03
– Refrigerating pipe or components are
installed in a position where they are unlikely
to be exposed to any substances which may
corrode refrigerant containing components,
unless the components are constructed of
materials that are inherently resistant to
corrosion or are suitably protected against
corrosion.
Repair and maintenance of electrical
components shall include initial safety
checks and component inspection
procedures. If a fault exists that could
compromise safety, then no electrical
supply shall be connected to the circuit
until the fault has been dealt with
satisfactorily. If the fault cannot be
corrected immediately but it is necessary to
continue operation, an adequate temporary
solution shall be used. This shall be
reported to the owner of the equipment so
that all parties are advised. Initial safety
checks shall include:
– That capacitors are discharged: this shall be
done in a safe manner to avoid the possibility
of sparking;
– That no live electrical components and wiring
are exposed while charging, recovering or
purging the system;
– That there is continuity of grounding.
When repairing sealed components, all
electrical supplies shall be disconnected
from the equipment being worked upon
prior to any removal of sealed covers, etc.
If it is absolutely necessary to have an
electrical supply to the equipment during
servicing, then a permanently operating
form of leak detection shall be installed at
the most critical point to warn of a
potentially hazardous situation.
Particular attention shall be paid to the
following to ensure that by working on
electrical components, the casing is not
altered in such a way that the level of
protection is affected. This shall include
damage to cables, an excessive amount of
connections, terminals not made to their
original specification, damage to seals,
incorrect fitting of glands, etc.
Ensure that the apparatus is mounted
securely.
Ensure that seals or sealing materials have
not degraded to the point that they no
longer prevent the ingress of flammable
materials. Replacement parts shall conform
with the manufacturer’s specifications.
Do not apply any permanent inductive or
capacitance 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 flammable gases. 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
which has leaked into the surroundings.
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.
Under no circumstances shall potential
sources of ignition be used while searching
for or detection of refrigerant leaks. A halide
torch (or any other detector using a naked
flame) shall not be used.
Electronic leak detectors may be used to
detect refrigerant leaks but, in the case of
flammable refrigerants, the sensitivity may
not be adequate, or may need re-calibration.
(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 LFL of the refrigerant and
shall be calibrated for the refrigerant
employed, and the appropriate percentage
of gas (25 % maximum) is confirmed.
If a leak is suspected, all naked flames shall
be removed/extinguished.
If a leakage of refrigerant which requires
brazing is found, 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.
When opening the refrigerant circuit to
make repairs – or for any other purpose –
conventional procedures shall be used.
However, for flammable refrigerants it is
important that best practice is followed
since flammability is a consideration. The
following procedure shall be followed:
– Remove refrigerant;
– Purge the circuit with inert gas;
– Evacuate;
– Purge 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 process may need
to be repeated several times. Do not use
compressed air or oxygen for this task.
Flushing shall be achieved by breaking the
vacuum in the system with OFN and
continuing to fill until a working pressure is
achieved, then venting to the surroundings,
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.
