Initial safety checks shall include:
that capacitors are discharged, this shall be done in a safe manner to avoid possibility of sparking
there shall be no live electrical components and wiring are exposed while charging, recovering or purging the system;
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.
Replace components only with parts specified by the manufacturer.
Leak detection methods
Ensure that the detector is not a potential source of ignition (for example a halide torch) and is suitable for the refrigerant
used. Leak detection equipment shall be set at a percentage of the LFL of the refrigerant (for R32, LFL is 13%) 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.
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 pipe-work are to take place. Ensure that the
outlet for the vacuum pump is not close to any ignition sources and there is ventilation available.
Labelling
This unit shall be labelled ‘de-commissioned and emptied of refrigerant’. This label shall be dated and signed. Ensure that
there are labels on the equipment stating the equipment contains flammable refrigerant.
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