anchoring safely

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The Steamship MutualUnderwriting Association

[B ermudal Limited



VID EOTEL PRODUC TIONS ANCHORING SAFELY

ANCHORING SAFELY A VIDEOTEL PRODUCTION

In association with

The Steamship Mutual Underwriting Association [Bermuda] Limited

AUTHOR

Johnathan Priest

rnVIDEOTEL productions

84 Newman Street , London wn 3EU

Telephone : +44(0]20 7299 1800Facsimile: +44(0]20 7299 1818

E-mail: mail0videotelmail.com

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VID EOTE l PRODUC TIONS ANCHORING SAFELY

ANCHORING SAFE Y AVIDEOTEL PRODU CTION

In association with

The Steamship Mutual Underwriting Association [Bermudal Limited

THE PRODUCERS WO ULD LIKE TO ACKNOWLEDGE THE ASSISTANCE OF

The Master, Officers and Crew of MV Berge Nord

Bergesen d.y. ASA

International Maritime Organization

The Maersk Company

The Steamship Mutual Underwriting Association [Bermudal Ltd

United Salvage Ltd

Warsash Maritime Centre

World Wide Shipping

CONSULTANTS

Sir William Codrington

Captain Allan MacDowall

PRODUCER

Peter Wilde

WRITER/DIRECTOR

Charles Leigh-Bennett

PRINT AUTHOR

Johnathan Priest

WARNING

Any unauthorised copying, hiring, lending, exhibition diffusion, sale, public performance or othe'r exploitation of this video is strictly prohibited

and may result in prosecution .

© COPYRIGHTVideotel2005

This video is intended to reflect the best available techniques and practices at the time of production, it is intended purely as comment. .

No responsibility is accepted by Videotel, or by any firm, corporation or organisation who or which has been in any way concerned, with the

production or authorised translation, supply or sale of this video for accuracy of any information given hereon or for any omission herefrom



VI DE OTEL PRO DU CTION S AN CHORING SA FELY

INTRODUCTION 4

What subject does this training cover? 4

How to use this guide? 4

What does this guide provide for trainers? 4

SECTION 1 ANCHORING - THE HAZARDS 5

SECT ION 2 ANCHORING EQUIPMENT 6

2.1 The anchor 6

2.2 The windlass 6

2.3 Preventing damage to the windlass motor and clutch 7

2.4 Preventing damage to the windlass brake 8

SECTION 3 PREPARING TO ANCHOR · 9

3.1 Lying at single anchor 9

3.2 Basic procedure 10

SECTION 4 ANCHORING A VERY LARGE VESSEL 12

4.1 Is equ ipment keeping pace? 12

4.2 The traditional Fore & Aft [in-line] approach 13

SECTION 5 AN ALTERNATIVE APPROACH TO

ANCHORING 16

5.1 The U-turn method 16

5.2 Axial verses rotational forces 16

SECTION 6 USING THE U-TURN METHOD 18

6.1 Operational br iefing 18

6.2 Approach to anchorage 19

SECTION 7 ANCHOR WATCH AND SECURITY 21

SECTION 8 WEIGHING ANCHOR 22

SECTION 9 CONTRIBUTORS 24

3



VIDEOTEL PR ODUC TIO NS ANCHORING SAFELY

WHAT SUBJECT DOES THIS TRAINING GUIDE COVER?

This training guide examines the general principles of safe anchoring for

medium to large vessels including VLCCs and bulk carriers . The need to

review anchoring procedures is born out of an increased incidence of

personal injuries, damage to anchoring equipment and even loss of shipscaused by the difficulties of anchoring large vessels. An overview is

provided of the proper use of anchoring equipment and its mechanical

tolerances. An alternative to the traditional approach to laying anchor is

also described.

HOW TO USE THIS GUIDE?

The guide is published in an association with a video of the same title

'Anchoring Safely' which provides an overview of anchoring and which

demonstrates some of the techniques described herein. The guide

provides the theoretical background to anchoring procedures

demonstrated in the video and describes them in far greater detail.

To this day, anchoring remains a hotly debated topic and companies and

their masters have strongly hel.d opinions as to how it should be carried

out, many of which are also a matter of company policy. The publishers

wish to make it clear that the information provided in the video and guide

is based on widely accepted best practice but is in no way intended to

provide anything other than guidance.

WHAT DOES THIS GUIDE PROVIDE FOR TRAINERS?

This video and guide provide trainers with a concise overview of the basic

principles of safe anchoring and will help them to increase awareness of

this vitally important aspect of seamanship. The procedures described are

based on a sound understanding of engineering tolerances of anchoring

equipment and the dangers to personnel and equipment associated its

misuse. The main procedures for laying and weighing anchor are

described as well as the requirements for anchor watch . The trainer's

experience and expertise remain essential in interpreting these

procedures in the context of the variety of physical conditions and local

constraints that mariners will encounter.

4



VIDEOTEL PRODUCTIONS AN CHORING SAFELY

ANCHORING - THE HAZARDS

Anchoring is a highly skilled operation that requires

leadership, teamwork and the utmost vigiLance from thetime the ship arrives at port to the moment the anchor is

weighed. Ships often have to go to anchor unexpectedly

either due to changes in berth availability or weather

conditions. Anchors and windlasses need to be well

maintained and ready for use at any time in port

approaches and harbours.

Pressure on berths around the world means that merchant ships may

have to remain at anchor for long periods . This is demanding on masters,

pilots and crews, especially on the largest vessels where exceptional care

is required to anchor safely and without causing damage to other shipping

or port facilities.

There have been increasing reports of accidents to ships while lying at

anchor including drifting, collision and stranding caused by dragging. Many

accidents and equipment losses also occur when the anchor is being laid or

weighed. Reported incidents tell of vessels losing the anchor due to the

cable parting, of vessels whose windlass brake caught fire and more than

one vessel whose cable was pulled from the locker with such force as tonot only part the bitter end, but fracture the bulkhead on which it was

mounted. A major consideration is that such inc idents are often associated

with personal injuries and

even loss of life and is

therefore a concern for ship

owners and masters alike.

It is an unfortunate fact

that many of these

accidents have been

caused by poor basicseamanship and failure to

plan ahead. The advent of

very large vessels such as

VLCCs and bulk carriers

has added to these

concerns, where not only

are the costs and

consequences of anchoring

accidents that much greater, the technical challenge of anchoring such

large vessels is also greatly increased. It is therefore timely to reviewanchoring procedures and to see how the risk of accidents can be reduced.

to a minimum.

5



VIDEOTEL PRO DUCTIONS AN CHORIN G SAFELY

ANCHORING

EQUIPMENT

SPECIFICATION

for 150,000 tonne

deadweight ship

ANCHORING EQUIPMENT

2.1 THE ANCHOR

The requirement of an anchor is to bite firmly into the seabed, provide enough holding power and to remain in the

right position without overturning even when pulled over

the sea bed.

The total mooring power of an anchor is the sum of the holding power of

the anchor combined with the resistance created by the cable on sea bed.

The cable also has an important role in maintaining the stability of the

anchor. Maritime vessels are generally equipped with 11 to 14 shack les of

cable, each shackle being 27 .5 metres in length. The amount of cable paidout will vary according to the depth of the water and the conditions and

this will be specified as part of the anchoring plan.

2.2 THE WINDLASS

Oamage to anchoring equipment and numerous personal injuries have

been caused by incorrect use of the windlass . A typical example of misuse

is the windlass motor [rather than the brake! being used to payout the

cable . This may result in motor over-pressurisation causing excess internal

surface to surface forces and then fracture of the motor casing . If the

windlass brake is misused, the lining can in extreme cases actually catch

fire, a situation often compounded by inadequate maintenance .

ICab le "4"."M"9""'i't',In'

Spur li ng pipe

From the diagram, you can see that the only piece of equipment on board

that is designed to take the full weight of the vessel is the bow stopper,

with a rating of 480 tonnes. By contrast, the windlass motor has a lifting

power of just 32 tonnes [3 shacklesl or 38 tonnes [4 shackles!' It is

designed to l ift or lower an anchor and three shackles of cable through a

maximum of 82 meters of water in a verticallift.l

6 I Th ere IS a proposa l by the lACS (International Asso cIatIon of Cla sslflcalion Soc ietlesl that the wi ndlass should be cap ab le 01 ifting the anchor and

cable in 110 me r s of wa ter The wind speed of 14 m/sec 128 knots l. and a three kn ot cur re nt lunchang ed l. at a speed of 0 I Sm /se c 19m/m in i

thoug h this has not been adopted . Alm osl all ships are deS gned to the 82 metre rule.



VIDEOT EL PR ODUCTIONS ANCH ORING SAFELY

The crew should have a clear understanding of the implications of any

variation from the vertical [up-down] position of the cable while the anchor

is being manoeuvred. Any angle out of the vertical indicates horizontal

force that includes part of the ship 's mass, which strictly speaking is not

allowed for in the specification. Any changes in the alignment of the cablerelative to the hull should be communicated to the bridge immediately so

that the position of the ship can be altered to remove the load on the

cable.

A 150,000 tonne deadweight ship has the following anchor equipment

rated 'as new' according to the Classification Society rules:

LIFTING POWER OF ANCHOR WINDLASS 38 TONNES FORCE

WINDLASS BRAKE HOLDING POWER 279 TONNES FOR CE

CABLE STOPPER S , ~ F E WORKING LOAD 480 TONNES FORCE

ULTIMATE TENSIL E STRENGTH OF CABLE 600 TONNES FORCE

LENGTH OF 1 CABLE - I SIDE 13 SHACKLES

WEIGHT OF 1 SHACKLE OF CABLE 7.2 TONNES FORC E

WEIGHT OF 1ANCHOR 10.6 TONNES FORCE

Tankers are also fitted with two bow stoppers each rated at 200 tonnes

force for SBMs.

2.3 PREVENTING DAMAGE TO THE WINDLASS MOTOR

AND CLUTCH

Whether electric, hydraulic or steam, the windlass is designed purely to

control the weight of the anchor and three [or fourl shackles of cable. In

particular, the windlass gearbox should not be used as a low ratio box as

in a motor vehicle where the gears are used to slow its descent down hill.

If the gear bo x is subject to such reverse forces, serious mechanical

damage is likely to result.

Exceeding the designed limits of hydraulically powered windlasses willcause the system to become over pressurised. If bearing pressures within

the motor are exceeded, metal will be shaved off its components . These

shavings pass through the coarse filter and into the pump . Further

increase in bearing pressure can cause the casing to crack . In such a

situation, the veered cable cannot be recovered.

External forces appl ied to the valve/slide gear

of steam windlasses will cause the drive to be

driven. This can result in failure of the eccentric.

The dog clutch may jump out of engagement

due to the parting force at the dogs and theclutch operating fork will deform from its bed

within the annular groove on the dog.

7



VIDEOTEL PRODU CTIONS ANCHORING SAFELY

Failure to insert the clutch lever securing pin will also lead to clutch

disengagement. If the faces are badly worn, the clutch can jump out of

gear even if the clutch operating lever is properly pinned because the fork

is not sufficiently strong to resist the force pushing the dogs apart. The

fork may also have become distorted.

2.4 PREVEN TING DAMAGE TO THE WINDLASS BRAKE

The windlass brake, not the motor, should be used for paying out the cable.

This is because the brake has a rated static applicable force some 10 times

that sustainable by the motor. However, use of the brake relies heavily on

the skill of the crew and the proper 'as new' maintenance of the brake

mechanism. On larger vessels, the brake should always be manned by two

crew members as the rated force cannot be applied by one man alone.

A NUMBER OF SITUAT IONS WILL LEAD TO BRAKE DAMAGE

• Brake has been screwed up tight but the vessel's momentum

causes it to slip

• Slipping causes heat generation and the brake to fade

• Heat causes the brake band to expand and so become less tight

• Heating by friction causes the brake to fade even more

LIKE THE MOTOR. THE BRA KE HAS VERY SPEC IFIC DES IGN LIMITATIONS:

• The windlass brake is designed to control the cable running out

and to stop it vertically without the ships weight on it

• The windlass brake is not designed to arrest the motion of the ship

• The windlass brake is not designed to hold the mass of the ship

Brake use should ideally be practiced a minimum of once a month fo r each

windlass. Failure to do this will quickly lead to seizure of parts because sea

water causes very rapid rust build-up . Talking through the procedure is

also a helpful way to remind crew of the precise sequence of events. In an

emergency, having the skill and ability to drop the anchor will save the day.

Use of the motor rather than the brake could have insurance implications

due to improper use of equipment.

The bow stopper must be engaged and the motor declutched when the drop

is finished, with the cable in the up and down position . As you can see from

its load specification, the bow stopper has 1.7 times the holding power of

the brake and is the only piece of equipment that is designed to take the

full load of the ship at anchor. However, in order to be effective, the bar of

the bow stopper must lie on the horizontal link with the locking bar in place

with no gap that could allow the tongue to lift, otherwise the bow stopper

could ride over the vertical link when weight comes on the cable and distort

the locking bar.

8



VID EOTEL PRODUCTIONS AN CHORING SAFELY

PREPARING TO ANCHOR

Advanced planning and excellent communications

between the bridge and the anchoring team are essential

to safe anchoring. The master will ensure that the crew is

trained in the use of the anchoring equipment and has

access to accurate and up-to-date information about the

anchorage so that an anchoring plan can be prepared.

The master should select an anchorage that is sheltered, with good

holding ground and an appropriate depth, depending on the ships own

manoeuvrability and conditions. Weather and sea conditions and dangers

such as submarine cables, pipes and wrecks should al l be taken into

consideration.

3.1 LYING TO A SINGLE ANCHOR

Although the method varies depending on the depth of an anchorage, lying

at a single anchor is most frequently used because of its handling

simplicity when dropping and weighing anchor.

In this pattern the anchor is usually let go under very slight sternway. The

ship s speed is reduced according to the plan, the engine is stopped just

before the anchorage and ships advances only by its momentum. The engineis put astern just before the anchoring point so that the ship stops at the

intended spot. The anchor is le t go just after the ship is dead in the water.

9



VIOEOTE L P ODUCTIO 5 ANCHORING SAFELY

3.2 BASIC PROCEDURE

Here is the basic procedure for anchoring a small to medium size vessel:

BEFORE ARRIVAL AND AS PART OF THE ANCHORING PLAN

• Select the position of the anchorage and plan the approach

• Determine how to reduce the ship's speed from the initial approach

to the intended anchorage

• Establish the depth of water, nature of bottom, which anchor to use

and how much cable to payout

• Decide manning for anchoring including the personnel on bridge,

engine room, fo'c'sle, pilot ladder or gangway if required

• Brief the anchoring team

SHORTLY BEFOR E ARRIVAL

• Clear the anchors, hawse and spurling pipes

• Test the windlass and brake

• Test communications

• Prepare to display anchor signal. (ball daytime, lights at night]

ON NEARING THE ANCHfJRAGE , AMEND TH E PI..AN TO INCORPORATE:

• Other ships in the anchorage

• Local weather and sea conditions

• Local navigation warnings and regulations

• Orders from the authorities

• Advice from the pilot or Vessel Traffic Services

APPROACH THE ANCHORING POSITION BY HEADING INTO THE

PREDOMINANT FORCE IEITHER WIND OR CURRENT/TIDAL STREAM,

USUALLY THE LADER)

TAKE WAY OFF THE SHIP AND THEN MAKE VERY SLIGHT STERNWAY

LET GO THE ANCHOR. CONTROLLING WITH THE BRAKE ONCE THE

ANCHOR IS ON THE SEA BED AND SLOWLY PAYING OUT AS THE SHIP

MOVES ASTERN

DISPLAY THE PROPER SIGNAL FOR A VESSEL AT ANCHOR AT NIGHT,

SWITCH OFF THE STEAMING L1GH S

10



VIDEOTEL PRODUCTIONS ANCHORING SAFELY

KEEP THE BRIDGE INFORMED WHETHER THE CABLE IS TIGHT AND HOW IT

IS LEADING , tOR EXAMPLE "UP AND DOWN" OR '·TIG HT AND LEAD IN G'

TELL THE MASTER HOW MANY DEGREES THERE ARE BETWEEN THE

ANCHOR AND THE BOW , SO THAT HE CAN ASSESS WHETHER THE

ANCHOR IS UNDER ANY STRAIN

WHEN THE CABLE HAS BEEN PAID OUT TO THE AGREED SHACKLE MAR K

['FOUR IN THE WATER ' "SIX ON DECK : OR SIMILAR!, THEN APPLY THE

BRAKE THE BOW STOPPER SHOULD THEN BE APPLIED AND SECURED

WITH THE PIN, THE SHIP SHOULD BE STOPPED OVER THE GROUND US IN G

THE ENGINE

WAIT FOR THE CABLE TO COME TAUT AND THEN SLACKE N TO SHOW THE

SHIP IS ' BROUGHT UP" (WATCH FOR THE CABLE GO IN G TAUT AND THEN

SLACK , TAUT AND THEN SLACK, OR JUDDERING WH ICH MEANS THE

ANCHOR IS DRAGGING)

CHECK THAT THE BRAKE IS SCREWED UP TIGHT AND THE BOW STOPPER

SECURE .

SET ANCHOR WATCH ON THE BRIDGE AND SECURITY WATCHES

DISPLAY ANCHOR LIGHTS / ANCHOR BALL

11



VID EOTE L PROOU CTIO S ANCHORING SAFELY

SECTION 4

, 1I

, . ~ '

ANCHORING A VERY LARGE VESSEL

4.1 IS EQUIPMENT KEEPING PAC E?

While the general principles described for small tomedium sized vessels also apply to very large vessels

such as VLCCs, the hazards associated both with Laying

anchor and while lying at anchor are greater with a large

vessel, as are the likely consequences of any accidents.

It is a widely held belief that these failures are in part due to the

specifications of anchoring equipment not keeping pace with the

increasing size of vessels . However, an examination of classification

society specifications reveals this not to be the case . In the vast majority ofincidents, accidents are related to a combination of inadequate

preparation fo r anchoring, poor seamanship, lack of communication

between bridge and fo' c'sle, misuse of anchoring equipment and

inappropriate anchoring procedures. Concerns about the increased risks

associated with anchoring very large vessels have led some companies to

issue instructions to the effect that the anchor must be walked out al l the

way, regardless of the depth in which the vessel might be anchoring.

DESIGN CRIT ERIA-

EQUIPMENT LETTER

Derived from: f:... 113 ';' 2BH i AIIO

Where: = SUMMER DISPLACEMENT IN TONNES

B'= MOULDED BREADTH IN METRES

H = SUMMER FREEBOARD IN METRES

,:J., = AREA OF THE PROFILf OF THE HULL IN SQU RE METRES

The various classification societies arrive at the equipment letter through

the above formula which confirms that the design capabilities are directly

related to the size of the vessel,

12



VIDE OTEL PR ODUC TI O S ANCHORING SAFELY

I

I

SECTION 4

......

.~ ,

4.2 THE TRADIT IONAL FORE & AFT (IN-LINE]

APPROACH

In the traditional in-line approach, where the anchor islaid in line with the ship's fore and aft axis, walking the

anchor and cable back the whole way is permissible,

provided the cable is kept up and down the whole time and

that the design speed of the windlass is not exceeded.

While this is easy enough to say in practice, with a very

large vessel thiS is a difficult manoeuvre and risk of

damaging the windlass is relatively high .

13



SECTION 4

VIDEOTEL PRODUCT IO I S ANCHORING SAF ELY

A WORST CASE SCENARIO

A vessel is to anchor in the traditional in-line method. The anchor is

walked back just clear of the water, the engines are put astern and

when the wake has reached the bridge wing the engines are stoppedand the order given to le t go. The cable is allowed to run freely as the

vessel moves slowly astern. At eight shackles on deck the cable is

snubbed and at ten on deck, the brake is screwed up tightly. Inability to

arrest the vessel within the very small distance twixt up and down and

bar taught results in a cable with no elasticity left. Even though the

brake is screwed up tightly, the vessels momentum exceeds the

brake's 279 tonnes resistance and the brake begins to fade. Fading

causes heat generation which, through volumetric expansion, enlarges

the internal diameter of the brake band, thus allowing more fading.

Despite checking the astern motion, the motion of the vessel is too

great and it continues to move astern. The brake band is now so hot it

has expanded such that the cable is now accelerating . Before the

vessel can be brought to a complete stop, the three remaining shackles

have been drawn from the locker. Detachment of the bitter end or

certainly deformation of the chain locker is likely to follow.

The momentum of the cable and its direction of motion are such that

the cable will leave the gypsy and arc above it. When the end finally

parts, energy within the cable is quite sufficient to punch a hole

through 20mm plate and carry away any deck fittings in its path .

Given that putting out 10 shackles with the motor takes in excess of half

an hour at 5cms per second, it is exceedingly difficult, especially with

larger, diesel-powered vessels, to control sternway to such a fine degree.

The long period of time required to payout the anchor cable sometimes

leads to masters using less cable than they should. There have been

incidents where this has lead to anchor dragging and consequent

grounding. Even the most experienced master may run into difficulties andthis is because the traditional approach to anchoring already places him at

a mechanical disadvantage.

Take the example of a vessel anchoring in 50 metres of

water with 10 shackles:

The difference in horizontal distance between the position of the vessel

when the cable is up and down and if, it became bar taut would be

approximately 50 metres. Now, a 150,000 tonne vessel has a beam

approaching 50 metres. So the challenge is easy to visualise; the master istrying to stop a ship of say 300 metres within a distance roughly equal to

its beam.

14



VID OTEL PRODU CTIO NS ANCH ORIN G SAFELY

SECTION 4

ANCHOR ON SEABED

THE TRADITIONAL FORE &

AFT (IN-LINE) APPROACH

~ ~ ~ TIDE AND WIND

The engines should be used to take

sternway off the ship. Failure to halt the

astern movement will result in a bartaut cable with no elasticity left because

al l the catenary has been taken up. The

full mass of the ship comes onto the

windla ss. The force now being exerted

on the windlass is now about 1000

times maximum allowed l

15



VIDEOTEL PRODUC -I IONS ANCHORING SAFELY

The force required, at

the stern, to ') IE the

vessel in a straight

line is approximately

three times that

required to TURN the

vessel by applying a

force at right angles

to the stern

AN ALTERNATIVE APPROACH TO ANCHORING

5.1 THE U-TU RN METHOD

The U-turn or more precisely, orthogonal method of anchoring has a long

historical precedent and has been the practice of a number of masters for

many years. Its benefits have also been discovered during emergencies

when the master's quick reactions and knowledge of how to lay anchor on

the move have saved the day. However, prior to the mathematical and

mechanical analysis carried out by Captain Allan McDowaW, such a

procedure could not become mainstream and owners would have been

reluctant to incorporate it into their operational procedures .

The procedure is not without risk and its success depends on the crew

having a clear understanding of the procedure with appropriate training in

the use of the equipment. Because timing is critical, excellent

communications must be maintained between bridge and fo·c'sle. Masters

and crews who have not used this method before should ensure that

adequate sea room is available. With experience however, the manoeuvre

can be safely completed within a relatively compact area.

5.2 AXIAL VERSUS ROTATIONAL FORCES

The secret of the U-turn approach to

anchoring lies in separating the momentum of

the ship's hull from the forces necessary to

control the movement of the cable.Consider a block shaped vessel, it has a block

coefficient of 1. The force required to

accelerate the vessel in the fore and aft line is

three times that required to rotate it about its

pivot point . That is why it is easier to push a

small sailing boat sideways or rotate it round

its axis than move it in the fore aft line.

It follows that to decelerate the same block in

rotation would be one third the force required

to stop its axial momentum .

TURN a stationary vessel

Force r"qulre cl 10 I D ! ~ E . 16 ' Anchomg I_arge Vessels - A new ap proach. Ca pt C. A. McDowall. The Naut ical lnsll tute, 202 Lam beth Road, London SEI 7LQ. ISBN 1 87077 56 3



VIDEOTEL PRODUC TI ONS ANCH ORING SAFELY

This difference is because rotational inertia is less than the axial inertia; it

is a change from straightforward linear acceleration to one of angular

acceleration. A further contributory factor is that in the latter, the distance

from the axis of the centroid is part of the overall equation, whereas in the

former the distance from the axis of the centroid does not enter into the

equation.

However, a ship is not a rectangular block in plan view, but a diamond or

lozenge shape. Taking this as the best fit shape, the block coefficient is not

1 but 0.5. The radius of gyration of the new shape is now one third that of

the full box shape.

Since the radius of gyration is part of the equation which gave a one third

reduction in force required to decelerate the box shape, then it follows that

with a block coefficient of 0.5, the reductions is now one ninth. But the

mass has now been halved, so the factor of 9 must also be halved, giving a

final figure of 4 1/2. Thus for a block coefficient of 0.5 the reduction factoris 4 1/2, whilst for a block coefficient of 1, it is 3. The ship shape lies

somewhere between these two and can be assumed to be equal to 7/2.

Instituting a turn at the point where the anchor is

let go will change the force on the cable from one

of axial translation to one of rotational translation.

But one of the factors of rotational inertia is the

distance from the axis through the centroid. By

using the anchor and cable this distance has now

been increased by the length of the cable, a factor

of 6.5. By applying the two factors [7/2 X 13/2J onefinds the force on the cable is approximately 23

times less than the original case l

Clearly, keeping the cable at right angles to the

hull greatly reduces the likelihood of extreme

forces being applied to the anchoring equipment

which is why the U-turn method is very much

safer and is associated with far fewer accidents.

When the cable is at 90 degrees to the fore and

aft line, fore and aft movement does not affect

the tension of the cable, or only minimally. In this

way, it is very difficult to exceed the forces that

one is trying so hard to avoid with the fore and aft

method.

This technique is also more forgiving should the

master have misjudged the speed and is moving

too fast and especially in the event of engine

failure during the anchoring procedure. This is

quite impossible using the traditional, fore and aft

method. Having the skill to anchor a vessel which

is moving is one that can save the ship, possibly

your life and your job!

17




USING THE U-TURN METHOD

The anchor and gear is prepared as for any normaL

anchoring. The windLass is tested in both directions, the

Locker checked for obstructions, the dog clutch engaged,

the anchor walked out clear of the hawsepipe, brake on,

bow stopper/compressor on and clutch out. The master

shouLd always take personal responsibility for these

checks.

6.1 OPERATIONAL BRIEFING

Before the anchor is to be let go, there need to be two pre-operational

briefings. The first briefing is a training session to ensure that the

personnel concerned know exactly how the equipment works and should

be used. The second briefing is just before anchoring, to ensure that the

crew understands that :

SECOND BRIEFING :

• On large ships there should ideally be two men on the brake since

the rated force cannot be applied by one man alone.• The anchor will be lowered under power to an ordered number of

shackles on deck, say two, prior to taking out of gear and letting go .

on the brake.

• When the cable is released, the cable will be let out in a controlled

manner so that each !.ink can be followed with the eye.

• The cable is kept running out until the desired length is all out,

which avoids the brake fade caused by the more common practice

of stopping and starting.

• When the cable is out at the desired length, the cable is stoppedfrom moving by the brake then the bow stopper is put on. The safe

pin is fully engaged whilst the cable is stopped and still vertically

up and down .

• When the bow stopper is on, the bridge is to be kept informed of

the direction of the lead on the cable which must be kept on the

beam until all movement has ceased . Only then can the cable be

allowed to draw slowly ahead .

If the bottom is known to be very deep, or particularly rocky, it would beprudent to walk the anchor out until just clear of the seabed.

18




TIDE AND WINDApproach downwind/tide with

J, minimum steerage way of 2-3 knots. UJ, Hard a·starboard.

Dead slow ahead.

J,

Allow full scope to pay

out in one controlled

movement. Appty bra ke

and compressor

Short bursts of ahead

or as te rn power to keep

the lead as near

perpendicular to the

for ecastle as ispossible .

Short bursts of power

to co ntrol drift. Vessel

bought up . Cable in

s hallow bight on

seabed.

Only sideways drift (ftoP engines

Let go starboard anchor Observe sWing135 0 off course, all forward

\\ - ~ o ' ' ' ' ' ' 5<., '"9'""a." co"'''

\\)v V (

Tension in the cable now

snubbing the bow and the vesselis drifting astern under wind/tide.

r Sl .w."" ,

6.2 APPROACH TO ANCHORAGE

The objective is to let the anchor go with the bow moving sideways over the

sea bed at about 0.5 knots . The actual speed of the bow may be much

greater by this method and the manoeuvre has been successfully

accomplished by Captain McDowall at speeds of up to 4 knots ahead whilst

turning. The turn will always stop the ship. In cases where you cannot

afford to wait, some forward speed can be accommodated, provided the

cable is kept on the beam. The sideways movement is very slow.

Using the reverse of the normal approach, steam the vessel into the

anchorage downtide/wind with minimum steerage way, that is with

engines stopped and steerage being maintained by short bursts of ahead

power. When nearly abeam of the desired position, put the helm hard over

and give a kick of Dead Slow Ahead. Only at this point should the bowstopper/compressor be removed.

Once the swing has started and the vessel is seen to be turning the

correct way, take care because wind on the accommodation block can

cause the vessel to swing the opposite way, the engines must be rung

down to Stop again. When the heading has changed by about 45° put the

engines Slow Astern. The duration of this burst should only be sufficient to

take off the forward motion, it is not to get the vessel moving astern. If the

vessel is fine lined, the astern movement will have the effect of making

the turn tighter. However, this engine movement is usually unnecessary

because the act of turning and the ship's projected underwater side areastops the ship after a turn of around 120 degrees.

19



VIDEOTEL PRODUCT IONS ANCHORING SAFELY

By the time the vessel's heading has changed by 90° the greater

component of its motion will be sideways with only a very small proportion

being in the forward direction. At 135°, all forward motion should have

ceased and the vessel will only be experiencing a small sideways drift. A

short kick Slow Astern may be required to ensure this. The anchor is le t

go in one controlled operation, allowing the full scope to be payed out inone movement. The brake and compressor are applied along with safety

locking pins.

The vessel will continue its sideways drift and draw the cable along the

seabed at right angles to the fo'c'sle. Communication between bridge and

fo'c'sle are paramount to the success of this manoeuvre as the fo'c'sle

officer must keep the bridge informed of the direction of lead . Short kicks

of ahead or astern are given as required in order to keep the lead at right

angles to the vessel.

Eventually the tension in the cable will snub the bow and start to turn the

vessel towards her cable; at this point it may be necessary to use engine

movements to control the rate of turn. As the vessel points on her cable

the effect of the wind/tide will initiate astern motion, again it may be

necessary to check the effect of this by use of engines.

By the time the vessel is laying head to tide/wind the cable will have been

drawn out in an arc on the sea bed and will be acting as an additional

shock absorber.

Once you are accomplished in this manoeuvre, the speed of approach may

be increased just so long as the corresponding astern movement at the

commencement of the turn is also increased. This will not only have theeffect of reducing the forward motion more quickly but wil l also reduce the

radius of the turn.

TRIED AND TESTED

This manoeuvre has been tried and tested on a number of different types

and sizes of vessel. It takes approximately 12-15 minutes from initiation of

turn to bow stopper on . On one occasion it was performed in an

emergency due to main engine failure when the vessel was preceding

.downtide at a speed of 12 knots. One company which had previously been

plagued by accidents, incidents and dangerous occurrences has been

using this method for some five years and since then has not had any

further incidents of failure of anchor gear or other unsafe occurrences

whilst anchoring. However, it is for individual operators and their masters

to assess the most appropriate method of anchoring for their vessels and

this technique is described here purely as an alternative approach which

may have benefits in certain circumstances.

20



VIDEOTEL PRODUCTIONS AN CHORING SAFE LY

ANCHOR WATCH AND SECURITY

The main purpose of anchor watch is to keep the vessel

safe at all times. In particular, it will be necessary to look

out for signs of anchor dragging such as a swinging

motion of the ship, the ship moving sideways, weather

side constant, cable vibrating. cable constantly taut and

positional changes relative to nearby ships.

The ship 's position should be monitored by whatever means possible and

the master informed if the ship moves outside the scope of the cable. If

anchoring in silt, it may be necessary to weigh and let go anchor every day

or so. It is also important to keep a lookout for any craft approaching orpeople seeking to come on board to ensure that they are legitimate

visitors, following the procedures set out by the company in accordance

with the International Ship and Port Facility Security Code [ISPS Codel.

WATCH KEEPING DUTI ES :

• Monitor ships position

• Maintain continuous effective lookout

• Ensure suitable fire/piracy controls

• Monitor effective communication internally and externally

• Check anchor and cable are ranged correctly

• Ensure correct signals are displayed at correct times

• Note tide and flow changes

• Ensure vessel complies with COLREGs [Regulations fo r Prevention

of Collisions at Sea , Rule 30 Anchored vessels and vessels

aground]

• Inform Master of any changes affecting vessel

21



VIDEOTE L PR ODUCTIO NS AN CHORING SAFELY

WEIGHING ANCHOR

Weighing anchor requires similar preparations to

anchoring, in particular making sure that all theequipment is functioning properly and that the working

space around it is clear and safe.

Power supplies to the windLass must be switched on and checked and the

proper functioning of the clutch and brake tested, whiLe the cabLe is held

on the bow stopper. The chain locker, spurling pipe and hawse pipes

shouLd be checked . Communications with the bridge should also be

tested.

It must be remembered that the windLass is designed for a vertical lift of

one anchor plus three shackles (or 82 metres] of cabLe. If the anchor is

leading out of the verticaL, this may cause damage if forces in excess of

these limits are applied. The ship's engines and heLm can be used to

bring the cable as near vertical as possible.

When instructed to do so, the windlass should be put into gear, the bow

stopper released with the stopper removed before the brake is released.

No weight must be on the stopper when the locking bars/pins are removed

or a serious accident could ensue. Again when instructed to do so, start to

heave away, making sure the cable is clear and not fouling the ship's

structure, hosing off the mud and debris as the cable comes in .

Normally, the cable washers in the hawse pipe will clear any mud from

the anchor. If the cable is heaviLy coated with clay, then heaving more

slowly usually does the trick. Failing that, a powerful hose should be used .

If the anchor has picked up a cable or other obstruction the windlass

should be stopped immediately and the bridge informed .

If everything is normal, reports should be made to the bridge of how the

cable is leading, when it is clear of the sea bed, [this may not be obvious if

the cable is already vertical! and when it is clear of the water.

The anchor ball should be lowered or anchor Lights switched off when theanchor is weighed.

22



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- - -

VID EOT EL PRODUCTI ONS ANCHORING SAFELY

SECURING FOR SEA

When the anchor is clean and ready to be stowed, it should be heaved

home into the hawse pipe, the brake applied and bow stopper put on,

together with extra lashings as required. A tight lashing should ensure

that extra weight does not come on the bow stopper. If the anchor isneeded for use in an emergency, the bow stopper can be removed by

hand.

DURING THE VOYAGE

It should be remembered that anchor may s hift and become loose,

especially in heavy seas. The securing may need to be checked and

repeated during the voyage. A loose anchor moving in the hawse pipe can

cause serious damage

23



VIDEOTEL PRODUCTIONS ANCHORING SAFE

CONTRIBUTORS

The work of Captain Allan McDowall MSc CEng MIMechE MRINA FNI.

Drawings on pages 6, 16, & 19 adapted from originals by J N Wilde.

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anchoring safely

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