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12
found (which requires brazing), all refrigerants shall be recovered from the system, or isolated (by means
of shut off valves) in a part of the system that is situated remotely from the leak. Oxygen free nitrogen
(OFN) shall then be purged from 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. Considering flammability, follow best practices. Opening of the refrigeration
systems shall not be done by brazing. Adherence to the following procedures is a must:
a) Removing the refrigerant;
b) Purging the circuit with inert gas;
c) Evacuation;
d) Purging again with inert gas;
e) Opening 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 the atmosphere, and finally pulling down to a vacuum. This
process shall be repeated until no refrigerant is inside 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 near any ignition sources and that ventilation is
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 the charging equipment. Hoses or lines
shall be as short as possible to minimize the amount of refrigerant contained in them.
Cylinders shall be kept upright.
Ensure that the refrigeration system is earthed before charging the system with the refrigerant. Label the
system when the charging is complete (in case it has not been labeled yet).
Extreme care shall be taken to avoid overfilling the refrigeration system.
Prior to recharging the system, the pressure test with OFN must first be conducted. The system leak test
shall be performed upon completion of charging, but should be done prior to commissioning. A follow up
leak test shall be carried out before leaving the site.
14. Decommissioning
Before carrying out this procedure, it is essential that the technician is completely familiar with the
equipment and all necessary details. It is good practice that all refrigerants be recovered safely. Prior
to carrying out this task, an oil and refrigerant sample shall be taken in case analysis is required before
reusing the reclaimed refrigerant. It is essential that electrical power is available before this task
commences.
a) Become familiar with the equipment and its operation.
b) Isolate the system electrically.
c) Before attempting the procedure, ensure that:
Mechanical handling equipment is available, if required, for handling refrigerant cylinders;
Allpersonal protective equipment is available and being used correctly;
The recovery process is always supervised by a competent person and recovery equipment and
cylinders conform to the required standards.
d) Pump down the refrigerant system, if possible.
Important Safety Instructions
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