Section 2 Construction and installation

2.1.1 The selection of materials in piping systems for provision refrigeration systems is to recognise the following details:

1. Fluids, pressures and temperatures.

2. Location.

3. Compatibility of materials.

4. Fluid flow rates and static conditions.

5. Minimising corrosion and erosion through life of system.

6. 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 Vol 2, Pt 7, Ch 1 Piping Design Requirements.

2.1.3 Where applicable, the materials are to comply with the requirements of Vol 2, Pt 7, Ch 1 Piping Design Requirements.

2.2.1 Pressure vessels in provision refrigeration systems are to be in accordance with Vol 2, Pt 8, Ch 2 Other Pressure Vessels or a recognised Code.

2.2.2 Valves, flexible hose lengths, expansion pieces and pumps are to comply with the relevant requirements of Vol 2, Pt 7, Ch 1, 12 Valves.

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 is 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 Low temperature pipes in refrigeration systems are to be provided with suitable insulation.

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

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 wire with a lead seal or similar arrangement.

2.4.1 Refrigeration plants are to be provided and designed to be capable of extracting the defined heat load duty when operating in accordance with the conditions stated in the System Design Description required by Vol 3, Pt 1, Ch 2, 1.2 Documentation required for design review 1.2.2.

2.4.2 The compartments containing the refrigeration plants are to be provided with refrigerant gas detectors in accordance with Vol 2, Pt 9, Ch 11 Gas detection with an alarm.

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

2.4.4 Refrigeration systems are to be provided with relief devices, but it is important to avoid circumstances that would bring about an inadvertent discharge of refrigerant to the atmosphere. The system is to be so designed that pressure due to fire conditions will 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 flow capacity of the valve or disc is to exceed the full load compressor capacity on 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 valves 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 Vol 3, Pt 1, Ch 2, 2.4 Refrigerant systems 2.4.6, will be accepted where:

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

or

1. Vessels discharge into the low pressure side 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 hermetically sealed compressor units or semi-hermetic compressors with the electric motor cooled by the circulating refrigerant are installed, the following arrangements are to be made:

1. Each refrigeration system containing hermetically sealed compressor units or semi-hermetic compressors is to be independent of other refrigeration systems.

2. All hermetic motor-compressors are to be fitted with a thermal cut-out device that protects the motor against overheating.

3. Each refrigerant circuit is to be designed such that debris or contaminants from a motor failure, typically burn out of insulation, is contained and not distributed around the system.

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 Vol 2, Pt 8, Ch 2 Other Pressure Vessels and Vol 2, Pt 1, Ch 4 Requirements for Fusion Welding of Pressure Vessels and Piping as applicable. Plans are to be submitted for consideration as required by Vol 2, Pt 8, Ch 2, 1.6 Plans.

2.4.10 Sea-water systems for refrigeration condensers are to be capable of being supplied from not less than two independent sources. If specified, these sources are to be located in separate compartments and zones such that the loss of one zone or compartment will not result in the loss of all sea-water supply sources.

2.4.11 The capacity of each source of seawater required by Vol 3, Pt 1, Ch 2, 2.4 Refrigerant systems 2.4.10 is to be sufficient for the conditions stated in the System Design Description with any one source out of action.

2.5.1 Refrigerated spaces may be cooled by air coolers or cooling grids on the deckhead, bulkheads, and sides. In order to minimise the dehydration of the stores and the frosting of the air coolers or cooling grids, the installation is to be designed to maintain the required temperatures as defined in the System Design Description with a minimum of difference between the refrigerant and space temperatures.

2.5.2 The refrigeration capacity of the air cooler arrangement is to be such that the provisions room temperature conditions defined in the System Design Description can be maintained under normal operating conditions. The capacities of the fans are also to be such that they can maintain the required air flow rates and uniform air temperature throughout the refrigerated spaces, when part or fully loaded with stores.

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

2.5.4 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. Provision is to be made for the prevention of freezing of the condensate.

2.5.5 Air coolers are to be located such that when the refrigerated spaces are loaded with stores, adequate space is provided for the inspection, servicing and renewal of controls, valves, fans and fan motors.

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

2.6.1 A refrigerating unit is considered to comprise a compressor, its driving motor and one condenser. Where a secondary refrigerant, such as brine, is employed, the unit is also to include an evaporator (secondary refrigerant cooler) and a secondary refrigerant pump.

2.6.2 Two or more compressors driven by a single motor, or having only one condenser or evaporator/secondary refrigerant cooler, are to be regarded as one unit.

2.6.3 The refrigerating units of a classed provision stores installation are to be completely independent of any refrigerating machinery associated with air conditioning plant, unless full details of any proposal have been submitted and approved.

2.7.1 The design pressure of the system will be regarded as equal to its maximum working pressure.

2.7.2 The maximum working pressure is the maximum permissible pressure within the system (or part system) in operation or at rest. No relief valve 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 system.

2.7.4 The minimum design pressure of the high pressure side of the system (P _dh), is to be 1,11 × P _b, where P _b is an allowance for the compressor high pressure cut-out. P _b is to be at least equal to 1,11 × P _a, where P _a is the condenser working pressure, when operating in tropical zones and equates to the saturation pressure at 46°C.

2.7.5 Design pressures (bar g) applicable to refrigerants are to be not less than the values given in Table 2.2.1 Pressure limits when condensers are sea-water cooled. The design pressure for other refrigerants is to be agreed with LR.

2.8.1 Where applicable, having regard to their location and environmental conditions, insulation materials are to be:

• suitably resistant to fire;
• suitably resistant to the spreading of flame;
• adequately protected against penetration of water vapour; and
• adequately protected against mechanical damage.

2.8.2 The potential for smoke generation and its toxicity is to be in accordance with 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 for approval.