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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 take into account the
effects of aging or continual vibration from sources such as compressors or fans.
DETECTION OF FLAMMABLE REFRIGERANTS
· Under no circumstances shall potential 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.
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 of 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.
REMOVAL AND EVACUATION
· When breaking into the refrigerant circuit to make repairs – or for any other purpose –
conventional 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 absolutely 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
ventilation available.
CHARGING PROCEDURES
· In addition to conventional charging procedures, the following requirements shall be followed.
· Ensure that contamination of different refrigerants does not occur when using charging
equipment. Hoses or lines shall be as short as possible to minimise the amount of refrigerant
contained in them.
· Cylinders shall be kept upright.
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