Definitions

Unless otherwise stated below, definitions are as defined in SOLAS chapter II-2.

2.2.1 Accident means an uncontrolled event that may entail the loss of human life, personal injuries, environmental damage or the loss of assets and financial interests.

2.2.2 Breadth (B) means the greatest moulded breadth of the ship at or below the deepest draught (summer load line draught) (refer to SOLAS regulation II-1/2.8).

2.2.3 Bunkering means the transfer of liquid or gaseous fuel from land based or floating facilities into a ships' permanent tanks or connection of portable tanks to the fuel supply system.

2.2.4 Certified safe type means electrical equipment that is certified safe by the relevant authorities recognized by the Administration for operation in a flammable atmosphere based on a recognized standard.⁽¹⁾

2.2.5 CNG means compressed natural gas (see also 2.2.26 of the Guidelines).

2.2.6 Control station means those spaces defined in SOLAS chapter II-2 and additionally for the IGF Code, the engine control room.

2.2.7 Design temperature for selection of materials is the minimum temperature at which liquefied gas fuel may be loaded or transported in the liquefied gas fuel tanks.

2.2.8 Design vapour pressure "P0" is the maximum gauge pressure, at the top of the tank, to be used in the design of the tank.

Note 1:

Refer to IEC 60079 series, Explosive atmospheres and IEC 60092-502:1999 Electrical Installations in Ships – Tankers – Special Features

CR Classification Society

2.2.9 Double block and bleed valve means a set of two valves in series in a pipe and a third valve enabling the pressure release from the pipe between those two valves. The arrangement may also consist of a two-way valve and a closing valve instead of three separate valves.

2.2.10 Dual fuel engines means engines that employ fuel covered by the IGF Code (with pilot fuel) and oil fuel. Oil fuels may include distillate and residual fuels.

2.2.11 Enclosed space means any space within which, in the absence of artificial ventilation, the ventilation will be limited and any explosive atmosphere will not be dispersed naturally.⁽²⁾

2.2.12 ESD means emergency shutdown.

2.2.13 Explosion means a deflagration event of uncontrolled combustion.

2.2.14 Explosion pressure relief means measures provided to prevent the explosion pressure in a container or an enclosed space exceeding the maximum overpressure the container or space is designed for, by releasing the overpressure through designated openings.

2.2.15 Fuel containment system is the arrangement for the storage of fuel including tank connections. It includes where fitted, a primary and secondary barrier, associated insulation and any intervening spaces, and adjacent structure if necessary for the support of these elements. If the secondary barrier is part of the hull structure it may be a boundary of the fuel storage hold space.

The spaces around the fuel tank are defined as follows:

.1 Fuel storage hold space is the space enclosed by the ship's structure in which a fuel containment system is situated. If tank connections are located in the fuel storage hold space, it will also be a tank connection space;

.2 Interbarrier space is the space between a primary and a secondary barrier, whether or not completely or partially occupied by insulation or other material; and

.3 Tank connection space is a space surrounding all tank connections and tank valves that is required for tanks with such connections in enclosed spaces.

IACS Interpretation of 2.2.15.3

.1 A tank connection space may be required also for tanks on an open deck. This may apply to ships where the restriction of hazardous areas is safety critical. A tank connection space may also be necessary in order to provide environmental protection for essential safety equipment related to the gas fuel system like tank valves, safety valves and instrumentation.

.2 A tank connection space may also contain equipment such as vaporizers or heat exchangers. Suc h equipment is considered to only contain potential sources of release, but not sources of ignition.

2.2.16 Filling limit (FL) means the maximum liquid volume in a fuel tank relative to the total tank volume when the liquid fuel has reached the reference temperature.

Note 2:

See also definition in IEC 60092-502:1999

2.2.17 Fuel preparation room means any space containing pumps, compressors and/or vaporizers for fuel preparation purposes.

IACS Interpretation of 2.2.17

A tank connection space that has equipment such as vaporizers or heat exchangers installed inside is not regarded as a fuel preparation room. Such equipment is considered to only contain potential sources of release, but not sources of ignition.

2.2.18 Gas means a fluid having a vapour pressure exceeding 0.28 MPa absolute at a temperature of 37.8℃.

2.2.19 Gas consumer means any unit within the ship using gas as a fuel.

2.2.20 Gas only engine means an engine capable of operating only on gas, and not able to switch over to operation on any other type of fuel.

2.2.21 Hazardous area means an area in which an explosive gas atmosphere is or may be expected to be present, in quantities such as to require special precautions for the construction, installation and use of equipment.

2.2.22 High pressure means a maximum working pressure greater than 1.0 MPa.

2.2.23 Independent tanks are self-supporting, do not form part of the ship's hull and are not essential to the hull strength.

2.2.24 LEL means the lower explosive limit.

2.2.25 Length (L) is the length as defined in the International Convention on Load Lines in force.

2.2.26 LNG means liquefied natural gas.

2.2.27 Loading limit (LL) means the maximum allowable liquid volume relative to the tank volume to which the tank may be loaded.

2.2.28 Low-flashpoint fuel means gaseous or liquid fuel having a flashpoint lower than otherwise permitted under paragraph 2.1.1 of SOLAS regulation II-2/4.

2.2.29 MARVS means the maximum allowable relief valve setting.

2.2.30 MAWP means the maximum allowable working pressure of a system component or tank.

2.2.31 Membrane tanks are non-self-supporting tanks that consist of a thin liquid and gas tight layer (membrane) supported through insulation by the adjacent hull structure.

2.2.32 Multi-fuel engines means engines that can use two or more different fuels that are separate from each other.

2.2.33 Non-hazardous area means an area in which an explosive gas atmosphere is not expected to be present in quantities such as to require special precautions for the construction, installation and use of equipment.

CR Classification Society

2.2.34 Open deck means a deck having no significant fire risk that at least is open on both ends/sides, or is open on one end and is provided with adequate natural ventilation that is effective over the entire length of the deck through permanent openings distributed in the side plating or deckhead.

2.2.35 Risk is an expression for the combination of the likelihood and the severity of the consequences.

2.2.36 Reference temperature means the temperature corresponding to the vapour pressure of the fuel in a fuel tank at the set pressure of the pressure relief valves (PRVs).

2.2.37 Secondary barrier is the liquid-resisting outer element of a fuel containment system designed to afford temporary containment of any envisaged leakage of liquid fuel through the primary barrier and to prevent the lowering of the temperature of the ship's structure to an unsafe level.

2.2.38 Semi-enclosed space means a space where the natural conditions of ventilation are notably different from those on open deck due to the presence of structure such as roofs, windbreaks and bulkheads and which are so arranged that dispersion of gas may not occur.⁽³⁾

2.2.39 Source of release means a point or location from which a gas, vapour, mist or liquid may be released into the atmosphere so that an explosive atmosphere could be formed.

2.2.40 Unacceptable loss of power means that it is not possible to sustain or restore normal operation of the propulsion machinery in the event of one of the essential auxiliaries becoming inoperative, in accordance with SOLAS regulation II-1/26.3.

2.2.41 Vapour pressure is the equilibrium pressure of the saturated vapour above the liquid, expressed in MPa absolute at a specified temperature.

2.2.42 Ship constructed on or after 1 January 2024 means:

.1 for which the building contract is placed on or after 1 January 2024; or

.2 in the absence of a building contract, the keels of which are laid or which are at a similar stage of construction on or after 1 July 2024; or

.3 the delivery of which is on or after 1 January 2028.

2.2.43 (CR) Gas Combustion Unit(GCU)

“Gas Combustion Unit” (or “Thermal Oxidizer”) means a system used for controlling the pressure in the LNG storage tanks by burning the excess boil-off gas(BOG) from the tanks inside an enclosed combustion chamber under controlled and safe conditions.

Note 3:

Refer also to IEC 60092-502:1999 Electrical Installations in Ships – Tankers – Special Features

2.2.44 (CR) Hazardous areas See also 12.5 for further guidance.

Hazardous areas are divided into zones 0, 1 and 2 as defined below:

.1 Zone 0 is an area in which an explosive gas atmosphere is present continuously or for long periods or frequently.

.2 Zone 1 is an area in which an explosive gas atmosphere is likely to occur in normal operation occasionally.

.3 Zone 2 is an area in which an explosive gas atmosphere is not likely to occur in normal operation but, if it does occur, will persist for a short period only.

2.2.45 (CR) IGC Code

“IGC Code” means the International Code for the Construction and Equipment of Ships Carrying Liquefied Gases in Bulk, as amended.

2.2.46 (CR) Master Gas Fuel Valve

“Master Valve”, “Master Gas Valve”, or “Master Gas Fuel Valve” means an automatic shut-off valve in the fuel gas supply line to each consumer and which is located outside the machinery space of the consumer.

2.2.47 (CR) Natural Gas

“Natural Gas” (dry) is defined as gas without condensation at common operating pressures and temperatures where the predominant component is methane with some ethane and small amounts of heavier hydrocarbons (mainly propane and butane). The gas composition can vary depending on the source of natural gas and the processing of the gas.

The gas may be stored and distributed as CNG or LNG.

2.2.48 (CR) Pre-mixed Gas Fuel Engines

“Pre-mixed Gas Fuel Engines” are gas or dual fuel engines where the gas is introduced into the combustion air flow before it enters the cylinder or cylinder head port. For example, before the turbocharger.

2.2.49 (CR) Primary Barrier

“Primary Barrier” is the inner element designed to contain the fuel when the fuel containment system includes two boundaries.

2.2.50 (CR) Recognized Standard

A “Recognized Standard” is an international or national standard acceptable to the Society.