14
Safety precautions
7. The following leak detection
methods are deemed
acceptable for all refrigerant
systems
•
No leaks shall be detected when
using detection equipment with a
sensitivity of 5 grams per year of
refrigerant or better under a pressure
of at least 0.25 times the maximum
allowable pressure (>1.04 MPa, max
4.15 MPa), for example, a universal
sniffer.
•
Electronic leak detectors may be
used to detect fl ammable refrigerants,
but the sensitivity may not be
adequate, or may need re-calibration.
(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 and shall be calibrated
to the refrigerant employed and the
appropriate percentage of gas (25 %
maximum) is confi rmed.
•
Leak detection fl uids are also suitable
for use with most refrigerants,
for example, bubble method and
fl uorescent method agents. 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
fl ames 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. The
precautions in #8 must be followed to
remove the refrigerant.
8. 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 fl ammability is
a consideration. The following
procedure shall be adhered to:
remove refrigerant -> purge the circuit
with inert gas -> evacuate -> purge
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 purged with OFN
to render the appliance safe.
•
This process may need to be
repeated several times.
•
Compressed air or oxygen shall not
be used for this task.
•
Purging shall be achieved by
breaking the vacuum in the system
with OFN and continuing to fi ll until
the working pressure is achieved,
then venting to atmosphere, and
fi nally pulling down to a vacuum.
•
This process shall be repeated until
no refrigerant is within the system.
•
When the fi nal 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
potential ignition sources and there is
ventilation available.
OFN = oxygen free nitrogen,
type of inert gas.
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