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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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