Hi Margaret,
We also have a QT system with a 150 L liquefier dewar (nominal 20 L/day
production) and a 250 L transport dewar with a single neck. After 16 months
of operation our recovery rate is over 90%. Below are some responses to your
questions and a few thoughts.
* Our nominal liquefier pressure is around 6.5 psi. If the liquefier is
nearly full, it takes about 3 hours to get down to 2 psi. We typically start
the pre-transfer remotely using a VNC connection to the liquefier.
* Our transport dewar has a single neck on top, and the loss rate is about
2 L/day. At 7 L/day my first guesses are a touch or maybe a soft vacuum. Then
again, I’d suspect a touch would show a cold spot and a soft vacuum should
cryopump over time.
* Since some of our magnets don’t report accurate helium levels during
fills, we ordered a transport dewar with a superconducting gauge to measure
the volume of helium delivered. It works great for magnet fills but struggles
to report usable values during transport dewar fills. So, for those fills, we
rely on the superconducting gauge on the liquefier.
* In terms of transfers, ours generally go smoothly. We decided to change
the check valve between the transport dewar and the recovery header (just after
BV902 on your system) from 0.5 psi to 0.125 psi to minimize the pressure loss
when we have to open the transport dewar to atmosphere during a magnet fill. When
the dewar is cold, we see a flash loss of around 16–20% during transfers. When
the dewar is warm, it's challenging to keep the recovery pressure below the
0.40 psi venting point.
Happy to elaborate or chat over Teams. Overall, we’ve been very satisfied
with the QT system!
Best,
Sameer
--
Sameer Al-Abdul-Wahid, Ph.D. | Manager
Nuclear Magnetic Resonance Centre | University of Guelph
519-824-4120 ext. 58914 | s.wahid_at_uoguelph.ca
http://nmr.uoguelph.ca/
> From: main_at_ammrl.groups.io on behalf of Xia, Youlin via groups.io
> Date: Monday, October 21, 2024 at 12:16
> To: main_at_ammrl.groups.io <main_at_ammrl.groups.io>
> Subject: Re: [AMMRL] Quantum Technology all-metal helium recovery system questions: transport dewar and transfers
Hello, Margaret,
We installed a QT all-metal system for six magnets (1.1G, 850, 2x800, 2x700)
in April of this year. It has been running well for 6 six months. Both our
mother Dewar and transport Dewar are 250L. It does take several hours to
reduce the pressure in mother Dewar from 6.7 psi to 2 psi, but we transfer
earlier. Normally we start the pre-transfer at home around 8AM, then when
the pressure drops to less than 4psi in afternoon we start the transfer. Of
course if you wait for getting 2psi, you may need to transfer in evening.
We installed a computer for the system. Then we can use NoMachine or VNC to
remotely control the system. So we can start the pre-transfer process at home.
We have a scale to get the weight of transport Dewar. The loss of the transport
Dewar is about 2L/day on average . Your Dewar may have bad vacuum or leak.
By the way, another QT all-metal system will be delivered in December. We like
the system. Our recovery rate should be more than 90% since we have not
ordered external Helium for six months.
Best regards,
Youlin
St Jude Children's Research Hospital
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Received on Mon Oct 21 2024 - 16:00:14 MST