07/01/2022 NSK Europe Ltd
For use in submersible pumps that handle cryogenic gases such as hydrogen and LNG, NSK has developed bearings that do not require external lubrication. These stainless steel bearings with a self-lubricating fluoroplastic cage are increasingly being adopted in submersible pumps from major manufacturers.
A growing number of projects around the world are now promoting the use of hydrogen as an energy source. These projects often use special submersible pumps that can reliably pump gaseous and liquid media in continuous or intermittent operation – at low temperatures down to around -200°C.
In such pumps, the double bearing of the pump shaft is a critical design feature. Corrosion resistance is essential and no lubricants may be used other than wash media around the bearing. However, this tribology is unfavorable because it imposes strong constraints on the pairing of materials. In addition, the bearings must maintain a long service life, even at low temperatures.
NSK has therefore developed a series of deep groove ball bearings specifically for these exceptional operating conditions, where a number of key design features set them apart from conventional pump bearings. For example, the inner and outer rings are made of a stainless steel adapted to the specific requirements of the bearings.
A stable cage that occupies the entire internal volume of the bearing provides guidance for the rolling elements (also made of stainless steel), while the cage material, a self-lubricating fluoroplastic, ensures low-friction operation of the bearing without external lubrication. Additionally, the high-performance fluoroplastic is extremely hard-wearing and offers good low-temperature properties at speeds up to 3600 rpm. The cage is a two-piece design, with the two halves joined by stainless steel rivets. In laboratory tests and in practice, these deep groove ball bearings achieve a significantly longer service life than other bearings for this application, such as those with a hard phenolic resin cage.
NSK bearings are available in various sizes (30-100mm shaft diameter) and are ideal for use in large hydrogen pumping facilities and decentralized applications, such as hydrogen filling stations.
Of course, the bearings are also suitable for pumps handling other cryogenic gases such as nitrogen.
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