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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.
12. 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.
13. 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.
14. 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
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