• Stage 1: In this stage, the bearing is in perfect condition so that in the spectrum only the rotating frequency and possibly some of its harmonics are visible.
  • Stage 2: Vibration readings occur at high frequency, and they are the first symptom of the beginning of the deterioration of a bearing. These readings are due to impacts, caused by a small defect, which tend to excite the high-frequency natural frequencies of the bearing races. These measurements are taken from the acceleration spectrum in a band between 1 kHz and 20 kHz.
  • Stage 3: The characteristic fault frequencies and their harmonics appear. As the damage progresses, it increases both the amplitude of the fault frequencies and their harmonics as well as the high frequency vibration in acceleration. Monitoring their evolution allows us to plan for a replacement well in advance.
  • Stage 4: This is the final stage of the bearing. When it is considerably damaged, there are similar symptoms to looseness and friction. There is also a background noise clearly visible in acceleration at high frequency. It increases the amplitude of 1x RPM and its harmonics and decrease or disappear the amplitude of the fault frequencies as they become masked in the background noise.
Figure 9.11: Stage 1 of bearing deterioration
Figure 9.12: Stage 2 of bearing deterioration
Figure 9.13: Stage 3 of bearing deterioration
Figure 9.14: Stage 4 of bearing deterioration