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Introduction to Ship Anchoring
Anchoring Procedure onboard ships is one of the most important deck operations. Due to the dangers involved, a depth of knowledge and training must be acquired prior to any work relating to anchoring. Please now watch this introduction video to the anchoring operation.
When do Ships Anchor?
- When waiting for a berth, instructions from owners/charters, a change in tidal or weather conditions, to carry out maintenance, or to quarantine.
- Emergencies such as steering gear failure, engine failure, risk of collision or manoeuvring in shallow waters.
Different Types of Anchors
Permanent Anchor: The mushroom anchor display here is capable of grasping the ground no matter how it falls. The shape works best in soft bottoms where it creates suction that can be difficult to break. A deadweight anchor as the name implies is just a heavyweight object to hold something in place. Lightships, navigational buoys and moorings will use these type of anchors.
This anchor consists of two long pivoting flukes which are designed to reduce jamming with mud and grass. With a range from 1.5 kilograms to nearly 90 kilograms, these anchors are generally made of cast galvanised metal or a lightweight aluminium composite. When dropped, the flukes of the anchor dig into the bottom burying the anchor. Good for small boats. Works best in hard sand or mud. Poor holding in grassy or rocky seabeds.
This anchor is a top choice with boats, due to its good holding power in a wide variety of bottom types such as sand, pebbles, rocks, grass, kelp and coral. It consists of either a fixed shank or a pivoting shank. These are generally made of galvanised metal or stainless steel. As this anchor works best by digging into the seabed it will not hold as well in mud, soil or any other loose materials.
This is the most common type of anchor found onboard merchant vessels due to no unnecessary parts, and ease of handling/storing. It consists of a Shank, Crown, Flukes and Shoulders. The Flukes pivot on the same plane perpendicular to the shank, the weight of the shank together with that of the anchor chain, keeps the anchor lying flat on the seabed. Not best for anchoring in soft seabeds such as soil or sand.
This type of anchor is very inexpensive and very popular with small boats such as kayaks, canoes and dinghies. The holding power comes from hooking onto an object such as a rock or coral, and with that said, when used in soft bottoms such as sand, soil or mud it does not have much-holding power. Most grapnel anchor models are made of galvanised steel.
The Claw anchor is constructed of high-grade steel and is suitable for use on various seabeds. This anchor sets effortlessly and stows easily on the bow of most boats. Best used in rocky seabeds, this anchor hooks into the rocks at the bottom. Unfortunately, it is not as good with sand, silt or mud.
This is a more traditional style of anchor with arks, flukes and a stock. It is best used in the rocky seabed, heavy grass bottoms, weed bottoms or hard sand. In the mud and loose sand, these anchors do not tend to work due to the flukes not being able to dig into the seabed. This is generally used for very large vessels and not suitable for recreational use due to the weight of it.
Anchoring Equipment & Machinery
A successful anchoring procedure needs all of these components in full working order and to be operated by qualified personnel. Let us explain each of them in turn:
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Windlass; This is the main machinery used for anchor handling, depending on the size/composition of the ship there may be more than one on deck.
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Gypsy Drum or Wildcat; This is the unit used to raise and lower the anchor cable through the Spurling pipe from the chain locker. The wheel itself has snugs in which the studs of the anchor chain fit and grip whilst moving.
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Dog Clutch; This is a type of clutch that couples two rotating shafts or other rotating components (in this case the gypsy drum) not by friction but by clearance fit. The work of the Dog Clutch is to engage with the gypsy wheel on the windlass and rotate it.
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Riding Powel; The Riding Powel is a small rotating drum forward of the gypsy wheel. This drum works identically to the gypsy and is used to carry the anchor chain from the deck into the hawse pipe.
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Chain or Cable Stopper, and Devil’s Claw; The Chain Stopper or Guillotine is a lever fitted on the Riding Powel used to secure the chain when at anchor and take off the strain from the windlass. Additionally, it is also used as a means of lashing the anchor in place once it is retrieved.
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Brake Assembly; This is a very simple assembly for the windlass. There is an operating wheel to control lowering the anchor. It is good to note, that the brake has a very important part in the lowering procedure especially when the 'Let Go' method is being used.
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Hawse Pipe; This is an opening in the deck guiding the chain from the riding powel on deck to the outside of the shell plating. It is constructed to a size large enough to ensure the smooth running of the anchor chain and to provide secure stowage for the anchor, permitting it to drop freely when released without jamming or risking damage to the ship’s hull.
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Anchor Wash; The Hawse Pipe also consists of water spray holes that enable the anchor wash. This washes any dirt or mud off the anchor chain or the anchor itself as it is being heaved up. Having excess material in the chain locker can weigh extra on the vessel, 'gum up' the chain as it hardens within the chain locker and spray material at the surrounding crew.
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Spurling Pipe; This is an opening in the deck guiding the chain from the chain locker to the gypsy wheel on the windlass. A metal covering is usually provided for both the Spurling Pipe and Hawse Pipe to ensure that nothing goes through when the anchoring operation is done and also for safety reasons to avoid trips or falls due to these openings.
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Chain Locker; This is the storage space for the anchor chain. The bitter end of the chain is secured to the side or top structure of the chain locker by an arrangement that incorporates means for emergency release.
Markings and Components of the Anchor Cable
The markings on the anchor cable are used to indicate the number of shackles and make it easily identifiable to the anchor party. These are important as the Master on the bridge requires proper reporting to ensure enough cable is paid out to hold the vessels safely in place in the expected weather conditions.
A shackle is made up of 27.5 meters of cable/chain.
The Detachable Link, also known as the Kenter Shackle, is the link from where we count. This shackle is usually painted red, and on either side of it, you will find links that are painted white.
The number of white links on either side of the Kenter Shackle (red link) indicates the number of shackles
Anchor Chain Markings