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
ß
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 con
Þ
rmed.
• Leak detection
ß
uids are also suitable
for use with most refrigerants,
for example, bubble method and
ß
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
ß
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
ß
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
Þ
ll until
the working pressure is achieved,
then venting to atmosphere, and
Þ
nally pulling down to a vacuum.
• This process shall be repeated until
no refrigerant is within the system.
• When the
Þ
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.
ACXF55-24700_FULLSET.indb 14
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