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components and wiring are exposed while charging,
recovering or purging the system; that there is continuity
of earth bonding.
REPAIRS TO SEALED COMPONENTS
♦ During repairs to sealed components, all electrical sup-
plies 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 equipment during servicing, then a permanently oper-
ating form of leak detection shall be located 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, excessive number
of connections, terminals not made to original specifi-
cation, damage to seals, incorrect fitting of glands, etc.
Ensure that apparatus is mounted securely. Ensure
that seals or sealing materials have not degraded such
that they no longer serve the purpose of preventing
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 effec-
tiveness 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 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 a flammable atmosphere. The test
apparatus shall be at the correct rating. Replace com-
ponents 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.
(Original instructions)
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 ac-
ceptable for systems containing flammable refrigerants.
Electronic leak detectors shall be used to detect flamma-
ble refrigerants, but the sensitivity may not be adequate,
or may need recalibration. (Detection equipment shall
be calibrated in a refrigerantfree area.) Ensure that the
detector is not a potential source of ignition and is suit-
able 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 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. Ox-
ygen 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 consideration.
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 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
ENGLISH
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