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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 –
conventional 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
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.
8.
Charging procedures
In addition to conventional charging procedures, the following requirements shall be
followed.
– Ensure that contamination of different refrigerants does not occur when using charging
equipment. Hoses or lines shall be as short as possible to minimize the amount of
refrigerant contained in them.
– Cylinders shall be kept upright.
– Ensure that the refrigeration system is earthed prior to charging the system with
refrigerant.
– Label the system when charging is complete (if not already).
– Extreme care shall be taken not to overfill the refrigeration system.
