Helium is a scarce natural resource, used for medical scanning devices, academic low-temperature research and particle detectors. Once released, helium escapes our atmosphere and is lost for future generations. Efficient recovery is therefore important for sustainability. The finite earth depositories of helium also imply an ever growing helium price. Recovery therefore also has an economic incentive. Here we provide information and suggestions for good helium practice - a must read for helium users of our department.
To reduce helium loss, following practice is recommended:
- Figure out when dewars arrive (typically Tuesday and Thursday at 9 am) to UZH and get them connected as soon as possible to a recovery line.
- "Empty" dewars are collected at these delivery times (Tuesday and Thursday at 9 am). Therefore send "empty" dewars to the logistic center Monday or Wednesday late afternoon (for example 16h30).
- Returned dewars should still be about 10% filled to keep them cold.
The first two points optimize the recovery and point three reduces "cost" to re-cool the dewar.
Daily check list
Much helium loss originates from human lapses. Most common points are:
- Helium dewar is left "open" without connection to the recovery system.
- Helium dewar is "closed". Pressure then builds-up and helium is eventually released through the safety valve and therefore lost (forever).
- When pumping on the exhaust line, ensure no air contamination.
- Instruments not connected to the recovery system.
- Contaminate the return line with nitrogen.
Good to know:
- Switzerland has no natural helium resources, we thus import from countries like Qatar.
- Currently, we "pay" about 4 CHF/liter recovered helium and 17 CHF/liter unrecovered helium. So unrecovered helium is 4 times more expensive.
- In low performing years, we have 30% helium loss. Our mission is to bring losses below 10%. This would earn us a economic saving of more than 20'000 CHF per year.