The weak link
The pitch bearing is often called the blade bearing or slewing ring bearing. It’s bolted to the blade root on one side and the rotor hub on the other. The pitch system is the whole assembly to rotate the blade changing their angle of attack and lift. They are either rotated via hydraulics and a piston or by an electric motor and gearing. Collective pitch is when all three blades pitch together. Individual pitch is where each blade can be independently rotated by the pitch system.
The industry is facing ongoing challenges in the reliability of these bearings. It’s a challenging application, they are installed packed with grease and we hope they will rotate back and forwards for 20 odd years without needing to be replaced. Lifting the rotor down for repair often has the owner wondering, replace just one or replace all three?
In this post we link to our webinar Current Challenges of Failing Pitch Bearings in the Wind Industry where we discuss:
Pitch bearing failures and design – process for dis-assembly and inspection, determining the primary failure mode, metallurgical investigation and common causes of failure. Challenges in designing pitch bearings. Retrofit solutions to extend life on problem bearings.
One from the archive: Early days Romax modelling of a pitch bearing for analysis of the bearing rolling element contact mechanics incorporating the flexure of the blade root and hub (2006).