Helium liquefaction for the University of Bristol [ Return towards References ]

Air Liquide has supplied and started up a HELIAL liquefaction system for use in recovering, purifying, and re-liquefying the gaseous helium produced by the different laboratories at the University of Bristol (UK).

The Bristol project

The different laboratories of the University of Bristol use liquid helium for their experiments. After being vaporised and heated during experiments, the helium is collected through a piping network and stored at high pressure before being purified and re-liquefied by the HELIAL. It can then be stored in a 2,000 L Dewar flask before being redistributed to users.

The liquefaction system consists of a 55 kW KAESER cycle compressor, an oil removal system, a HELIAL 1000 cold box complete with internal purifier, a dryer and the liquefier’s remote control system. The HELIAL liquefier set up at Bristol can produce 17 L/hr of liquid helium at 4.5 K without nitrogen pre-cooling. The facility is completed by the helium recovery equipment (200 bar recovery compressors, high pressure impure gas storage cylinders, recovery tank, etc.) and connection pipe system.

Air Liquide expertise

The technical challenge for Air Liquide revolved mainly around designing, implementing and building the purification and liquefaction system into the University’s existing facility, and starting the unit up. The liquefaction unit had to be able to provide a permanent supply of liquid helium to the different users and therefore needed to be fully reliable.

It has an efficient remote control system complete with user-friendly monitoring interfaces which makes it easy to use. The capacity of the HELIAL supplied to Bristol is open-ended and may be increased through initial nitrogen pre-cooling (an option already built-in), then by using a cycle compressor of larger capacity. Upgrading in this way will potentially increase the liquefaction rate up to 80 L/hr. As a result, the liquefaction centre will easily be able to meet the growing demand for liquid helium in the years to come.

Innovation: an automatic helium liquefaction system

Air Liquide has supplied the university of Bristol with an appliance from the standard range of automatic helium liquefiers known as HELIAL. With robust components and an efficient control system, the range offers liquefaction centre operators reliable devices that are straightforward to use. They can also be monitored, diagnosed and controlled from Air Liquide DTA through remote connections.