Ceramic cryogenic bearings' performance in super-cooled fuels

UK-based precision bearing manufacturer Carter Manufacturing said its cryogenic bearings present a smoother path to the maritime energy transition in contrast to conventional bearings

With specific regard to the growing natural gas segment, the company noted LNG presents significant challenges to fuel systems and pumps dealing with extreme temperatures. 

As fuel systems approach operating temperatures of absolute zero (0ºK) the ability to utilise liquid lubrication becomes increasingly challenging, which means dry running bearings are mandatory. At this temperature, Carter Manufacturing said standard steel bearings are rendered ineffective, offering poor performance and short service life.

Bearings that can withstand extreme temperatures while being fully submerged in LNG at temperatures ranging from -196ºC, or in the case of liquid hydrogen, -253 ºC, are vital components in LNG pumps. 

In addition to the challenges of lubrication, the expansion and contraction of the different materials used in the bearing housings, as aligned with the coefficient of the required thermal expansion, becomes even more critical for bearing efficiency. Another challenge is balancing the pump system, to account for the contraction of the materials. 

Carter Manufacturing noted bearing cage failure is a common occurrence in cryogenic applications, making material selection crucial. To account for many engineering plastics which become brittle at cryogenic temperatures, Carter offers customers lower-cost options such as PEEK and PTFE with custom additives, or Durafilm or PCTFE can be specified.

Carter has also developed a proprietary two-piece riveted cryo cage design for deep-groove ball bearings for increased performance.

Unlike traditional bearings using liquid lubricants between the steel rolling elements, which minimises metal-to-metal contact and the resulting risks of micro-welding adhesion, bearings in applications involving cryogenic temperatures cannot use this option.

Instead, Carter offers ceramic bearings, such as silicon nitride, intended to eliminate the need for liquid lubricants and significantly reduce the mass and increase the bearings’ speed capabilities.

The company said this, in conjunction with the application of a dry-film lubricant such as tungsten disulphide, rated AMS2530, are the other important factors for cryogenic bearing success.

Carter said its significant market share “ensures an extensive stock of cryogenic bearings, enabling customers to choose the best design and materials to suit their application,” citing its expertise and established procedures in proprietary heat treatment, internal quality controls and testing procedures as attractive propositions for potential customers.

Last month, the company continued its expansion, signing an exclusive distribution agreement with Australian company CGB Precision Products for sales in Australasia.