Date: Thu, 9 Nov 2023 23:54:02 +0000
Hello Alvaro,
Here is a picture (from our microimaging system) of what we implemented on
our magnets. The ball valve is closed during normal operation and the boil
off routed through the flow gauge that used to be on the magnet. We open the
ball valve part way during a fill. Part way because then some helium still
goes through the flow gauge. The change in flow is our indicator of the magnet
being full. And if you miss that, don’t worry, liquid nitrogen will
start condensing off the corrugated stainless tubing.
So in principle the pressure in the system goes up and thus the pressure in
the helium wells of the other magnets does as well, but it is small. The 600
does have a back pressure controller and the 800 is pumped which acts as a
back pressure controller. The other systems are used for less demanding
(line shape wise) experiments like X-nuclei, imaging, and solids and they
are not heavily used.
Hope this helps!
Jeff
[cid:FE68A7FB-F14F-4592-A71D-AE2757C0A408]
On Nov 6, 2023, at 11:43 AM, Baber, James (NIH/NIDDK) [E] wrote:
Hello Alvaro,
I tee in a 20 mbar Technoflex relief valve at the inlet of the heat exchanger
used to warm the recovered gas for fills of non-pumped magnets. For our
pumped 2K magnets, I tee in a 50 mbar Technoflex valve at the same spot. I
find that I don't really need a flow meter to warn of the fill endpoint when
using these relief valves. Pressures generated at the end of the fill
cause the relief valve to open indicating the fill is over. These Technoflex
valves are identical to the ones found on the helium exhaust ports of Bruker
2K magnets. They can be purchased from Bruker. If someone knows of an
alternate source in the U.S., please share. Full disclosure: I am not an
engineer. Please take this advice at your own risk. At this point, your
magnet vendor should also be able to offer formal advice.
I will also point out that I disconnect the other magnets from the recovery
system before capturing helium from a magnet fill. This, even though I have
0.5 psi relief (tee'd in) and one-way valves downstream of each magnet exhaust
from which I am collecting the boil-off. I worry that pressure changes may
cause the fields of some of our magnets to wonder. Plus, it just seems a lot safer.
regards,
-Dusty Baber
------------------------------------------------
James (Dusty) Baber
LCP/NIDDK/NIH
Bldg 5, Rm B1-01
5 Memorial Drive
Bethesda, MD 20892
Office: (301) 402-7239
e-mail: jamesbaber_at_niddk.nih.gov<mailto:jamesbaber_at_niddk.nih.gov>
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