Anchors and anchoring
Anchoring is a fundamental part of basic seamanship. The oral exam syllabus requires that OOWs have an understanding of:
proper procedures for anchoring and mooring…Vessel preparations for anchoring and mooring
Chief officer and Master level candidates must demonstrate an understanding of:
choice of anchorage; anchoring with one or two anchors in limited anchorages and factors involved in determining the length of anchor cable to be used…dragging anchor; clearing fouled anchors
Different types of anchors and their advantages and disadvantages, preparation for anchoring, anchoring in a tideway and in confined water, operation of anchoring with a single anchor and use of a second anchor, dragging anchor, clearing a foul anchor and hawse, hanging off an anchor, breaking and slipping cables, getting under way
Relevant documents and M-notices: SOLAS, MSC Circ. 1175, MGN 592, MGN 315, COSWP Chapter 26, MGN 661
Anchors and fittings
SOLAS Chapter II-1 Regulation 3.8
Ships shall be provided with arrangements, equipment and fittings of sufficient safe working load to enable the safe conduct of all towing and mooring operations associated with the normal operation of the ship.
Anchors form part of our hull survey items. As such, they are surveyed for the issue and upkeep of the Cargo Ship Safety Construction Certificate for cargo vessels and the Passenger Ship Safety Certificate for passenger vessels.
Before we go any further, some vocabulary:
Bitter end - the end of the cable that is attached to the vessel. This will normally be at the aft end of the chain locker and must be accessible and releasable under load.
Cable - It is normal to refer to the chain connecting the anchor and the vessel as the cable. Also known as the rode, or warp.
Catenary - This is the name given to the shape of a flexible hanging chain or cable.
Anchor a-cockbill - The anchor is hanging vertically, clear of any pocket.
Windlass - This is the winch that raises and lowers the anchor.
Gypsy - This is the slotted wheel on the windlass over which the cable runs before going down the spurling pipe into the chain locker. Sometimes known as the sprocket wheel.
Spurling pipe - This is the opening in the deck that allows cable to leave and return to the chain locker.
Chain locker - This is where the cable is stored when not in use. It is an enclosed space.
Hawsepipe - This is the hold in the deck that allows the cable to run from the windlass to the anchor.
Devils claw - This is a means of securing the anchor against accidental release.
Guillotine - or chain stopper. When the ship is at anchor the weight of the chain should be on the guillotine or chain stopper. The windlass brakes are designed to hold the cable, not the ship. Guillotines/chain stoppers are designed to have at least 80% of the breaking strength of the cable; they will break before the cable does.
Shackle - 27.432m but generally 27.5m is used for convenience sake.
Sleeping cable - When two anchors are deployed, if the weight of the ship is on only cable only the other cable is called the sleeping cable.
Riding cable - In the scenario with the sleeping cable, the cable with the weight on it is the riding cable.
Walking out/walking back the anchor - This is to lower the anchor under control using the windlass rather than letting it go. This puts a degree of strain on the windlass. It is common to walk an anchor back to sea level in preparation for letting go in order to reduce the chance of the anchor damaging the ships hull, especially if she has a bulbous bow.
Pocket - many ships feature pockets that house the anchors when they are not in use.
Lead - this is the direction that the cable is pointing relative to the ship. Usually given in points (e.g. ‘ leading four points to starboard’) though sometimes given as hours of the clock (‘cable at two o’clock’).
Stay - This is used to describe how the cable is leading away from the vessel. The cable can be up-and-down (hanging vertically), at short stay (with a slight angle on it), medium stay (a more severe angle on it) or long stay (a significant angle on it).
Classification of anchoring equipment
The windlass and ancillary mooring equipment must meet standards laid down by the vessels classification society. The anchoring arrangement must be suitable to hold the vessel on a temporary basis in moderate conditions (that is, no more than force 7). Anchors are normally supplied with certification from the major classification societies.
Windlasses of most vessels are rated to lift the vessels anchor and three shackles (82.5m) of chain. This restricts these vessels to anchoring in depths of 82.5m or less. Some vessels have a deep-water anchoring (DWA) notation, which will state the depth of water that they are able to anchor in. Most vessels carry eight to twelve shackles of cable in chain lockers on each side; this information should be available on the bridge.
Cable markings
Cables are marked every shackle. Every shackle there will be a Kenter link; this is just as strong as every other link but can be dismantled.
The cable is marked in such a way that the officer in charge of the anchor station can inform the bridge how much cable is out. The kenter links, every shackle, are painted red. On either side of these will be links painted white. If there is one link each side painted white, this is one shackle from the anchor. If there are two links on each side painted white, this is two shackles from the anchor and so on. Often copper wire wrapped round the last white painted shackle from the kenter link on each side, to act as an indicator in case the paint is no longer visible.