CAUTION
7.Leak detection methods
• Electronic leak detectors shall 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 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 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.
Oxygen free nitrogen (OFN) shall then be purged through the system both before
and during the brazing process.
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 consid-
eration.
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 “fl 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 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 atmos-
pheric 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.
9.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 minimize 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 overfi ll 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 commissioning.
• A follow up leak test shall be carried out prior to leaving the site.
10.Decommissioning
• Before carrying out this procedure, it is essential that the technician is completely
familiar with the equipment and all its details.
• 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.
a) Become familiar with the equipment and its operation.
b) Isolate system electrically.
c) Before attempting the procedure ensure that:
• mechanical handling equipment is available, if required, for handling refriger-
ant 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 standards.
d) Pump down refrigerant system, if possible.
e) If a vacuum is not possible, make a manifold so that refrigerant can be removed
from various parts of the system.
f) Make sure that cylinder is situated on the scales before recovery takes place.
g) Start the recovery machine and operate in accordance with manufacturer’s
instructions.
h) Do not overfi ll cylinders. (No more than 80 % volume liquid charge).
i) Do not exceed the maximum working pressure of the cylinder, even temporarily.
j) When the cylinders have been fi lled correctly and the process completed, make
sure that the cylinders and the equipment are removed from site promptly and
all isolation valves on the equipment are closed off.
k) Recovered refrigerant shall not be charged into another refrigeration system
unless it has been cleaned and checked.
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