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19 - MAINTENANCE
During the unit operating life the service checks and tests
must be carried out in accordance with applicable national
regulations.
If there are no similar criteria in local regulations, the
information on checks during operation in annex C of
standard EN 378 can be used.
External visual checks: annex A and B of standard EN378.
Corrosion checks: annex D of standard EN 378. These
controls must be carried out:
•
After an intervention that is likely to affect the resistance
or a change in use or change of high-pressure refrigerant,
or after a shut down of more than two years. Components
that do not comply, must be changed. Test pressures
above the respective component design pressure must
not be applied (annex B and D).
• After repair or significant modifications or significant
system or component extension (annex B).
•
After re-installation at another site (annexes A, B and D).
•
After repair following a refrigerant leak (annex D). The
frequency of refrigerant leak detection can vary from
once per year for systems with less than 1% leak rate
per year to once a day for systems with a leak rate of
35% per year or more. The frequency is in proportion
with the leak rate.
NOTE: High leak rates are not acceptable. The necessary
steps must be taken to eliminate any leak detected.
NOTE 2: Fixed refrigerant detectors are not leak detectors,
as they cannot locate the leak.
19.1 - Soldering and welding
Component, piping and connection soldering and welding
operations must be carried out using the correct procedures
and by qualified operators. Pressurised containers must not
be subjected to shocks, nor to large temperature variations
during maintenance and repair operations.
Any technician attending the machine for any purpose must
be fully qualified to work on refrigerant and electrical circuits.
WARNING: Before doing any work on the machine ensure
that the power is switched off. If a refrigerant circuit is
opened, it must be evacuated, recharged and tested for leaks.
Before any operation on a refrigerant circuit, it is necessary
to remove the complete refrigerant charge from the unit with
a refrigerant charge recovery unit.
All removal and refrigerant draining operations must be
carried out by a qualified technician and with the correct
material for the unit. Any inappropriate handling can lead
to uncontrolled fluid or pressure leaks.
If an oil draining or recovery operation becomes necessary,
the fluid transfer must be made using mobile containers.
19.2 - General system maintenance
•
Keep the unit itself and the space around it clean and
free of obstructions. Remove all rubbish such as packing
materials, as soon as the installation is completed.
• Regularly clean the exposed pipework to remove all
dust and dirt. This makes detection of water leaks easier,
and they can be repaired before more serious faults
develop.
• Confirm that all screwed and bolted connections and
joints are secure.
• Secure connections prevent leaks and vibration from
developing.
• Check that all foam insulation joints on the heat
exchanger piping are in good condition.
•
Regularly check that the vibration levels remain acceptable
and close to those at the start of using the unit.
19.3 - Refrigerant undercharge
If there is not enough refrigerant in the system, this is
indicated by gas bubbles in the moisture sight glass.
If the undercharge is significant, large bubbles appear in the
moisture sight glass, and the suction pressure drops. The
compressor suction superheat is also high. The machine must
be recharged after the leak has been repaired.
Find the leak and completely drain the system with a
refrigerant recovery unit. Carry out the repair, leak test and
then recharge the system.
IMPORTANT: After the leak has been repaired, the circuit
must be tested, without exceeding the maximum low-side
operating pressure shown on the unit name plate.
The refrigerant must always be recharged in the liquid phase
into the liquid line. The refrigerant cylinder must always
contain at least 10% of its initial charge. For the refrigerant
quantity per circuit, refer to the data on the unit name plate.
During applications with option 272 (brine to water) and
with positive evaporation, bubbles will appear in the
sight-glass. This is normal, when the charge is optimised
for improved efficiency in brine applications.
19.4 - Refrigerant guidelines
Refrigeration installations must be inspected and maintained
regularly and rigorously by specialists. Their activities must
be overseen and checked by properly trained people. To
minimise discharge to the atmosphere, refrigerants and
lubricating oil must be transferred using methods which
reduce leaks and losses to a minimum.
•
Leaks must be repaired immediately.
•
If the residual pressure is too low to make the transfer
alone, a purpose-built refrigerant recovery unit must be
used.
•
Compressor lubricating oil contains refrigerant. Any oil
drained from a system during maintenance must
therefore be handled and stored accordingly.
• Refrigerant under pressure must never be discharged
to the atmosphere.
Summary of Contents for 30WG 020
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