Hi Bert,
For my fills these days I use a "new" (2021) transfer line. It's from
Cryofab and it breaks apart into two pieces - I have two "fill lances"
of different sizes. I've never pumped it. I guess I assumed that it was
good when I got it. It doesn't have any cold spots though. Once the fill
gets going, the whole thing (including the top of the section that goes
into the dewar) is warm and dry. Would it still be a good idea to pump
it? I do have access to a turbopump.
Since installing the helium recycling system and being able to quantify
the boiloff gas, I've always recovered ~30% as gas. I have used several
different transfer lines, and the boiloff amount has always been roughly
the same (although none of the other ones had been recently pumped down
either).
OK, I guess I've answered my own question: I'll try pumping the line and
see if I get less boiloff gas.
-Robert
On 2025-07-30 00:28, Spin-Doc wrote:
> _at_ Robert:
>
> A loss of a whopping 30% at each refilll does sound a bit excessive to
> me and triggers some questions:
> - do you use one single helium transfer line each time? Sure that its
> vacuum is still OK? Tried to open its valve, clean & re-grease the
> O-ring and pump out on a turbo for a few hours?
> - what is the pressure in the helium dewar used during transfer?
>
> -> Sent via mobile <-
>
> Spin-Doc
> Magnetic resonance equipment, service, training & more
> Dr. rer. nat. Bert Heise
>
> Owner, applications scientist
> Kiefernweg 13
> 58239 Schwerte
> Germany
> Web http://www.spin-doc.net
> Mail: bert.heise_at_spin-doc.net
> Phone: +49-171-5135315
>
> Representing MestreLab, Stelar & Barthel HF
>
>> Am 30.07.2025 um 02:49 schrieb Kim, Yong Wah via groups.io:
>
>> Hello,
>>
>> We have just installed a Medium pressure Helium recovery system by
>> Quantum Design, QD. We had recently transferred 119 liters of
>> liquid into our 600 MHz magnet. Our Renner helium compressor seems
>> to be able to keep up with the boiloff during liquid helium
>> transfer. We are told by the installers to keep the oil temperature
>> of the compressor below 60C. I would love to hear about your
>> experience with a similar system.
>>
>> We had chosen the QD system with 3 X '1000-Liters' storage tanks
>> because the contamination level is much lower than the "bag' system.
>> So far it seems to be a robust system. We opted for a mechanical
>> backpressure controller and the pressure in the magnet do goes
>> through cycles of pressure fluctuations of less than 0.3 inches of
>> H2O every 90 seconds. No impact on NMR data has been detected so
>> far. The tanks have 29" diameter and 92" high.
>>
>> Best regards
>>
>> Yong-Wah Kim,
>>
>> -------------------------
>>
>> From: main_at_ammrl.groups.io on behalf of Sebastian Kemper via groups.io
>> Sent: Tuesday, July 29, 2025 8:30 AM
>> To: 'main_at_ammrl.groups.io' <main_at_ammrl.groups.io>
>> Subject: [EXTERNAL] [AMMRL] Helium recovery - bag size
>>
>> Hello everyone,
>>
>> I would like to modify my helium recovery system so that I can
>> collect helium during the filling procedure. Due to the relatively
>> limited space, I have a few questions about balloon size and
>> compressor performance and I would be very grateful for any
>> experience from colleagues so that I can purchase the right
>> equipment.
>>
>> - How much helium will be produced with a fill of 80-90 liters? I
>> calculated for 80 liters with a fill loss of 15% that max. 16 m³
>> will be released during the fill (assuming the cold replaced gas
>> will warm up from 4 K to 298 K). What are the real numbers? Are
>> there any empirical values?
>>
>> - I probably only have space for a balloon of 10-12 m³. Do you have
>> a setting where the compressor starts during filling and compensates
>> for a balloon that is ‘too small’? A colleague told me, that it
>> is possible, but I don't want to miscalculate and it would be very
>> helpful to hear about other cases. If you have such a setting, what
>> size balloon do you have? What is the compressor's flow rate? At
>> what percentage of the balloon volume does the compressor activate?
>>
>> Best regards,
>>
>> Sebastian
>
>
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Received on Thu Jul 31 2025 - 10:26:40 MST