DNV GL certifies NSK´s Super-TF bearing material

The rolling bearings of wind energy systems have to attain very long service life under harsh operating conditions. To overcome this challenge, NSK set about developing its Super-Tough (Super-TF) bearing steel, a proprietary material for very high load applications.

Looking to gain independent certification for the material, NSK commissioned the world-renowned test house DNV GL to verify rolling bearings made of Super-TF with respect to ISO 281:2001 (Rolling bearings - Dynamic load ratings and Rating life).

The verification confirmed NSK's published specifications and, in a Statement of Conformity dated 15.11.2017, certified that when Super-TF material is used, the basic dynamic load rating can be improved by 23% in roller bearings and 26% in ball bearings. This is equivalent to a doubling of bearing fatigue life in comparison with ordinary bearings.

Wind power system OEMs and their customers now have the assurance that NSK´s Super-TF bearings achieve significantly longer service life. The bearings are therefore suited to this extremely demanding application, where bearing specifications call for a service life of up to 220,000 hours without major maintenance.

One of the major factors enhancing the performance of Super-TF is its proven ability to reduce surface-induced wear from contaminated lubricant. In addition, the material prevents or retards the appearance of white etching cracks (WEC). These are non-specific symptoms of damage which form below the surface and can lead to premature bearing failure. Through a series of tests, NSK has shown that Super-TF prolongs bearing operating life until the onset of damage.