28
V 02/22
---That no live electrical components and wiring are exposed while charging, recovering or purging the system;
---That there is continuity of earth bonding.
Repairs to sealed components
During repairs to sealed components, all electrical supplies shall be disconnected from the equipment being worked
upon prior to any removal of sealed covers, etc. lf it is absolutely necessary to have an electrical supply to equipment
during servicing, then a permanently operating form of leak detection shall be located at the most critical point to warn of
a potentially hazardous situation.
Particular attention shall be paid to the following to ensure that by working on electrical components, the casing is not
altered in such a way that the level of protection is affected. This shall include damage to cables, excessive number of
connections, terminals not made to original specification, damage to seals, incorrect fitting of glands, etc.
•
Ensure that the apparatus is mounted securely.
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Ensure that seals or sealing materials have not degraded to the point 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 can inhibit the effectiveness of some types of leak detection equipment. lntrinsically
safe components do not have to be isolated prior to working on them.
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.
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 beat 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.
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.
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.
Leak detection methods
The following leak detection methods are deemed acceptable for all refrigerant systems.
Electronic leak detectors may be used to detect refrigerant leaks but, in the case of flammable refrigerants, 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 chiarine shall be
avoided as the chiarine 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. For appliances containing flammable
refrigerants, oxygen free nitrogen (OFN) shall then be purged through the system both before and during the brazing
process.
Removal and evacuation
When breaking into the refrigerant circuit to make repairs or for any other purpose conventional procedures shall be
used. However, for flammable refrigerants 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;
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purge again with inert gas;
•
open the circuit by cutting or brazing.
The refrigerant charge shall be recovered into the correct recovery cylinders.
For appliances containing flammable refrigerants, 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 purging refrigerant
systems.
For appliances containing flammable refrigerants, 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 that ventilation is available.
Charging procedures
In addition to conventional charging procedures, the following requirements shall be followed.