edges or any other adverse environmental
effects. The check shall also take into account
the effects of aging or continual vibration from
sources such as compressors or fans.
DETECTION OF FLAMMABLE REFRIGE-
RANTS
- Under no circumstances shall potential sources
of ignition be used in the searching for or
detection of refrigerant leaks. A halide torch (or
any other detector using a naked ame) shall
not be used.
LEAK DETECTION METHODS
- The following leak detection methods are
deemed acceptable for systems contain-
ing ammable refrigerants. Electronic leak
detectors shall be used to detect ammable
refrigerants, but the sensitivity may not be
adequate, or may need recalibration. (Detection
equipment shall be calibrated in a refriger-
ant-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 LFL of the
refrigerant and shall be calibrated to the refrig-
erant employed and the appropriate percentage
of gas (25 % maximum) is conrmed. Leak
detection uids are suitable for use with most
refrigerants but the use of detergents contain-
ing 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 ames 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.
REMOVAL AND EVACUATION
- When breaking into the refrigerant circuit to
make repairs – or for any other purpose – con-
ventional procedures shall be used. However, it
is important that best practice is followed since
ammability is a consideration. The following
procedure shall be adhered to: remove refriger-
ant; 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 cylin-
ders. The system shall be “ushed” 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 ll until
the working pressure is achieved, then venting
to atmosphere, and nally pulling down to a
vacuum. This process shall be repeated until
no refrigerant is within the system. When the
nal 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.
CHARGING PROCEDURES
- In addition to conventional charging proce-
dures, the following requirements shall be
followed.
- Ensure that contamination of different refrig-
erants 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 overll 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.
DECOMMISSIONING
- Before carrying out this procedure, it is essen-
tial that the technician is completely familiar
with the equipment and all its detail. It is rec-
ommended 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:
