MICAN 64330001, User Manual

Page: 290 / 294

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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.