anchoring

ANCHORING
• Anchoring is as frequent operation on board as loading and
unloading a cargo
• Anchoring is routine job
• Number of incident during anchoring or while at anchor suggest that we might not have yet
mastered the art of anchoring a ship effectively
• Knowing about the correct anchoring procedures and their limitations is one of the best way
to avoid anchoring related fatalities and damages
HOW AN ANCHOR HOLDS THE SHIP?
• when an anchor is dropped, the crown of the anchor is the first to hit the sea bottom. as the ship
moves back, the flukes takes its position and embed itself into the sea bed
• it does not matter from what height the anchor is dropped, the crown will alway hit the bottom
first.
• the flukes will only dig into the sea bed once the ship moves aft and flukes are facing
downwards in to the sea bottom
HOW AN ANCHOR HOLDS THE SHIP?
• opposite happens when we pick up the anchor
• when the chain is all picked up, the flukes face upwards and gets uprooted from the bottom
HOLDING POWER OF ANCHORS
• all other factors being common, there are three things that affects holding power of anchors:
• first is the construction of anchor
• second is the nature of seabed
• third is the scope of the cable
HOLDING POWER DUE TO ANCHOR
CONSTRUCTION
• a ship’s equipment number decides the weight of the anchor and length of the chain
• the fluke area determines the holding power of the anchor
• international association of classification societies (iacs) governs the rules for anchors
• iacs enlist three types of anchors:
1.
normal holding power anchors
2.
high holding power anchors
3.
super high holding power anchors
HOLDING POWER DUE TO ANCHOR
CONSTRUCTION
HOLDING POWER DUE TO ANCHOR
CONSTRUCTION
• even though anchor weight has nothing to do with holding power per se, it contributes to some
extent in holding a ship in its position
• more weight of the anchor would need more force to push the ship from its position
• for this reason, anchor weight is more often used as a function of holding power
HOLDING POWER DUE TO NATURE OF SEABED
• sand is considered to be the strongest holding ground
• soft mud is the least holding ground (anchor embeded into soft mud would leave the bottom easily
compared to more harder surface like sand)
HOLDING POWER DUE TO SCOPE OF THE ANCHOR
CABLE
• correct scope is essential for safe anchoring and better holding of the anchor
• scope is the ratio of depth of the water to the length of the cable deployed
• more the scope, better an anchor will hold the ship
• the idea of having more scope is that the angle of chain with respect to sea bottom should be
minimum
• more the angle, lesser the holding power
HOLDING POWER DUE TO SCOPE OF THE
ANCHOR CABLE
• as a thumb rule, scope of 6 is advisable for anchoring
• that is when anchoring into a depth of 20 meters, we should pay at least 120 meters of cable
• when anchoring in areas of strong wind or current, we should have scope of more than 6, up to 10
sometimes
PREPARING FOR ANCHORING
• preparing the vessel for anchoring can start days before arrival
• master checks the charts for marked anchorage areas days before arrival
• anchorage area for the vessel could also be suggested in the agent’s pre-arrival message
PREPARING FOR ANCHORING
• anchorage area must be physically checked in the chart to ensure that:
1.
it is designated for the type of ship
2.
the depths complies with the ukc requirement of the company
3.
depths are less than the maximum depth ship can anchor
4.
anchorage is clear of any cables, pipeline, wrecks or other obstructions
5.
the nature of sea bed is appropriate for anchoring
PREPARING FOR ANCHORING
• when checking the charts for underwater obstructions, attention should be paid to the chart symbol
“#”
• this symbol means there is a foul ground and shall be avoided for anchoring
• it is also important to be aware of the ship’s windlass lifting capacity
• most of the ship’s windlass are able to lift the weight of the anchor and about 3 shackles
PREPARING FOR ANCHORING
ANCHOR GEAR
• anchor gear (or ground tackle) is located on the forecastle and consists of all the equipment used in
anchoring
• this includes:
 the anchors
 the anchor windlass
 anchor cables or chain
 chain stoppers and the connecting devices (shackles, swivels)
 etc.
ANCHOR GEAR
ANCHOR GEAR
• a ship is normally fitted with ten shackles (shots in us) of cable, each shackle about 27.5 metres in length,
and connected to another shackle (length of chain) by an accessory fitting called kenter joining- shackle
• the cable is secured on the forecastle deck by stoppers, devil-claws and anchor lashings
• the chain is held by the windlass brake
• an anchor windlass is a machine that restrains and manipulates the anchor chain, allowing the anchor to
be raised and lowered
• brake is provided for control and the windlass is usually powered by an electric or hydraulic motor
operating via a gear train
ANCHOR GEAR
ANCHORING PROCEDURE
• prior to any anchoring operation, crew involved in operation is gathered and toolbox meeting is
held.
• during toolbox meeting, “risk assessment” is carried out and crew involved in operation are being
familiarized with dangers involved in operation in hand
• once captain calls “anchor crew proceed to anchor station” crew is well prepared and ready for
task in hand
ANCHORING PROCEDURE
• master identifys a suitable anchoring position before entering the anchorage area, conducts a
planned approach including speed reduction in ample time and orienting the ships head prior
anchoring
• once the ship is close to anchorage area, crew is called to anchor station
• 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
• master decides on which method of anchoring to be used and the number of shackles depending
on the depth of water, expected weather and holding ground
ANCHORING PROCEDURE
• simple rule in determining length of cable to use:
1.
standard condition:
length of cable = [(depth of water in meters * 2) + 90 ] / 27.5
2.
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
ANCHORING PROCEDURE
• prior to anchoring, the chief officer should be aware of:
1.
approximate anchoring position
2.
method of approach
3.
which anchor to use
4.
depth of water
5.
method of anchoring
6.
final amount of chain cable to be lowered
PROCEDURE OF THE INTRODUCTION TO
ANCHORING
• at the forecastle:
1.
check brakes are on and clear the voyage securing devices
(anchor lashings, bow compressed bar etc.)
2.
start hydraulic(source of) power of windlasses
3.
check anchor shape / light
4.
check communication with the bridge
5.
check lighting on forecastle including torch , at night time
6.
ensure all personnel are wearing safety helmets, safety shoes and goggles
PROCEDURE OF THE INTRODUCTION TO
ANCHORING
• before letting go anchor :
1.
the chief officer shall confirm that there is no craft or any obstacle under the bow and inform to
the bridge
2.
the master shall ensure that the vessels gps speed at the time of anchoring is near-zero or
indicates a slight sternway
3.
the speed should be verified by visual transits and/or radar ranges of landmarks, if available
or other fix conspicuous targets
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 ):
1.
walk out the anchor to half a shackle above the sea bottom
2.
hold the cable on the brake and take the windlass out of gear
3.
stop the vessel over ground
4.
drop the anchor
5.
control the speed of cable flow by the brake , while not allowing pile-up
6.
bring anchor cable direction forward and confirmed anchor holds its position
ROUTINE ANCHORING OPERATION
• method 2 (suggested for tankers / depths over 50m ):
1.
stop the vessel over ground
2.
walk out the anchor under power until the complete length of required cable is paid out and
anchor holds it position on the seabed
3.
bring anchor cable direction forward and confirmed anchor holds its position
ANCHOR WATCH
• once anchor position is set and vessel holds it position, anchor watch is set on the bridge
• vessel engine is usually set to short notice or to stand by which is on masters discretion
• modern radar system have integrated option for anchor watch so once the position is set and
radius of safety circle decided. radar automatically keeps track of ships movement
• it is also important that anchoring check list is followed and carried out (ref. to company ISM
manual)
Rev. 12/13
Whilst at anchor
ANCHOR WATCH
Wilhelmsen Ship Management
B08
Rev. 12/13
Bridge Procedures - Anchoring and Anchor Watch Check List
1.
Determine and plot ship position as soon as anchored. Establish
swinging circle
2.
Anchor brakes on, stopper engaged. Anchor windlass disengaged.
3.
Have instructions been issued to the OOW on determining and
regular checking of anchor position using minimum two methods.
4.
Ensure that the state of readiness of the main engines and other
machinery is maintained in accordance with Master’s instructions
Notice for engines______________________
5.
Comply with Bridge Procedure Manual & SSMM Ch 7.28
6.
Proper lookout maintained. Watch level established as per BPM.
7.
GPS anchor watch alarm ON? Alarm is set on 1)____ NM 2)____NM
8.
Echo sounder alarm ON ?Alarm is set on: DW_____ Mtr, SW____Mtr
9.
Weather forecast received/checked and reported to Master/ Engine
room in case of expected weather deterioration?
Call Master if winds reaches _________ knots or dragging anchor is
suspected
10.
VHF watch established/maintained on dedicated channels?
VHF log maintained?
Dedicated channels are : 1) _______ 2)_______ 3)________
11.
Frequent monitoring of ships and nearest targets established as per
Anchor position log? Frequency of plotting position is ______ MIN
12.
Anchoring equipments limitations know to all (sea and weather
conditions)
Vessel : _________________
Preparations
Item
Description
1.
Has an anchoring plan been prepared?
2.
Does it take into account speed reduction in ample time?
3.
Does it take into account direction/strength of wind, sea & current?
4.
Does it take into account tidal stream when manoeuvring at low
speeds
5.
Has the Depth of Water and Nature of the Sea Bed at the proposed
anchor position been taken into consideration?
6.
Does it take into account the need for adequate sea room, particularly
to seaward?
Check
Initials
7.
Master informed of the time of”stand by” for anchoring?
8.
Engine room informed of the time of”stand by” for anchoring?
9.
Anchor Party informed of the time of”stand by” for anchoring?
13.
If bad weather is expected, leaving anchorage to be considered
10.
Anchor(s) ready for use?
14.
11.
Lights/shapes and sound signalling apparatus ready for use?
Ensure that the ship exhibits the appropriate lights and shapes and
that appropriate sound signals are made in accordance with all
applicable regulations.
12.
Sound signalling apparatus ready for use?
15.
Is S-VDR / VDR operational
13.
Has an anchor watch been established?
16.
Conduct and record fire/ safety/ security rounds of the ship
Scope of anchor cable required. ________________
17.
Ensure access control is maintained in respect of vessel security
18.
Take measures to protect the environment from pollution by the ship
and comply with applicable pollution regulations.
14.
15.
Has the anchor position been reported to the port authority?
16.
Vessel specific Risk Assessment for anchoring consulted
Enter in Deck Log Book when completed
ANCHOR WATCH
• Drag Circle
r = chain + dist. (hawsepipe to pelorus)
All subsequent fixes should fall within the drag circle; if they do
not, the anchor should be considered to be dragging
Drag Circle
Anchor Chain
Anchor Location
• Swing Circle
r = chain + ship
Verify there are no obstructions (above, below or on the water)
within the ship’s Swing circle
Swing Circle
ANCHORING (CONCLUSION)
• knowing about the correct anchoring procedures and their limitations is one of the best way to
avoid anchoring related fatalities and damages