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 encourages/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 Mon Apr 27 2026 - 11:14:16 MST