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. O
xygen free
nitrogen (ofn) shall then be purged through the system both
before and during the brazing process.
Removal and evavuation. 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. T
he
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.
T
his
process
may
need
to
be
repeated
several
times.
Compressed
air or oxygen shall not be used for this task.
F
lushing
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. T
his
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
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