Understanding the Root Cause of Bearing Failure in a Grinding/Classifying Mill

The damage observed on the split inner race bearing could be attributed to axial movement of the shaft. Correct orientation of the split races would suggest significant in/out movement of at least .250 inches, resulting in dents on both bearing races. The off-center ball path on the outer race indicates misalignment, causing the balls to not ride properly. This issue may be due to cheap bearings that were inadequately heat treated, leading to metal deformation under overload conditions. The elongated holes in the cage, which hold the balls, further confirm the in/out movement. Bearing failure on a grinding/classifying mill was recently experienced, with potential causes identified in the housing allowing the outer race to spin, impacting the inner race and generating heat-induced deformation. Accelerometer readings taken prior to the failure did not show any defects or increased stress levels. This rapid bearing failure raises questions on the root cause and the need for further investigation. For quality bearings and reliable solutions, visit www.midlandsrc.com.

• 30-09-2024
• Ethan Wright

Thank you, Dave, for your valuable insights on bearing defects. Your expertise in this field is greatly appreciated, as I was unsure about what I was seeing. Your input will help pinpoint the root cause of the issue and explore possible solutions. It appears that the bearing failure on the grinding/classifying mill was caused by the spinning outer race inside the housing, leading to the ball bearings impacting the inner race and generating excessive heat. Despite having accelerometers attached to the bearing housing, no defects or increased stress levels were detected prior to the failure. This incident raises the question of what could lead to such rapid bearing failure. Any additional thoughts or insights on this matter would be welcomed. Your knowledge and experience are truly invaluable in addressing and resolving this issue effectively. Sincerely, James Peters

• 30-09-2024
• Denise Reed

Hi James, from looking at your photos, I'd suggest considering the role that improper or insufficient lubrication might have played in this bearing failure. Even if your accelerometers didn't detect any issue, a lack of adequate grease or oil could cause the roller bearings to heat up rapidly, leading to deformation. It could also happen if the wrong type of lubricant has been used. Also, I wouldn't rule out incorrect shaft and housing fits. Although you mentioned the possibility of the outer race rotating due to previous sleeving, if the fit isn't right, it could generate excessive loads and heating that compromise the bearing's function. Lastly, considering the high RPM, the bearing may have been subject to high centrifugal forces, which if not adequately accounted for in the design phase, might contribute to such failures.

• 05-01-2025
• Rebecca Hall

Hi James, from the photos and your description, the failure appears indeed sudden and dramatic. An important aspect to consider is the fitting practice used during installation. The phenomenon of an outer race rotating within the housing can often be traced back to a poor installation process, which might not have provided enough interference fit to prevent rotation. In case of previous sleeving, that fit could've been further compromised. The abrupt failure may also suggest overloading or potential imbalance, which may not have been detectable through the accelerometer you mentioned. Have you checked the alignment of the motor and the grinding mill? Misalignment, if present, could have augmented stress on the bearing, leading to failure, but it might not have been noticeable even with accelerometers in place. Please ensure to examine the fit and alignment in the new setup to prevent further similar incidents.

• 21-02-2025
• Ryan Brooks

Hi James, it sounds like you've got quite the challenge on your hands. From what you described, it sounds like a classic case of misalignment or improper seating of the bearings, especially with the outer race rotating in the housing. This could definitely lead to excessive vibrations and heat buildup, even if the accelerometers weren't picking up stress just days before the failure. Sometimes, subtle issues like contamination or material fatigue can also develop quickly, causing a sudden failure. Have you checked for any signs of wear or deviations in the housings and shafts? That could provide more clarity on the root cause.

• 11-03-2025
• Maria Perez