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IMPORTANT SAFETY INSTRUCTIONS
7. 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 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 components only with parts specified by the manufacturer. Other parts may result
in the ignition of refrigerant in the atmosphere from a leak.
8. 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.
9. 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.
10.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. 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. Oxygen free nitrogen
(OFN) shall then be purged through the system both before and during the brazing process.
11.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 pipe-work are to take place. Ensure that the outlet for the
vacuum pump is not close to any ignition sources and there is ventilation available.
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