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This shall include damage to cables,
excessive number of connections, terminals
not made to original specification, damage to
seals, incorrect fitting of glands, etc.
Ensure that apparatus is mounted securely.
Ensure that seals or sealing materials have not
degraded such that they no longer serve the
purpose of preventing the ingress of flammable
atmospheres.
Replacement parts shall be in accordance with
the manufacturer's specifications.
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.
8.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.
9.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 aging or continual vibration from
sources such as compressors or fans
10.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
11.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.
12.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 pipe-work are to take place.
Ensure that the outlet for the vacuum pump is
not close to any ignition sources and there is
ventilation available.
13.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.
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