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• Repair to intrinsically safe components
Do not apply any permanent inductive or capacitance loads to the circuit without
ensuring that this will not exceed the permissible voltage and current permitted
for the equipment in use. Intrinsically safe components are the only types that
can be worked on while live in the presence of a ammable atmosphere. The test
apparatus shall be at the correct rating. Replace components only with parts
specied by the manufacturer. Other parts may result in the ignition of refrigerant
in the atmosphere from a leak.
• Cabling
Check that cabling will not be subject to wear, corrosion, excessive pressure,
vibration, sharp edges or any other adverse environmental eects. The check shall
also take into account the eects of aging or continual vibration from sources
such as compressors or fans.
• Detection of ammable 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 ame) shall not be used.
• Leak detection methods
The following leak detection methods are deemed acceptable for systems
containing ammable refrigerants. Electronic leak detectors shall be used to
detect ammable refrigerants, but 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 conrmed. Leak detection
uids 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 ames 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 o 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.
• 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 ammability 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 ushed 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 ll until the working pressure is achieved, then venting to
atmosphere, and nally pulling down to a vacuum. This process shall be repeated
until no refrigerant is within the system. When the nal 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.
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