Saturated Vapour Pressure

The pressure at which a vapour is in equilibrium with its liquid at a specified temperature (see 2.15).

Secondary Barrier

The liquid-resisting outer element of a cargo containment system designed to provide temporary con­tainment of a leakage of liquid cargo through the primary barrier and to prevent the lowering of the temperature of the ship's structure to an unsafe level (see 3.2.2).

Sensible Heat

Heat energy given to or taken from a substance which raises or lowers its temperature.

Shell and Tube Condenser

A heat exchanger where one fluid circulates through tubes enclosed between two end-plates in a cylindrical shell and where the other fluid circulates inside the shell.

Silica Gel

A chemical used in driers to absorb moisture (see 4.7.1).

Sl (Systeme International) Units

An internationally accepted system of units modelled on the metric system consisting of units of length (metre), mass (kilogram), time (second), electric current (ampere), temperature (degrees Kelvin), and amount of substance (mole).

SIGTTO

Society of International Gas Tanker and Terminal Operators Limited.

Slip Tube

A device used to determine the liquid-vapour interface during the ullaging of semi and fully pressurised tanks. See also Restricted Gauging (see 4.9.1).

SOLAS

International Convention for the Safety of Life at Sea, 1974; as amended.

Span Gas

A vapour sample of known composition and concentration used to calibrate gas detection equipment (see 9.7.3).

Specific Gravity

The ratio of the density of a liquid at a given temperature to the density of fresh water at a standard temperature (see 8.3.2).

Temperature will affect volume and the comparison temperature must therefore be stated; e.g. specific gravity 60/60°F — substance and water at 60°F; specific gravity 15/4°C — substance at 15°C, water at 4°C. (The use of this term is being superseded — see Relative Liquid Density.)

Specific Heat

This is the quantity of energy in kiloJoules required to change the temperature of 1 kg mass of the substance by 1°C. For a gas the specific heat at constant pressure is greater than that at constant volume.

Spontaneous Combustion

The ignition of material brought about by a heat-producing chemical reaction within the material itself without exposure to an external source of ignition (see 2.20).

Static Electricity

Static electricity is the electrical charge produced on disimilar materials caused by relative motion between each when in contact (see 2.22).

Submerged Pump

A type of centrifugal cargo pump commonly installed on gas carriers and in terminals in the bottom of a cargo tank. It comprises a drive motor, impeller and bearings totally submerged by the cargo when the tank contains bulk liquid (see 4.2).

Superheated Vapour

Vapour removed from contact with its liquid and heated beyond its boiling temperature.

Surge Pressure

A phenomenon generated in a pipeline system when there is a change in the rate of flow of liquid in the line. Surge pressures can be dangerously high if the change of flow rate is too rapid and the resultant shock waves can damage pumping equipment and cause rupture of pipelines and associated equipment (see 4.1.3).

Toxicity Detector

An instrument used for the detection of gases or vapours. It works on the principle of a reaction occurring between the gas being sampled and a chemical agent in the apparatus (see 9.7.4).

TLV

This is the abbreviation for Threshold Limit Value. It is the concentration of gases in air to which personnel may be exposed 8 hours per day or 40 hours per week throughout their working life without adverse effects. The basic TLV is a Time-Weighted Average (TWA). This may be supplemented by a TLV-STEL (Short-Term Exposure Limit) or TLV-C (Ceiling exposure limit) which should not be exceeded even instantaneously (see 9.3.1).

⇐ Предыдущая234567891011Следующая ⇒

Поделиться: