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●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.
– 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.
– Ensure that the refrigeration system is earthed prior to charging the system with refrigerant.
– Label the system when charging is complete (if not already).
– Extreme care shall be taken not to overfill the refrigeration system. Prior to recharging the system it shall be
pressure tested with OFN. The system shall be leak tested on completion of charging but prior to
commissioning. A follow up leak test shall be carried out prior to leaving the site.
– Purge the circuit with inert gas.
– Evacuate.
– Purge again with inert gas.
– Open the circuit by cutting or brazing.
●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.
Repair to intrinsically safe components
●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 ageing or continual vibration from
sources such as compressors or fans.
Cabling Check
●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.
Detection of flammable refrigerants
●The following leak detection methods are deemed acceptable for systems containing flammable refrigerants.
●Ensure that the detector is not a potential source of ignition and is suitable for the refrigerant used.
●If a leak is suspected, all naked flames shall be removed/extinguished.
●Oxygen free nitrogen (OFN) shall then be purged through the system both before and during the brazing process.
●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.
●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.
●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.
●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.
●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.)
Leak detection methods
Removal and evacuation
●In addition to conventional charging procedures, the following requirements shall be followed.
Charging procedures
6
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All right reserved.Only training and service purposes.
Safety Precautions
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