Case Study

Removing Leaks from Pitch-Bearing Seals


To design an OEM retrofit pitch-bearing seal that eliminated significant grease leakage and water ingress negatively affecting warranty claims costs, O&M costs, optimal performance and environmental concerns.


A seal designed specific to the turbine conditions with upgraded material, design features and improved installation tools.


Six-month testing proved the seal to be virtually flawless.
The redesign mitigated financial risk for both the wind turbine manufacturer and owner operator.

A global wind turbine manufacturer that had commissioned several hundred turbines in Texas faced with a significant pitch-bearing, grease-retention issue throughout the wind farm.

The leaks could be seen from the ground, sparking operational and environmental concerns. The turbines were still within their warranty period, and the OEM began to see the issue as a financial threat.   

The windfarm owner-operator addressed the leaks with the turbine manufacturer. It was soon decided that an immediate corrective-action plan was needed, as well as a long-term solution. 

An inadequate seal design incapable of withstanding bearing deflections was found to be the cause of the leaks. The seals could not maintain contact during the deflections. The OEM bearing and seal suppliers began searching for a redesign solution.

After two redesign attempts and failed testing by the OEM seal supplier, the wind turbine manufacturer contacted System Seals for help. System Seals’ Wind Engineering Center began with finite element analysis, in-depth bearing and seal-design compatibility reviews and up-tower inspections to better understand the faulty seals. The team identified key issues and multiple approaches.

The team settled on one standout solution – to convert the existing seal design to an engineered pitch-bearing seal, specific to that condition, while improving the profile, material and installation process. The redesign was tested rigorously for six months with flawless results.

Satisfied with the results, the turbine manufacturer implemented the System Seals solution. They retrofitted all of the problematic turbines and began using the seal in new installations throughout the United States. System Seals continued to provided field assistance, up-tower installation training, and they even created custom tools to improve installation efficiency.

The turbine manufacturer said that the System Seals solution alleviated a significant financial burden related to warranty claims, potential bearing failures and additional O&M costs incurred by the owner-operator.