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1.GENERAL INFORMATION
degraded such that they no longer serve the
purpose of preventing the ingress of flammable
atmospheres. Replacement parts shall be in NOTE
The use of silicon sealant may inhibit the
effectiveness of some types of leak detection
equipment. Intrinsically safe components do not
have to be isolated prior to working on them.
Repair to intrinsically safe components:
Do not apply any permanent inductive or
capacitance loads to the circuit without ensuring
that this will not exceed the permissible voltage
and current permitted for the equipment in use.
Intrinsically safe components are the only types
that can be worked on while live in the presence of
a flammable atmosphere. The test apparatus shall
be at the correct rating.
Replace components only with parts specified by
the manufacturer. Other parts may result in the
ignition of refrigerant in the atmosphere from a leak
Cabling:
Check that cabling will not be subject to wear,
corrosion, excessive pressure, vibration, sharp
edges or any other adverse environmental effects.
The check shall also take into account the effects
of ageing or continual vibration from sources such
as compressors or fans.
Detection of flammable refrigerants:
Under no circumstances shall potential sources of
ignition be used in the searching for or detection of
refrigerant leaks. A halide torch (or any other
detector using a naked flame) shall not be used.
Leak detection methods:
The following leak detection methods are deemed
acceptable for systems containing flammable
refrigerants.
Electronic leak detectors shall be used to detect
flammable 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
confirmed.
Leak detection fluids are suitable for use with most
refrigerants but 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 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.
Oxygen free nitrogen (OFN) shall then be purged
through the system both before and during the
brazing process.
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 flammability is a
consideration.
The 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. This
process may need to be repeated several times.
Compressed air or oxygen shall not be used for
this task.
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 pressure to enable work to take place.
This operation is absolutely vital if brazing
operations on the pipework are to take place.
Ensure that the outlet for the vacuum pump is not
close to any ignition sources and there is ventilation
available.
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.
-- Cylinders shall be kept upright.
-- Ensure that the refrigeration system is earthed
prior to charging the system with refrigerant.
-- Label the system when charging is complete
(if not already).
-- Extreme care shall be taken not to overfill the
refrigeration system.
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