Broken Bearing with Outer Race Defect Case
Ultrasonic FFT analysis revealed high energy levels and repetitive impacting in a critical motor bearing, indicating elevated friction and a potential defect. Grease injection reduced friction but repetitive impacting persisted, suggesting a broken bearing with a ball pass frequency outer race defect.
While performing a condition-based lubrication route, our customer, a Lubrication Technician at a Canadian Pulp & Paper Plant recorded the following two measurements on one of their critical motors.
In Figure 1, we observe the Ultrasound FFT before the grease injection, and in Figure 2 we can see the effect the grease injection had on the asset.
When taking the initial measurement as seen in Figure 1, the technician noticed lots of impacting while listening through his headphones.
Examining the ultrasonic FFT closer in UAS3, we can observe high energy levels which could indicate elevated friction and the need for lubrication. We can also see the repetitive impacting that was noticed by the technician while listening through their headphones.
In Figure 2, we observe the ultrasonic FFT after the grease injection. The energy levels dropped significantly, indicating the friction decreased; however, we still see lots of repetitive impacting, most likely meaning the bearing is broken.
Using the Bearing Toolbox Ultrasound Fault Frequency Calculator, an add on to the UAS3 software, the technician was able to determine that this bearing had a ball pass frequency outer race defect. It will be monitored closely and replaced the next planned shutdown.
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