5 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.
6 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 sensitivity may not be adequate,
or may need recalibration. (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 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. 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 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 – con-ventional 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: 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 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
pipework are to take place.
Ensure that the outlet for the vacuum pump is not close to any ignition
sources and there is ventilation available.
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