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Idiomas disponibles
Idiomas disponibles
account the effects of ageing or continual vibration from sources such as compressors
or fans.
Detection of flammable refrigerants
Under no circumstances shall potential 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 methods
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 appropriate 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 refrige-
rant 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
system remote from the leak. Oxygen free nitrogen (OFN) shall then be purged throu-
gh 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 adhe-
red 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 sys-
tem 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.
Flushing shall be achieved by breaking the vacuum in the system with OFN and conti-
nuing 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 ena-
ble work to take place. This operation is absolutely vital if brazing operations on the
pipe-work are to take place.
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