The Multilife Bearing: Improving Gearbox Reliability in Offshore Turbines

Prof. Rob Dwyer-Joyce 

Dr. Matt Marshall 

Ricardo UK

The vagaries of British weather put much strain on wind turbines. On days of gentle breeze the blades and gearbox rotate leisurely before being subjected to much higher forces when the winds pick up. Gearboxes rarely achieve anywhere near their
design life of 20 years, despite good engineering practices and improvements made on past designs.

Replacing one bearing can cost up to £400,000, sometimes more in the case of offshore turbines, where extreme weather and rough seas complicate matters further. This project has found a way to increase the life span of wind turbines.

During rotation many of the bearings have a single point which continually receives the highest load. On the gearbox bearing, this is on the inner raceway which is static. This region is worn down on every rotation while the remainder of the race is left undamaged.

The solution involves having an inner race which is periodically repositioned, so that the area which wears most quickly is not always in the same place. Wear is then distributed across the whole circumference of the inner race, which markedly increases its lifespan.

By using ultrasonic sensors, we are also able to monitor the lubricant film thickness within the inner race. This allows us to predict when it will need to be repositioned, eliminating downtime and potentially saving turbine companies thousands of pounds.

Ricardo have embarked on a major project to design and prove a revolutionary new bearing concept for the offshore wind turbine industry. The Multilife™ bearing incorporates a hydraulic indexing system that maximises the useable life of the bearing components. Ricardo have teamed up with the researchers in the Leonardo Centre to realise this concept and test effectiveness on a bespoke test rig. The Leonardo Centre has unique expertise in the development of sensors that can predict bearing lubrication performance and they have applied their skills in bearing technology to design indexing strategies. The synergy between Ricardo and the Leonardo Centre promotes success in this important new venture. I have been impressed by the calibre and dedication of their research staff and PhD students. Jonathan Wheals, Chief Engineer – Innovation, Driveline & Transmission Systems, Ricardo UK Ltd.