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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.
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.
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.
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.
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:
1.
Remove refrigerant.
2.
Purge the circuit with inert gas.
3.
Evacuate.
4.
Purge again with inert gas.
5.
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
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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.
Charging procedures
•
In addition to conventional charging procedures, the following requirements shall
be followed.
1.
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.
2.
Cylinders shall be kept upright.
3.
Ensure that the refrigeration system is earthed prior to charging the system
with refrigerant.
4.
Label the system when charging is complete (if not already).
5.
Extreme care shall be taken not to overfill the refrigeration system.
6.
Prior to recharging the system it shall be pressure tested with OFN.
7.
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.
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.
•
Become familiar with the equipment and its operation.
•
Isolate system electrically.
•
Before attempting the procedure ensure that:
1.
Mechanical handling equipment is available, if required, for handling
refrigerant cylinders.
2.
All personal protective equipment is available and being used correctly.
3.
Pump down refrigerant system, if possible.
4.
If a vacuum is not possible, make a manifold so that refrigerant can be
removed from various parts of the system.
5.
Make sure that cylinder is situated on the scales before recovery takes place.
6.
Start the recovery machine and operate in accordance with manufacturer's
instructions.
7.
Do not overfill cylinders. (No more than 80% volume liquid charge).
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