I every system is so unique- we also have the QT system with no bag- and
when we fill our magnets we use the same rate as we always did (~1psi low
field, 2.7psi for the 800) and the fills take the same time, with pressure
in the line (as measured at the recovery compressor) at 0.3-0.34 psi. The 0.4
psi blowoff valve will sometime open right at the beginning, or at the end
for a few seconds, but never during.
Our the liquefier is always on, so it is as liquefying as fast as it can during
fills, at the same time the recovery compressor is compressing excess gas into
the MPS storage (that may be different from Ulli?).
Tara
*********************************************
Tara Sprules
0.6 FTE, Working days: Monday, Wednesday and Thursday
QANUC
Quebec/Eastern Canada High Field NMR Facility
http://www.nmrlab.mcgill.ca
phone: (514) 398-1721
fax: (514) 398-8254
3420 University St., Rm 023
McGill University
Montreal, QC, H3A 2A7
SHIPPING ADDRESS:
Department of Chemistry, McGill University
Rm. 41 801 Sherbrooke St. W
Montreal QC
H3A 0B8
*********************************************
> From: main_at_ammrl.groups.io on behalf of Ulrike Werner-Zwanziger via groups.io
> Date: Friday, April 3, 2026 at 11:16 AM
> To: main_at_ammrl.groups.io
> Subject: Re: [AMMRL] AMMRL: Helium Fills with Exhaust Recovered
Hello Jerry,
I am quite surprised that most responses do not see an increase in helium fill
times into the recovery system. Our fill time on our 400MHz magnet (Magnex)
has about doubled. We have a QT system with medium storage pressure tanks and
the liquifier, i.e, we do not capture the helium into a bag. Maybe that is
where the difference comes in. We regulate the flow into the transfer tank so
that the 0.4psi blow off valve in the liquifier unit stays closed, typically
around 0.3psi. And yes, that flow into the transfer dewar is about half of
what we used to use when filling into the open air. I do not raise the pressure
into the source dewar much. That mostly depends on the diameter of the transfer
line. But most importantly it is set for keeping the blow off valve (0.4psi )
from doing its business as mentioned. I am mostly worried about not damaging
the magnet with too much pressure, so we take the extra time.
The "overhead", i.e. gas volume per liquid helium filled into the magnet has
not changed much. I don't worry about that, because it is recovered.
I hope this helps.
Happy resonating and Easter,
Ulli
On Fri, Apr 3, 2026 at 10:38 AM gregory.wylie via groups.io wrote:
Hi Jerry
We have kept records on fills from before and after our recovery system. We
see no change in duration, helium used, or pressure in the supply dewar. We
consistently use the same Dewar PSI and flow before and after recovery system
install, we also are very consistent on when we fill magnets so helium used
and duration of fills are consistent.
I have put pressure gauges on our recovery lines during fills and never had
anything go over 0.1 PSI. This was just after our heat ex-changers and further
down the main line as well.
Design of your system can be a factor here too! If you try to use too small of
an exhaust line or main line you could have issues.
Hope that helps
Greg
Gregory P. Wylie, Ph.D
NMR Facility Manager
Texas A&M University
Department of Chemistry #3255
580 Ross St.
College Station, TX 77843-3255
gpwylie_at_tamu.edu<mailto:gpwylie_at_tamu.edu>
979.458.0705 (voice)
979.845.4719 (fax)
706.206.0007 (cell)
http://nmr.tamu.edu
--
Dr. Ulrike Werner-Zwanziger
Adjunct Professor
Department of Chemistry, NMR-3,
Dalhousie University
6245 Castine Way
PO BOX 15000
Halifax, NS B3H 4R2
e-mail: Ulli.Zwanziger_at_Dal.ca
Tel. 1 902 494 8085
FAX: 1 902 494 1310
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Received on Fri Apr 03 2026 - 11:08:05 MST