purpose of preventing 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. lntrinsically 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 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.
4 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.
5 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.
6 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 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.
7 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.
8 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. 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.
4
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