3.1.1 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
release of ozone-depleting or high global warning potential substances to the
atmosphere, refrigerant recovery units are to be provided for evacuation of a system
prior to maintenance.
3.1.2 Refrigeration systems are to be designed to prevent discharge of
refrigerant to atmosphere; however, relief devices are to be provided to protect the
system from overpressure in the event of a fault, or emergency such as fire. Where
discharge of refrigerant gas to atmosphere is unavoidable, arrangements are to be
made to prevent discharge into ventilation systems.
3.1.3 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, a
servo-operated valve 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.
3.1.4 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
provided with two pressure relief valves or two bursting discs, or one of each,
controlled by a changeover device.
3.1.5 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 the purpose of Vol 2, Pt 11, Ch 4, 3.1 General 3.1.4, provided that
the interconnecting pipework does not prevent effective venting of any pressure
vessel.
3.1.6 Omission of one of the specified relief devices and changeover device,
as required by Vol 2, Pt 11, Ch 4, 3.1 General 3.1.4,will be
accepted where:
- vessels are of less than 300 litres internal gross volume;
or
- vessels discharge into the low-pressure side by means of a
relief valve.
3.1.7 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.
3.1.8 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:
- Each refrigeration system containing hermetically sealed
compressor units or semi-hermetic compressors is to be independent of other
refrigeration systems.
- All hermetic motor-compressors are to be fitted with a
thermal cut-out device that protects the motor against overheating.
- 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.
3.1.9 Seawater systems for refrigeration condensers are to be capable of being supplied
from not less than two independent seawater supplies. If required by the System
Design Description, these supplies 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
the seawater supply to the refrigeration condensers.