Hi all,
I am dealing with an interesting problem on our Unity Inova 600, which has
an AS600 Oxford magnet.
In the span of less than 48 hours, the nitrogen sensor (image attached) went
from reading at a steady state to fluctuating wildly and being approx 40%
below the actual fill level. When left alone, it fluctuates randomly, generally
in a 1% range of the decreased fill reading. We have liquid coming out of
the ports with the sensor reading 60%, with plumes coming from the two venting
stacks. We've also checked and the stack that we use to fill plumes normally
as well. For example, after filling the magnet to the point where liquid
came out the venting stacks, it fluctuates between 59% and 58%, going down
and back up again in less than 15 seconds. Previously (on Saturday), this
value would hold steady for over half an hour before dropping. Hopefully,
the video I attached of the sensor fluctuating comes through.
We've also observed it going to a high percentage (99%) when the nitrogen fill
dewar is attached but once we disconnect it (after filling gradually until
there is liquid coming out), it plummets straight back down to the 59-60% range.
We are also finding liquid droplets around the fill stacks and are concerned
that they are not sealing tightly. The manual references there being o rings
in them, but we can't find the dimensions of them or locate them in the fill
stack covers. If anyone can provide more detail about these o rings, I
would really appreciate it.
We've probed the magnet a bit with the thump rod through the stacks and can't
feel any ice, but we've also never dealt with ice in a magnet before and
don't have the practical experience to know what we are looking for.
We fill the NMRs every week and make sure to purge the nitrogen line before
attaching it to the stack. Our 400 MHz JEOL is filled from the same dewer
and not experiencing these problems.
So far, the possible causes we have come up with are ice on the sensor or in
the magnet (but not blocking the stacks), a faulty sensor (picture attached,
the manual says this is a resistor sensor), busted o rings in the fill stack
covers, a faulty cable/connection going from the sensor to the display, ice
in the dewer (the 600 gets filled last of our three NMRs), or a combination
there of.
The question I have for you all, is if there's anything about what I've told
you that leans more towards one problem or another.
Many thanks!
-Emily
Dr. Emily Crull
Director of Chemistry Shared Instrumentation
CRL 261 | emily.crull_at_mail.wvu.eud
West Virginia University
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Received on Tue Aug 05 2025 - 10:23:52 MST