Fault Diagnosis of a Double-Row Spherical Roller Bearing for Induction Motor Using Vibration Monitoring Technique

Vibration monitoring techniques employing sophisticated instruments are widely used in industries for regular inspection and diagnosis of the health condition of rotating machinery. This paper discusses fault diagnosis of the spherical roller bearing for a 630-kW induction motor in a local industry through vibration monitoring technique using a fast Fourier transform analyzer. The main attraction of this technique is that it can be performed even while the equipment is in normal working condition, thus saving precious downtime and avoiding production loss. Accelerometer sensors are kept on drive and non-drive ends of the motor. Vibration data on motor housing are collected in the triaxial direction in the form of amplitude, spectrum and time waveform signals in full-load and no-load conditions. These signals are analyzed and faults identified from the vibration characteristics. From the data, it is found that the dominating amplitude peaks have appeared in the axial direction at 3960 cpm which is matching with harmonic frequencies of motor RPM. Theoretical calculations were also performed to find the bearing fault frequencies, and it is observed that the vibration readings are matching with sub-harmonics of bearing ball pass frequency of outer race. These investigations and calculations help the maintenance personnel in locating bearing faults and also in detecting the exact cause that leads to bearing deterioration so that a suitable remedy can be suggested, tested and implemented.