7
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 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 reclaimed refrigerant. It is essential that electrical power is available before the task is
commenced.
a) Become familiar with the equipment and its operation.
b) Isolate system electrically.
c) Before attempting the procedure ensure that :mechanical handling equipment is available, if required,
for handling refrigerant cylinders; all personal protective equipment is available and being used correctly;
the recovery process is supervised at all times by a competent person; recovery
equipment and
cylinders conform to the appropriate standards.
d) Pump down refrigerant system,if possible.