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1.9. Verification of electrical devices
Repair and maintenance of electrical components should include initial safety checks and
component-inspection procedures. If there is a fault that may compromise safety, then no
power supply should be connected to the circuit until the fault is satisfactorily dealt with. If
the fault cannot be corrected immediately, but continued operation is necessary, a suitable
temporary solution must be used. This should be reported to the owner of the equipment so
as to inform all parties.
During initial safety checks, make sure
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that capacitors are unloaded–this must be done in a safe manner to avoid sparks;
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that no live wiring or electrical components are exposed while loading, recovering, or
purging the system;
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that there is continuity in the earth connection.
2. Repair of sealed components
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During the repair of sealed components, all power supplies should be disconnected from
the equipment being worked on prior to any removal of sealed covers, etc. If it is absolutely
necessary to have a power supply to the equipment during service, then a permanently
operating form of leak detection should be placed at the most critical point to warn of a
potentially hazardous situation.
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Particular attention must be paid to the following to ensure that, when working on electrical
components, the housing is not altered in such a way as to affect safety. This must include
damage to cords, an excessive number of connections, terminals not conforming to the
initial specification, damage to seals, incorrect fitting of the stuffing box, etc.
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Ensure that the instrumentation is securely mounted.
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Ensure that seals or sealing materials have not degraded until no longer being useful to
preventing the penetration of flammable atmospheres. Spare parts must be in accordance
with the manufacturer's specifications.
NOTE:
the use of silicone sealant may inhibit the effectiveness of some types of leak-
detection equipment. Intrinsically safe components do not have to be isolated before work.
3. Repair of intrinsically safe components
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Do not apply any permanent inductive or capacitive load to the circuit without ensuring
that it will not exceed the permissible voltage and current rating for the equipment in use.
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Intrinsically safe components are the only type of components that can be worked on
in a flammable atmosphere. The test instrumentation must have the correct assigned
features.
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Replace components only with parts specified by the manufacturer. Other parts can ignite
the refrigerant in the atmosphere from a leak.
4. Wiring
Verify that the wiring is not subject to wear, corrosion, excessive pressure, vibration, sharp
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FORCECLIMA 14600 SOUNDLESS HEATING
edges, or any other environmental effects. The verification should also take into account the
effects of ageing or continuous vibration from sources such as compressors or fans.
5. Detection of flammable refrigerants
Under no circumstances should potential ignition sources be used in the search for or detection
of refrigerant leaks. Do not use a halide lamp or any other detector using a naked flame.
6. Leak-detection methods
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The following leak-detection methods are considered acceptable for systems containing
flammable refrigerants.
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Electronic leak detectors should be used to detect flammable refrigerants, but the
sensitivity may not be adequate, or may need recalibration (the detection equipment should
be calibrated in a refrigerant-free area). Ensure that the detector is not a potential ignition
source and that it is suitable for the refrigerant used. The leak-detection equipment must
be set to a percentage of the lower flammability limit of the refrigerant and calibrated for
the refrigerant used with the appropriate percentage of gas (maximum 25%) confirmed.
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Leak-detection fluids are suitable for use with most refrigerants, but the use of detergents
containing chlorine must be avoided, as chlorine can react with the refrigerant and corrode
copper pipes.
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If a leak is suspected, all naked flames must be eliminated/extinguished.
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If a refrigerant leak is found and requires brazing, all refrigerant must be recovered from
the system, or isolated (by means of shut-off valves) in a part of the system far away from
the leak. Oxygen-free nitrogen must then be purged through the system both before and
during the brazing process.
7. Removal and evacuation
When intervening in the cooling circuit for repairs or any other purpose, conventional
procedures must be followed. However, it is important that best practices are followed, as
flammability is a matter to be taken seriously. The following procedure is to be followed:
1.
Remove the refrigerant.
2.
Purge the circuit with inert gas.
3.
Evacuate.
4.
Purge again with inert gas.
5.
Open the circuit by cutting or brazing.
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The refrigerant charge must be recovered from the correct recovery cylinders. The system
must be flushed with oxygen-free nitrogen to render the unit safe. This process may need
to be repeated several times. Oxygen or compressed air must not be used for the task.
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Cleanliness must be achieved by breaking the vacuum in the system with oxygen-
free nitrogen and continuing to fill until working pressure is reached, then venting to
atmosphere, and finally pushing to a vacuum. This process must be repeated until there
is no refrigerant left in the system. When using the oxygen-free nitrogen end-charge,
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