Hi Robert,
ah OK I see - looks like a quite speedy refill right there, so I'd not expect
any losses because of "long contact time" ;-)
Somehow (not sure why actually) helium transport dewars here in Europe only
very rarely have internal pressure builders (via electrical heater, right?
) - usually none of those supplied by helium suppliers have them but I've
seen some "private" ones owned by sites with helium recovery installed.
Cheers
Bert
> Am 01.08.2025 um 19:13 schrieb Robert Peterson via groups.io <peterson==
mbi.ucla.edu_at_groups.io>:
>
> Hi Bert,
>
> For fills on certain magnets I use the storage dewar's pressure builder and
> built-in pressure gauge (which I know isn't terribly accurate). In that
> case, I try to keep the pressure on that gauge around 3-5 PSI. (If you just
> keep the pressure builder on, it cycles between ~3 and 6 PSI - I usually turn
> it on and off to prevent the pressure from getting too high)
>
> For other magnets I use a helium cylinder to pressurize the dewar. With that
> setup I have a pressure gauge and flow meter between the incoming gas and the
> vent. In that case I keep the pressure shown on that gauge between 2 and 3 PSI.
>
> In both cases I watch the pressure gauge on the recovery line closely. During
> the bulk of the fill, that one will show between zero and 0.5 PSI (mostly
> depending on how full the collection bag is). When the bag is near empty,
> that pressure gauge will read near zero even when I'm using the pressure
> builder and the dewar gauge reads 5 PSI. When the magnet is full, that
> pressure gauge shoots up quickly. I turn the flow off before it hits 1 PSI.
>
> I feel like I do my fills relatively quickly. On a couple of ancient Oxford
> 500s, the fill volume is ~30L and I try to keep the pressure as low as
> possible (say 2 PSI on the gauge going into the vent). Those fills take about
> 15 minutes. On my 800 US2 magnet, I use the pressure builder and higher
> pressure and I fill 100L in ~30 minutes.
>
> Thank you to everybody - this has been a really useful thread!
>
> -Robert
>
>
> On 2025-07-31 14:55, Spin-Doc wrote:
>> Hi Robert,
>> What is the pressure in the storage dewar you use during transfer?
>> And how much back pressure do you have in the recovery line next to
>> the magnet during refill?
>> Both of these will determine the speed at which you fill the magnet -
>> the slower it is the longer the contact time of liquid helium inside
>> the transfer line. And losses will be higher with longer contact time
>> (only to be even worse if the vacuum is bad). All I’m saying is your
>> vacuum may be perfect but you may still have losses if filling slowly…
>> Cheers
>> Bert
>> -> 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 31.07.2025 um 19:26 schrieb Robert Peterson via groups.io:
>>> 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
>>>>> <Yong-Wah.Kim=utoledo.edu_at_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'
>>>>> 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
>
>
>
Magnetic resonance equipment, service, training & more
Selling & buying used NMR equipment (all vendors)
Dr. rer. nat. Bert Heise
Owner, Applications Scientist
Spin-Doc Bert Heise
Kiefernweg 13
58239 Schwerte
Germany
Mobile: +49 171 5135315
Email: bert.heise_at_spin-doc.net
Web: http://www.spin-doc.net
Representing:
Stelar Fast Field Cycling NMR Relaxometers (
http://www.stelar.it)
MestreLab NMR Software (
http://www.mestrelab.com)
Barthel HF Amplifiers (
http://www.barthel-hf.de)
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