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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.
Removal and evacuation
Electronic leak detectors may be used to detect refrigerant leaks but, in the case of
flammable refrigerants, the sensitivity may not be adequate, or may need re-calibration.
(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 percenta
ge of gas (25
% maximum) is confirmed.
remove refrigerant;
purge the circuit with inert gas; evacuate;
purge again with inert gas;
open the circuit by cutting or brazing.
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. For appliances containing flammable refrigerants, oxygen free nitrogen
(OFN) shall then be purged through the system both before and during the
brazing process
When breaking into the refrigerant circuit to make
repairs – or for any other purpose –
conventional procedures shall be used. However, for flammable refrigerants it is important
that best practice is followed since flammability is a consideration. The following procedure
shall be adhered to:
Charging procedures
Ensure that the outlet for the vacuum pump is not close to any ignition sources and that
ventilation is available.
The refrigerant charge shall be recovered into the correct recovery cylinders.
For appliances containing flammable refrigerants, 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 purging refrigerant systems.
In addition to conventional charging procedures, the following requirements shall be followed.
For appliances containing flammable refrigerants, flushing shall be achieved by
breaking the vacuum in the sys
tem 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 pipe-work are
to take place.
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