Date: Tue, 12 Aug 2025 14:09:59 -0700
Hi Sebastian,
Regarding question #1, I can't answer your exact question since our plumbing
size is different, but I can give you some data that hopefully provides a bit
of insight. We have a 2" main helium line that connects each of our
manifolds at the magnet. The main trunk is probably over 200ft in length
(and branches out in multiple areas), with parallel taps for each of our magnet
manifolds in various places along its entire length. The magnet manifolds
themselves are primarily made up of 1" ID copper on small magnets, so that is
the bottleneck during our helium transfers.
We have pressure sensors at the manifolds and near the bag (on the main trunk),
so we are able to see a differential pressure at all times. Im attaching 3
plots:
1) a helium fill on our 850 typically done around 2psi on the dewar, which shows
the manifold pressure is a bit higher than the main line.
2). a helium fill on our old varian 400 which we typically do at 4psi on the dewar.
3) a helium transfer from the recovery plant (cryomech 28L/day) to our transport
dewar, also done at 4PSI on the dewar.
As you'll see in the data, there isn't a huge difference in pressure between the
1" manifold and the 2" main trunk in the 850 fill where we typically transfer about
160L in about 45mins.
On the 800 fill where we transfer ~200L in about 35mins, the main line pressure hits
around .45PSI max (you'll also notice the waves in this fill... these are due to the
4PSI pressure builder turning on and off in the dewar). Transfers to the
transport dewar typically cause the largest spikes in our main helium line near 0.8PSI
(this is because we typically collect the gas as the line is cooling down. The
rapid spikes are due to throttling the valve to keep the pressure below our safety
relief valve. We obviously don't do this during fills on magnets!).
Not sure what size magnets you are filling and what flow rates, but this suggests that
a line around 1" OD might you might be pushing pressures over 0.5PSI. I do think
its necessary to keep a larger line as you approach the bag as it creates a pressure
differential to drive the gas towards the bag.
Hope this helps in some way.
Best,
Samrat Amin
Magnetic Resonance Research Center
Arizona State University
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(image/png attachment: 800Fill.png)
(image/png attachment: 850Fill.png)
(image/png attachment: TransportDewar.png)