A monitoring system for a ball bearing of a rotating machine is schematically shown in Figure P4.20a. It consists of an accelerometer to measure the bearing vibration and an FFT analyzer to compute the Fourier spectrum of the response signal. This spectrum is examined over a period of one month after the installation of the rotating machine in order to detect any degradation in the bearing performance. An interested segment of the Fourier spectrum can be examined with high resolution by using the "zoom analysis" capability of the FFT analyzer. The magnitude of the original spectrum and that of the spectrum determined 1 month later, in the same zoom region, are shown in Figure P4.20b.
(a) Estimate the operating speed of the rotating machine and the number of balls in the bearing.
(b) Do you suspect any bearing problems?
Figure P4.20
