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 - 07:32:11 MST