19
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:
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.
remove refrigerant;
purge the circuit with inert gas; evacuate;
purge again with inert gas;
open the circuit by cutting or brazing.
tion.(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
andshall 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 deter-
gents containing chlorine shall be avoided as the chlorine may react with the refriger-
ant 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.
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. Com-
pressed 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 pres-
sure to enable work to take place. This operation is absolutely vital if brazing opera-
tions 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.
Specialist's Manual
