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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 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.
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 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.
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 continual 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 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.
7 Removal and evacuation
When breaking into the refrigerant circuit to make repairs – or for any other purpose – con- ventional 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 for the vacuum pump is not close to any ignition sources and there 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.
9 Decommissioning
Before carrying out this procedure, it is essential that the technician is completely familiar with the equipment and all its
detail. It is recommended good practice that all refrigerants are recovered safely. Prior to the task being carried out, an oil
and refrigerant sample shall be taken in case analysis is required prior to re-use of reclaimed refrigerant. It is essential that
electrical power is available before the task is commenced.
a) Become familiar with the equipment and its operation.
b) Isolate system electrically.
c) Before attempting the procedure ensure that :mechanical handling equipment is available, if required, for handling
refrigerant cylinders; all personal protective equipment is available and being used correctly; the recovery process is
supervised at all times by a competent person; recovery equipment and cylinders conform to the appropriate standards.
d) Pump down refrigerant system,if possible.
e) If a vacuum is not possible, make a manifold so that refrigerant can be removed from various parts of the system.
f) Make sure that cylinder is situated on the scales before recovery takes place.
g) Start the recovery machine and operate in accordance with manufacturer's instructions.
h) Do not overfill cylinders. (No more than 80 % volume liquid charge).
