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7.3.2 - evaporator
The evaporator is a shell-and-tube type with two refrigerant
circuits. 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
seamless copper tubes are finned on the refrigerant side
and expanded onto the tube sheets.
The heat exchanger shell has a thermal insulation of 19 mm
polyurethane foam, and is equipped with a water drain and
purge.
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.
NOTES: 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 recommenda-
tions.
•
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. 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 take possible maximum pressure
differences, as indicated in (2) above into consideration.
•
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
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.
•
710000 cycles (start-ups) with a maximum difference of
6 K between two neighbouring points in the container,
based on 6 start-ups per hour over 15 years at a usage
rate of 90%.
excess corrosion thickness
•
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.
7.4 - Electronic expansion device (EXV)
These are an option for sizes 30HZ/HZV 043-065. The
microprocessor controls the EXD through the EXV board
module. Inside this EXV is a linear actuator stepper motor.
The stepper motor moves in increments and is controlled
directly by the processor module. As the stepper motor
rotates, motion is transferred into linear movement by the
lead screw. Through the stepper motor and lead screws, 1500
discrete steps of motion are obtained. The large number of
steps and long stroke result in very accurate control of
refrigerant flow. At initial start-up, the EXV position is at
zero. After that, the microprocessor keeps accurate track of
the valve position in order to use this information as input
for the other control functions. It does this by initializing the
EXVs at start-up. The processor sends out enough closing
pulses to the valve to move it from fully open to fully closed,
then resets the position counter to zero. From this point
on, until the initialization, the processor counts the total
number of open and closed steps it has sent to each valve.
7.5 - Refrigerant
30HZ/HZV standard units operate with refrigerant R-407C.
7.6 - high-pressure safety switch
30HZ/HZV units are equipped with a high-pressure safety
switch, calibrated to 2700 kPa for 30HZ units and 2900 kPa
for 30HZV units. This switch is located on the central block
of each lead compressor.
7.7 - Moisture indicator
Located on the liquid line, permits control of the unit charge
and indicates moisture in the circuit. The presence of bubbles
in the sight-glass indicates an insufficient charge or non-
condensables in the system. The presence of moisture changes
the colour of the indicator paper in the sight-glass.
7.8 - Filter drier
The role of the filter drier is to keep the circuit clean and
moisture-free. The moisture indicator shows, when it is neces-
sary to change the elements. A difference in temperature
between the filter inlet and outlet shows that the elements
are dirty.