Case Study

A Groundbreaking Rotary Seal That Redirects Grease Back Where It Belongs


To cost-effectively prevent leaks in a main bearing that was not originally designed to accept traditional seals.


System Seals developed an abrasion-resistant, helical-style seal that redirects leaking grease back toward the raceway as the turbine spins.


The new design stopped main-bearing leaks in the field and prevented the wind turbine manufacturer from redesigning the main bearing for new builds. The solution provided significant overall cost reductions.

To seal grease, a global wind turbine manufacturer developed a main bearing that relied on a labyrinth design for grease retention. The principle works well on certain applications. However, a wind turbine is not one of them.

Making matters worse, the bearing ring surface was not designed to accept a traditional rotary seal. A significant machined lead angle created a rough surface, and grease was being pumped away from the raceway.       

Grease was leaking from hundreds of wind turbines at an increasing rate, creating an accelerated need for maintenance – from two to four times per year. The issue severely impacted O&M costs. More significantly, the leaks increased up-tower safety and the risk for bearing failure.

System Seals set out to resolve the issue. Engineers utilized polyurethane seal technology they developed years ago for legacy rotary seals used in other industry applications. System Seals proprietary abrasion-resistant materials have withstood some of the roughest sealing surfaces on old forging presses that became scored from decades of use. 

A second innovation proved revolutionary: System Seals created a helical-style seal that redirects leaking lubricant back toward the raceway as the turbine spins. The auger seal, as it was dubbed, was a stroke of genius that caused a global wind turbine manufacturer to retrofit all of its labyrinth designs with the new seal. System Seals has since been awarded a patent on the design and will launch its use in multiple industries.

Before a widescale retrofit was set into motion, System Seals spent more than a year refining the design and testing prototypes, installation methods and tooling – both in the lab and in the field. System Seals also provided initial installation training and ongoing evaluations to monitor performance.       

The design was so effective, it afforded the turbine manufacture a cost-out opportunity by avoiding additional engineering resources and increased costs associated with redesigning the main bearing for new builds. This System Seals solution lowered O&M costs, as well as driving costs out of new builds.