Re: [AMMRL] Helium Transfer Lines - Refreshing vacuum. #poll-notice

From: Alex Paterson via groups.io <alpaterson=wisc.edu_at_groups.io>
Date: Thu, 31 Jul 2025 17:37:39 +0000

Hi Ulli,

We use a Varian Turbo-V 70 turbopump (pictured), pumping down to somewhere
between 10-5 and 10-6 torr.

Best,
Alex

> From: main_at_ammrl.groups.io On Behalf Of Ulrike Werner-Zwanziger via groups.io
> Sent: Thursday, July 31, 2025 8:36 AM
> To: main_at_ammrl.groups.io
> Subject: Re: [AMMRL] Helium Transfer Lines - Refreshing vacuum. #poll-notice

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<mailto: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 - 11:37:56 MST