Dear all,
I echo Sameer's and Tara's statements. Our system is similar to Sameer's
and Tara's. We regularly observe that the magnet's boil-off, as
instantaneously measured by the flow meters on the magnet exhausts, varies
depending on the atmospheric pressure and the state of the system (transfer
happening, just happened, or all settled down).
Happy resonating
Ulli
On Fri, Feb 6, 2026 at 10:13 AM Tara Sprules via groups.io wrote:
> Hello,
>
> Despite the closed loop and no bag- we also have a QT system- the pumped
> magnet pressure during a fill is directly correlated to the atmospheric
> pressure. I don't know if having an APD related to the pressure control for
> the pumped magnet is what affects that (Sameer?).
>
> I've never calculated it out, but have always felt that after a few days
> of higher or lower than usual atmospheric pressure there is a small
> difference in liquid levels. We recover around 90% and assume that we are
> still losing around the old flowmeters on the oxford/varian magnets that
> we've never removed- so I guess the system isn't 100% closed...
>
> 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 <main_at_ammrl.groups.io> on behalf of Sameer
> Al-Abdul-Wahid via groups.io <s.wahid=uoguelph.ca_at_groups.io>
> *Date: *Friday, February 6, 2026 at 7:42 AM
> *To: *main_at_ammrl.groups.io <main_at_ammrl.groups.io>
> *Subject: *Re: [AMMRL] Helium Boil Off Question
>
> Hi Luke,
>
> We have a Quantum Technologies HRS with medium‑pressure storage tanks. I’d
> describe our system as *almost *closed-loop, since the recovery header
> pressure is held at ~0.2 psi above atmospheric via a regulator which
> effectively “senses” atmospheric pressure.
>
> When we first brought the system online, we noticed that the amount of
> passive boil‑off we collected varied slightly from day to day. After adding
> an atmospheric pressure sensor to our monitoring setup, we saw a pattern:
> on days when atmospheric pressure is rising, we collect less helium; when
> it’s falling, we collect more. For us, the day‑to‑day swing is under ±10%
> even when the weather brings big pressure changes.
>
> Best,
> Sameer
>
> --
> *Sameer Al-Abdul-Wahid*, Ph.D.
> Manager, *Nuclear Magnetic Resonance Centre < http://nmr.uoguelph.ca/>
> University of Guelph
> 519-824-4120 x58914 / *s.wahid_at_uoguelph.ca <s.wahid_at_uoguelph.ca>*
>
> *From: *main_at_ammrl.groups.io <main_at_ammrl.groups.io> on behalf of Michael
> Groves via groups.io <mgrovesnmr=yahoo.com_at_groups.io>
> *Date: *Thursday, February 5, 2026 at 19:08
> *To: *main_at_ammrl.groups.io <main_at_ammrl.groups.io>
> *Subject: *Re: [AMMRL] Helium Boil Off Question
>
> Hi Luke,
>
> "Maintaining accumulated volume but failing to liquefy any additional
> gas" So the level of liquid in the magnets is dropping but the level in
> the storage dewar stays the same? You sure you don't have a leak
> somewhere? Unless it was all somehow getting shoved into the MPTs and just
> sitting there.
>
> I would also expect an instrument with that kind of liquefier to be pretty
> insensitive to air pressure changes, but if there was a leak then that
> would provide a mechanism for the ambient pressure to affect the boiloff
> rate.
>
> Anyway, that's my $0.02. Worth more or less depending on the local
> exchange rate...
>
> Cheers,
> Mike
>
> On Thursday, February 5, 2026 at 02:24:21 PM MST, Fulton, Luke via
> groups.io <fko24003=uconn.edu_at_groups.io> wrote:
>
>
> Hi spinlanders,
>
> We (hopefully) finished troubleshooting an issue with our helium recovery
> system this week. It was maintaining the accumulated volume but failing to
> liquify any additional gas into the production dewar. Turned out the
> automated threshold settings were out of sync with our magnet's boil off
> rates. During our communications with the manufacturer a curious question
> came up.
>
> The HRS design is a closed loop. We have medium pressure storage tanks
> rather than a gas collection bag, and it's an all-in-one system. Gas is
> pulled directly from the header into a purifier, and from there goes to the
> liquefier. Under high exhaust conditions, such as a helium fill, the gas is
> temporarily redirected towards the MPT's, and purified/liquefied later. We
> discussed variable boil off rates due to weather patterns, and the
> manufacturer suggests that under this system the magnet boiloff should be
> agnostic to atmospheric changes.
>
> Now I can empirically attest that my magnets are still an effective
> weather-wise. And it has me pondering, why? Perhaps the manufacturer was
> mistaken on this detail. Or, perhaps it's a clue that something else still
> requires my attention. My instincts lean towards the former, but I've
> learned to check the alternative just in case. Anyone have an opinion
> they'd be willing to share?
>
> Kind regards,
> Luke
>
> Luke Fulton, PhD CHEM BLDG R003
> NMR Core Facility Director Unit 3060
> COR2E & Department of Chemistry 55 N Eagleville Road
> University of Connecticut Storrs, CT 06279
>
>
>
--
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
-=-=-=-=-=-=-=-=-=-=-=-
Groups.io Links: You receive all messages sent to this group.
View/Reply Online (#3191): https://urldefense.com/v3/__https://ammrl.groups=
.io/g/main/message/3191__;!!PvDODwlR4mBZyAb0!U3LQyon_pFoXDDLhm3B4-De1PkxQC7=
3kgacLIMom8fye-6QDiSozPLenN8eYVJxcJ6vHo28gjWLWTtb_PMGTHLlCiczd$
Mute This Topic: https://urldefense.com/v3/__https://groups.io/mt/117661513=
/7559972__;!!PvDODwlR4mBZyAb0!U3LQyon_pFoXDDLhm3B4-De1PkxQC73kgacLIMom8fye-=
6QDiSozPLenN8eYVJxcJ6vHo28gjWLWTtb_PMGTHJOwVocl$
Group Owner: main+owner_at_ammrl.groups.io
-=-=-=-=-=-=-=-=-=-=-=-
Received on Fri Feb 06 2026 - 07:16:55 MST