25
The following leak detection methods are deemed acceptable for all refrigerant systems.
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 percentage of gas (25 % maximum) is confirmed.
Leak detection fluids are also 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.
NOTE
Examples of leak detection fluids are:
•
Bubble method,
•
Fluorescent method agents.
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. Removal of refrigerant shall be according to Clause Removal and evacuation.
Removal and evacuation
When breaking into the refrigerant circuit to make repairs – or for any other purpose – conven-
tional procedures shall be used. However, for flammable refrigerants it is important that best prac-
tice be followed, since flammability is a consideration. The following procedure shall be adhered
to:
a) Safely remove refrigerant following local and national regulations;
b) Purge the circuit with inert gas;
c) Evacuate (optional for A2L);
d) Purge with inert gas (optional for A2L);
e) Open the circuit by cutting or brazing.
The refrigerant charge shall be recovered into the correct recovery cylinders if venting is not
allowed by local and national codes. For appliances containing flammable refrigerants, the system
shall be purged with oxygen-free nitrogen to render the appliance safe for flammable refrigerants.
This process might 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 achieved by break-
ing 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 (optional
for A2L). This process shall be repeated until no refrigerant is within the system (optional for A2L).
When the final oxygen-free nitrogen charge is used, the system shall be vented down to atmo-
spheric pressure to enable work to take place.
Ensure that the outlet for the vacuum pump is not close to any potential ignition sources and that
ventilation is available.
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