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Encyclopedia of Marine Technology


85 results


Moving forward, a ship imparts the forward motion to the water at the stern. It is known as the wake

Wake equalization duct

The propulsion improving device, especially for full block ships, developed by Professor Schneekluth.

Wake fraction coefficient

The speed of advance of the propeller “VA” relative to the water in which it is working is lower than the observed speed of the vessel “V”.


When the ship is sailing ahead, the friction of the hull will create a boundary layer of water around the hull.

Warping head, warping end, gypsy head

A cylinder-like fitting at the end of winch or windlass shafts. The fiber line or wire rope is hauled or slacked by winding a few turns around it, the free end being held taut manually as it rotates


The waves and ripples spreading out from a vessel when underway.

Wash bulkhead

A perforated bulkhead fitted into a cargo or deep tank to reduce the sloshing or the movement of liquid through the tank.

Washing machines

Tank washing machines either fixed or portable. They consist of revolving nozzles moved by water-driven gearing to create a spherical wash pattern or “cycle”.


Useless or superfluous matter which is to be discarded. Incineration of burnable waste is the most efficient means of disposal.

Waste heat boiler

A boiler which uses the exhaust gas from an engine to produce low pressure saturated steam.

Waste heat recovery (WHR)

The energy from the combustion process in an internal combustion engine not converted into useful work, e.g. energy in the exhaust gas or cooling water.

Waste management plan

Collection, treatment and disposal of waste.

Waste water

Drainage from dishwater, showers, laundry, bath and washbasin drains and does not include drainage from toilets, urinals, hospitals and cargo spaces. Galley water can contain oil, fats and detergents...

Waste water treatment systems

Plants installed to treat any intended discharges overboard.


A time period, usually of four hours, e.g. 12-4, 4-8, 8-12, which operates round the clock.

Watch alarm

An alarm that is transferred from the bridge to the master and the backup navigator in the event deficiency (absence, lack of alertness, no response to another alarm/warning, etc.), of any officer on watch.

Watch alarm system

The watch alarm system urges the officer on watch at a predetermined time to acknowledge his watch-keeping awareness.

Water curtain

Some tankers have a fixed system to give a protective water curtain between the cargo deck and the superstructure.

Water fog

A suspension in the atmosphere of water divided into coarse drops by delivery through a special nozzle for use in fire fighting.

Water level gauge

A device to provide a visible indication of water level in the boiler.

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