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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 take into account the effects of aging or continual vibration from
sources such as compressors or fans.
5 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.
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 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.
7 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.