Hi Josh,
It’s probably fine with shielded magnets, I have been using a dewar
for 25 years whose gauge reads full or empty depending on which side of the
magnet it is standing…
However, I’d be much more worried about why the previous owners of
your replacement dewar did not want to take it with them.
Makes you wonder what they did to it or how good the vacuum is. Whether it
is clean inside or has some rust or other crud that may come out?
Why risk it? Have the culprits pay the 4-5K for a new dewar.
Best Regards,
Jürgen
_______________________________________________
Jürgen Schulte, Ph. D.
NMR Specialist
Binghamton University
SN Building, RM 1024
25 Murray Hill Road
Vestal, NY 13850
Ph.: 607-777-4405
Fax: 607-777-4478
schulte_at_binghamton.edu
http://nmr.binghamton.edu/Schulte.html
> From: main_at_ammrl.groups.io On Behalf Of Josh Kurutz via groups.io
> Sent: Wednesday, October 23, 2024 10:18 AM
> To: main_at_ammrl.groups.io
> Subject: [External Email] [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 indic=
ates the main body is basically nonmagnetic. See video here:
https://uchicago.box.com/s/u4qn83bjy9ywaadj976q7g313itf0716
o The casters and wheels are magnetic, which may not be a problem
o The misc hardware and gauges on top of the dewar feel basically nonmagnetic
o 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 <mailto:jkurutz_at_uchicago.edu>
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Received on Wed Oct 23 2024 - 08:50:54 MST