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they no longer serve the purpose of prevent-
ing the ingress of flammable atmospheres.
Replacement parts shall be in accordance with
the manufacturer's specifications.
- NOTE The use of silicon sealant may inhibit the
effectiveness of some types of leak detection
equipment. Intrinsically safe components do not
have to be isolated prior to working on them.
REPAIR TO INTRINSICALLY SAFE COMPO-
NENTS
- Do not apply any permanent inductive or ca-
pacitance loads to the circuit without ensuring
that this will not exceed the permissible voltage
and current permitted for the equipment in
use. Intrinsically safe components are the only
types that can be worked on while live in the
presence of a flammable atmosphere. The
test apparatus shall be at the correct rating.
Replace components only with parts specified
by the manufacturer. Other parts may result
in the ignition of refrigerant in the atmosphere
from a leak.
CABLING
- Check that cabling will not be subject to wear,
corrosion, excessive pressure, vibration, sharp
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 flame) shall
not be used.
LEAK DETECTION METHODS
- The following leak detection methods are
deemed acceptable for systems containing
flammable refrigerants. Electronic leak detec-
tors shall be used to detect flammable refriger-
ants, but the sensitivity may not be adequate, or
may need recalibration. (Detection equipment
shall be calibrated in a refrigerantfree area.) En-
sure 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 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 pipework. If
a leak is suspected, all naked flames shall be
removed/extinguished. If a leakage of refriger-
ant 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. Oxy-
gen 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
flammability 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 "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 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
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