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9 - MAJOR SYSTEM COMPONENTS AND OPERATION DATA
9.1 - Direct-drive twin-screw compressor with
variable capacity slide valve
- 30XAS units use the 06T geared twin-screw compressor
equipped with a variable capacity slide valve for continuous
control between 30% and 100% of full load.
- Nominal capacities range from 235 to 484 kW. The five
models used in the 30XAS range are economised.
9.1.1 - Oil filter
The 06T screw compressor has an independent oil filter attached
to the oil separator. This filter is field replaceable.
9.1.2 - Refrigerant
The 30XAS is a water chiller operating only with refrigerant R-134a.
9.1.3 - Lubricant
The 06T screw compressor is approved for use with the following
lubricants:
- Castrol Icematic SW220 (Carrier specification PP47-32)
- Lubrizol Emkarate RL220H (Carrier specification PP47-13)
9.1.4 - 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.
9.1.5 - Suction and economizer screens
To increase the reliability of the compressor, a screen has been
incorporated as a standard feature into suction and economizer
inlets of the compressor.
9.1.6 - Capacity control system
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.
9.2 - Pressure vessels
General
Monitoring during operation, re-qualification, re-testing and re-
testing dispensation:
- Follow the regulations on monitoring pressurised equipment.
- It is normally required that the user or operator sets up and
maintains a monitoring and maintenance file.
- Follow the control programmes of EN 378, annexes A, B, C
and D.
- If they exist follow local professional recommendations.
- 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.
- Regularly check for possible presence of impurities (e.g. silica
grains) in the heat exchange fluids. These impurities maybe
the cause of the wear or corrosion by puncture.
- Filter the heat exchange fluid check and carry out internal
inspections as described in EN 378, annex C.
- In case of re-testing please refer to the maximum operating
pressure given on the unit nameplate.
- The reports of periodical checks by the user or operator must
be included in the supervision and maintenance file.
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Repair
Any repair or modification, including the replacement of moving
parts:
- must follow local regulations and be made by qualified
operators and in accordance with qualified procedures,
including changing the heat exchanger tubes.
- must be made in accordance with the instructions of the
original manufacturer. Repair and modification that
necessitate permanent assembly (soldering, welding,
expanding etc.) must be made using the correct procedures
and by qualified operators.
- 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:
- prolonged storage of 15 years under nitrogen charge with a
temperature difference of 20 K per day.
- 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%.
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.
9.2.1 - Evaporator
30XAS chillers use a flooded shell-and-tube evaporator. The water
circulates in the tubes and the refrigerant is on the outside in the
shell. The tubes are 3/4" diameter copper with an enhanced
surface inside and out. There is just one water circuit with two
water passes.
The evaporator has a thermal insulation of 19 mm thick
polyurethane foam, an aluminium sheet (option) and is equipped
with water drain and purge. It has been tested and stamped in
accordance with applicable pressure codes for a maximum
operating pressure of 2100 kPa refrigerant-side and 1000 kPa
water-side.
The water connection of the heat exchanger is a Victaulic
connection. As an option the evaporator is available with frost
protection (evaporator frost protection option).
The products that may be added for thermal insulation of the
containers during the water piping connection procedure must be
chemically neutral in relation to the materials and coatings to which
they are applied. This is also the case for the products originally
supplied by Carrier.
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