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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.
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 pipework are to take place.
· Ensure that the outlet for the vacuum pump is not close to any ignition sources and there
is ventilation available.
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 minimise 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.
· Prior to recharging the system, it shall be pressure tested with OFN. The system shall be
leak tested on completion of charging but prior to commissioning. A follow up leak test
shall be carried out prior to leaving the site.
DECOMMISSIONING
· Before carrying out this procedure, it is essential that the technician is completely familiar
with the equipment and all its detail. It is recommended good practice that all refrigerants
are recovered safely. Prior to the task being carried out, an oil and refrigerant sample shall
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