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3
sources such as compressors or fans.
Under no circumstances shall potential sources of ignition be used in the searching for or detecting refrigerant leaks.
A halide torch (or any other detector using open flames) shall not be used.
Electronic leak detectors shall be used to detect flammable refrigerants, but the sensitivity may be inadequate, or
may need re-calibrating. (Detection equipment shall be calibrated in a refrigerant-free area.) Ensure that the detector
is not a potential source of ignition and is suitable for the refrigerant used. Leak detection equipment shall be set at a
percentage of the lower flammability limit (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 open flames shall be removed/extinguished.
If a leakage of refrigerant is found which requires brazing, all of the refrigerants shall be removed from the system, or
isolated (by means of shut-off valves) in a part of the system which is remote from the leak. Oxygen free nitrogen
(OFN) shall then be purged through the system both before and during the brazing process.
When entering 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
procedures shall be adhered to:
- remove refrigerants;
- purge the circuit with inert gas;
- evacuate;
- purge again with inert gas;
- open the circuit by cutting or brazing.
The refrigerant 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 filling the refrigerant system with OFN. Boost the pressure by filling OFN
continuously until the working pressure is achieved, and then lower the pressure to release OFN. Repeat the steps
until there is no refrigerant remains in the system. This process shall be repeated until no refrigerant is in the system.
When the final OFN charge is used, the system shall be vented down to atmospheric pressure for work. 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.
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 minimize the amount of refrigerant contained in them.
– Cylinders shall be kept upright.
–
Ensure that the refrigeration system is earthed before filling 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.
Before recharging the system, it shall be pressure-tested with OFN. The system shall be leak-tested on completion of
charging but before the commissioning. A follow-up leak test shall be carried out before leaving the site.
Before carrying out this procedure, it is essential that the technician is completely familiar with the equipment and all
its details. It is recommended that all refrigerants are recycled safely. Before the task being carried out, an oil and
refrigerant sample shall be taken in case analysis is required before the re-use of reclaimed refrigerant. It is essential
that electrical power is available before the task is commenced.
a) Be 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;
--all personal protective equipment is available and being used correctly;
--the recovery process is supervised at all time by qualified personnel;
--recycling the equipment and cylinders conform to the appropriate standards.
d) Pump down the refrigerant system if possible.
e) If a vacuum state can’t be achieved during the vacuum-pumping process for the refrigerant system, install a
manifold so that the refrigerant can be totally removed from various parts of the system. Make sure that the
cylinder is leveled and balanced before recycling.
f) The recycle and operation of the machine should be conducted in accordance with manufacturer's instructions.
g) Do not overfill cylinders (no more than 80 % of the liquid volume).
h) Do not exceed the maximum working pressure of the cylinder, even temporarily.
i) When the cylinders have been filled correctly and the process completed, make sure that the cylinders and the
equipment are removed from site promptly and all isolation valves on the equipment are closed off.
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