Revolvo insulated bearing technology gains market share

Closer to home, Revolvo has recently supplied electrically insulated bearings for new passenger rolling stock, freight locomotives used in the Channel tunnel rail link; and in Rapid Transit Trams operating in Manchester and Tyne and Wear in the North of England. Train operating companies are looking for lower maintenance costs and more intensive train utilisation for running very high operational distances for new generations of electricity powered trains, with the expectation of a 10 year traction motor life. This is up to twice that of previous generation trains equipped with AC traction motors; hence the longevity of the electric motors is crucial to meeting these ambitious targets.

Traction motor bearings, and other bearings used in high-load electrical applications, have to be electrically insulated in order to prevent current passing through the bearing. When electrical current flows through a motor’s bearings to earth it can damage the bearing. The extent of the damage depends upon the strength of the current and the duration of the conditions, but it usually results in erosion and cratering of the bearing raceway and rolling element surfaces, resulting in premature bearing failure.

Revolvo use a process of Plasma spraying, using aluminium oxide to insulate the outer surface of either the inner or outer bearing raceway in order to insolate it from the electrical current. This method is superior to other processes such as flame spraying and epoxy coating as the plasma sprayed coating is harder and thinner, leading to both greater accuracy and durability.
Either the inner race, or outer race of the bearing is machined down to accommodate the thickness of the insulating coating, the coating is then plasma sprayed, a sealer applied and heat cured, and then the bearing ring is hard turned and finished ground to its correct fitting size. The sealer used after the plasma spraying process impregnates the slightly porous oxide coating and seals the surface to eliminate moisture ingress. It also prevents significant deterioration of electrical resistance when the bearings are exposed to high temperatures.

This insulating process can either be applied retrospectively to conventional bearings from Revolvo’s stock profile of ISO standard sized bearings, or Revolvo can manufacture complete customised insulated bearings from basic raw materials where required. Revolvo manufactures its own large sized ball and roller bearings on demand, typically offering much shorter lead times than the major premium brand global bearing manufacturers, where current lead times can be in excess of 12 months, whereas Revolvo can often manufacture large sizes in a matter of weeks. Electrically insulated bearings up to 360mm O/D are manufactured by Revolvo.

In recent years Revolvo has cemented its worldwide growth with investments in new premises as well as state-of-the-art grinding machines and heat treatment facilities. This has allowed it to become a global player whilst totally re-writing the industry standards for lead times on medium and large sized bearings. This investment has given its R&D team the resources required to develop an insulation process that provides the reliability and durability that is required by today’s applications.