2　Terms

2.0.1　Operating pressure

Assumed gauge pressure for the overhead vapour space under operating conditions.

2.0.2　Design pressure

Assumed maximum positive pressure（gauge）for the overhead vapour space in the tank.

2.0.3　Design negative pressure

Assumed maximum negative pressure for the overhead vapour space in the tank.

2.0.4　Test pressure

Air pressure（gauge）in the overhead space of the tank during testing.

2.0.5　Set pressure

Pressure at which the pressure relief device first opens.

2.0.6　Minimum design temperature

Assumed temperature of the medium，for which the tank is designed.

2.0.7　Design metal temperature

Minimum temperature for which the metallic component is designed.

2.0.8　Maximum design liquid level

Maximum permissible liquid level for a tank.

2.0.9　Maximum normal operating level

Maximum liquid level that will be maintained during normal operation.

2.0.10　Single containment tank

A tank consisting of only one primary liquid container with insulation or a tank consisting of a primary liquid container and a vapour container.

2.0.11　Double containment tank

A tank consisting of a primary liquid container and a secondary container that is capable of containing any leakage of the refrigerated liquid but incapable of containing any vapour resulting from this leakage.

2.0.12　Full containment tank

A tank which is defined as a tank consisting of a primary liquid container and a secondary container capable of containing both any leakage of the liquid and any vapour resulting from this leakage.

2.0.13　Primary liquid container

Part of a single，double or full containment tank that contains the low temperature refrigerated liquid during normal operation.

2.0.14　Secondary liquid container

Part of the outer container of a double or full containment tank that contains the low temperature refrigerated liquid.

2.0.15　Inner tank

Metallic self-supporting cylindrical primary container.

2.0.16　Outer tank

Self-supporting cylindrical secondary container made of steel or concrete.

2.0.17　Roof

Structure on the top of a shell or wall containing the vapour pressure and sealing off the contents from the atmosphere.

2.0.18　Shell/wall

Metal or concrete vertical cylinder.

2.0.19　Vapour container

Part of a single，double or full containment tank that contains the vapour during normal operation.

2.0.20　Supporting roof of tank

A type of tank roof for which its load is supported by beams，columns，trusses or other structures.

2.0.21　Self-supporting roof of tank

A type of tank roof for which its loads are only supported by tank shell.

2.0.22　Rollover

Uncontrolled mass movement of stored liquid，correcting an unstable state of stratified of different densities and resulting in a significant evolution of product vapour.

2.0.23　Thermal protection system

Thermally insulating and liquid tight structure in order to protect the outer tank against low temperature.

2.0.24　Vapor barrier

Barrier to prevent entry of water vapour and air into the insulation or into the outer tank.

2.0.25　Percentage of plastic elongation

The percentage of plastic elongation is the permanent percentile increase of the original gauge length corresponding to tensile strength.