Hi Tianzhi,
Could you please clarify a bit the timeline of the events and what the issue
you are trying to solve is?
The way I understand it, about a year ago, your fridge pressure went from
15 to 21 and your boil off increased by 10%. At that time you swapped the
pump on the pump station but that had no effect on either the fridge pressure
or the boil off. What you are trying to troubleshoot is why the fridge
pressure change happened and why the boil off increased. Do I have this right?
So, they can both be related or not. Do you have a manostat? Is it keeping
pressure? If it isn't the increased boil off can be due to a leak on that
side of the magnet.
Can you send us a picture of the pump station and pump control station?
Depending on the vintage of your station there are few things that may be
failing.
You also said you tried touching the needle valve but it was too hard. Did
you try both? If needle valve 1 is hard, it may be due to ice. Try gently
forcing it (almost paradoxical but I hope you get what I'm saying) open and
close a few times and try returning it to the same spot. If it's really hard
to move it, try closing it completely and open needle valve 2. You will need
to spend some time figuring out how much to open it. I also would suggest
that you send the pictures before trying this as it may not be necessary
to do anything with them.
Best,
Paulo
--
Paulo Falco Cobra | Scientist II - Facility Manager
NMRFAM (
https://nmrfam.wisc.edu/ ) - University of Wisconsin Madison
*E* paulo_at_nmrfam.wisc.edu
*P* (608) 265-3303
*A* 433 Babcock Drive, Madison, WI. 53706
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Received on Thu Oct 16 2025 - 09:11:15 MST