Anchoring Procedures Flashcards
Lowering procedure
- Ease the break off slowly.
- After the 1st or 2nd shackle, check.
- Continue in stages.
- Keep the Bridge informed at all times.
- Anchor lead.
- Weight.
- Brought Up.
- Display signals.
Resultant force
Factors:
- Bottom nature.
- Shape & weight of anchor.
- Total chain paid out.
- Anchor aspect in relation to seabed.
- Calculated holding capacity and pull on the anchor.
- When the shaft is lifted by 15 deg the loss of hold will be 25%.
- At 15 deg the loss becomes 50%.
- The chain contributes both weight and holding power to the anchor.
If the holding power of the anchor is less than the exerted by an external force the anchor will drag.
Monitoring dragging
Methods:
- Range and bearings.
- Radar bearing and Range rings.
- GPS anchor watch
- Regular rounds of the anchor (Check marks or vibration).
- Use of a lead line.
Steps:
- Monitor the vessel’s position.
- Monitor the weather conditions.
- Confirm to standing orders.
- If in doubt, call the Master.
- Notify port control.
- Ready the engines.
- Anchor party on standby.
Methods of preventing dragging.
- Pay out more cable.
- Use rudder to reduce yaw.
- Utilise the engines.
- Run out a second anchor.
- Heave up and steam around.
What is anchor mooring?
It is anchoring of the vessel between 2 anchors.
This restricts swinging room, reduces yaw and increases holding power.
Different types of anchor mooring and where are they commonly used.
Running or Standing Moor
Most commonly used in tidal rivers, canals or harbours.
Open Moor
Carried out in non-tidal conditions, gives greater holding power when anchor in a constant stream flow.
Mediterranean Moor
Normally used for small vessels, and in areas where no current and weather conditions are being experienced.
Baltic Moor
Developed in the Baltic when securing to a very old and fragile timber berth. Idea is to come alongside without any weight on the berth.
Running Moor
Complete moor will have 5 shackles out on each cable.
Vessel must let go weather anchor 4 shackles distance before intended position.
Vessel must approach at slow speed and continue ahead while lowering anchor.
Vessel must go beyond the intended postion about 4 shackle distance and when about 9 shackles out on the weather anchor, let go lee anchor. By the 10th shackle, vessel may stop.
Let go lee anchor while picking up on the weather anchor until 5 shackles on each.
Standing Moor
Complete moor will have 5 shackled out on each cable.
Vessel proceed at slow speed ahead of the intended position by 4 shackles distance and let go lee anchor.
The cable is then paid out 10 shackles as the vessel falls back on the current.
Then put it on gear and let go weather anchor.
While heaving up on the lee anchor, continue to
let go weather anchor to finish with 5 shackles on
each cable.
- If strong current use engines while heaving up of lee anchor.
Open Moor
- Normally vessel will be anchored with the weather anchor. (usually port anchor).
- When the ship has brought up, walk back the anchor to 9 shackles.
- Hold the weather anchor, angle the ship approximately 60deg. to lee side and slowly steam ahead.
- When the ship is abeam the weather anchor position and the weather cable is at 90 deg. to the ship, let go the lee anchor.
- With the engine now stopped weather anchor cable now heaved in to 6 shackles and the lee anchor let go out to 6 shackles.
- The ship, when brought up to the new position, will now have 6 shackles now on each anchor and an angle of 90 deg. between them.
Mediterranean Moor
- At a distance of approximately twice the ship length, the starboard anchor is let go and, when on the bottom, let out a little to hold the weight on the break.
- The head way on the ship will snub the cable, causing the vessel to come around. Engine and wheel hard over can be used to take the vessel around.
- Once the ship has turned around let the other anchor go and put the engine stern to back towards berth, letting out cables as it become tight.
- Some tension remains on the cable as this acts as a break when the engine is stopped, the ship will instantly start to come out.
- Approaching parallel to the berth and deploying running moor with calculated distance is another way of setting the two anchors for this mooring, and engines and bow thruster could be used to turn the vessel around (twin screws are much easier to turn around).
Baltic Moor
- A good stern line to the bow and then sending a person overside to shackle it with the off-shore anchor just above the anchor shackle.
- Vessel approach parallel to the berth, keeping a reasonable distance to achieve a good scope of the anchor at the end of the manoeuvre.
- Once in the position let go the off shore anchor, seizing line retaining the rope will break and rope will go in to the water together with the anchor.
- Once the anchor is in the bottom, with mooring ropes on the windlass ship moved ahead, letting out the cable until ship is off the intended position.
- Send the breast lines away and the ship is heaved towards the berth, anchor should be put on the gear, distance and the angle can be adjusted using the anchor and spring and other ropes.
Kedging and dredging anchor
Dredging an anchor is a safe and controlled way for backing a vessel.
Usually done with a short scope usually 1.5 times the distance between the hawse pipe and sea bottom on the chain and the engines.
Such a length does not permit the flukes to dig into the seabed, if a vessel increases its speed over the ground, this does not increase the strain on the cable.
All that happens is the anchor drags along at the same speed which can help to slow down a ship in ballast.
- When a ship is loaded the effect is not as strong
- These effects can be used to maneuver the ship, but how?
- When a vessel remains virtually motionless at anchor, the pivot point remains
forward of the midship section - This allows a large rudder turning moment
- Control of a vessel can be maintained by the rudder and low engine revolutions.
