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https://logbooks.jlab.org/entry/3916838

Note

Do If > 20' were lost before restarting the chiller, do not go directly to -18C. It is recommended to bring the detector to the setpoint temperature using the step by step procedure.

Remember to put a - (minus) sign at the chiller setpoint temperature and press enter when the set point temperature is changed in EPICS.


Fast recovery of the chiller

1) Open HPS_EPICS => Devices => SVT PLC

2) Ac power DIS   (turns off the AC box)

3) Ac power ENA  (turns on the AC box)

4) Disable the SVT Chiller interlocks (for example if flow = 0 and flow interlock is enable you won't be able to start the chiller. HEnce disable the interlock)

5) Chiller Ctrl Stop

6) Chiller Ctrl Start

7) Set the setpoint temperature (if needed. See Step-by-step if the chiller was off from bit of time) and press ENTER

8) Re-enable the interlocks (when all is Green) in the SVT-PLC

Step-by-step procedure


  • Prepare a myaPlot of the following quantities (from hps_epics click on the ! next to StripCharts and select myaPlot
    • HPS_SVT:PLC:i:RTD_SVT_Return-Value  ===> This is the return temperature from the SVT measured by an RTD (During a run is usually 4C higher than the Supply. 2C higher if not running)
    • HPS_SVT:PLC:i:RTD_SVT_Supply-Value  ===> This is the supply temperature read from the RTD. Usually 2C higher than the Chiller temperature
    • HPS_SVT:CHILLER:TEMP:RD_                 ===> The chiller temperature setpoint
  • The SVT temperature at the restart of the chilling procedure will be unknown. One can try to find a good starting point by setting a temperature of the Chiller such that the Supply-Value is about 1 - 2 C below the Return Value and one can see the Return-Value decreasing. If the Return-Value RTD is increasing, it means that the Chiller setpoint temperature needs to be lowered.  (see figure below at around 2:10 AM we were trying to find the proper setpoint temperature (green) and trying to put the Supply (blue) below the Return (gold)
  • Gradually bring the setpoint temperature down trying to maintain about ~2C spread (ideally) between the Return and the Supply. In the figure below a spread of about 4C was used. One can notice that the supply temperature flattens  faster at fixed setpoint but keeps bringing the return down. Try to go down in temperature to more or less maintain the temperature gradient more or less constant to optimise time
  • At the end of the procedure, wait a bit to have the SVT at around -13.8C – -14C.
  • At that point the Various interlocks can be restored

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