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6. Leak-detection methods
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The following leak-detection methods are considered acceptable for systems
containing flammable refrigerants.
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Electronic leak detectors should be used to detect flammable refrigerants, but
the sensitivity may not be adequate, or may need recalibration (the detection
equipment should be calibrated in a refrigerant-free area). Ensure that the
detector is not a potential ignition source and that it is suitable for the refrigerant
used. The leak-detection equipment must be set to a percentage of the lower
flammability limit of the refrigerant and calibrated for the refrigerant used with
the appropriate percentage of gas (maximum 25%) confirmed.
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Leak-detection fluids are suitable for use with most refrigerants, but the use of
detergents containing chlorine must be avoided, as chlorine can react with the
refrigerant and corrode copper pipes.
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If a leak is suspected, all naked flames must be eliminated/extinguished.
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If a refrigerant leak is found and requires brazing, all refrigerant must be recovered
from the system, or isolated (by means of shut-off valves) in a part of the system
far away from the leak. Oxygen-free nitrogen must then be purged through the
system both before and during the brazing process.
7. Removal and evacuation
When intervening in the cooling circuit for repairs or any other purpose, conventional
procedures must be followed. However, it is important that best practices are followed,
as flammability is a matter to be taken seriously. The following procedure is to be
followed:
1.
Remove the refrigerant.
2.
Purge the circuit with inert gas.
3.
Evacuate.
4.
Purge again with inert gas.
5.
Open the circuit by cutting or brazing.
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The refrigerant charge must be recovered from the correct recovery cylinders. The
system must be flushed with oxygen-free nitrogen to render the unit safe. This
process may need to be repeated several times. Oxygen or compressed air must
not be used for the task.
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Cleanliness must be achieved by breaking the vacuum in the system with oxygen-
free nitrogen and continuing to fill until working pressure is reached, then
venting to atmosphere, and finally pushing to a vacuum. This process must be
repeated until there is no refrigerant left in the system. When using the oxygen-
free nitrogen end-charge, the system must be vented to atmospheric pressure to
allow for work. This operation is absolutely vital if brazing operations are to take
place on pipes.
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Ensure that the vacuum pump outlet is not near any source of ignition and that
ventilation is available.
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CLIMA P9 3 IN 1
