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this will not exceed the permissible voltage and current permitted for the equipment in use.
Intrinsically safe components are the only types that can be worked on while live in the presence
of a flammable atmosphere. The test apparatus shall be at the correct rating. Replace
components only with parts specified by the manufacturer. Other parts may result in the ignition
of refrigerant in the atmosphere from a leak.
4 CABLING
Check that cabling will not be subject to wear, corrosion, excessive pressure, vibration, sharp
edges, or any other adverse environmental effects. The check shall also consider the effects of
aging or continual vibration from sources such as compressors or fans.
5 DETECTIONS OF FLAMMABLE REFRIGERANTS
Under no circumstances shall potentially sources of ignition be used in the searching for or
detection of refrigerant leaks. A halide torch (or any other detector using a naked flame)
shall not be used.
6 LEAK DETECTION METHODS
The following leak detection methods are deemed acceptable for systems containing
flammable refrigerants. Electronic leak detectors shall be used to detect flammable refrigerants,
but the sensitivity may not be adequate, or may need recalibration. (Detection equipment shall
be calibrated in a refrigerant-free area.) Ensure that the detector is not a potential source of
ignition and is suitable for the refrigerant used. Leak detection equipment shall be set at a
percentage of the LFL of the refrigerant and shall be calibrated to the refrigerant employed and
the appropriate percentage of gas (25 % maximum) is confirmed. Leak detection fluids are
suitable for use with most refrigerants but the use of detergents containing chlorine shall be
avoided as the chlorine may react with the refrigerant and corrode the copper pipe-work. If a leak
is suspected, all naked flames shall be removed/extinguished. If a leakage of refrigerant is found
which requires brazing, all the refrigerant shall be recovered from the system, or isolated (by
means of shut off valves) in a part of the system remote from the leak. Oxygen free nitrogen
(OFN) shall then be purged through the system both before and during the brazing process.
7 REMOVAL AND EVACUATION
When breaking into the refrigerant circuit to make repairs – or for any other purpose – con-
venational procedures shall be used. However, it is important that best practice is followed
since flammability is a consideration. The following procedure shall be adhered to: remove
refrigerant; purge the circuit with inert gas; evacuate; purge again with inert gas; open the circuit
by cutting or brazing. The refrigerant charge shall be recovered into the correct recovery
cylinders. The system shall be "flushed" with OFN to render the unit safe. This process may need
to be repeated several times. Compressed air or oxygen shall not be used for this task. Flushing
shall be achieved by breaking the vacuum in the system with OFN and continuing to fill until the
working pressure is achieved, then venting to atmosphere, and finally pulling down to a vacuum.
This process shall be repeated until no refrigerant is within the system. When the final OFN
charge is used, the system shall be vented down to atmospheric pressure to enable work to take
place. This operation is vital if brazing operations on the pipework are to take place.
Ensure that the outlet for the vacuum pump is not close to any ignition sources and there is
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