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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 preventing the ingress of flammable atmospheres. Replacement
parts shall be in accordance with the manufacturer's specifications.
NOTE: The use of silicone sealant may inhibit the effectiveness of some types of the leak.
8) 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 currently permitted for the equipment in use.
Intrinsically safe components are the only types that can be worked on whillivingve 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.
9) 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.
10) Detection of flammable refrigerants
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.
11) 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 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 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 pipe-work.
12) 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 the 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 pipe-work are to take
place.
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