Johnson AURUM R290 M Serie Guide D'utilisation page 60

Sealed electrical components
WARNING
Sealed electrical components shall not be
repaired.
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.
The following leak detection methods are deemed
acceptable for all refrigerant systems.
Electronic leak detectors may be used to detect
refrigerant leaks but, in the case of flammable
refrigerants, the sensitivity can be inadequate, or can
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,
percentage of gas (25 % maximum) is confirmed.
Leak detection fluids are also suitable for use with
most refrigerants but the use of detergents containing
chlorine shall be avoided as the chlorine can react
with the refrigerant and corrode the copper
pipe-work.
NOTE Examples of leak detection methods are
– bubble method,
– fluorescent agent method.
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. Removal
of refrigerant shall be according to Clause 8.
CAUTION
Oxygen free nitrogen (OFN) shall then be
purged through the system both before and
during the brazing process.
Refrigerant removal and circuit evacuation
When breaking into the refrigerant circuit to make
repairs
– or for any other purpose
–conventional procedures shall be used. However,
for flammable refrigerants it is important that best
practice is followed since
consideration. The following procedure shall be
adhered to:
– safely remove refrigerant following local and
national regulations;
– evacuate;
– purge the circuit with inert gas (optional for A2L);
– evacuate (optional for A2L);
– continuously flush with inert gas when using flame
to open circuit;
– open the circuit.
The refrigerant charge shall be recovered into the
correct recovery cylinders.
and the appropriate
flammability is a
An inert gas, specifically, is dry oxygen free
nitrogen(OFN).
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
purging refrigerant systems.
Purging of the refrigerant circuit shall be achieved by
breaking the vacuum in the system with inert gas 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. 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 of the vacuum pump is not
close to any potential ignition sources and that
ventilation is available.
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 in an appropriate position
according to the instructions.
– Ensure that the refrigerating system is earthed prior
to charging the system with refrigerant.
– Label the system when charging is complete (if not
already labelled).
– Extreme care shall be taken not to overfill the
refrigerating system.
Prior to recharging the system, it shall be
pressure-tested with the appropriate purging gas.
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
recovered 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.
3) Before attempting the procedure, ensure that:
a) mechanical handling equipment is available, if
required, for handling refrigerant cylinders;
b) all personal protective equipment is available and
being used correctly;
c) the recovery process is supervised at all times by a
competent person;
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CAUTION
CAUTION
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