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10 - MajOR sysTEM COMPONENTs aND
OPERaTION DaTa
10.1 - Direct-drive twin-screw compressor with
variable capacity slide valve
•
30XA units use 06T geared twin-screw compressors
equipped with a variable capacity slide valve for
continuous control between 30% and 100% of full
load.
•
Nominal capacities range from 120 to 530 kW. The
seven models used in the 30XA range are economised.
10.1.1 - Oil filter
The 06T screw compressor has an independent oil filter
attached to the oil separator. This filter is field replaceable.
10.1.2 - Refrigerant
The 30XA a water chiller operating only with refrigerant
R134a.
10.1.3 - lubricant
The 06T screw compressor is approved for use with the fol-
lowing lubricant: CARRIER MATERIAL SPEC PP 47-32.
10.1.4 - 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.
10.1.5 - 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.
10.1.6 - 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 control-
led by the action of a piston controlled by two solenoid
valves on the oil return line.
10.2 - 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 378-2, 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.
38
•
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.
•
Filter the heat exchange fluid check and carry out
internal inspections as described in EN 378-2, 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.
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 proce-
dures 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.
10.2.1 - evaporator
30XA chillers use a flooded multi-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 units have three refrigerant circuits with two evaporators
connected in series on the heat transfer fluid.
The evaporator shell has a thermal insulation of 19 mm
thick polyurethane foam, an aluminium sheet and a water
drain and purge.
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