Detection of Lubrication State in a Field Operational Wind Turbine Gearbox Bearing Using Ultrasonic Reflectometry

Abstract

Fully flooded lubrication is the ideal state for a rolling bearing; this is especially true in the aggressive environment of a wind turbine transmission where bearings are subject to intermittent operation and highly variable loading. In this paper, a novel ultrasonic reflection method is used to detect the presence of oil between rollers in the bearing. Ultrasonic sensors were instrumented on the static inner (lab) and outer (field) bearing raceways and reflections were captured as the rollers travelled past the sensor. The proportion of the sound wave reflected (known as the reflection coefficient, R) is dependent on the acoustic mismatch of the materials either side of the interface. Changes in R indicate either a steel–air or steel–oil interface as R values transitioned from 1 to 0.95, respectively, and even lower for a steel–roller interface. Consequently, it was possible to detect the presence of lubricant on the raceway between roller passes. From the laboratory measurements, the recurring reflection coefficient patterns between roller passes were used to identify the lubrication condition of the raceway. An absence of these patterns between roller passes indicated the absence of lubricant on the bearing surface. For the field measurements, three bearing lubrication conditions (partial, insufficient, and fully lubricated) were observed. Partially and insufficiently lubricated datasets were found to occur mostly during transient operation. As transient operation is often accompanied by overloading and torque reversals, coupled with the lubrication issues, these all act to increase the risk of premature bearing failure.

Review of Tribological Failure Analysis and Lubrication Technology Research of Wind Power Bearings

“…Nicholas et al [ 190 ] modified the ultrasonic reflection method by proposing a new ultrasonic reflection method to monitor the variation of oil volume amongst bearing rollers in wind turbine gearboxes. An ultrasonic sensor mounted on the outside of the bearing raceway (see in Figure 23 ) was used to measure the minute vibrations generated by the ball of the bearing raceway to obtain the reflection coefficient R, which is used to determine the lubrication status of the bearing roller raceway.…”

Methods of Condition Monitoring and Fault Detection for Electrical Machines

“…Regarding lubricant conditions, which directly impact the bearing's durability, authors in [117] use ultrasonic sensors that were instrumented on the inner and outer bearing raceways to detect lubricant conditions. In [118], the authors propose an improved grey k-means clustering model for monitoring bearing wear conditions.…”

Analysis of the Gearbox Oil Maintenance Procedures in Wind Energy II

“…The content of the information that accompanies each oil sample structure can be defined by two parties: the maintainer and the laboratory. Considering that there are several laboratories [19] and maintainers [18], the consequence is that the information that the laboratories receive is not widely standardized.…”

“…Recent works [14] have covered general aspects of different issues related to the wind energy industry and its maintenance procedures, including: (i) the significant growth of the wind industry in recent years [1] and the current and future growth trends, (ii) maintenance evolution [2], with the emergence of new tools and spare parts and wider knowledge of assets or (iii) the specific circumstances that hinder the operation and maintenance of a wind farm [15], including the particular features of the wind turbines. More specifically, it is also examined in [14] the gearbox of a wind turbine [16], its maintenance (predictive, preventive and corrective) [2,17] with different techniques that are used to analyse the different issues [18], and the difficulties of collecting and analysing the data [19,20].…”