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Leak detection methods
The following leak detection methods are deemed acceptable for systems containing fl ammable
refrigerants:
• Electronic leak detectors shall be used to detect fl ammable 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
confi rmed.
• Leak detection fl 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 or
pipe-work.
• If a leak is suspected, all naked fl ames shall be removed or 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.
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 the best practice is followed since fl ammability is a
consideration. The following procedures 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
fl 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 fi ll until
the working pressure is achieved, then venting to atmosphere and fi nally pulling down to a vacuum.
This process shall be repeated until no refrigerant is within the system. When the fi 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 is 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.
Important Safety Information
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