Section 3 Refrigerating machinery and refrigerant storage compartments

3.1.1 Refrigerating machinery is to be located in a well ventilated compartment. In general, the arrangements are to be such that all components of the refrigerating machinery can be readily opened up for inspection or replacement. Space is to be provided for the withdrawal and renewal of the tubes in `shell-and-tube' type evaporators (brine coolers) and condensers. Proposals for alternative arrangements are to be submitted for consideration. See Pt 6, Ch 3, 3.2 Arrangements for compartments housing machinery using ammonia for refrigerating machinery using ammonia.

3.1.2 Refrigerating machinery using toxic and/or flammable refrigerants is to be located outside the main machinery space in a separate gastight compartment.

3.1.3 Where the refrigerating machinery is located in a separate gastight compartment, outside the main machinery space, this compartment is to be equipped with effective mechanical ventilation to provide 30 air changes per hour based upon the total volume of the space. The mechanical ventilation is to have two main controls, one of which is to be operable from a place outside the compartment.

3.1.4 Refrigerating machinery using non-toxic and non-flammable refrigerants will not, in general, be required to be located in a separate compartment outside the main machinery space.

3.1.5 Openings for pipes, electrical cables and other fittings in the bulkheads and deck are to be fitted with gastight seals.

3.1.6 Ammonia piping is not to pass through accommodation spaces.

3.2.1 Where ammonia refrigerant is used, the refrigerating machinery shall be installed in a dedicated gastight compartment. See also Pt 6, Ch 3, 3.2 Arrangements for compartments housing machinery using ammonia 3.2.9.

3.2.2 The compartment containing ammonia refrigerating machinery and any access ways are to be provided with independent mechanical ventilation capable of:

• removing the heat generated by the equipment installed in the compartment;
• maintaining the atmosphere in the compartment at acceptable vapour threshold levels under normal operating conditions; and
• disposing of ammonia vapour safely and quickly in the event of a major leakage.

3.2.3 The ventilation system is to be of the negative pressure type where abnormal stoppages of the extraction fans activate an audible and visual alarm.

3.2.4 Compartments containing ammonia refrigerating machinery, including process vessels, are to be provided with:

• a negative ventilation system, independent of ventilation systems serving other spaces, having a capacity of not less than 30 air changes per hour based upon the total volume of the space. Other suitable arrangements which ensure an equivalent effectiveness may be considered;
• fresh air inlets, located at a low level in the machinery compartment and arranged so as to provide a supply of fresh air and to minimise the possibility of re-cycling the exhaust air from the outlet;
• exhaust outlets, located at a high level and arranged so as to promote good air distribution throughout the compartment;
• a fixed ammonia detector system with alarms inside and outside the compartment;
• water screens above all access doors, operable manually from outside the compartment in all ambient conditions;
• an independent bilge system;
• where the charge is greater than 50 kg, emergency body shower and eye wash facilities shall be installed locally outside the compartment. The water for the shower is to be thermostatically controlled so as to avoid low temperature shock.

3.2.5 Compartments are to have at least two access doors, opening outwards, one of which is to be an emergency exit giving direct access to the open deck. The doors are to be fitted with an easily operated opening mechanism to facilitate rapid escape in an emergency. In the case of small compartments where more than one door would be impractical, the emergency exit only is to be provided.

3.2.6 At least two sets of self-contained breathing apparatus and protective clothing are to be provided, readily available in the vicinity of the compartment but external to the area of risk. See Pt 6, Ch 3, 8.1 Personnel safety equipment 8.1.4.

3.2.7 The location of the exhaust duct, from the compartment or area, is to be free from obstruction and be such as not to cause danger. Where practicable, they are to be 10 m, where practicable, in the horizontal direction from other ventilation intakes and openings to accommodation and other enclosed areas, and at least 2 m above the surrounding deck.

3.2.8 Ventilation fans are not to produce a source of vapour ignition in either the ventilated compartment/area or ventilation system. Ventilation fans and fan ducts, in way of fans only, are to be of non-sparking construction.

3.2.9 In the case of ammonia plants on fishing ships under 55 m overall length, or ammonia plants with a charge of ammonia not greater than 25 kg, the refrigerating machinery may be located in the main machinery space provided it complies with the following requirements:

• The entrance to the machinery space is properly illuminated and marked and has warning signs permanently posted.
• The area where the ammonia machinery is installed is served by a hood with a negative ventilation system, so as not to permit any leakage of ammonia dissipating into other areas.
• A water spray system is provided for the area.
• Coamings, of not less than 150 mm in height, are installed around the ammonia machinery area.
• A fixed ammonia detector system with alarms inside and outside the main machinery space is provided.
• Means are provided for stopping the ammonia compressor prime movers from a position outside the machinery space.
• At least two sets of self-contained breathing apparatus and protective clothing are to be provided readily available in the vicinity of the compartment but external to the area of risk. See Pt 6, Ch 3, 8.1 Personnel safety equipment 8.1.4.
• Air intakes of other machinery are located away from the ammonia machinery area as far as is practicable.

3.3.1 Portable steel cylinders containing reserve supplies of refrigerant are to be stored in a well ventilated compartment reserved solely for this purpose.

3.3.2 The compartment is to be provided with a mechanical ventilation system providing 10 air changes per hour and is to have at least one door opening outwards giving direct access to open deck.

3.3.3 Bulk storage tanks holding more than 150 kg of replacement carbon dioxide are to be located in a separate compartment. The compartment is to be provided with a mechanical ventilation system having a minimum capacity of 6 air changes per hour. The ventilation system exhaust ducting is to remove air from the base of the compartment. The compartment is to be fitted with a gas tight access door opening outward.

3.3.4 The compartment is to be provided with a refrigerant vapour detection system.

3.3.5 The compartment is to be provided with suitable water drainage arrangements not connected with the main machinery spaces.

3.3.6 Steel storage cylinders are to be of an approved type, supplied by the refrigerant manufacturer and are to be filled to a level suitable for an ambient temperature of plus 46°C.

3.3.7 The compartment is to be provided with racks to facilitate secure stowage of the cylinders.

3.4.1 Self closing gas tight access doors are to be provided between each compartment and the dedicated escape routes. See Pt 6, Ch 3, 5.1 General 5.1.5.

3.4.2 In compartments which are normally occupied and where the volume of ventilation required by Pt 6, Ch 3, 3.1 General 3.1.3 is not desirable, such as production areas on fishing vessels, a negative pressure ventilation system, capable of 10 air changes per hour, is required to be fitted. This ventilation system is to be automatically activated when, in the event of a leak the concentration of carbon dioxide reaches a predetermined level but in no case higher than the threshold limit value of 5,000 ppm.