Hull roughness is the result of fouling, corrosion, flaking of old paint, mechanical damages during service, etc.

The ratio of thrust power to effective power, which is usually higher than one.

Any protruding part of the hull structure that is below the waterline (rudder, bilge keels, thrusters, propeller brackets etc).

The structural body of a ship, including shell plating, framing, decks, bulkheads, etc.

A speed trial evaluation method developed by the Hamburg Ship Model Basin (HSVA) in order to improve the significance of full-scale measurements.

A vessel riding on a cushion of air formed under it. It is very manoeuvrable and is also amphibious. There are two types of hovercrafts: the fully skirted and the sidewall.

Work involving sources of ignition or temperature sufficiently high to cause the ignition of a flammable gas mixture.

A test carried out to demonstrate the tightness of structural items not subjected to hydrostatic or leak testing and to other components which contribute to watertight or weathertight integrity of the hull.

The welding position in which the weld is on the upper side of an approximately horizontal surface and against an approximately vertical surface.

Metallic or non-metallic hose with end fittings, ready for installation.

The position of a pipe joint in which the axis of the pipe is approximately horizontal and welding is performed in the flat position by rotating the pipe.

The position of a pipe joint in which the axis of the pipe is approximately horizontal, and the pipe is not rotated during welding.

Tanks used for ballast or for stability when carrying certain cargoes in bulk carriers. Also referred to as topside wing ballast tanks or bottom hopper tanks.

A ship equipped for carrying spoils or dredged material. Split hopper unit opens longitudinally around hinges.

A barge which loads material dumped into it by a dredger and discharges it through the bottom.

The securing bolts which are usually fitted for fixing main propulsion machinery and thrust blocks.

A milling machine equipped with concentric gears with conical surfaces that grind heavy fuel oil as it is pumped through the treatment system. Homogenisers are used to disperse any sludge and water remaining in the fuel after centrifuging.

A tank used for collection and storage of sewage, (MARPOL).

The space enclosed by the ship structure in which a cargo containment system is situated, (IGC Code).

The space enclosed by the ship structure in which an independent cargo tank is situated, (IBC Code).