The eye can be

long or short, all depending on thepurpose. When the item to be lifted haslugs welded on it, a sling with talurits andshackles can be used. In other cases longeyes are more versatile. These eyes can

be taluritclamped, but better is a Flamisheye, with a swaged clamp.

The strongest sling is the grommet. Agrommet is very flexible and very strong.The heaviest grommets, for offshore lifts,

reach a calculated MBL of 7500 tons.Testing is not possible, but the MBL of theindividual wires is a known filgure, foundfrom a breaking test of a sample.

Slings


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Slings

Modem slings are fabric. Woven frommodem fibres very light and strong band-type slings are made, with onedisadvantage: they can easily be damaged

by sharp items. But strength-weight ratioscan be extremely high, when modem fibresas Dyneema, Aramide, or other carbons areused. Very flexible and soft slings are madefrom Dyneema in long straight threads, not

laid, inside a canvas tubing. This type ofsling is very friendly to machined orpolished steel objects.

Forces and stresses


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Forces and stresses

Some definitions

Safe Working Load (SWL) orWorking Load Limit (WLL) is themaximum acceptable bad on anitem (shackle, hook, wire, derrick,crane, etc.).

Minimum Breaking Load (MBL) is theguaranteed minimum load at which


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guaranteed minimum load at whichan item, when tested to destruction

as a sample for a large number ofidentical items, will fail. So, onaverage, most items will fail at ahigher load. The load-stretch diagram

below shows that the tested chainactually failed at a higher load thanthe MBL. The diagram also showsthat proof loading by the

manufacturer is done to 2.5 times thesafe working bad. For a re-certification test, the proof bad willbe 2 times the SWL.

Forces and stresses


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Forces and stresses

Normally used figures for the ratioWLL/MBL (or SWL/MBL) are:

For chains: 1:4

For steel wires and shackles: 1:5

For ropes: 1:6 or1:7

Forces and stresses


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Forces and stresses

6.000 tonshook


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hook

Shackles readyfor testing

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