Section 2 Construction and installation

2.1.1 The selection of materials for piping systems in provision store refrigeration systems is to take account of the following:

1. The pressures and temperatures of the refrigerant fluids.

2. Locations of systems and equipment.

3. Compatibility of materials.

4. Fluid flow rates and static pressure conditions.

5. Minimising corrosion and erosion through life of system.

6. Refrigerant flammability and toxicity.

2.1.2 Pipes, valves and fittings are in general to be made of steel, ductile cast iron, copper, copper alloy, or other approved ductile material suitable for the intended purpose. The use of plastics materials is also acceptable subject to the restrictions in Pt 5, Ch 12, 5 Plastic pipes.

2.1.3 Where applicable, the piping systems are to comply with the requirements of Pt 5, Ch 12 Piping Design Requirements.

2.2.1 Pressure vessels in provision store and air-conditioning refrigeration systems are to be in accordance with Pt 5, Ch 11 Other Pressure Vessels.

2.2.2 Valves and flexible hose lengths are to comply with the relevant requirements of Pt 5, Ch 12 Piping Design Requirements.

2.2.3 Pipes in piping systems are to be permanent pipes made with approved pipe connections to enable ready removal of valves, pumps, fittings and equipment. The pipes are to be efficiently secured in position to prevent chafing or lateral movement.

2.2.4 Suitable means for expansion are to be made, where necessary, in each range of pipes.

2.2.5 Suitable protection is to be provided for all pipes and equipment situated where they are liable to mechanical damage.

2.2.6 All moving parts are to be provided with guards to minimise danger to personnel.

2.2.7 Primary refrigerant pipework, serving AHUs and FCUs, which pass through bulkheads and deckheads is to comply with the requirements of SOLAS Chapter II-2, 3 Penetrations in fire-resisting divisions and prevention of heat transmission.

2.3.1 Valves are to be fitted in places where they are readily accessible at all times.

2.3.2 Relief valves are to be adjusted and bursting discs so selected that they relieve at a pressure not greater than the design pressure of the system. When satisfactorily adjusted, relief valves are to be protected against tampering or interference by a locking wire with a lead seal or similar arrangement, see also Pt 7, Ch 15, 2.4 Refrigerant systems 2.4.4.

2.4.1 The primary refrigerants ammonia, hydrocarbons or carbon dioxide shall not be used in direct expansion FCUs located in accommodation spaces. The use of these refrigerants in machinery spaces, such as a separate AHU compartment, may be accepted subject to suitable safety arrangements being provided to the satisfaction of Clasifications Register (hereinafter referred to as LR).

2.4.2 Compartments containing refrigeration plant are to be provided with refrigerant gas leak detectors with an alarm. See Pt 7, Ch 15, 4 Refrigerant detection systems.

2.4.3 The design of refrigeration systems is to permit maintenance and repair without unavoidable loss of refrigerant to atmosphere. To minimise refrigerant release to the atmosphere, refrigerant recovery units are to be provided to allow evacuation of a system prior to maintenance.

2.4.4 Refrigeration systems are to be provided with relief devices which are arranged with sufficient margins to avoid circumstances that would allow an inadvertent discharge of refrigerant to the atmosphere. The system is to be so designed that overpressure due to fire conditions can be safely relieved.

2.4.5 A pressure relief valve and/or bursting disc is to be fitted between each positive displacement compressor and its gas delivery stop valve, the discharge being led to the suction side of the compressor. The refrigerant flow capacity of the valve or disc is to exceed the full load compressor capacity for the particular refrigerant at the maximum potential suction pressure. For these internal relief valves, servo-operated valves will be accepted. Where the motive power for the compressor does not exceed 10 kW, the pressure relief valve and/or bursting disc may be omitted.

2.4.6 Each pressure vessel which may contain liquid refrigerant and which is capable of being isolated by means of a stop or automatic control or check valve is to be protected by two pressure relief valves or two bursting discs, or one of each, controlled by a changeover device. Pressure vessels that are connected by pipework without valves, so that they cannot be isolated from each other, may be regarded as a single pressure vessel for this purpose, provided that the interconnecting pipework does not prevent effective venting of any pressure vessel.

2.4.7 Omission of one of the specified relief devices and changeover device, as required by Pt 7, Ch 15, 2.4 Refrigerant systems 2.4.6, will be accepted where:

1. vessels are of less than 300 litres internal gross volume; or

2. vessels discharge into the low pressure side of the system by means of a relief valve.

2.4.8 Sections of systems and components that could become full of liquid between closed valves are to be provided with pressure relief devices relieving to a suitable point in the refrigerant circuit.

2.4.9 Where any hermetic or semi-hermetic compressor has the electric motor cooled by the circulating refrigerant, the following arrangements are to be provided:

1. Refrigeration circuits are to contain no more than one hermetic or semi-hermetic compressors.

2. Each compressor motor is to be fitted with a thermal cutout device to protect the motor against overheating.

3. Each refrigerant circuit is to contain a suitable arrangement to allow debris or contaminants from a motor failure to be removed.

4. The pressure envelope of any hermetic or semi-hermetic compressor exposed to the refrigerant pressure is to be designed and constructed in accordance with the requirements of Pt 5, Ch 11 Other Pressure Vessels and Pt 5, Ch 17 Requirements for Fusion Welding of Pressure Vessels and Piping as applicable. Plans are to be submitted for consideration as required by Pt 5, Ch 11, 1.6 Plans.

2.5.1 Evaporator coils as fitted to direct expansion AHUs are to be considered for approval and plans are to be submitted, see also Pt 7, Ch 15, 1.2 Plans and information 1.2.2. All other equipment fitted to an AHU, such as air filtration, dehumidification, heating and humidification systems are outside the scope of these Rules and are the responsibility of the Shipyard and Owner.

2.5.2 Each AHU is to be provided with suitable drip trays and drainage arrangements to remove any condensate which may form.

2.5.3 The installation arrangements of AHUs are to be such as to allow sufficient space for the withdrawal and replacement of the refrigerant cooling coil.

2.6.1 Air cooler fan motors are to be suitably enclosed to withstand the effects of moisture.

2.6.2 Means are to be provided for effectively defrosting air coolers. Air coolers are to be provided with trays of suitable depth arranged to collect all condensate. The trays are to be provided with drains at their lowest points to enable the condensate to be drained away when the refrigerated spaces are in service. When a store operates at temperatures at, or lower than 0°C, provision is to be made for the prevention of freezing of the condensate.

2.6.3 The installation arrangements of air coolers are to be such that when the refrigerated spaces are loaded with provisions, adequate space is provided for the inspection, servicing and renewal of controls, valves, fans and fan motors.

2.6.4 Steel air cooler circuits and cooling grids are to be suitably protected against external corrosion.

2.7.1 The design pressure of the system will be regarded as equal to its maximum working pressure, see Pt 7, Ch 15, 2.7 Design pressures 2.7.5.

2.7.2 The maximum working pressure is the maximum permissible pressure within the system (or part system) in operation or at rest. No pressure relief valve or other protective device is to be set to a pressure higher than the maximum working pressure.

2.7.3 The design pressure of the low pressure side of the system is to be the saturated vapour pressure of the refrigerant at plus 46°C. Due regard is to be taken of defrosting arrangements which may cause a higher pressure to be imposed on the low pressure side of the system. For carbon dioxide design pressures, see Pt 7, Ch 15, 2.7 Design pressures 2.7.6.

2.7.4 The minimum design pressure of the high pressure side of the system (P _dh), is to be determined from 1,11 × P _b, where P _b is an allowance for the compressor high pressure cut-out. P _b is to be not less than to 1,11 × P _a, where P _a is the condenser working pressure, when operating in tropical zones and equates to the saturation pressure of the refrigerant at plus 46°C.

2.7.5 Design pressures applicable to refrigerants are to be not less than the values given in Table 15.2.1 Design pressure limits when condensers are sea-water cooled. The design pressure for other refrigerants and condensing arrangements is to be agreed with LR.

2.7.6 The proposed design pressure for a carbon dioxide system is to be stated, taking account of the maximum working pressure and the maximum pressure at rest conditions. Where the maximum pressure at rest condition is maintained by the fitting of a supplementary refrigeration unit, condensing the vapour in a holding vessel, supporting calculation is to be provided to show that this can be undertaken with a local ambient temperature of 45°C. The holding vessel is to be thermally insulated to prevent the operation of the relief devices within a 24 hour period after stopping the supplementary refrigeration unit at an ambient temperature of 45°C and an initial pressure equal to the starting pressure of the refrigeration unit.

2.7.7 Where a carbon dioxide system is designed for hot gas defrosting, due regard is to be given to the possibility of a higher pressure being imposed on the low pressure system. The design pressure for the hot gas defrosting section of the system is to be 10 per cent greater than the maximum pressure experienced during defrosting.

2.8.1 Where applicable, having regard to their location and environmental conditions, insulation arrangements are to have:

1. materials suitably resistant to fire;

2. insulation lining suitably resistant to flame spread;

3. effective protection against penetration of water vapour; and

4. adequate protection against mechanical damage.

2.8.2 The potential for smoke generation and toxicity of insulation materials is to be in accordance with SOLAS Chapter II-2, Part B, Regulation 6 - Smoke generation potential and toxicity.

2.8.3 Where the in situ foam type of insulation is proposed, full details of the process are to be submitted.

2.8.4 Prefabricated panel systems are to be fitted with suitable pressure equalising devices.

2.8.5 All low temperature pipework, valves and fittings are to be provided with suitable thermal insulation. See Pt 6, Ch 3, 4.11 Piping systems 4.11.10.

2.9.1 Pressure vessels satisfying the conditions listed in Pt 5, Ch 11, 1.6 Plans 1.6.1 are to be constructed in accordance with the requirements of Pt 5, Ch 11 Other Pressure Vessels and Pt 5, Ch 17 Requirements for Fusion Welding of Pressure Vessels and Piping. Plans are to be submitted for consideration as required by Pt 5, Ch 11, 1.6 Plans.

2.9.2 Other equipment, apart from applicable pressure vessels and heat exchangers, used for air-conditioning or provision stores refrigeration systems are not required to be constructed under survey.

2.9.3 All major items of equipment, containing refrigerant, such as compressors, condensers, AHU cooling coils and FCUs shall be supplied with a manufacturer’s works certificate providing details of the design and test pressures.