Section 1 Ship Arrangements And System Design

101. General

1. For any new or altered concept or configuration, a risk analysis is to be conducted in order to en- sure that any risks arising from the use of gas-fuelled engines affecting the structural strength and the integrity of the ship are addressed. Consideration is to be given to the hazards associated with installation, operation, and maintenance, following any reasonably fore- seeable failure.

2. The risks are to be analysed using acceptable and recognized risk analysis techniques and loss of function, component damage, fire, explosion and electric shock are as a minimum to be considered. The analysis is to ensure that risks are eliminated wherever possible. Risks which cannot be elimi- nated are to be mitigated as necessary. Details of risks, and the means by which they are miti- gated, are to be included in the operating manual.

3. An explosion in any space containing open gas sources is not to:

(1) cause damage to any space other than that in which the incident occurs;

(2) disrupt the proper functioning of other zones;

(3) damage the ship in such a way that flooding of water below the main deck or any progressive flooding occur;

(4) damage work areas or accommodation in such a way that people who stay in such areas under

normal operating conditions are injured;

(5) disrupt the proper functioning of control stations and switchboard rooms for necessary power distribution;

(6) damage life-saving equipment or associated launching arrangements;

(7) disrupt the proper functioning of fire-fighting equipment located outside the explosion-damaged space; or

(8) affect other areas in the vessel in such a way that chain reactions involving, inter alia, cargo,

gas and fuel oil may arise.

102. Material requirements

1. Materials used in gas tanks, gas piping, process pressure vessels and other components in contact with gas are to be in accordance with Rules for Steel Ships Pt. 7 Ch. 5, Sec. 6, Materials of construction. For CNG tanks, the use of materials not covered by the Rules for Steel Ships Pt. 7 Ch. 5 may be specially considered by the Society.

2. Materials for piping system for liquefied gases are to comply with the requirements of the Rules for Steel Ships Pt. 7 Ch. 5 602. Some relaxation may, however, be permitted in the quality of the material of open-ended vent piping, provided the temperature of the gas at atmospheric pressure is

-55°C or higher, and provided no liquid discharge to the vent piping can occur. Materials are in general to be in accordance with recognized standards.

3. Materials having a melting point below 925°C are not to be used for piping outside the gas tanks except for short lengths of pipes attached to the gas tanks, in which case the low melting point materials are to be wrapped in class A-60 insulation.

103. Location and separation of spaces

1. The arrangement and location of spaces

The arrangement and location of spaces for gas fuel storage, distribution and use are to be such that the number and extent of hazardous areas is kept to a minimum.

2. Gas compressor room

(1) Compressor rooms, if arranged, are to be located above freeboard deck, unless those rooms are arranged and fitted in accordance with the requirements of these Guidance for tank rooms.

(2) If compressors are driven by shafting passing through a bulkhead or deck, the bulkhead pene-

tration is to be of gastight type.

3. Machinery spaces containing gas-fuelled engines

(1) When more than one machinery space is required for gas-fuelled engines and these spaces are separated by a single bulkhead, the arrangements are to be such that the effects of a gas ex- plosion in either space can be contained or vented without affecting the integrity of the adjacent space and equipment within that space.

(2) ESD-protected machinery spaces for gas-fuelled engines are to have as simple a geometrical shape as possible.

4. Tank rooms

(1) Tank room boundaries including access doors are to be gastight.

(2) The tank room is not to be located adjacent to machinery spaces of category A. If the separa- tion is by means of a cofferdam, the separation is to be at least 900 mm and insulation to class A-60 is to be fitted on the engine-room side.

104. Arrangement of entrances and other openings

1. Direct access through doors, gastight or otherwise, is generally not to be permitted from a gas-safe space to a gas-dangerous space. Where such openings are necessary for operational reasons, an air lock which complies with the requirements of the Rules for Steel Ships Pt. 7 Ch. 5, 306(para 2 to 7) is to be provided.

2. If the compressor room is approved located below deck, the room is, as far as practicable, to have an independent access direct from the open deck. Where a separate access from deck is not practi- cable, an air lock which complies with the requirements of the Rules for Steel Ships Pt. 7 Ch. 5,

306 (para 2 to 7) is to be provided.

3. The tank room entrance is to be arranged with a sill height of at least 300 mm.

4. Access to the tank room is as far as practicable to be independent and direct from open deck. If the tank room is only partially covering the tank, this requirement is also to apply to the room surrounding the tank and where the opening to the tank room is located. Where a separate access from deck is not practicable, an air lock which complies with the requirements of the Rules for Steel Ships Pt. 7 Ch. 5, 306(para 2 to 7) is to be provided. The access trunk is to be fitted with separate ventilation. It is not to be possible to have unauthorized access to the tank room dur- ing normal operation of the gas system.

5. If the access to an ESD-protected machinery space is from another enclosed space in the ship, the entrances is to be arranged with self-closing doors. An audible and visual alarm is to be provided at a permanent manned location. Alarm is to be given if the door is open continuously for more than 1 min. As an alternative, an arrangement with two self-closing doors in series may be

105. Pipe design

1. This requirements apply to gas piping. The Society may accept relaxation from these requirements for gas piping inside gas tanks and open-ended piping after special consideration, such as risk assessment.

2. Gas piping is to be protected against mechanical damage and the piping is to be capable of assim- ilating thermal expansion without developing substantial tension.

3. The piping system is to be joined by welding with a minimum of flange connections. Gaskets are to be protected against blow-out.

4. The wall thickness of pipes is not to be less than:

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