Hi Jun,
Thank you for sharing this helpful summary. I was not able to attend ENC this
year, but I wanted to add a few observations from our experience at Guelph with
Quantum Technologies (QTC) helium recovery and Cryomech cryogen-free magnet
systems, in case they are useful to others.
For our helium recovery system, QTC recommends replacing the cold head every
three years. We are approaching that mark now, and the system is still producing
above the 20 L/day specification.
For our cryogen-free magnet, the Cryomech PT cold head has been operating for 14
years. We did replace the compressor around year nine. Cryomech indicated to us
that the PT cold head itself may last a very long time, since there are apparently
no moving parts in the cold region.
After commissioning our HRS, we did not need to regenerate the purifier for the
first year. We now need monthly regenerations. During regeneration, we collect
approximately 20 mL of water when we “blow out” the purifier, even though our
system has an upstream desiccant dryer. Our current suspicion is that water
accumulated in the purifier material over the first year of operation, and that
the material may now be saturated despite vacuum regenerations, but I would be
interested to hear whether others have seen something similar.
We have also been very satisfied with our Restek detector: https://www.restek.com/ca/en_CA/p/28500
It is not MR-rated, but we have used it carefully near our magnets without incident.
Finally, we had been using Tygon tubing with tightly clamped hose barbs and achieved
approximately 94% recovery efficiency. We recently replaced all of the Tygon tubing
with Swagelok fittings and tubing to see whether that helps address the water issue.
Thank you again for putting this summary together.
Best,
Sameer
--
Sameer Al-Abdul-Wahid, Ph.D.
Manager, Nuclear Magnetic Resonance Centre
<
http://nmr.uoguelph.ca/>
University of Guelph
519-824-4120 x58914 / s.wahid_at_uoguelph.ca
> From: main_at_ammrl.groups.io on behalf of Gu, Jun via groups.io
> Date: Monday, April 27, 2026 at 14:14
> To: ammrl_at_groups.io <ammrl_at_groups.io>
> Subject: [AMMRL] Helium Recovery system maintenance
Hello NMR colleagues,
As requested by the AMMRL committee, I would like to share some information
regarding the helium recovery system maintenance, based on discussions at
the ENC AMMRL meeting.
Based on the ENC Helium Town Meeting, more than 50% NMR facilities currently
have helium recovery systems in place. These include full recovery & liquefaction
systems as well as gas recovery systems for off-site liquefaction. Approximately
12 facility managers participated in the AMMRL discussion on helium recovery
system maintenance. The general view was that a service contract is not necessary,
instead, most facilities opt to request cold head replacement services on an
as-needed basis.
Before summarizing the key points, I would like to acknowledge and thank Alex
Paterson (NMRFAM), Jesse Sears (PNNL), Ping Yu and Theo Rusmore (UC Davis) for
sharing their valuable experiences. Both NMRFAM and UC Davis have Quantum Design
systems, while PNNL uses both custom-built and Quantum Technology systems.
Key points:
1. The recommended service interval depends on the type of cold head. For
example, a GM cold head needs service every 10k hours, whereas a PulseTube (PT)
cold head needs service every 40k hours. Special thanks to Arifin Budihardjo
from Bluefors for providing this information.
2. A best practice is to record the temperature and pressure of the purifier
and the liquefier on a daily basis. If the liquefier cannot reach the expected low
temperature, or if the pressure differential in the purifier begins to rise, for
example, the output pressure becomes significantly lower than the input pressure,
this may indicate contamination or blockage. If the situation persists after a
complete warmup, it is likely time to replace cold head. Monitoring helium recovery
rate can also serve as a useful diagnostic indicator.
3. The frequency of purifier regeneration depends on helium gas purity.
Typically, QD purifier requires cold regeneration approximately once per month.
4. Quantum Design provides cold head replacement service and also encouages/supports
customers DIY. UC Davis uses Quantum Design services, and cold head replacements at
NMRFAM have been performed by facility staff for years.
5. Cold head can be purchased from your venders such as Quantum Design.
6. Sumitomo sometimes runs cold head refurbishment courses.
7. Avante Health Solutions was mentioned as a potential source for cold head services.
8. A helium detector is very helpful. NMRFAM has a GasCheck TESLA helium sniffer
and finds it useful, but does not run near magnets; recommends people investigate the
updated “Panther Helium and Multi-Gas Handheld Leak Detector”
9. If a power shutdown or chilled water interruption is scheduled, it is advisable
to keep the downtime as short as possible in order to preserve liquid helium. Another
option is to have a pre-cooled helium dewar available for temporary storage of liquid helium.
10. Tygon tubing used for low-pressure boiloff should be kept as short as possible to
minimize the risk of leaks. There were no specific experiences reported regarding tubing materials.
I hope you find this information helpful. I would appreciate any thoughts or
experiences you would like to share.
Best,
Jun
Jun Gu, PhD
Director of NMR facility
Department of Chemistry
University of Pennsylvania
231 South 34th street
Philadelphia, PA, 19104-6323
Phone: 215-898-1302
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Received on Tue May 05 2026 - 05:46:55 MST