Auto-ignition Temperature

The lowest temperature to which a liquid or gas requires to be raised to cause self-sustained spon­taneous combustion without ignition by a spark or flame (see 2.20).

Avogadro's Law

Avogadro's Hypothesis states that equal volumes of all gases contain equal numbers of molecules under the same conditions of temperature and pressure.

BLEVE

This is the abbreviation for a Boiling Liquid Expanding Vapour Explosion. It is associated with the rupture, under fire conditions, of a pressure vessel containing liquefied gas (see 2.20).

Boil-off

Boil-off is the vapour produced above the surface of a boiling cargo due to evaporation. It is caused by heat ingress or a drop in pressure (see 4.5).

Boiling Point

The temperature at which the vapour pressure of a liquid is equal to the pressure on its surface (the boiling point varies with pressure) (see 1.1).

Booster Pump

A pump used to increase the discharge pressure from another pump (such as a cargo pump) (see 4.2).

Bulk Cargo

Cargo carried as a liquid in cargo tanks and not shipped in drums, containers or packages.

Canister Filter Respirator

A respirator consisting of mask and replaceable canister filter through which air mixed with toxic vapour is drawn by the breathing of the wearer and in which the toxic elements are absorbed by activated charcoal or other material. A filter dedicated to the specific toxic gas must be used. Sometimes this equipment may be referred to as cartridge respirator. It should be noted that a canister filter respirator is not suitable for use in an oxygen deficient atmosphere (see 9.9.1).

Carbamates

A white powdery substance produced by the reaction of ammonia with carbon dioxide (see 7.2).

Carcinogen

A substance capable of causing cancer.

Cargo Area

That part of the ship which contains the cargo containment system, cargo pumps and compressor rooms, and includes the deck area above the cargo containment system. Where fitted, cofferdams, ballast tanks and void spaces at the after end of the aftermost hold space or the forward end of the forwardmost hold space are excluded from the cargo area. (Refer to the Gas Codes for a more detailed definition).

Cargo Containment Systems

The arrangement for containment of cargo including, where fitted, primary and secondary barriers, associated insulations, interbarrier spaces and the structure required for the support of these elements. (Refer to the Gas Codes for a more detailed definition) (see 3.2).

Cascade Reliquefaction Cycle

A process in which vapour boil-off from cargo tanks is condensed in a cargo condenser in which the coolant is a refrigerant gas such as R22 or equivalent. The refrigerant gas is then compressed and passed through a conventional sea water-cooled condenser (see 4.5.2).

Cavitation

A process occurring within the impeller of a centrifugal pump when pressure at the inlet to the impeller falls below that of the vapour pressure of the liquid being pumped. The bubbles of vapour which are formed collapse with impulsive force in the higher pressure regions of the impeller. This effect can cause significant damage to the impeller surfaces and, furthermore, pumps may loose suction (see 4.2).

Certificate of Fitness

A certificate issued by a flag administration confirming that the structure, equipment, fittings, arrangements and materials used in the construction of a gas carrier are in compliance with the relevant Gas Code. Such certification may be issued on behalf of the administration by an approved classification society (see 3.7.1).

 

Certified Gas Free

A tank or compartment is certified to be gas-free when its atmosphere has been tested with an approved instrument and found in a suitable condition by an independent chemist. This means it is not deficient in oxygen and sufficiently free of toxic or flammable gas for a specified purpose.

Cofferdam

The isolating space on a ship between two adjacent steel bulkheads or decks. This space may be a void space or ballast space.

Condensate

Reliquefied gases which collect in the condenser and which are then returned to the cargo tanks.

Compression Ratio

The ratio of the absolute pressure at the discharge from a compressor divided by the absolute pressure at the suction.

Critical Pressure

The pressure at which a substance exists in the liquid state at its critical temperature. (In other words it is the saturation pressure at the critical temperature) (see 2.12).

Critical Temperature

The temperature above which a gas cannot be liquefied by pressure alone (see 2.12).

Cryogenics

The study of the behaviour of matter at very low temperatures.

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