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Note: The use of silicon sealant may inhibit the effectiveness of some types of leak detection equipment.
Intrinsically safe components do not have to be isolated prior to working on them.
K. 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.
L. 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.
M. 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.
N. 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.
O. 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.
P. Charging procedures
In addition to conventional charging procedures, the following requirements shall be followed. Ensure that
contamination of different refrigerants does not occur when using charging equipment. Hoses or lines shall
be as short as possible to minimise the amount of refrigerant contained in them.
Cylinders shall be kept upright.
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