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percentage of the LFL of the refrigerant and shall be calibrated to the refrigerant
employed and the appropriate percentage of gas (25 % maximum) is confirmed. Leak
detection fluids 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 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 –
con-
ventional 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.
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 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.
9 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 be taken in case analysis is required prior to re-use of
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