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11
Dehumidifier
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.
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 commissioning. A follow up leak test shall be carried out prior to leaving the site.
14. 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.
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 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 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 overfill 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 filled 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.
15. Labelling
Equipment shall be labelled stating that it has been de-commissioned 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.
16. Recovery
When removing refrigerant from a system, either for servicing or decommissioning, 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 is
available. All cylinders to be used are designated for the recovered refrigerant 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
cylinders 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 flammable 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.
