Hi Cecile,
We do have a system like that, sort of. We have a small service room
adjacent to our two main NMR labs. We keep nitrogen dewars in that room,
and we have piping that runs from the dewars in the service room to
seven NMR magnets in the two labs.
The whole thing was installed about 30 years ago by Jane Strouse, who
was the NMR director here for almost 40 years. She got ultra thin-walled
stainless steel tubing (I don't remember the wall thickness, but it was
the thinnest one that anyone manufactured). She drilled holes through
the walls from the service room, hung the tubing from pipes and things
near the ceiling using cable ties, and then covered the tubing with
insulation. She installed bursting valves at the end near the dewars so
the pressure in the tubing wouldn't get too high. At the end of each
line near the magnets, she installed solenoid shutoff valves to control
the flow. The ends are connected to the dewars and to the magnets with
rubber hoses.
I'm pretty sure that the only way Jane was able to get away with all of
that was to not tell anyone she was doing it :)
But anyway, we've been using it for all nitrogen fills for the last 30
years. It's very convenient - we don't have to cart nitrogen dewars into
the lab very close to lots of magnets.
There's an interesting side note: in 2004 our department built a new
building (well, a large room) to house our new 800 US2 magnet. We had a
nitrogen system built that's similar to our old one. Near the entrance,
there are restraints against the wall for nitrogen dewars. And they
built an insulated stainless steel tubing system for nitrogen delivery
from the dewars to the magnets. However, these were part of the room's
official plans, and so had to be built to code. And the code did not
allow the ultra thin-walled tubing (even though we knew that anything
thicker than that would be useless). So we have a system that looks
really really good: the pipe is absolutely straight, the corners are
exactly 90 degrees, the exit ports are uniformly spaced, and the
insulation looks like it was machined to perfection. But it doesn't work
- if you put liquid nitrogen into one end of it, it takes more than 30
minutes for liquid to come out the other end (and your dewar is half
empty). The heat capacity of the thicker tubing is just too large.
So one thing to keep in mind is that you absolutely have to use ultra
thin-walled tubing if you're going to use it to transport liquid
nitrogen. I just went and measured the wall thickness: I got about ~2mm.
I don't think it will work well if it's any thicker than that. Also, I
don't think the lines can be too long. Our longest line is about 40 feet
(from the nitrogen dewar to the port near the magnet). And even with the
ultra thin-walled tubing and insulation, if I fill that magnet first
(when the line starts out warm), it takes about 10 minutes to cool the
line enough to attach it to the magnet, and about 2 more minutes until
liquid comes out.
I hope this helps.
-Robert
On 6/7/23 06:31, Cecile Le Duff wrote:
>
> Dear colleagues,
>
> As part of the design of a new Chemistry building, we are looking into
> getting some liquid N2 "on tap", directly into the NMR room.
>
> I am only aware of one NMR lab so far having implemented this (aside
> from biology colleagues with small rooms, purpose-built for decanting)
> so I thought I’d pick the brains in our community.
>
> 1/ Do you have such system installed and what do you use it for
> (decanting into open top dewars, filling magnets, etc )?
>
> a/ What are your safety features?
>
> b/ Do you have specific training requirements for all coming into of the NMR facility?
>
> c/ if you are filling magnets with the system, are the flow rate/pressure reliable?
>
> d/ have you had any leaks?
>
> 2/ If you have considered such a system and have decided NOT to
> implement it, why did you decide against it?
>
> a/ price?
>
> b/reliability?
>
> c/resistance from Safety Services?
>
> d/other
>
>
> Any experience/comments you shared on this will be greatly appreciated. Thank you!
>
> I'll summarize the responses for the benefit of the group/archive.
>
> Kind regards,
>
>
> Cecile
>
> ------------------------------------
>
> Dr Cecile S. LE DUFF
>
> NMR Experimental Officer
>
> School of Chemistry
>
> University of Birmingham
>
> Edgbaston B15 2TT
>
> UK
>
> Tel. + 44 (0) 121 414 4419
>
> c.s.leduff_at_bham.ac.uk
>
> ------------------------------------
>
>
--
-----------------------------------------------
Robert Peterson, Ph.D.
Facility Manager - NMR Technology Center
UCLA-DOE Institute for Genomics and Proteomics
UCLA Dept. of Chemistry and Biochemistry
phone: (310)825-1816
fax: (310)825-0982
peterson_at_mbi.ucla.edu
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Received on Wed Jun 07 2023 - 13:49:16 MST