Large wind turbine blade bearings depend on sealing systems that keep lubricant inside the bearing and keep dirt, dust and moisture out over an entire service life. How well those seals perform is strongly influenced by two factors: the relative movements of the bearing rings during operation and the pressure that builds up inside the grease. A new preprint under review at Wind Energy Science examines both factors for a grease-lubricated, 5-metre three-row roller blade bearing, combining finite element simulations with full-scale laboratory measurements.
The study was carried out by Matthis Graßmann, Marlene Bantz, Frank Schönberg and Arne Bartschat, using the BEAT6.1 test rig at Fraunhofer IWES. Two of the authors, Marlene Bantz and Frank Schönberg, were employed by sealing manufacturer Freudenberg FST GmbH, while the remaining authors declare no conflicting commercial or financial relationships. The work was distributed under a Creative Commons Attribution 4.0 license and posted as a preprint on 27 October 2026, meaning it is still undergoing peer review.
To assess how the bearing rings move under load, the researchers built a finite element model that includes not only the bearing itself but also the adjacent support structures that emulate the stiffness properties of the blade and the hub. The team reports that this model was validated against measurements.
The simulations predicted maximum radial gap variations between -0.29 mm and +0.59 mm, along with maximum axial displacements of up to 0.41 mm. In this case, the predicted movements remained well below the sealing system’s allowable movement range of ±1.5 mm, leaving a substantial margin between what the model predicts and what the seal can accommodate.
The second part of the study addressed internal grease pressure. High pressure inside a blade bearing can push grease past the seals or otherwise interfere with their function, so the researchers measured pressure experimentally under representative operating conditions and under extreme scenarios in which the grease outlets were closed. During normal operation, the measurements showed no significant pressure increase, indicating that everyday pitch motion and grease flow do not create conditions that would threaten the seals.
The extreme scenarios told a different story. With blocked grease outlets and no pitch movement, pressures rose to as much as 2 bar. That figure should be read carefully: it reflects an artificial worst case rather than expected service conditions. Notably, when pitch movement was introduced, the pressure dropped rapidly to below 0.5 bar, showing how strongly the motion of the bearing itself redistributes grease and relieves internal pressure.
Taken together, the results indicate that the investigated sealing concept is capable of accommodating both the predicted ring deformations and the pressure levels associated with a large three-row roller blade bearing.
As with any preprint, the findings should be interpreted with the usual caveats: the study covers one specific 5-metre bearing design tested on one rig, the deformation figures come from a finite element model rather than direct measurement of every operating state, and the pressure extremes were deliberately unrealistic. Peer review may still refine the results. Nevertheless, for engineers concerned with whether seals can survive the deformations and pressures of ever-larger blade bearings, the study offers a concrete, quantified answer for at least one design: the movements stay within ±1.5 mm with room to spare, and pressure only becomes a concern under conditions that real turbines are not expected to experience.
Subject of Research: Ring deformations and internal grease pressure in a 5 m three-row roller wind turbine blade bearing, assessed for seal design
Article Title: Assessment of ring deformations and internal grease pressure for seal design in a 5 m three-row roller wind turbine blade bearing
Article References: Graßmann, M., Bantz, M., Schönberg, F., & Bartschat, A. (2026). Assessment of ring deformations and internal grease pressure for seal design in a 5 m three-row roller wind turbine blade bearing. https://doi.org/10.5194/wes-2026-192
Image Credits: AI Generated
DOI: 10.5194/wes-2026-192
Keywords: wind turbine blade bearing, sealing systems, ring deformation, grease pressure, finite element simulation, Fraunhofer IWES, three-row roller bearing, full-scale testing, lubricant retention, pitch motion, preprint, Assessment
News Source: Faith Mcneil. (October 27, 2026). Simulations and Full-Scale Tests Show Blade Bearing Seals Can Handle Ring Deformations and Grease Pressure. Scienmag.
