20
NOTE: The use of silicon sealant may
inhibit the eectiveness 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 ammable atmosphere.
The test apparatus shall be at the correct
rating. Replace components only with
parts specied by the manufacturer.
Other parts may result in the ignition of
refrigerant in the atmosphere from a leak.
Check that cabling will not be subject
to wear, corrosion, excessive pressure,
vibration, sharp edges or any other
adverse environmental eects. The check
shall also take into account the eects of
aging or continual vibration from sources
such as compressors or fans.
Cabling
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 ame) shall not be used.
Detection of ammable refrigerants
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
ammability 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 following leak detection methods
are deemed acceptable for systems
containing ammable refrigerants.
Electronic leak detectors shall be used
to detect 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 conrmed.
Leak detection uids 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 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 o 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
Leak detection methods
be located at the most critical point
to warn of a potentially hazardous
situation.
2.
Particular attention shall be paid to the
following to ensure that by working on
electrical components, the casing is
not altered in such a way that the level
of protection is aected. This shall
include damage to cables, excessive
number of connections, terminals not
made to original specication, damage
to seals, incorrect tting 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 ammable
atmospheres. Replacement parts
shall be in accordance with the
manufacturer’s specications.
The refrigerant charge shall be recovered
into the correct recovery cylinders. The
system shall be “ushed” 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
