What would indicate a ball fault in vibration analysis?

A ball fault in vibration analysis is indicated by the presence of a specific frequency peak along with sidebands associated with the cage rate. This is due to the interaction between the balls and the raceways within the bearing. When a ball fault occurs, it typically manifests itself through the repetitive impact as the faulty ball passes over the damaged area, which generates frequency components at the fundamental frequency of the cage rotation.

The presence of sidebands around the peak frequency is crucial, as it signifies these repetitive impacts caused by the balls interacting with the faulty area of the raceway. The spacing of the sidebands typically corresponds to the cage frequency, indicating that the fault is related to the balls rather than other potential issues.

In contrast, a flat spectrum would indicate a lack of any significant faults, while a peak with no sidebands may suggest a fault that does not involve specific impacts from the ball, such as a continuous wear rather than a localized fault. Similarly, a peak with shaft rate sidebands usually indicates issues related to the shaft itself or other types of faults not specifically associated with the balls in the bearing system. Therefore, for identifying a ball fault, observing a peak with cage rate sidebands is essential.