Bearings for extreme environments

Oxfordshire-based specialist bearings company Carter Manufacturing, established 25 years ago, specialises in these demanding applications, helping engineers specify the most advanced bearings for ultra-high vacuum and cryogenic environments.

Where ultra-high vacuum systems operate at pressures below 1 x 10^-6 torr the challenges are extreme. For example, even tiny amounts of gas released by material can contaminate the chamber or interfere with sensitive results. Furthermore, traditional oils and greases may evaporate, while equipment can also face high-temperature bake-out cycles of approximately 200 to 450 degrees C, before later operating at extremely low temperatures. Materials, clearances, lubrication, and cleanliness therefore must be considered as part of one complete engineering problem.

A good example of where these extreme challenges have occurred is at a major German Research Centre at Helmholtz-Zentrum Berlin fuer Materialien und Energie (HZB). Its BESSY II facility produces an exceptionally bright photon beam for the study of matter. Researchers there developed the Pente.Ax cryomanipulator for angle and spin-resolved photoelectron spectroscopy, a technique used to investigate the electronic and magnetic properties of crystals.

The Pente.Ax cryomanipulator instrument needs to position samples with great precision through both linear and rotational movement. Its mechanism operates in ultra-high vacuum and is cooled by liquid helium, creating conditions in which ordinary bearings and lubricants would be unsuitable. Silicon nitride ceramic UNASIS bearings supplied by Carter were selected for the gears, wheels, and rotating sample stage along with Carter engineers providing technical support to confirm that the bearings matched the operating conditions.

According to the project leader, Dr Andrei Varykhalov: “The bearings proved mechanically robust and the cryomanipulator operated almost continuously for more than a year without requiring maintenance. The project demonstrated how careful material selection and application engineering can enable precise, reliable movement in environments where contamination, temperature and dimensional stability are critical."

The same principles extend beyond spectroscopy. Ultra-high vacuum and cryogenic bearing technology supports particle physics, semiconductor manufacture, space systems, and equipment handling liquefied gases. Cryogenic bearings may use combinations of specialist steels, ceramics, precision cages, and dry-film coatings, with internal clearances engineered for the different rates at which materials contract during cooling. Carter's cryogenic bearings are also submerged in liquid nitrogen for quality-control checks including torque, running accuracy and dimensional stability.

Carter Manufacturing is located close to the UK Atomic Energy Authority and Rutherford Appleton Laboratory and is proud to be part of an Oxfordshire engineering community supporting scientific discovery. Its specialist bearing expertise illustrates how a small component, carefully engineered for an extreme environment, can become a critical part of research into the fundamental properties of matter.

Karl Brundell, Managing Director, Carter Manufacturing comments: “What makes us exceptional is our team. We have the best bearing engineers and technical support in the industry which allows us to solve our customers’ most challenging applications. This expertise is extremely important, supporting engineers in specifying the most advanced bearings for ultra-high vacuum and cryogenic environments."

www.carterbearings.co.uk