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61
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CAUTION
6. 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.
7.
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.
8.
Detection of flammable refrigerant
• 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
9.
Leak detection methods
• Electronic leak detectors may be used to detect
refrigerant leaks but, in the case of flammable
refrigerants, 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 of
f
valves) in a part of the system remote from the
leak.
•
For appliances containing flammable refrigerants,
oxygen free nitrogen (OFN) shall then be purged
through the system both before and during the
brazing process.
10. Removal and 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 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.
•
For appliances containing flammable refrigerants,
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.
•
For appliances containing flammable refrigerants,
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 that ventilation is
available.
11. Charging procedures
•
In addition to conventional charging procedures, the
following requirements shall be followed.
– Ensure that contamination of dif
ferent 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 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.
12. 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.
13. Labelling
•
Equipment shall be labelled stating that it has been
de-commissioned and emptied of refrigerant.
The
label shall be dated and signed.
•
For appliances containing flammable refrigerants,
ensure that there are labels on the equipment
stating the equipment contains flammable
refrigerant.
14. 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 are 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-of
f 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 all appropriate refrigerants
including, when applicable, 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.
15. Other safety precautions
•
A
brazed, welded, or mechanical connection shall
be made before opening the valves to permit
refrigerant to flow between the refrigerating system
parts.
• Flammable refrigerant used, refrigerant tubing
protected or enclosed to avoid mechanical damage
(IEC/EN 60335-2-40/A1).
•
T
ubing protected to extent that it will not be handled
or used for carrying during moving of product (IEC/
EN 60335-2-40/A1).
•
Flammable
refrigerant used, low temperature solder
alloys, such as lead/tin alloys, not acceptable for
pipe connections (IEC/EN 60335-2-40/A1).
•
When there is flare connection, it must be installed
outdoor
.
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