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circuit until it is satisfactorily dealt with. lf 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 all parties are advised. lnitial safety checks shall include:
• that capacitors are discharged: this shall be done in a safe manner to avoid possibility of sparking;
• that there no live electrical components and wiring are exposed while charging, recovering or purging the
system;
• that there is continuity of earth bonding.
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REPAIRS TO SEALED COMPONENTS
2.1 During repairs to sealed components, all electrical supplies shall be disconnected from the equipment being
worked upon prior to any removal of sealed covers, etc. lf it is absolutely necessary to have an electrical supply
to equipment during servicing, then a permanently operating form of leak detection shall be located at the
most critical point to warn of a potentially hazardous situation.
2.2 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 specification, 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 preven-
ting 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. lntrin-
sically safe components do not have to be isolated prior to working on them.
3
REPAIR TO INTRINSICALLY SAFE COMPONENTS
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 tor the equipment in use.
lntrinsically safe components are the only types that can be worked on while live in the presence of a flam-
mable 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.
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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 continua! vibration
from sources such as compressors or fans.
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DETECTION OF FLAMMABLE REFRIGERANTS
Under no circumstances shall potential sources of ignition be used in the searching for or detection of refrige-
rant leaks. A halide torch (or any other detector using a naked flame} shall not be used.
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LEAK DETECTION METHODS
The following leak detection methods are deemed acceptable for systems containing flammable refrigerants.
Electronic leak detectors shall be used to detect flammable refrigerants, but the sensitivity may not be ade-
quate, or may need recalibration. (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 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.
lf a leak is suspected, all open flames shall be removed/extinguished.
lf 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.
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REMOVAL AND EVACUATION
When breaking into the refrigerant circuit to make repairs - or for any other purpose - conventional 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 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 operation is absolutely vital if brazing operations on the pipework are to take place. Ensure
that the outlet tor the vacuum pump is not close to any ignition sources and !here is ventilation available.
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