- Leak detection methods
The following leak detection methods are considered acceptable for systems containing
flammable refrigerants.
Electronic leak detectors must be used to detect flammable refrigerants, but their
sensitivity may not be adequate or may require recalibration. (Detection equipment must
be calibrated in an area without refrigerant.) Ensure that the detector is not a potential
source of ignition and is suitable for the refrigerant used. The leak detection equipment
must be set to a percentage LFL of the refrigerant and must be calibrated to the fluid used
and the appropriate percentage of gas (maximum 25%) is confirmed.
Leak detection fluids are suitable for use with most refrigerants, but the use of detergents
containing chlorine should be avoided as chlorine can react with the refrigerant and
corrode the copper piping.
In the event of a suspected leak, all open flames must be eliminated/extinguished.
If a refrigerant leak is found and brazing is required, all the refrigerant in the system must
be recovered or isolated (by means of shut-off valves) in a part of the system remote from
the leak. The oxygen-free nitrogen must then be purged through the system both before
and during the brazing process.
- Removal and evacuation
When working on the refrigerant circuit for repairs - or for any other purpose - conventional
procedures must be used. However, it is important to follow best practice as flammability
is a concern. The following procedure must be followed:
- remove the refrigerant;
- purge the circuit with an inert gas;
- proceed with the evacuation;
- purge again with an inert gas;
- open the circuit by cutting or soldering.
The refrigerant charge must be collected in correct recovery bottles. The system must be
drained with oxygen-free nitrogen to make the element safe. This process may have to be
repeated several times. Do not use compressed air or oxygen for this task.
Drainage must be achieved by cutting the vacuum in the system with oxygen-free nitrogen
and continuing to fill until the operating pressure is reached, then venting into the
atmosphere and finally creating the vacuum. This process must be repeated until there is
no refrigerant left in the system. When the final oxygen-free nitrogen charge is used, the
system must be returned to atmospheric pressure to allow operations to proceed. This
operation is absolutely vital if brazing operations are to take place on the pipes.
Make sure that the outlet of the exhaust pump is not close to an ignition source and that
there is ventilation.
- Loading procedures
In addition to conventional loading procedures, the following requirements must be met.
Ensure that no contamination of different refrigerants occurs during the use of the loading
equipment. The pipes or ducts should be as short as possible to minimise the amount of
refrigerant they contain.
