25
GB
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.
• Repair to intrinsically safe components
Do not apply any permanent inductive or capacitance loads to the circuit without en-
suring 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.
• 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 systems containing
flammable refrigerants. Electronic leak detectors shall be used to detect flammable refri-
gerants, but the sensitivity may not be adequate, or may need re-calibration. (Detection
equipment shall be calibrated a refrigerant-free area.) Ensure that the detector is not a
potential source of ignition and is suitable for the refrigerant used. Leak detection equip-
ment 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 refri-
gerant 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 nitrogen (OFN) shall then
be purged through the system both before during brazing process.
• 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 con-
tinuing 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
