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Different types of machines are used on a ship's deck for the overall and smooth functioning of deck procedures. Deck procedures such as cargo handling, berthing and anchoring represent a lion's share of a vessel's total working operations.
Anchoring is one such process that is carried out when the ship requires a stoppage at mid sea or at the port. For this an anchor is used for holding the ship at one place, to remain unaffected by waves and weather. Bigger the ship, larger and heavier is the anchor. The anchoring process requires dropping and lifting of the anchor from the sea. Windlass is the device used for anchor handling on all the ships.
Usually, a ship is provided with a pair of anchors. On almost all the ships, a single marine windlass handles both the anchors, but if the size of the ship is more , dedicated windlasses known as split windlasses are used for individual anchor. Read on to find more on anchor windlass.
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Ideal Windlass Arrangement
An ideal windlass assembly consists of a cable lifter, mooring drum and a warp end. All these are rotating equipments that work together for the anchoring process. The cable lifter has cable shaped snugs that are used to grip the anchor cable on the drum. The cable from the cable lifter goes around a mooring drum, which guides the cables by paying out or letting go of the mooring wires. A warp end is used to hold the cable at the desired position and is always driven in association with the mooring drum for efficient carrying out of the warping duties.
Although all these units work together, they can also be individually controlled. A dog clutch is used to separately engage or disengage each of this unit. All the rotating parts are connected to a motor with the help of a spur gear assembly, which is used to transmit the motor drive to the shaft where various dog clutches enable the power take off. Moreover, separate band brakes are used to lock the cable lifters and the mooring drums to prevent any kind of accidental movement when the power of the motor is turned off.
The cable lifter guides the anchor by raising and lowering the cable through the spurling pipe. The spurling pipe is located at the top and centre of the chain or the cable locker. Snugs in the cable lifter are used not only to grip the cables but also to hold the band brakes and the cables.
Anchor capstans, which are windlasses that rotate in the horizontal direction about a vertical axis, also have cable lifters that rotate about the same axis. This arrangement is generally used for heavy anchors and have the cable lifter unit located on the deck with the driving machinery on the deck below. The same unit which drives the cable lifter is used to drive the warping end, which is generally positioned near the cable lifter.
Nowadays, different types of windlasses are used according to the weight of the anchor and various other vessel requirements. The driving unit can be electrical, pneumatic or hydraulic, which also depends on the ship's system requirement.
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Images: Great Lakes and Seaway Shipping website