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Safety precautions
5. 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.
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 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.
7. 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
EN
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.
8. Charging procedures
In addition to conventional charging procedures,
the following requirements shall be followed.
•
Ensure
that
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.
9. 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
contamination
of
different
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