12 Explosion Prevention
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Statutory Documents - IMO Publications and Documents - International Codes - IGF Code - International Code of Safety for Ships Using Gases or Other Low-Flashpoint Fuels - Part A-1 - Specific Requirements for Ships Using Natural Gas as Fuel - 12 Explosion Prevention

12 Explosion Prevention

12.1 Goal

The goal of this chapter is to provide for the prevention of explosions and for the limitation of effects from explosion.

12.2 Functional requirements

This chapter is related to functional requirements in 3.2.2 to 3.2.5, 3.2.7, 3.2.8, 3.2.12 to 3.2.14 and 3.2.17. In particular the following apply:

The probability of explosions shall be reduced to a minimum by:

  • .1 reducing number of sources of ignition; and
  • .2 reducing the probability of formation of ignitable mixtures.

12.3 Regulations – General

12.3.1 Hazardous areas on open deck and other spaces not addressed in this chapter shall be decided based on a recognized standard.footnote The electrical equipment fitted within hazardous areas shall be according to the same standard.

 12.3.2 Electrical equipment and wiring shall in general not be installed in hazardous areas unless essential for operational purposes based on a recognized standard.footnote

 12.3.3 Electrical equipment fitted in an ESD-protected machinery space shall fulfil the following:

  • .1 in addition to fire and gas hydrocarbon detectors and fire and gas alarms, lighting and ventilation fans shall be certified safe for hazardous area zone 1; and
  • .2 all electrical equipment in a machinery space containing gas-fuelled engines, and not certified for zone 1 shall be automatically disconnected, if gas concentration above 40% LEL is detected by two detectors in the space containing gas-fuelled consumers.

12.4 Regulations on area classification

12.4.1 Area classification is a method of analysing and classifying the areas where explosive gas atmospheres may occur. The object of the classification is to allow the selection of electrical apparatus able to be operated safely in these areas.

12.4.2 In order to facilitate the selection of appropriate electrical apparatus and the design of suitable electrical installations, hazardous areas are divided into zones 0, 1 and 2.footnote See also 12.5 below.

 12.4.3 Ventilation ducts shall have the same area classification as the ventilated space.

12.5 Hazardous area zones

 12.5.1 Hazardous area zone 0

This zone includes, but is not limited to the interiors of fuel tanks, any pipework for pressure-relief or other venting systems for fuel tanks, pipes and equipment containing fuel.

12.5.2 Hazardous area zone 1footnote

This zone includes, but is not limited to:

  • .1 tank connection spaces, fuel storage hold spacesfootnote and interbarrier spaces;
  • .2 fuel preparation room arranged with ventilation according to 13.6;
  • .3 areas on open deck, or semi-enclosed spaces on deck, within 3 m of any fuel tank outlet,footnote gas or vapour outlet, bunker manifold valve, other fuel valve, fuel pipe flange, fuel preparation room ventilation outlets and fuel tank openings for pressure release provided to permit the flow of small volumes of gas or vapour mixtures caused by thermal variation;
  • .4 areas on open deck or semi-enclosed spaces on deck, within 1.5 m of fuel preparation room entrances, fuel preparation room ventilation inlets and other openings into zone 1 spaces;
  • .5 areas on the open deck within spillage coamings surrounding gas bunker manifold valves and 3 m beyond these, up to a height of 2.4 m above the deck;
  • .6 enclosed or semi-enclosed spaces in which pipes containing fuel are located, e.g. ducts around fuel pipes, semi-enclosed bunkering stations;
  • .7 the ESD-protected machinery space is considered a non-hazardous area during normal operation, but will require equipment required to operate following detection of gas leakage to be certified as suitable for zone 1;
  • .8 a space protected by an airlock is considered as non-hazardous area during normal operation, but will require equipment required to operate following loss of differential pressure between the protected space and the hazardous area to be certified as suitable for zone 1; and
  • .9 except for type C tanks, an area within 2.4 m of the outer surface of a fuel containment system where such surface is exposed to the weather.

 12.5.3 Hazardous area zone 2footnote

12.5.3.1 This zone includes, but is not limited to areas within 1.5 m surrounding open or semi-enclosed spaces of zone 1.

12.5.3.2 Space containing bolted hatch to tank connection space.

Parent topic: Part A-1 - Specific Requirements for Ships Using Natural Gas as Fuel
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