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Procedure for Filling the Fridge with LHe

The latest official procedure is posted on DocDB 10375.  The procedure described below is expected to replace (improve) it in future.

The fridge is supposed to have no LHe.  The filling It should be done once or twice per day to keep the liquid in the fridgeper two days.

1. Change the separator flow to 12 20 SLM (from 7 SLM usually).

2. Wait for 5 minutesas long as 2 hours.
3. Change the separator flow to 25 SLM.

4. Open the bypass valve at 2.0 turns.

   Wait for 5 minutes.  Confirm

    Confirm that the fridge return flow goes up.

5. Change Go into the separator flow to 20 SLMcave to fully open the gate-valve bypass.
6. Set Open the bypass valve at 23.5 turns0 turns.
7. Change the separator flow to 30 SLM.

8. Wait until the Ann-Plate Top resistor goes up to 1400 Ohm, which indicates that the liquid started accumulating.

   1. It usually takes 30 minutes from step #3.  If it takes longer than 40 minutes, search for unexpected conditions.
9. Wait until the nose LHe level reaches 100%.
   1. It usually takes 15 minutes from the previous step.
10. Wait until the Heat-Ex Bottom resistor goes down from 1400 Ohm and then up.
    1. It usually takes 10 minutes from the previous step.

11. Wait until the Heat-Ex Top resistor goes up to 1400 Ohm, which indicates that the liquid is as high as Heat-Ex Top.Wait for 1-2 minutes as you need to fill an extra amount of LHe

    1. It usually takes 10 minutes from the previous step.

12. Close the bypass valve.

    1. The bypass valve should be automatically closed to 0.5 turns by the software interlock.
    2. You should then set it at 0 turns manually.

13. Change the separator flow to 7 SLM.

14. Go into the cave to partially close the gate-valve bypass.
    1. Move the valve handle until it gently hits its stopper, where a spacer is attached to the stopper so that the gate-valve bypass is closed only partially.
15. Make an elog entry to record the time and the mount of this filling.

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