Advertisement
Available languages
Available languages
6. Leak detection methods
The following leak detection methods are deemed acceptable for systems
containing flammable refrigerants.
Electronic leak detectors should be used to detect flammable refrigerants,
but the sensitivity may not be adequate, or may need re-calibration.
(Detection equipment should 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 should be set at a
percentage of the LFL of the refrigerant and should 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 should be avoided as the
chlorine may react with the refrigerant and corrode the copper pipe-work. If
a leak is suspected, all naked flames should be removed/extinguished. If a
leakage of refrigerant is found which requires brazing, all of the refrigerant
should 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) should then be purged through the system both before and during the
brazing process.
7. Removal and evacuation
When breaking into the refrigerant circuit to make repairs, or for any other
purpose, conventional procedures should be used. However, it is important
that best practice is followed since flammability is a consideration. The
following procedure should 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 should be recovered into the correct recovery
cylinders. The system should be "flushed" with OFN to render the unit safe.
This process may need to be repeated several times. Compressed air or
oxygen should not be used for this task. Flushing should 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 should be repeated until no
refrigerant is within the system. When the final OFN charge is used, the
system should be vented down to atmospheric pressure to enable work to
take place. This operation is absolutely vital if brazing operations on the
11
Advertisement
