Liquid cooling systems: Leakless v.2
CMS / SILICON TRACKER COOLING TEST
TECHNICAL SPECIFICATIONS
The unit is composed by 2 independent circuits and all
the operating parameters are controlled by a central Programmable Logical
Controller:
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The primary (fridge) circuit is a closed evaporative circuit
with an hermetic compressor, a liquid condenser connected to a cold source
through a pressostatic valve and a plate evaporator. The liquid refrigerant
pressure is reduced through an expansion valve at the entrance of the evaporator.
The compressor is equiped with oil sight glass, crankcase
heater and 3 ways valves. It is protected on both high and low pressure
by a switch automatic reset.
Fridge power : 6000 W with evaporative temperature –25°C
and condensing temperature +40°C.
This power is controlled via a variable speed drive (programmable
frequency controller).
Refrigerant : R404A (HFC). A filter drier (molecular sleeve
3A) and a sight glass control the humidity of the fluid.
Condenser with 3 ways valves on the refrigerant circuit,
sight glass for refrigerant level and pressostatic valve to control cooling
water flow.
Recommended water temperature :
-
The secondary is a closed liquid circuit connected to the
heat exchangers of the components to be cooled. A circulator pump moves
the fluid from a pressurized storage tank to the exchangers through the
plate evaporator and resistance heater.
Fluid : C6F14 (PF5060 from 3M).
The operating pressure and flow are controlled by the
storage tank pressure and the circulator speed.
The pressure of the storage tank is controlled by a membrane
vacuum pump and an electronic pressure transmitter.
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Vacuum pump :
max. flow : 12 l/mn
min.pressure : 240mbara
-
Pressure transmitter : range : 0 / 1 bara
Output : 0/10V
Vertical multistage centrifugal pump with PID pressure control
(3 phase frequency converter):
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Flow max : 5 m3/h at head max 60m.
An autotuning PID controller adjusts the temperature of the
fluid by regulating the electrical resistance heater from a RTD Pt100.
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Resistance power : 6 kW.
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Temperature controller : PID autotuning
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LCD display
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Sampling cycle 0.1sec.
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Accurency 0.1%
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8 memory areas
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Output SSR drive (pulse voltage)
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3 points alarm
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Remote setpoint
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Retransmission output: 0-10 V
As the fridge circuit a purifier and sight glass controls
the quality of the fluid. The purifier is renewable and in a 3 valves by-pass
configuration.
Additionnal controls :
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Proportional level controller of the fluid in the storage
tank : Output 0-10 V.
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Pressure transmitter at the ouput manifold : Range 0-10 bara.
- Output 0-10 V.
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Electronic Flowmeter for each output channel : Range 6-40
l/mn - Output 4-20 mA
-
Electronic differential pressure gauge: Range 0-1 bar
- Output 4-20 mA
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Security :
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Relief valve on the storage tank – 1mbara.
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Thermostat switch-off on the heater – 70°C.
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HP/LP pressostat on the fridge compressor.
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P.L.C. :
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1 terminal LCD display
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32 inputs 24Vdc isolated
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4 analog input
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32 output 24Vdc
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32 output relay
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4 analog output ±10V
OPERATION
The pressure in the storage tank (and therefore the
pressure in the exchangers on the electronic) is controlled by the vacuum
pump via a pressure sensor ; if the pressure goes higher than the operating
pressure (setting point fixed by the PLC) the vacuum pump starts, the 3
ways electrovalve is actuated after 1 sec. and the pressure goes down to
the lowest setting point pressure (the minimum admissible pressure).
A third maximum pressure point is fixed to stop the fridge,
the circulator and the heater (case of main leak).
The whole system is stopped and needs to be resetted if
the vacuum pump works for more than 10 minutes.
If the pressure value is contained between the operating
setting point and the lowest point the circulator, the fridge and the temperature
regulation (heater and controller) run. The vacuum pump and the electrovalve
are off. This is the running mode.
The heater has an maximum temperature switch off at 70°C
and the level of the fluid in the storage tank is controlled by a proportional
transmitter (setting point on the PLC). Both cut the resistance and the
fridge. Pressure control remains in mode run.
A manual vaccum pump switch lets the operator to active
it in order to gas out the circuit or to fill the storage tank with perfluorocarbone.
A gas pressure regulator is connected to the storage tank
in order to flow Nitrogene in the whole circuit for cleaning.
(to be continued)
OPERATING FUNCTIONS
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The circulator is on if:
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The pressure in the circuit is correct or the vacuum pump
works for less than 10 mn.
-
The temperature switch off of the heater is not actived.
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The liquid level in the storage tank is correct.
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The temperature regulation is on if:
-
The pressure in the circuit is correct or the vacuum pump
works for less than 10 mn.
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The temperature switch off of the heater is not actived.
-
The liquid level in the storage tank is correct.
-
The fridge is on if:
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HP/LP pressostat of the compressor is not actived.
-
The pressure in the circuit is correct or the vacuum pump
works for less than 10 mn.
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The temperature switch off of the heater is not actived.
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The liquid level in the storage tank is correct.
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The vacuum pump is on if:
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The pressure in the circuit is higher than the setting point.
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The continuous time of pumping is under 10 mn.
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Its manual switch is on.
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The 3 ways electrovalve is on if:
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The vacuum pump is actived since 1 seconde.
CERN/P.BONNEAU/31/05/99