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Safe anchoring - planning and operational guidance for cargo ships

Planning for Anchoring

Master Shall Identify a suitable anchoring position before entering the anchorage area. Conduct a planned approach including speed reduction in ample time and orienting the ships head prior anchoring to
(a) Same as similar sized vessels around or (b) Stem the tide or wind whichever is stronger

Decide on which method of anchoring to be used and the number of shackles depending on the depth of water, expected weather and holding ground. A simple rule in determining length of cable to use:

Standard condition:
Length of cable = [(Depth of water in meters * 2) + 90 ] / 27.5
When good holding power can not be expected:

(e.g. Strong Wind, Strong Current, Harder Sea bottom)

Length of cable = [(Depth of water in meters * 3) + 140 ] / 27.5

It is suggested the use of radar parallel indexing technique, an effective tool in maneuvering approach to anchoring position. A fix reference point is necessary in establishing the intended anchoring position relative to this fix point.


Preparation for Anchoring

The Chief Officer (or another experienced officer in lieu) must supervise letting go or weighing the anchors and should only assign experienced crew members to anchor work.

Prior to Anchoring, the Chief Officer should be aware of:

a. Approximate anchoring position

b. Method of approach

c. Which anchor to use

d. Depth of water

e. Method of Anchoring

f. Final amount of Cables


Procedure of the Introduction to Anchoring

At the Forecastle:

Check brakes are on and clear the voyage securing devices

(Anchor Lashings, Bow Compressed Bar etc.)

a. Start Hydraulic(Source of) Power of Windlasses

b. Check Anchor Shape / Light

c. Check Communication with the Bridge

d. Check Lighting on Forecastle including torch , at night time

e. Ensure all personnel are wearing Safety Helmets, Safety Shoes and Goggles.


Before Letting Go Anchor :

The Chief Officer shall confirm that there is no craft or any obstacle under the bow and inform to the Bridge.

The Master shall ensure that the vessels GPS speed at the time of anchoring is near-zero or indicates a slight sternway.

The speed should be verified by visual transits and/or Radar ranges of Landmarks, if available or other fix conspicuous targets.

Where means of communication between Bridge and the Anchoring party is by Portable radio, the identification of the ship should be clear to avoid misinterpretation of instructions from other user of such equipment in the vicinity.


Routine Anchoring Operation

There are 2 methods for Anchoring according to depth of the water:


Method 1 (Preferable for Container Ships / Depths up to 50m )

a. Walk out the anchor to Half a shackle above the sea bottom

b. Hold the cable on the brake and take the windlass out of gear

c. Stop the vessel over ground

d. Drop the anchor

e. Control the speed of cable flow by the brake , while not allowing pile-up

f. Bring anchor cable direction forward and confirmed anchor holds its position.


Disadvantages:

If the brake fails, or there is too much speed over ground, the cable will run out to the bitter end with consequent damage. The brake lining could also be damaged due to this Dynamic load (the Static load on brakes to restrain movement of an anchored vessel is much less).


Method 2 (Suggested for Tankers / Depths over 50m )

a. Stop the vessel over ground

b. Walk out the anchor under power until the complete length of required cable is paid out and anchor holds it position on the seabed.

c. Bring anchor cable direction forward and confirmed anchor holds its position.


Disadvantages:

Vessel must be completely stopped to avoid major damage to Windlass.



Particular Caution for VLCCs

VLCCs, because of their inertia require great caution while anchoring.

They can suffer equipment failure if attempting to anchor whilst moving at speeds as low as half a knot over the ground.

Hence, the vessel must be nearly stopped not only in the linear direction but axial too, meaning the bow should not be swinging much either while anchoring.

The depth at which the vessel can safely anchor is about 110m or less, beyond which the windlass may have extreme difficulty in recovering the anchor.

Refer Further Practice of anchoring / VLCC in deep water for more details.


Emergency Anchoring

Anchors should be ready for letting go on arrival and departure port, when in anchoring depths. At least, any wire lashings are to be removed and the anchors held on brake. In critical situations, to arrest the movement of the vessel, after stopping/reversing the main engine , it is preferable to let go both anchors simultaneously instead of one.


Anchor retrieval

For weighing in the anchors, to reduce the load on the windlass, and keep the cable near vertical ,as required, short movements to be given on the main engine (and Bow Thruster used, where is applicable)

The stay and direction of the cable and the residual shackles are to be continuously reported to the bridge.

Anchor Wash to be run to clean the chain and the anchor.

When anchor is fully hove, the brake is to be applied and the windlass taken out of gear.

The bow stopper is to be put when it is deemed safe to do so.

Note:

If it does not engage properly on the chain, then it is to be lowered across the chain as far as possible and lashed down in this position in such a manner, that if the cable does slip, the bar will fall into place across the chain.


Anchor watch

An anchor watch is to be always kept when the ship is at anchor. Anchor Watch Checklist is to be used




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