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Leak detection methods
The following leak detection methods are acceptable
for systems containing flammable refrigerant.
Electronic leak detectors shall be used to detect flam-
mable refrigerants, but the sensitivity may not be ade-
quate, or may need recalibration (Detection equip-
ment shall be calibrated in a refrigerant-free area.)
Ensure that detector is not a potential source of igni-
tion and is suitable for the refrigerant used.
Leak detection fluids are suitable for use with most
refrigerants but the use of detergents containing chlo-
rine 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 leak of refrigerant is found which requires brazing,
all of the refrigerant shall be recovered from the sys-
tem. Oxygen free nitrogen (OFN) shall then be
purged through the system both before and during
the brazing process.
Removal and evacuation
When breaking into the refrigerant circuit to make
repairs-or for any other purpose-conventional proce-
dures shall be used. However, it is important that best
practice is followed since Flammability is a consider-
ation. 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 pro-
cess may need to be repeated several times. Com-
pressed 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 atmos-
phere, and finally pulling down to a vacuum. This pro-
cess shall be repeated until no refrigerant is within the
system. When the final OFN charge is used, the sys-
tem 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.
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
minimize 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.
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Prior to recharging the system, it shall be pressure
tested with OFN. The system shall be leak tested on
completion of charging but prior commissioning. A
follow up leak test shall be carried out prior to leaving
the site.
Decommissioning
Before carrying out this procedure, it is essential that
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 reuse of
reclaimed refrigerant. It is essential that electrical
power is available before the task is commenced.
A. Become familiar with the equipment and its oper-
ation.
B. Isolate system electrically.
C. Before attempting the procedure ensure that:
– mechanical handling equipment is available, if
repaired, 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.
E. If a vacuum is not possible, make a manifold so
that refrigerant can be removed from various
parts of the system.
F. Make sure that cylinder is situated on the scales
before recovery takes place.
G. Start the recovery machine and operate in accord-
ance with manufacturer's instructions.
H. Do not overfill cylinders (No more than 80% vol-
ume liquid charge).
I. Do not exceed the maximum working pressure of
the cylinder, even temporarily.
J. When the cylinders have been filled correctly and
the process completed, make sure that the cylin-
ders and the equipment are removed from site
promptly and all isolation valves on the equipment
are closed off.
K. Recovered refrigerant shall not be charged into
another refrigeration system unless it has been
cleaned and checked.
Labelling
Equipment shall be labeled stating that it has been
decommissioned and emptied of refrigerant. The
label shall be dated and signed. Ensure that there are
labels on the equipment stating the equipment con-
tains flammable refrigerant.
Recovery
When removing refrigerant from a system, either for
servicing or decommissioning, it is recommended
good practice that all refrigerants are removed safely.
When transferring refrigerant into cylinders, ensure
that only appropriate refrigerant recovery cylinders
are employed. Ensure that the correct number of cyl-
inders for holding the total system charge are availa-
ble. All cylinders to be used are designed for the
recovered refrigerant and labeled for that refriger-
ant(i.e.special cylinders for the recovery of refriger-
ant). Cylinders shall be complete with pressure relief
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