chain cable

7/18/2019 Chain Cable

http://slidepdf.com/reader/full/chain-cable 1/13

＜ Chain Cable ＞

13. Anchor Chain CableWhen the ship is anchored the holding power is not only ancor itself but the total weight of

anchor chain cables on the sea bed.

Genellaly common rink of anchor chain cable has a stud and studless chain is not used as

an anchor chain cable. Studless chain is used as lashing, hand rail etc.

During an anchor chain inspection, the chain cables should be ranged out on the dockfloor and visually inspected for wear and the link diameter is measured .Generally the

overhauling of each shackle has been omitted. Especially the opening up the kenter

shackle is very difficult and not so important for the maintenance of chain cable.

Phto.1 Cahin cable in dry dock(1)

Phto.1 Cahin cable in dry dock(2)

13.1 Kind

of chain cable

13.1.1 Type and maunfacturing process

Chin rinks are made of steek bar or cast steel. In case of ULCC and VLCC almost all are

of cast steel.

(1) TypeAll ancor chains are stud chain. Studless chain is not used as an anchor

cain cable.

(2)

Length and Joining

The length of chain is defined as the distance between the inside edge of the link at one

1.Introduction

2.Docking Survey

3.Survey Item

4.Type of Dry Dock

5.Safety in Dock

6.Procedure of BottomInspection

7.Course in Dock

8.Shell Defect

9.Stern Frame

10.Rudder

11.Propeller

12.Anchr

13.Chain Cable

14.Sea Valves

Hull Surveywelcome to

n cable http://docking.ship-doctor.com/13/13_1.html

13 6/25/2015 12:40 PM



end and also the inside edge of the link at another end.

In the past, the length of chain cable was 24.0 m, but today almost all

are are 27.5 m. These chains are joined with shackles to form a length that complies with

the requirements of the Equipment Number. The number of links in a chain is an odd

number so the shackle always comes at the same position on the gypsy wheel of the

windlass. To remove the twists of chain cable, a swivel piece is sometimes connected

between anchor and the chain cable. The number of links in the swivel piece is even

number.

(3) Matufacturing process

i) Forging

In these days forged chain is not used as an anchor chain .ii) Welding

The almost all chains are made by electrically welding.

iii) Cast steel

The big chain for ULCC and VLCC is manufactured by casting. By casting different

strength steel chain can be made.

(4) Strength

There are three kinds of chain cables depends on the maerial as follows:

1) Normal strength

2) High strength

3) Extra high. strength

4) The diameter of the chain

The diameter of the chain is that of the common link.

Fig.13-1 Cahin Diameter, the piece between upper and lower pieces is

called stud.

When a large tensile load is applied to this chain, the studs bare the compression load,

therefore, deformation of the link is small and the total strengh of the stud chain is stronger

than the studless chain.

13.1.2 Kind of chain cableThere are two kinds of chain cable depends on the joining means.

(1

With end and enlarged link at both ends

When connect using a ordinary joining shackle, both end links do not have studs for

inserting the head of shackle. Then the diameter is bigger than the common link.The links

of both ends are called end link and the next one to the end link is called second link.

Both links have a bigger diameter .Without the two links at the ends, all other links are

called common links.

(2) Common links only

When connection using a kenter shakles, there are neither end link nor second link. All are

common links.

Fig.13-2 Studless chain (short link chain)

Fig.13-3 Stud chain without end link (Join with kenter shackle)

13.1.3 Connection of Chain Cable

The length of anchor chain cable is 24m or 27.5m. So it is necessary to jion each other

using shackles. There are two type of shackles.

One is a joining shackle and the others is a kenter shackle.


13 6/25/2015 12:40 PM



Fig.13-3 Joining with joining shackle

Fig.13-4 joining with kenter shackle

(1) Joining shackle

When the chain is connected with joining shackle, the ends of the chain cable have no

end links so that the head of the joining shackle can pass through. The second link

(enlarged) is an intermediate link used for connecting the end link and the common link.

Fig.13-5 End rink (above) and Joining shackle (down)

(2) Kenter shackle

When the chain is joined with Kenter shackle, chain cable has neither end link nor second

link. All chain cable consists of common links only.

The construction of this shakle is not a simple like the joining shackle and more expensive

. But it is very useful because the chain can be joined at any position when it is broken. In

case of chain is connected with joining shackle and broken at the common link, it is

impossible to join the broken common link with the jionung shackle. So in case of allchains connected with joining shackle, generally the ship has one or two kenter shakles

to join the broken common link.


13 6/25/2015 12:40 PM



Fig.13-6 Dismantling of kenter shackle

(1) Pull out the taper pin

(2) Remove the stud

(3) Dismantle the two parts of the link by sliding them apart; however, if rust has formed

the parts, slide the parts is very difficult ; therefore, sometimes opening?up may be

omitted .

Assembling the Kenter shackle is by reversing procedure. But , if the top and bottom of

the stud are not assembled correctly, the taper pin cannot be inserted.

Photo 2. Overhauled kentere shackle


13 6/25/2015 12:40 PM



Phto 3. Special kenter shaclle

13.1.4 Accessory to Anchor Chain Cable

Acccessories to anchor chain cable are as follows:

(1) Anchor shackle

Large shackle used for connecting the chain cable and the anchor

(2) Joining shackle

AS above mentioned, shackles used for connecting two chain cables; if studless end linksare not provided at both ends , this shackle cannot be used.

(3) Kenter shackle

Shackles used for connecting a chain consisting of common links only

and no end links.

This shackle has a split construction, therefore, it can be used to connect a broken chain,

irrespective of where the break has occurred. It is more expensive than the joining

shackle; dismantling this shackle is a little difficult.

(4) Swivel

Swivel is ijoined close to the anchor, it has the role of preventing twists in the chain cable

due to its rotation. If a swivel is not provided in the chain, the links in the chain may be

twisted

Fig.13-7 Swivel

(5) Buoy shackle (Harp shackle)

This is a special shackle used for connecting the chain directly to a buoy after removing

the anchor when mooring a ship to a buoy. This shackle is a shipowner's option and is not

a rule requirement. The buoy shackle isthe similar form of a harp so, called a harp shackle.

Fig.13-8 Buoy shakle

13.2 Damage to Chain and Check Point during Inspection

13.2.1 Links

(1) Breaks

A chain cable is broken at the shoulder part of a link due to shearing force as shown


13 6/25/2015 12:40 PM



below. If the link breaks at the parallel part, it is due to a welding defect.

If the link breaks the chain and the anchor drop into the sea. In this case lost chain cables

and anchor should be discovered and pull up from the seabed. unless otherwise ancor

and chain cables should be renewed.

Fig.13-9 Broken link at the tensile test in the manufacturer

In Grade 2 flash butt chain of diameter 32 mm, the chain broke at a load of 85.9 tons

compared to the rule tensile load of 59.4 tons (44.6% over). Not broken links have no big

deformation.

Fig.13-10 Normal breaking

A fully welded chain elongates adequately and breaks at the shoulder (A) due to shearing.

Depending on the impact, the link might also break at (B) and the stud might be

separated.

Fig.13-11 Breaking at welding joint If welding is defective, the link break at the welded section.

(2) Bending and twisting

Sometimes bending or twisting happens in the links near the anchor in a chain with no

swivel. This occurs when the anchor rotates while it is suspending. In case of excessive

bending or twisting, the chain cannot pass the gypsy wheel of the windlass; In this case it

has to be taken to the manufacturer and repaired.

Photo.13-10 Bent rink


13 6/25/2015 12:40 PM



(3) Blow hole

In case of cast steel chain, sometimes blow holes appear on the surface, which did not appear during inspection at the manufacturer's works. Blow

holes normally appear in a solid link or in every joining link

A chain with blow holes, when taken to the manufacturer's works and

proof?tested to the specified load showed no decrease in strength; therefore, blow holes

can be ignored depending on the number.

Photo.13-11 Blow hole

13.3.2 Stud

A stud is piece of steel inserted into the link; when a tensile load acts on both ends of thelink, it keeps the link form and holds it firmly. However, if it is subjected to a large

transverse impact, it sometimes works loose and comes off.

(1) Loss of stud

If the stud is missing, the strength of the chain decreases considerably; therefore, repairs

should be carried out promptly. If transporting to the manufacturer is difficult , the easy

way to repair is to insert an appropriate steel piece similar to stud in the link to serve as a

stud and weld one end of the piece to the link. In this case, welding is only one end not

both ends.

Fig.13-12 Stud insert

(2) Slack

If you strike the stud with a test hammer , you can find whether the stud is slack or not. If

in doubt, touch the stud with your finger while striking it with a hammer; you shall feel a

slight looseness at your finger. If the stud is slack, either tighten it or weld one end only . If

both ends of the stud

are welded, abain crack appears in welded one end.

Fig.13-13 Examination of stud sluck


13 6/25/2015 12:40 PM



Fig.3-14 Stud sluck

Fig.13-15 Lost stud

(3) Cracks

Aged ships have a forge?welded chains. Sometimes, crack appears in stud end. the studs

in these chains are made of tempered iron.

Fig.13-16 Crack in stud

14.3.3 Swivel

The swivel might be provided optionally by the shipowner; it is not provided in some small

ships. The points to be checked in the swivel

are: wear at the neck; if wear is excessive, the eye piece might work loose and drop off,causing the anchor to fall into the sea. Either the swivel

Fig.13-17 Abrasion of Swivel


13 6/25/2015 12:40 PM



should be taken to the manufacturer's works to replace the eye piece, or the entire swivel

should be replaced.

14.3.4 Joining shackle

Fig.13-18 Abrasion of shackle

14.3.5 Anchor shackle

The bolt of anchor shackle should come to the anchor side. If it comes to the opposite

side, when the anchor is heaved up, the anchor shackle might bite into the bell- mouth

and open the shackle, resulting in the

anchor falling.

Before making a connection, confirm that the head of the anchor shackle

can be inserted into the end link, as shown in the figure above. This may not be possible

with some anchor shackles.

The connection is generally made as shown in the above figure ;

however, when the anchor is stowed, the anchor shackle catches at the

bell?mouth as shown in the figure to the right, the anchor shackle opens

and the anchor drops. Such instances have been reported.

Fig.13-19 Connection anchor to chain cable

Fig.13-20 Bell mouth and anchor shckle

13.4 Measurement of chain diameter

13.4.1 Chain diameter

In small ships that operate on short voyage , anchoring is so frequent. therefore, the chain

wears out faster. There have been instances where a chain reached its wear limit within

eight years and had to be renewed. The anchoring frequency is low for large ships and the


13 6/25/2015 12:40 PM



diameter of the chain is also large; therefore, wear is small. For both types of ship, the

chain diameter should be measured during the Docking Survey.

Fig.13-21 Chain diameter

13.4.1 What is the diameter ?

The diameter of the chain in old ships is reduced due to wearing out. The original diameter

is given in the survey report but sometimes the original diameter is unknown because of

the report cannot be found on site.

We can guess the original diameter measuring the length of the link

and divide it by 6. The result will be the original diameter. The length of the link, even in

old ships, shows practically no change.

13.4.2 Exchange the both ends of the chain cable

The chain cable is always stowed in the chain locker. The part of the chain near the

anchor wears out rapidly than the remaining cable in the chain rocker. Therefore, to

prolong the life of the chain cable, it is better to

change the arrangement at anchor side and end in the chain rocker.

Docking survey is very good oportunity to change the arrangement of the

chain cable. Exchanging the both ends also eliminates rust in the part of the chain cable

in the chain locker.

13.4.3 Measuring of cahin diameter

The measuring position is shown in Fig.13-22.

It is difficult to measure the diameter of all links in the limited docking period, so they pick

out 2 or 3 cables on both P and S-side at random and measure the diameter of both end

and middle link . The avarage value is the chain diameter.Measured diameter should be entered in the survey report for the next

docking survey.

The wear limit was 10% according to conventional rules, but after the unification of the

IACS standards, this limit has been amended to 12%.

When the rule diameter of the chain is 100 mm, a diameter up to 88 mm may be

acceptable. If the avarage value of measured diameter is exceeds

12% the chain cable shuld be renewed.

But the chain cable is a productio by order so it is impossible to get the new one

immediaetly. Generally surveyor makes an outstanding recommendation within six

months or so.

Fig.13-22 measurement of chain diameter

The diameter is the average of "a" and "b"

13.4.4 bigger

diameter

When the chain is manufactured, round bars are bent and welded; during these

processes, the diameter is sometimes reduced. Taking this reduction, the diameter of

round bar is 2% ~ 3% larger than the rule diameter. Consequently, in a new ship, the

measured results sometimes show a larger than the rule requirement. At the owners

opton, some ships have a chain with one step above the rule requirement . In such cases,


f 13 6/25/2015 12:40 PM



the wear limit shall correspond to the diameter prescribed by rules.

The measured diameter should be written in the survey report.

13.4.5 Renewal of chain cable

For the renewal of chain cable there are many items. If one of the

following items is not complied, new cahin cable may be useless.

The following items are carefully check in the certificate of chain cable kept on board.

1). Size

Daimeter and length

2) Material

Depends on the steel, there are two kinds of steel is used for chain cable. One is mildsteel for welded chain and another is cast steel.

And also there are three kinds of mild steel and two kinds of cast steel depends on the

strenght of each steel.

3) Kind of jioning

One is the joining shackle and another is kenter shackle.

When to order a new chain cable, it is better to attach the copy of the certificate of existing

chain cable to ship-chandler. Unless otherwise , for example, the following items have to

be report to order book.

"Diameter 45 mm using Kenter shackle, length 27.5 m, Grade 2 flash butt chain". If one

item is different、 delivered new chain cable is useless.

13.5 Hawse Pipe and Chain Pipe

In old ships both hawse pipe and chain pipe have to be carefully examined. Sometimes crack, deform and heavy corrosion are found.

13.6 Chain Locker

Chain lockers in large ships have structures that looks like huge cylinders suspended on

both sides; some chain lockers can be accessed only

by descending the Jacob's Ladder.

Inside the chain locker it is dark and there is a shortage of oxygen because of rusting, So

adequate precautions should be taken when you descend into the chain locker.

We have to carefully examine the deformation, corrosion around the bilge well and end

connection of chain cable.

Fig.13-23

chain Locker side view


f 13 6/25/2015 12:40 PM



Fig.13-24 In the chain locker (1)

Fig.13-24 In the chain locker (2)

Fig.13-25 End connection (1)


f 13 6/25/2015 12:40 PM



Fig.13-26 End connection (2)

?Back ｜ Home ｜ Next? ＞▲PageTop

If the chain is connected using Kenter shackles, the entire chain consists of common links

only without second link and end link.

(C) Copyright My Blog All rights reserved. Since 2010.


chain cable

Documents