Outline

  • Deck machinery includes anchor, windlass, mooring winches, cranes, davits, capstans, shark jaws, chain-stoppers, bulk handling systems, etc.

Detail

Anchor
Anchor is a heavy forging or casting shaped to grip the sea bottom, and by means of a cable or rope, holds a ship or other floating structure in a desired position regardless of wind and current. Anchoring equipment is designed for temporary mooring a vessel within a harbour or sheltered area when the vessel is awaiting berth, etc. It is assumed that under normal circumstances a ship will use only one bow anchor and chain cable at a time.

Different types are in use: stock-anchors, stockless anchors (SPEK or HALL type), High Holding Power (HHP) anchors, Super Holding Power (SHHP) anchors. High holding power (HHP) anchor has holding power is at least two time the holding power of a conventional anchor of the same weight. As soon as the predicate “High Holding Power” is obtained a weight reduction of 25% compared to the conventional anchor is allowed. Super high holding power anchor (SHHP) have a holding power of at least four times the holding power of a conventional anchor.

Windlass
windlass is the device used for lowering and raising the anchor it does this in tandem with the bow or chain stopper which prevents chain slippage when anchored and when raising the anchor. The anchor chain passes from the anchor and through the hawse pipe, over the windlass and down into the chain locker where the end is secured. The windlass is driven by a motor, either electric or hydraulic, and features a brake and clutch for use in different operations.

Winches
A winch is a marine deck equipment device for handling wires or ropes and works by spooling the wire or rope on a drum with a horizontal axis. The winch can be powered by electric or hydraulic motors; steam winches were once common but are now obsolete. Winches on ships are fixed and used for specific purposes. As previously mentioned, cargo derricks are now much less common and so the winches needed to provide power for these have also been more or less abandoned.

The most common use of a winch is for mooring meaning the winches are mostly located on the fore and after decks at both sides of the ship. Tugs and offshore vessels such as AHTS, seismic survey and OSVs will also be equipped with work winches designed for the very heavy duty work these ships are used for.

The power source for any winch systems can be, as required by the customer, low-pressure hydraulic, high-pressure hydraulic, frequency-converter electric drive or pole-change electric drive.

Cranes
Cranes are used for cargo handling and other operations. Cranes are required to hoist, luff and slew. Separate motors are required for each motion. There are various types of cranes.

  • Cargo cranes are used for bulk cargo, containers, general cargo, or palletized cargo.

 

  • Construction cranes are used for carrying out assembly-work in calm water as well as in unprotected waters.

 

  • Deck cranes include provision cranes, hose handling cranes.

 

  • Floating cranes are provided with large cranes used for various heavy lift tasks, salvage and wreck removals. Semi-submersible crane ships are used to carry out offshore installation work.

 

  • Gantry crane usually on rails, having a lifting hook suspended from a car, which is movable horizontally in a direction transverse to its rails.

 

  • Hose-handling cranes are used to handle tanker cargo hoses. They are explosion-proof.

 

  • Hose-handling cranes are used to handle tanker cargo hoses. They are explosion-proof.

 

  • Monorail provision crane are rail-mounted trolley that can be moved athwartship and is fitted with rack and pinion drive.

 

  • Offshore cranes include a range of shipboard cranes and floating cranes that work offshore, also cranes mounted on offshore installations.

 

  • Offshore supply cranes are located on fixed or floating offshore installations for loading and unloading supply vessels.

 

  • Twin cranes can usually be operated independently, when required the two cranes can be linked together to operate in a twin mode. In this case, both cranes are controlled from the cab of one of them.


Lift Davits
A davit is a type of crane for hoisting or launching small craft, especially lifeboats, over the side of a vessel. These devices can be found on different parts of the deck, depending on function. They are used to handle lifeboats, life rafts, rapid rescue craft, tenders, embarkation or provisioning ladders. The different types of davit include swinging, sliding, gravity, hydraulic and folding. Their usage includes the handling of rescue or lifeboats, provisioning, etc.

Capstans
A capstan is a vertical-axled rotating machine developed for use on sailing ships to multiply the pulling force of seamen when hauling ropes, cables, and hawsers. Modern capstans are powered electrically, hydraulically, pneumatically, or via an internal combustion engine. Typically, a gearbox is used which trades reduced speed, relative to the prime mover, for increased torque.

Shark Jaws
Remotely controlled chain and wire stoppers used onboard to unshackle lengths of wire on deck when carrying a loaded wire over the stern roller. It comprises a hydraulically-operated cylindrical unit which can be retracted flush with the working deck for stowage or raised to a working position. In the working position, the wire or chain is supported clear of the deck. The cylindrical unit is forked at the top and contains a pair of hydraulically-operated jaws. Two sets of jaws can be interchanged quickly; one for wire, the other for chain. The wire slides between the open jaws, the jaws are closed and the winch eases off the strain allowing the splice on the wire to be pulled against the jaws, thus enabling the buoy to be safely unshackled.

Chain Stoppers
A fitting used to secure the anchor chain when riding at anchor, thereby relieving the strain on the windlass, and also for securing the anchor in the housed position in the hawsepipe. Chain stopper usually consists of two parallel vertical plates mounted on a base with a pivoting bar or pawl which drops down to bear on a chain link.

Bulk Handling Systems
Equipment used for loading or discharging operations such as cargo cranes, side-loading system with conveyors, side shifters, elevators, belt conveyors, ro-ro cargo handling gear and cargo pumping systems. Cargo handling equipment varies depending upon the type of cargo. Tankers are fitted with pumping systems and pumps, with small cranes to handle hoses from shore, and with tank cleaning machines and inert-gas generating systems. Most dry-bulk carriers depend on shoreside facilities for cargo loading and discharge, but some bulk carriers have self-unloading features with conveyors below the cargo holds, or with cranes on deck. Reefer vessels are designed with refrigerated cargo holds fitted with large cargo-refrigeration systems.