Case Study

Pitch Bearing Seals for the Largest Wind Turbines in the World


Large-diameter seals in wind turbines became dislodged from their housings, causing loss of bearing grease, water ingress and significant damage to the pitch bearings.


System Seals redesigned the bearing groove dimensions and created a multi-faceted, high-performance seal.


The new seal performed flawlessly in initial lab tests and then for more than a year in the field. System Seals now produces all new pitch-bearing seals for one of the largest wind turbine manufacturers in the world.

As wind turbines increase in size and power, so does the likelihood for seal failure around the massive internal bearings. Driving through a windfarm, it’s not uncommon to discover large-diameter seals completely dislodged from their housings, hanging loose, with visible grease splattered on the spinning blades. 

One of the largest wind turbine manufactures in the world began work on a next generation platform. The manufacturer approached System Seals with a challenge: stop the pitch bearing seal problems altogether. The seals are exposed to the elements and required UV and ozone resistance. Installation needed to be field friendly, and the material had to withstand extremely low temperatures in cold weather. 

Large pitch bearings can experience deflections up to 3 millimeters, depending on the wind speed. The significant deflections are the root cause of most seal failures. The new seals needed to conform to constant deflections, while protecting internal lubricants without fail.   

System Seals’ Engineering Center started work on the 2.7-meter diameter seal from scratch. Using finite element analysis and proprietary fluid-compatibility testing, they designed a dual-lipped, robust seal with multiple geometric enhancements that increased the contact force and flexibility. System Seals even changed the groove dimensions on the bearings to ensure a tighter fit. To improve installation, they designed application specific installation tools.   

The turbine manufacturer conducted lab testing, then put the new seals to work in a field turbine for more than a year. The tests revealed that no outside water entered the internal grease. More importantly, the seals remained firmly in place without failure or leaks.

The manufacturer awarded System Seals the contract for retrofitting existing turbines and new builds with the new design.