Section 1 General

101. Application

1. This Guidance is to apply to ships classed or intended to be classed with the Society and in which natural gas-fuelled engine installations are installed, other than ships carrying natural gas in bulk.

2. The requirements in this Guidance are to apply in addition to other requirements in Rules for the classification of steel ships (hereafter referred to as "the Rules for Steel Ships").

3. The engines may be either single fuel engines(gas) or dual fuel engines(gas and oil), and gas may be stored in gaseous or liquid state.

102. Definitions

The definitions of terms are to be followed to the Rules for Steel Ships, unless otherwise specified in this Guidance.

1. "Accidents" means uncontrolled events that may entail the loss of human life, personal injuries, environmental damage or the loss of assets and financial interests.

2. "Certified safe type" means electrical equipment that is certified safe by a recognized body based on a recognized standard(refer to IEC 60079 series, explosive atmospheres and IEC 60092- 502 Electrical Installations in Ships-Tankers-Special Features). The certification of electrical equipment is to correspond to the category and group for methane gas.

3. "CNG" means compressed natural gas.

4. "Control stations" means those spaces defined in Part 8 of the Rules for Steel Ships and addi- tionally for this Guidance, the engine control room.

5. "Double block and bleed valve" means a set of three automatic valves located at the fuel sup- ply to each of the gas engines.

6. "Dual fuel engines" means engines that use oil fuel and natural gas as fuel and can burn natural gas and oil fuel simultaneously or operate on oil fuel or gas only.

7. "Enclosed space" means any space within which, in the absence of artificial ventilation, the ven- tilation will be limited and any explosive atmosphere will not be dispersed naturally(See also defi- nition in IEC 60092-502).

8. "ESD" means emergency shutdown.

9. "Explosion" means a deflagration event of uncontrolled combustion.

10. "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.

11.

12.

"Gas" means a fluid having a vapour pressure exceeding 0.28 MPa absolute at a temperature of

37.8 °C.

"Hazardous area" means an area in which an explosive gas atmosphere or a flammable gas (flash point below 60 °C) is or may be expected to be present, in quantities such as to require spe- cial precautions for the construction, installation and use of electrical apparatus. Hazardous areas are divided into zones 0, 1 and 2 as defined below(refer also to the area classification specified in Sec. 2.5 of IEC 60079-10-1, Part 10-1 :

(1) Zone 0 is an area in which an explosive gas atmosphere or a flammable gas with a flash point below 60 °C is present continuously or is present for long periods.

(2) Zone 1 is an area in which an explosive gas atmosphere or a flammable gas with a flash point

below 60 °C is likely to occur in normal operation.

(3) Zone 2 is an area in which an explosive gas atmosphere or a flammable gas with a flashpoint below 60°C is not likely to occur in normal operation and, if it does occur, is likely to do so

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13.

only infrequently and will exist for a short period only.

"Non-hazardous area" means an area which is not considered to be hazardous, i.e. gas safe, provided certain conditions are being met.

14. "High-pressure piping" means gas fuel piping with maximum working pressure greater than 1.0 MPa.

15. "IEC" means the International Electro-technical Commission.

16.

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

17. "LEL" means the lower explosive limit.

18. "LNG" means liquefied natural gas (refer to para.22).

19.

"Main tank valve" means a remote operated valve on the gas outlet from a gas storage tank, located as close to the tank outlet point as possible.

20. "MARVS" means the maximum allowable relief valve setting of a gas tank.

21. "Master gas fuel valve" means an automatic valve in the gas supply line to each engine located out- side the machinery space for gas-fuelled engines and as close to the gas heater (if fitted) as possible.

22. "Natural gas" means a 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).

23. "Open deck" means a deck that is open on both ends, or is open on one end and equipped with adequate natural ventilation that is effective over the entire length of the deck through permanent openings distributed in the side panels or in the deck above.

24. "Organization" means the International Maritime Organization (IMO).

25.

26.

"Risk" means the expression of the danger that an undesired event represents to persons, to the environment or to material property. The risk is expressed by the probability and consequences of an accident.

"Recognized standards" means applicable international or national standards acceptable to the Society or standards laid down and maintained by an organization which complies with the stand- ards adopted by the Organization and which is recognized by the Society.

27. "Safety management system" means the international safety management system as described in the ISM Code.

28. "Second barrier" means a technical measure which prevents the occurrence of a hazard if the first barrier fails, e.g., second housing of a tank protecting the surroundings from the effect of tank leaks.

29. "Semi-enclosed space" means a space limited by decks and or bulkheads in such manner that the natural conditions of ventilation are notably different from those obtained on open deck (refer also to IEC 60092-502 Electrical Installations in Ships-Tankers-Special Features).

30.

"Single gas fuel engine" means a power generating engine capable of operating on gas-only, and not able to switch over to oil fuel operation.

31. "SOLAS Convention" means the International Convention for the Safety of Life at Sea, 1974, as amended.

32. "Source of release" means any valve, detachable pipe joint, pipe packing, compressor or pump seal in the gas fuel system.

33.

"Tank room" means the gastight space surrounding the gas fuel tank, containing all tank con- nections and all tank valves.

103. Class notations

Ships satisfying the requirements of this Guidance may be given a notation "GFS (dual fuel, gas only)" as additional special feature notations.

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104. Hazards

Hazards referred in this Guidance means the hazards related to the arrangements for the storage, distribution and use of natural gas as a fuel.

105. Equivalence

Special equipment, which is not appropriate to apply the requirements of this Guidance or not specified in this Guidance, may be accepted by the Society provided that the Society is satisfied that such equipment is equivalent to or above those complying with the requirements of this Guidance.