EN-
45
POWERCIAT LX ST/HE/XE
11 - MAJOR SYSTEM COMPONENTS AND OPERATION DATA
11.1 - Direct-drive twin-screw compressor
with variable capacity slide valve
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LX units use 06T geared twin-screw compressors equipped
with a variable capacity slide valve for continuous control
between 30% and 100% of full load.
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Nominal capacities range from 120 to 750 kW. The ten
models in the LX range are equipped with an economiser.
11.1.1 -
Oil filter
The 06T screw compressor has an independent oil filter attached
to the oil separator. This filter is field replaceable.
11.1.2 - Refrigerant
The units in the LX range can operate with R-134a refrigerants.
11.1.3 -
Lubricant
The 06T screw compressor is approved for use with the following
lubricants:
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Castrol Icematic SW220 (CIAT specification PP47-32),
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Lubrizol Emkarate RL220H (CIAT specification PP47-13).
11.1.4 - Oil supply solenoid valve
An oil supply solenoid valve is installed on the oil return line as
standard to isolate the compressor from oil flow when the
compressor is not operating. The oil solenoid valve is field
replaceable.
11.1.5 -
Economiser and suction filters
To increase the reliability of the compressor, a screen has been
incorporated as a standard feature into suction and economizer
inlets of the compressor.
11.1.6 - Capacity control
The 06T screw compressor has an unloading system that is
standard on all compressors. This unloading system consists of
slide valve that permits changing the length of the screw used
for the refrigerant compression. This valve is controlled by the
action of a piston controlled by two solenoid valves on the oil
return line.
11.2 - Pressure vessels
General information
Monitoring during operation, re-qualification, re-testing and
re-testing dispensation:
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Follow the regulations on monitoring pressurised equipment.
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It is normally required that the user or operator sets up and
maintains a monitoring and maintenance file.
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If there are no regulations or to complement them follow the
control programmes of EN 378.
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If they exist follow local professional recommendations.
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Regularly inspect the condition of the coating (paint) to
detect blistering resulting from corrosion. To do this, check
a non-insulated section of the container or the rust formation
at the insulation joints.
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Regularly check for possible presence of impurities
(e.g. silicon grains) in the heat exchange fluids. These
impurities maybe the cause of the wear or corrosion by
puncture.
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Filter the heat exchange fluid check and carry out internal
inspections as described in EN 378.
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In case of re-testing please refer to the maximum operating
pressure given on the unit nameplate.
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The reports of periodical checks by the user or operator
must be included in the supervision and maintenance file.
Repair
Any repair or modification, including the replacement of moving
parts:
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Must follow local regulations and be made by qualified
operators and in accordance with qualified procedures,
including changing the heat exchanger tubes.
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Must be made in accordance with the instructions of the
original manufacturer; repairs and modifications that
necessitate permanent assembly (soldering, welding,
expanding, etc.) must be made using the correct procedures
and by qualified operators;
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An indication of any modification or repair must be shown
in the monitoring and maintenance file.
Recycling
The unit is wholly or partly recyclable. After use it contains
refrigerant vapours and oil residue. It is coated by paint.
Operating life
This unit is designed for:
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Prolonged storage of 15 years under nitrogen charge with
a temperature difference of 20 K per day.
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452000 cycles (start-ups) with a maximum difference of
6 K between two neighbouring points in the vessel, based
on 6 start-ups per hour over 15 years at a usage rate
of 57%.
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The service life has been used to calculate fatigue using
the highest number of start-ups authorised by the system;
however, this number is rarely encountered in practice over
the full duration. As a consequence, conduct an inspection
every 15 years to check there is no fatigue-related cracking
of the steel welded assemblies on the refrigerant circuit.
Assemblies with components featuring a break in their form,
such as plate or tapping type collars, are the most sensitive.
Use an endoscope to conduct an internal inspection
wherever possible.
Corrosion allowances:
Gas side: 0 mm
Heat exchange fluid side: 1 mm for tubular plates in lightly alloyed
steels, 0 mm for stainless steel plates or plates with copper-nickel
or stainless steel protection.
11.2.1 - Evaporator
LX coolers use a flooded shell-and-tube evaporator. The water
circulates in the tubes and the refrigerant is on the outside in the
shell. One vessel is used to serve both refrigerant circuits. There
is a centre tube sheet which separates the two refrigerant circuits.
The tubes are 3/4” diameter copper with an enhanced surface
inside and out. There is just one water circuit, and depending on
the size of the chiller, there may be one, two or three water
passes.
The evaporator has a thermal insulation of 19 mm thick
polyurethane foam, an aluminium sheet (option) and is equipped
with a water drain and purge.
