Dear all,
Thanks for this discussion. What kind of pumps do you use?
Happy resonating,
Ulli
On Wed, Jul 30, 2025 at 6:34 PM Matthias Brandl via groups.io wrote:
> Hi Ken,
>
> What exactly do you/the engineer consider "evidence of it having gone
> soft"? I could imagine any one of the following, but the sensitivity
> between them would vary widely:
>
> - Noticeable increase in transfer losses (with or without looking
> specifically)
> - Increased fill duration (due to the higher back pressure from the
> evaporation in the line)
> - Line getting cold/frosting during line cool-down (vacuum contamination
> with "condensibles")
> - Increased condensation on the line also during the fill (vacuum
> contamination with helium, possibly due to cracks/pinholes)
> - Decreased surface temperature of the line on the narrow parts (this is
> probably the most sensitive, but also the least obvious)
>
> Best,
> Matthias
>
>
> On 30/07/2025 18:26, Kenneth Sharp-Knott via groups.io wrote:
> > Just to follow-up... The reason I ask is the engineer mentioned that
> > most people wait far too long. By the time you see evidence of it
> > having gone soft, you have likely been losing quite a bit of helium due
> > to excessive boiloff for some time.
> > Apparently most transfer lines also come with the necessary equipment to
> > pump it down. They were some of the bit and pieces lying around the lab
> > that I had no idea of the purpose.
> >
>
> --
> Dr. rer. nat. Matthias Brandl (he/him or they/them)
>
> Technical University of Munich
> TUM School of Natural Sciences - BNMRZ
> Chair of Biomolecular NMR Spectroscopy (Prof. Sattler)
>
> Lichtenbergstr. 4 (postal)
> Ernst-Otto-Fischer-Str. 2 (physical)
> 85748 Garching b. Muenchen
>
> Phone +49 89 289-52617
>
> matthias.brandl_at_tum.de
> https://www.sattlerlab.de/
> https://www.bnmrz.org/
>
>
>
--
Dr. Ulrike Werner-Zwanziger
Adjunct Professor
Department of Chemistry, NMR-3,
Dalhousie University
6245 Castine Way (!!!new address!!!)
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 Thu Jul 31 2025 - 10:25:10 MST