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• Electronic leak detectors shall be used to detect flammable refrigerants, but the
sensitivity may not be adequate, or may need re-calibration. (Detection equipment shall
refrigerant used.
be calibrated in a refrigerant-free area.)
• Ensure that the detector is not a potential source of ignition and is suitable for the
shall be calibrated to the refrigerant employed and the appropriate percentage of gas
• Leak detection equipment shall be set at a percentage of the LFL of the refrigerant and
(25 % maximum) is confirmed.
containing chlorine shall be avoided as the chlorine may react with the refrigerant and
• Leak detection fluids are suitable for use with most refrigerants but the use of detergents
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:
• If a leak is suspected, all naked flames shall be removed/extinguished.
corrode the copper pipe-work.
recovered from the system, or isolated (by means of shut off valves) in a part of the
• If a leakage of refrigerant is found which requires brazing, all of the refrigerant shall be
during the brazing process.
• Oxygen free nitrogen (OFN) shall then be purged through the system both before and
system remote from the leak.
- Remove refrigerant.
• 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. 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. Ensure that the outlet for the
vacuum pump is not close to any ignition sources and there is ventilation available.
SAFET
Y
INSTRUCTIONS
EN
- Purge the circuit with inert gas.
- Evacuate.
- Purge again with inert gas.
- Open the circuit by cutting or brazing.
