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● 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 flammable atmosphere.
The test apparatus shall be at the correct rating. Replace
components only with parts specified by the manufacturer. Other
parts may result in the ignition of refrigerant in the atmosphere
from a leak.
● Check that cabling will not be subject to wear, corrosion,
excessive pressure, vibration, sharp edges or any other adverse
environmental effects. The check shall also take into account the
effects of aging or continual vibration from sources such as
compressors or fans.
● 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.
● 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 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
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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.
● When breaking into the refrigerant circuit to make repairs – or
for any other purpose – conventional procedures shall be used.
However, it is important to follow best practice 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 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.
● In addition to conventional charging procedures, the following
requirements shall be followed.
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