Many projects are being initiated around the world to promote the use of hydrogen as an energy source. Special submersible pumps that can reliably pump gaseous and liquid media in continuous or intermittent operation - at low temperatures down to around -200 ^oC- are often used.

In these pumps, the double bearing of the pump shaft is a critical design element. Corrosion resistance is a must, and no other lubricant can be used than the media that surround the bearing. However, this is tribologically unfavorable. Therefore, high demands are placed on the material pairing. In addition, the bearings must achieve a long service life even at low temperatures.

NSK has developed a series of deep groove ball bearings specially designed for these unusual operating conditions. These bearings differ from conventional pump bearings in key design features. For example, their inner and outer rings are made of a stainless steel that has been adapted to the special requirements of rolling bearings.

The rolling elements - also made of stainless steel - are guided in a stable cage that occupies the entire internal volume of the bearing. The cage material - a self-lubricating fluoroplastic - ensures low-friction running of the bearing without external lubrication. The high-performance plastic is also extremely wear-resistant and offers good low-temperature properties at speeds of up to 3600 ^rpm. The cage is made in two parts, the two halves are connected by stainless steel rivets.

In laboratory tests and also in practice, these deep groove ball bearings achieve significantly longer service lives than other bearings for this application, e.g. those with a cage made of phenolic hard fabric. They are manufactured in various sizes (shaft diameter 30 to 100 mm) and can therefore be used in larger pumping stations in the hydrogen infrastructure as well as decentralized, e.g. in hydrogen filling stations. Of course, the pump bearings are also suitable for pumping other cryogenic gases such as nitrogen.