CLIVET CRISTALLO MM2-Y 27M Handbuch Für Installation Seite 55

Maintenance
10. Repair of sealed components
10.1 While repairing sealed components, all electrical
utilities must be disconnected from the equipment
before removing the sealing covers, etc. If it is
absolutely necessary to have electrical power
supply during the intervention, a permanent
leakage detection method must be set up at the
most critical point that can signal any potentially
dangerous situations.
10.2 Particular attention must be paid to the following
aspects to ensure that, when working on electrical
components, the casing is not altered to such
an extent that the required level of protection
is compromised, including damage to cables,
excessive number of connections, use of terminals
that do not conform to original specifications,
damage to seals, incorrect assembly of glands, etc.
– Check that the device is securely mounted.
– Check that the seals or sealing materials have not
deteriorated to such an extent that they no longer
guarantee a perfect seal keeping flammable
atmospheres from entering. Spare parts must
comply with the manufacturer's specifications.
NOTE: The use of silicone sealants may make some types
of leak detection equipment less effective. Intrinsically
safe components do not need to be isolated before work
is carried out.
11. Reparation of intrinsically safe components
Before applying capacitance or permanent inductance
loads to the circuit, check that this operation does not
result in the permissible voltage and current values for
the equipment in use being exceeded. Intrinsically safe
components are the only types of components that
can be operated under voltage in the presence of a
flammable atmosphere. The test device shall have the
correct nominal characteristics.
For component replacement use only the parts specified
by the manufacturer. Other components may cause
ignition of refrigerant released into the atmosphere.
12. Wiring
Check that the wiring is not exposed to wear, corrosion,
excessive pressure, vibration, sharp edges or other
adverse environmental influences. The control should
also take into account the effects of ageing or continuous
vibration from compressors, fans or other similar sources.
13. Detection of flammable refrigerants
The use of potential ignition sources for the search or
detection of refrigerant leaks is prohibited under any
circumstances. The use of halogen torches (or other
open flame detection systems) is not permitted.
14. Leak detection methods
The following leak detection methods are considered
acceptable for systems containing flammable refrigerants.
Electronic leak detectors can be used to detect
flammable refrigerants, but their sensitivity may not be
adequate or require recalibration. (Detection equipment
must be calibrated in a coolant free area.) Check that the
detector is not a potential ignition source and is suitable
for the refrigerant. Leak detection equipment must be
configured at a percentage of the lower flammability
limit (LFL) of the refrigerant and be calibrated for the
refrigerant used with confirmation of the appropriate gas
percentage (max. 25%). Leak detection fluids are suitable
for use with most refrigerants but the use of chlorine
containing detergents should be avoided, as chlorine can
react with the refrigerant and corrode copper piping.
If a leak is suspected, it is recommended to remove
or extinguish all open flames. If there is a coolant leak
requiring brazing, all coolant must be removed from the
system, or isolated (by means of shut-off valves) in a part
of the system away from the leak. The system should then
be purged with oxygen-free nitrogen (OFN) both before
and during brazing.
15. Removal and evacuation
When the cooling circuit needs to be repaired or for other
purposes, conventional procedures can be followed.
However, it is important to follow recommended practices
taking flammability hazards into account. The following
procedure is recommended:
– extract the coolant;
– purge the circuit with inert gas;
– evacuate;
– purge again using inert gas;
– open the circuit by cutting or brazing.
The refrigerant charge can be recovered in the
appropriate cylinders. The system must be purged with
oxygen-free nitrogen to make the unit safe. It may be
necessary to repeat this procedure several times. Do not
use compressed air or oxygen for this operation.
Purging can be performed by introducing oxygen-
free nitrogen into the vacuum circuit in the system and
continuing to fill until operating pressure is reached, then
venting into the atmosphere and recreating the vacuum.
This procedure must be repeated until the refrigerant is
completely removed from the system.
When the last OFN charge is introduced, the system
must be vented to atmospheric pressure to allow work
to be performed. This operation is absolutely essential
if brazing operations are to be carried out on the piping.
Check that the output for the vacuum pump is not closed for
any ignition source and that good ventilation is available.
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