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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 lower
flammability limit (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
pipework.
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 octafluoronaphthalene
(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.
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