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6
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 recalibration. (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.
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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 im-
portant 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.
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Charging Procedures
In addition to conventional charging procedures,the following require-
ments 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.
Prior to recharging the system it shall be pressure tested with OFN. The
system shall be leak tested on completion of charging but prior to commis-
sioning. A follow up leak test shall be carried out prior to leaving the site.
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Decommissioning
Before carrying out this procedure, it is essential that the technician is
completely familiar with the equipment and all its detail. It is recommended
good practice that all refrigerants are recovered safely. Prior to the task
being carried out, an oil and refrigerant sample shall be taken in case
analysis is required prior to re-use of reclaimed refrigerant. It is essential
that electrical power is available before the task is commenced.
1. Become familiar with the equipment and its operation.
2. Isolate system electrically.
Service-Anleitung
3. Before attempting the procedure ensure that: mechanical handling
equipment is available, if required, for handling refrigerant cylinders; all
personal protective equipment is available and being used correctly;
the recovery process is supervised at all times by a competent person;
recovery equipment and cylinders conform to the appropriate stand-
ards.
4. Pump down refrigerant system, if possible.
5. If a vacuum is not possible, make a manifold so that refrigerant can be
removed from various parts of the system.
6. Make sure that cylinder is situated on the scales before recovery takes
place.
7. Start the recovery machine and operate in accordance with manufac-
turer's instructions.
8. Do not overfill cylinders. (No more than 80 % volume liquid charge).
9. Do not exceed the maximum working pressure of the cylinder, even
temporarily.
10. When the cylinders have been filled correctly and the process complet-
ed, make sure that the cylinders and the equipment are removed from
site promptly and all isolation valves on the equipment are closed off.
11. Recovered refrigerant shall not be charged into another refrigeration
system unless it has been cleaned and checked.
10. Labelling
Equipment shall be labelled stating that it has been decommissioned and
emptied of refrigerant. The label shall be dated and signed.
Ensure that there are labels on the equipment stating the equipment
contains flammable refrigerant.
11. Recovery
When removing refrigerant from a system, either for servicing or de-
commissioning, it is recommended good practice that all refrigerants are
removed safely. When transferring refrigerant into cylinders, ensure that
only appropriate refrigerant recovery cylinders are employed. Ensure that
the correct number of cylinders for holding the total system charge are
available. All cylinders to be used are designated for the recovered refrig-
erant and labelled for that refrigerant (i.e. special cylinders for the recovery
of refrigerant). Cylinders shall be complete with pressure relief valve and
associated shut-off valves in good working order. Empty recovery cylin-
ders are evacuated and, if possible, cooled before recovery occurs.
The recovery equipment shall be in good working order with a set of
instructions concerning the equipment that is at hand and shall be suitable
for the recovery of flammable refrigerants. In addition a set of calibrated
weighing scales shall be available and in good working order. Hoses shall
be complete with leak-free disconnect couplings and in good condition.
Before using the recovery machine, check that it is in satisfactory working
order, has been properly maintained and that any associated electrical
components are sealed to prevent ignition in the event of a refrigerant
release. Consult manufacturer if in doubt.
The recovered refrigerant shall be returned to the refrigerant supplier
in the correct recovery cylinder, and the relevant Waste Transfer Note
arranged. Do not mix refrigerants in recovery units and especially not in
cylinders.
If compressors or compressor oils are to be removed, ensure that they
have been evacuated to an acceptable level to make certain that flam-
mable refrigerant does not remain within the lubricant. The evacuation
process shall be carried out prior to returning the compressor to the
suppliers. Only electric heating to the compressor body shall be employed
to accelerate this process. When oil is drained from a system, it shall be
carried out safely.
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07.01.2021
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