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/
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Received on Wed Jul 30 2025 - 14:34:21 MST