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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 cylin-
ders. 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 work-
ing pressure is achieved, then venting to atmosphere, and
finally pulling down to a vacuum. This process shall be re-
peated 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.
8 CHARGING PROCEDURES
In addition to conventional charging procedures,the follow-
ing 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 al-
•
ready).
Extreme care shall be taken not to overfill the refrigera-
•
tion system.
Prior to recharging the system it shall be pressure tested
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