I wouldn’t worry about it. You could use a longer fill hose just to be safe
________________________________
> From: main_at_ammrl.groups.io on behalf of Josh Kurutz via groups.io
> Sent: Wednesday, October 23, 2024 9:18:07 AM
> To: main_at_ammrl.groups.io
> Subject: [AMMRL] AMMRL: Liquid nitrogen transport dewars - verifying "nonmagnetic enough"
Hi AMMRL Community. Happy Mole Day!
I’d like your help determining whether a particular liquid nitrogen transport dewar
is safe to use for magnet fills. According to its labeling, it’s a model LP230 from
Custom Biogenic Systems. I’m hoping my question about this dewar can lead to some
more general discussion about identifying liquid nitrogen dewars that are sufficiently
nonmagnetic for us to use.
Key points:
* Our dewar in question is NOT specifically labeled “non-magnetic”
like some others we use
* Applying a strongish non-rare-earth magnet to its main body indicates
the main body is basically nonmagnetic. See video here:
https://uchicago.box.com/s/u4qn83bjy9ywaadj976q7g313itf0716
* The casters and wheels are magnetic, which may not be a problem
* The misc hardware and gauges on top of the dewar feel basically nonmagnetic
* The cylindrical part at the center of the top of the dewar does feel weakly
magnetic, so I wonder what’s going on inside (see last part of the video)
* The manufacturer appears to have discontinued this product, since it’s not on
their website, and they don’t have the user manual or product information posted online
* A customer service rep (first name only) assured me the main body is
nonmagnetic stainless steel, the casters are magnetic, and the gauges are magnetic (though
they don’t feel magnetic to me)
* The user’s manual sent by the representative had no information about its magnetic
properties and contained no information about whether it was safe to use around MRIs or
other high-magnetic field environments. So we have no documentation that declares it is
safe in our environment.
OUR DECISION: Do we use this dewar or not? We were gifted it by staff who had broken one
of our good dewars. But this dewar is not new (seems to have belonged to a lab that left
the university without taking it), and may not even perform well. If is not suitable for
us, we would need to pressure these staff to buy us a new dewar that meets or our specs.
One consideration: the 5-gauss radii on all our magnetics are at most just outside our magnet legs.
What advice do you have for this situation? Many practical factors indicate
we could probably use it reasonably safely, but the lack of explicit safety guidance makes me
nervous. When shopping for a new dewar, what must we look for?
Thanks for your help.
* Josh
Josh Kurutz, PhD
NMR Facility Manager, Chemistry Dept.
University of Chicago
https://chemnmrlab.uchicago.edu/
jkurutz_at_uchicago.edu
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Received on Wed Oct 23 2024 - 08:16:00 MST