anchoring equipments

8/18/2019 Anchoring Equipments

1/32

ANCHOR Types1 .Stockless anchor Stockless anchor is the one generally used on board ship.

Consists of a short shank with a knob at the lower end which is

loosely retained in a socket in the anchor crown allowing the flutes

to swing 45’ on either side of shank. The crown is broad to resists

rotation when dragged and is shaped so as to force the fluke points

downwards for engagement at the bottom. The commercialstockless anchor has flukes shaped in symmetrical rounded points.

The weight of the head is at least 60 of the total anchor weight.


2/32

Stock anchors

2.

!re characteri"ed by the a trans#erse

bar or stock intended to lie parallel to

the bottom and hold the flukes in

proper position to dig in when theanchor is dragged at the bottom


3/32

ANCHOR Types

$.%anforth anchor

This remo#es the problem of stowing a stock anchor in the

hawse pipe. &n this the stock forms the hinge pin for the

flukes and stabili"es the anchor against rotation whiledragged at the bottom. This method allows the anchor to

be stowed in the hawse pipe easily.

4. Snug stowing anchor

This has a stock like pro'ection as a part of the crown and

this too gi#es good stability against rotation when dragged.

The small crown nests snuggly into the hawse pipe.

5. %eep sea anchor.


4/32

!nchor chains

(ach #essel is gi#en an e)uipment number which is calculated withuse of a formula and taken into account the #essels si"e* underwater

area and sail area. +rom this a ,look-up, table may be used to gi#e an

appropriate si"e of cable. The diameter of the chain may be read from

this table and differs depending on the grade of steel. steel. /ormal

strength stud link chain is made of medium steel with C& studspressed into the links to retain shape of the link under load and

pre#ent kinking.

Stud link chains are also made of cast steel and drop forged alloy

steel rated as high strength and etra high strength. The stud form

integral part of the link which are of uniform si"e. This uniformityassures a better fit of chain to the wild cat and reduces the chance of

chain 'umping off.


5/32

!nchor chainsShips are normally e)uipped with 1 bower anchors and the chains.

(ach set is designed to hold the ship under design conditions. These

conditions #ery according to ser#ice conditions.2ut for ships epected to anchor in deep harbors under relati#ely

eposed condition* the anchoring system is designed to hold the ship

in firm sand against a 30 knot wind and a 4 knot current in 40 fathom

water. The pull must be applied hori"ontally at the bottom to de#elop

the anchor’s maimum holding power and to a#oid breaking theanchor out of the bottom. +or this reason * the anchor chain is usually

much hea#ier than would be re)uired to withstand the tensile load

alone. The chain hangs in a catenary between the hose pipe and the

anchor* and selected so that the lower end of the catenary will be

hori"ontal when the tension at the anchor shackle is e)ual to the

maimum holding power of the anchor.

The chain and anchor si"es are determined by calculation or by the

classification society rules.


6/32

Anchor Handling Efficient working of the anchor windlass is essential to the safety

of

the ship. t!s design and perfor"ance is s#$%ected to strict

classification society r#les.

&asically they re'#ire that Ca$le lifter $rake shall $e capa$le of

controlling the ca$le and anchor when disconnected fro" the gearing when dropping.

The A(. Speed of ca$le shall $e )*+ ",s.

The hea(ing capacity shall $e -* ti"es the weight of one anchorat

speeds $etween / and 1) "ts,"in#te. The lifting wt shall $e

$etween 20*+0 tonnes.

The $raking effort o$tained at the lifter shall at least -0 of the $reaking strength of the ca$le.


7/32

Anchor handling arrange"ents

indlassClassification rule re)uire a windlass of sufficient capacity suitable for

the anchor chain. The ship’s specs. usually call for a windlass ha#ing

enough power to lift each anchor and 0 mtr of chain at an a#. Speed of

m7min.

8r

Specifically The windlass must be capable of pulling the anchor from a

depth of 15 of the total cable carried * i.e. 50 of the length of chain on

one side &t should be capable of lifting the anchor from 91.5m to 13.5mat m7min.

!nchor handling arrangements are determined by the type of anchor

and windlass to be used.


8/32

Hori3ontal windlass deck arrange"ent.

The most common arrangement utili"es a stockless anchor and a

hori"ontal windlass wherein the wild cats are mounted on ahori"ontal shaft. &n this arrangement *the centerline of the deck

opening of each hawse pipe is placed about inline with the centre

line of the wild cats so that the anchor chain will lead fairly to that.

+or #ery large ships and ships with big bulbous bows* it is

necessary to split the windlass and set each wildcats at an angle tothe centerline to get proper lead to the hawse pipe. The windlass is

located so that the chain lead from the hawse pipe to the wild cat

will allow ample space for fitting a chain stopper and a de#il’s claw

and the chain opening in the windlass bedplate shall plumb the

chain locker. ! hinged tongue is fitted in the chain stopper whichmay be dropped between two links of the chain so that chain is

pre#ented from running out when the brake is released also holds

the chain when the ship is riding at anchor.


9/32

4ertical windlass deck arrange"ent

:arge passenger and na#al ships are e)uipped with #ertical

windlass where each wildcat is mounted on a #ertical shaft.

;assenger ships normally ha#e 1 wild cats and $ hawse

pipe


10/32

Chain pipes and co#ers

Chain pipes are usually made of pipe or welded sheets.&nside dia of the pipe is usually made about 6.5 times the

dia of the chain. The lower end of the pipe is fitted with a

half round or casting forming a bell mouth to pre#ent the

chain from catching when the anchor is dropped. The leadto the chain locker shall be straight as practicable and

nearly #ertical. ! co#er made of steel plate in hal#es is

fitted at each chain pipe to protect from water entry.

The chain is led o#erboard by a strengthened and

reinforced pipe called a Hawser . 8ne of the reasons for

bow flare is to allow the anchor and chain to lie well clear

of the hull when in use* pre#enting damage.


11/32

Chain lockers Chain lockers are normally designed to hold the total

#olume of the chain plus close to 1 meters from the topof the stowed chain to the bottom of the bell mouth on

the chain pipe. The chain locker is usually situated

immediately forward of the fore peak bulkhead. ! false

bottom is fitted to the chain locker consisting of aperforated plate. This allows water and mud to be

remo#ed from the space. The inboard end of the chain is

attached to the hull by a )uick release mechanism

known as the ,bitter end, usually at the bottom of the top

deck plate The strength of this will not be sufficient topre#ent a run away un braked chain. The arrangement

must be easily accessible.


12/32

Chain lockers


13/32

Hori3ontal windlass deck

arrange"entThe anchoring e)uipment fitted to the ma'ority of #essels consists of twomatched units* offering a degree of safety.

These units consists of an anchor* chain


14/32

>ooring

=hen the ship is moored in a pier or dock the ship is secured at bow* stern*

spring and breast lines to restrain the #essel from surge* sway and yaw. =hen

e#er the wind load is perpendicular to the centerline of the ship* produce the

greatest force on the mooring lines that must be resisted by the mooring line.Current loads like 1 knots too is to be added. The mooring lines and e)uipments

are to be selected to pro#ide a #ery high factor of safety of $-5 especially lines.

?sually wire rope lines are pro#ided with constant tension winches.

@oller chokes are pro#ided at bow and stern to reduce wear on the lines when

warping into pier


15/32

5ooring E'#ip"ent

6#ties of warping capstans and "ooring winches (ary $etween 7*70

tonnes 8 1)*70 "eters per "in#te and twice the speed for reco(eringlight lines. Steel rope #p to a "a9. circ#"ference of 1-0 "" is #sed

5ooring winches tightens the wire #p to the stalling capacity of the

winch :nor"ally 1.) ti"es f#ll load; then the load is held $y the "otor

$rake

A#to "ooring winches incorporates controls which let off or o(erha#l at

preset tension. There is a certain range of tension associated with each

action. This is to li"it the ha#ling capacity of the winch< safe g#ard

against rope $reakage< and slackness etc. Spring loaded gear wheels<

torsion $ars and fl#id press#re sensing are co""on as sensing de(ice

in the a#to syste" "onitors

To facilitate easy re(ersing spur gears are #sed howe(er

wor" gearing is also pop#lar


16/32


17/32

Towing

(#ery sea going #essel is e)uipped with a towline. =hen a#essel is being towed at sea on a fied tow line* a weight

may be hung at about mid length of the tow line. This shall

ease the shocks on the tow line due to surging of the

#essels. :arge sea going tug boats* which participate in

sal#age operation are e)uipped with a towing machine. The

tow lines are steel wire ropes usually as big as 65 mm dia

and length of up to 900 mts wound on drums of the towing

machine. The free end is lead to the towed #essel where it

may be shackled to a towing bridle or to a good length ofthe anchor chains after the anchor has been dismantled.

=hen the chains are being connected it is lead thro’ a stern

roller chock e)uipped with hori"ontal and #ertical rollers to

protect the railing


18/32

Classification rules

%esign :oads due to >ooring 8peration - %esign load is

based on the maimum load for which the mooring winch is

rated.

%esign load with winch brake effecti#e consistent withre)uirements for anchor windlass on the assumption that

winch brake is designed to be stronger than the braking

strength of the rope. 00 percent of the brake holding load*

noting that 8C&>+ guidance recommends that the brake

should be set at 60 to 90 percent of the line’s breaking

strength.


19/32

=ire @ope2ending fatigue* corrosion* abrasi#e wear* combined with bearing

pressure on the outer wires of the strand are the causes for thedeterioration of the wire ropes in the running rigging. These ropes are

constantly being bent on shea#es and drums e#entually causing breaks

in the wires. 2reaks in outer wire with no e#ident indication of ecessi#e

wear are usually an indication that the wire rope dia is disproportionately

large for the si"e of the shea#e being used or shea#e dia is too small for

the wire rope. Dea#ily loaded wire ropes on small dia shea#es results inhigh bearing pressures between the rope and the shea#e and between

the wires in the rope causing nicksE in the wires where they cross in

making up the strands. This nicking tendency coupled with repeated

bending* e#entually breaks the wires* locks the strands into a solid unit

pre#enting the sliding mo#ement of the wire which slows it to carry itsshare of the load. 8uter strands already nicked and locked become o#er

loaded and accelerate the rope failure.


20/32

@elation of wire rope to shea#e si"e.

&t ad#isable to use the largest shea#e dia with the smallest wire ropes.

The wire rope is bend around the cur#ed groo#e machined around the

periphery of the shea#e or pulley. &t should fit snugly with out pinching

to obtain a proper bearing support there by distributing the load o#er a

maimum no. of strand and wires* thus entering and lea#ing theshea#e groo#e with minimum side wear and friction.

To support a wire rope properly under tension* the shea#e groo#e

should ha#e diameter slightly greater than the rope diameter. @ope

will then be well supported o#er approimately half it’s circumference.

&f the shea#e groo#e is too large it will fail to offer support to wire rope*

and will result in the rope flattening out under tension* increasing

fatigue in the indi#idual strands* leading to early failure of the wires

and rope.


21/32

Capstans and winches.

Capstans* warping winches gypsy heads on cargo winches or anchor windlassesare pro#ided to hea#e in mooring lines. This is done to sa#e on repeat

in#estment and to sa#e precious deck space. These dri#es are designed to gi#e

a speed of up to 40 mtrs per minute.

(lectric both !C and %C and electro hydraulic dri#es are )uite popular.

Typically the no. winches can be eight


22/32

General•

8b'ecti#e of the maintenance schedule is to keep thee)uipment to its original condition as possible. Thee)uipment manufacturer will pro#ide maintenanceschedule. 2ut conditions #ery drastically between type ofships* cargo carried* ports of call* en#ironment etc. andthe schedule too shall #ary accordingly.

• ! few minutes spent on operating and greasing theworking parts when the lubricant has been washed outby rain or spray* can sa#e many hours at a later date.

• !t suitable inter#als inspection shall be carried out forchecking any change in condition of the working partsand made good any gaps.

• (lementary precautions shall see the e)uipment thro’many trouble free years of ser#ice


23/32

>aintenance

!s the location is #ery #ulnerable* the selection of the e)uipmentshall be such that it shall demand less maintenance and also the

design and layout should reflect this.

%esign on ade)uate margin of the strength rather than on life is

the main criteria while on the planning stage.

Slipping clutches safe guard against shocks.

(nclosed oil lubricated gear trains and 8pen type gears too are

common depending on si"es.

/ormally the e)uipments are controlled locally like manual

application of brake while dropping the anchor* stopping and

starting of motors etc. .

2ut remote controls are getting popular in the recent times


24/32

>aintenance

The Chief Officer is normally in charge of lubrication

schedule as .He will liaise with the Chief Engineer for

any defects observed in deck equipment or for any

advice required on correct use of lubricants for the deck

machinery. The Chief Engineer with order lubricants

required by the deck department. A oint inspection by

the !aster along with Chief Engineer " Chief Officer to

be carried out at regular intervals not e#ceeding $

months.


25/32

Chains

%uring docking the anchor chain is lowered from the chain locker to the

dock bottom and laid out for inspection.

This allows the inspection of the chain for broken or lost chain studs. !

random set of links are measured from each shackle length < Shackle

refers to a standard length- nominally 13.5m* of chain 'oined to other

shackle lengths by a splitable link. There is an allowable wear limit allowed

nominally 1. The link showed below has wear in ecess of this and the

shackle length re)uired replacement.

Anchor designs


26/32

>aintenance controls• Ship’s deck e)uipment like windlass and mooring winches

employs relati#ely simple control schemes and a logicalmethod of elimination is the )uickest method.

• (lectrical and electronic e)uipments are usually pro#idedwith manufacturer’s control charts which details the logical

steps for the maintenance.• The simplest of suspects like a 'ammed limit switch* a

blown control fuse* weak relay coil* a loose or broken wireetc should ne#er be o#erlooked.

• >echanical or pneumatic timing de#ices can be checked

with power off howe#er electrical timing circuits or encodersneeds to be energi"ed.

• ! detailed knowledge and operating eperience of a controlsystem is essential for speedy faulty finding* a calm orderly

and logical approach will definitely produce results.


27/32


28/32

Dandling of the controls

The brake holding test of all self storing mooring winchesshould not eceed 1 months inter#al


29/32


30/32


31/32


32/32

anchoring equipments

Documents