Status of Fridge Valves

As of 2022-12-22.

• The run valve is always closed.
• The bypass valve is always controlled remotely (i.e. Cryo Control Panel).
• Do not manually turn the run and bypass valves.  It will mess up the valve positions in the remote control.
• In case of trouble, you should fully close the bypass valve remotely or manually.  To do that manually, the motor power has to be disabled on VI, or remove the motor from the valve shaft.  A black Allen wrench is taped on the motor support.

Procedure for Filling the Fridge with LHe to Start the "Standby" Mode

It is to prepare for the shielding block installation conducted in the week of 2022-12-19 (Mo).

1. Stop the automated control.
   1. Sit in front of the target computer and open "Fridge_Valve_Main.vi" (if not opened) by pressing the "Open" button at the right side of Cryo Control Panel.
   2. Confirm that the automated control of the bypass valve is running.  If not, this procedure might not be applicable.
   3. Disable the automated control, by clicking the toggle switch labelled "Automated Bypass-Valve Control".
2. Fill the fridge with LHe.
   1. Disable the SMS (Discord) alarm, by clicking the toggle switch labelled "SMS".
   2. Set the turn of the bypass valve to "1.0", by entering the value to the "Set Turns" box (or clicking the up arrow of the box multiple times).
   3. Confirm that the Main Return flow increases on the right-side strip chart in this page;  https://e906-gat1.fnal.gov/data-summary/e1039/target-par-preset/return_flow.php
   4. Increase the turn step-by-step (wait for 20 seconds per +0.1 turns), until the Main Return flow reaches about 50-80 SLM.  Usually the turn should be 1.4-1.8.
   5. Wait until the nose LHe level becomes 100%.
      • If the change is too slow, you can increase the flow upto 100 SLM, with closer attention.
   6. Start watching the fridge temperatures on the left-side strip chart opened above.
   7. Wait until the "Heat-Ex Top" temperature goes above 1,400 Ohm.  Be prepared to make the next step immediately, since the change is sudden
   8. Set the turn to "0", by entering "0" to the "Set Turns" box.
   9. Confirm that the Main Return flow becomes ~5 SLM or less.
3. Pause the fill.
   1. Open "THCD_401_Main.vi" on the target computer.
   2. Change the Separator Return flow from 12 to 8 SLM (try 10 SLM on 2022-12-22).

Procedure for Resuming from the "Standby" Mode

1. Change the Separator Return flow from 8 to 12 SLM, using "THCD_401_Main.vi".
2. Wait for 5 minutes.
   1. This step is to accumulate LHe in the separator.
3. Fill the nose with LHe manually.  Can skip this step if the nose LHe level is already high, >70%.
   
   1. Set the turn of the bypass valve to "1.0", by entering the value to the "Set Turns" box (or clicking the up arrow of the box multiple times).
   2. Confirm that the Main Return flow increases on the right-side strip chart in this page;  https://e906-gat1.fnal.gov/data-summary/e1039/target-par-preset/return_flow.php
   3. Increase the turn step-by-step (wait for 20 seconds per +0.1 turns), until the Main Return flow reaches about 50-80 SLM.  Usually the turn should be 1.4-1.8. 
   4. Wait until the nose LHe level becomes 80%.  A higher level (80-100%) is acceptable, but never keep filling above 100%.
      1. If the level does not start going up in 5 minutes; close the valve, wait for 10 minutes, and try again.
   5. Close the bypass valve, by setting the turn to "0".
   6. Confirm that the Main Return flow is ~5 SLM or less, and the nose LHe level is going down slowly.
4. Enable the automated control of the bypass valve.
   
   1. Confirm that the "Set Point of He Level" is 75%.
   2. Click the toggle switch labelled "Automated Bypass-Valve Control".
   3. Enable the SMS (Discord) alarm, by clicking the toggle switch labelled "SMS".
   4. Report on Discord that the automated control has started.  Kenichi has to check the behavior at the beginning.