Preamble

  1 These Interim Guidelines have been developed to provide an international standard for ships, other than vessels covered by the IGC Code, with natural gas-fuelled engine installations.

  2 The goal of these Interim Guidelines is to provide criteria for the arrangement and installation of machinery for propulsion and auxiliary purposes, using natural gas as fuel, which will have an equivalent level of integrity in terms of safety, reliability and dependability as that which can be achieved with a new and comparable conventional oil-fuelled main and auxiliary machinery.

  3 To achieve this goal, the functional requirements described below are embodied in the relevant parts of these Interim Guidelines:

• .1 Minimize hazardous areas as far as is practicable to reduce the potential risks that might affect the safety of the ship, personnel and equipment.

• .2 Minimize equipment installed in hazardous areas to that required for operational purposes. Equipment installed in hazardous areas should be suitable and appropriately certified.

• .3 Arrange hazardous areas to ensure pockets of gas cannot accumulate under normal and foreseeable failure conditions.

• .4 Arrange propulsion and electrical power generating installation to be capable of sustained or restored operation in the event that a gas-fuelled essential service becomes inoperative.

• .5 Provide ventilation to protect personnel from an oxygen deficient atmosphere in the event of a gas leakage.

• .6 Minimize the number of ignition sources in hazardous spaces by design, arrangements and selection of suitable equipment.

• .7 Arrange safe and suitable gas fuel storage and bunkering arrangements capable of taking on board and containing the gas fuel in the required state without leakage and overpressure.

• .8 Provide gas piping systems, containment and overpressure relief arrangements that are of suitable design, construction and installation for their intended application.

• .9 Design, construct, install, operate and protect gas-fuelled machinery, gas system and components to achieve safe and reliable operation consistent with that of oil-fuelled machinery.

• .10 Arrange and locate gas storage tank rooms and machinery spaces such that a fire or explosion in either will not render the machinery/equipment in other compartments inoperable.

• .11 Provide safe and reliable gas-fuel control engineering arrangements consistent with those of oil-fuelled machinery.

• .12 Provide appropriate selection of certified equipment and materials that are suitable for use within gas systems.

• .13 Provide gas detection systems suitable for the space concerned together with monitoring, alarm and shutdown arrangements.

• .14 Provide protection against the potential effects of a gas-fuel explosion.

• .15 Prevent explosion and hazardous consequences.

• .16 Provide fire detection, protection and extinction measures appropriate to the hazards concerned.

• .17 Provide a level of confidence in a gas-fuelled unit that is equivalent to that for an oil-fuelled unit.

• .18 Ensure that commissioning, trials and maintenance of gas utilization machinery satisfy the goal in terms of reliability, availability and safety.

• .19 Provide provision for procedures detailing the guidelines for safe routine and unscheduled inspection and maintenance.

• .20 Provide operational safety through appropriate training and certification of crew.

• .21 Provide for submission of technical documentation in order to permit an assessment of the compliance of the system and its components with the applicable rules and guidelines.

  4 The Interim Guidelines address the safety of ships utilizing natural gas as fuel.

  5 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).

  6 The gas composition can vary depending on the source of natural gas and the processing of the gas. Typical composition in volume (%):

 The gas may be stored and distributed as compressed natural gas (CNG) or liquefied natural gas (LNG).