UFESA PAC Alaska 7, Instruction Manual, Page: 63 / 200

63
Detection 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.
Leak detection method
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 sensi -
tivity 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 lower flammability limit
(LFL) of the refrigerant and shall be calibrated to the refrigerant employed and the appro-
priate percentage of gas (25 % maximum) is confirmed.
Leak detection fluids are suitable for use with most refrigerants but the use of deter -
gents 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 sys -
tem 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 intervening into the refrigerant circuit to make repairs- or for any other purpose-
conventional procedures should be used. However, for flammable refrigerants it is im -
portant 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 with inert gas;
• open the circuit by cutting or brazing.
The refrigerant charge shall be recovered into the correct recovery cylinders. For
appliances containing flammable refrigerants the system shall be purged with oxy -
gen-free nitrogen to render the appliance safe for flammable refrigerants. This process
may need to be repeated several times. Compressed air or oxygen shall not be used for
purging refrigerant systems.
For appliances containing flammable refrigerants, refrigerants purging shall be achie-
ved by breaking the vacuum in the system with oxygen-free nitrogen 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 remains within the
system. When the final oxygen-free nitrogen 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 be realized.
Ensure that the outlet for the vacuum pump is not close to any potential ignition sour-
ces and that ventilation is available.