Measuring your bearings prior to failure can save countless money and downtime. A rolling element bearing may go through the following 4 stages before it comes to a total failure.
Stage 1. At this stage there is no visual distress on the bearing race way or on the rolling element surface. Usually there is no visible vibration signal on the velocity spectrum.
Stage 2. At this stage magnification may indicate early surface faults. The natural frequencies of bearing parts begin to appear on the vibration spectrum.
Stage 3. At this stage minor or extensive wear pattern can typically be viewed. The characteristic frequencies of the bearing begin to appear on the vibration velocity spectrum. The bearing should be replaced as soon as possible to prevent from catastrophic failure.
Stage 4. At this stage visual damage is typically observable on the bearing parts. As the wear progresses, the bearing frequencies are well developed, and phenomena of looseness causes noise floor and harmonic signal to increase on the velocity spectrum. The machine should stop operating at this stage for the total failure of bearing is imminent.
It is very important to monitor the bearing faults in its early stage. At early stage 2, the natural frequency signal of bearings is an effective indication of bearing condition. By taking advantage of demodulation technology, we can monitor the development of bearing defects on the demodulated spectrum. The following example shows how we identify the early stage bearing faults by demodulating the high frequency vibration signal.
A damaged bearing shows repeated spikes in time waveform. These spike signals may excite the structure's resonance up to very high frequency band (1 kHz or higher)
By means of demodulation technology, one may see the bearing's fault frequencies on a demodulated spectrum. In this example, the outer race of the bearing NTN 4T30203 is damaged, and the damage signal is shown on the frequency of BPFO.
Envelope scanning conducts envelope spectrum measurements with envelope filters at different center frequencies and show th eresults in a waterfall plot. From the above plot we can see that for this bearing the envelope spectrum shows best quality with a envelope filter centered at 3.25 kHz and 12.5 kHz.
Build in bearing database of up to 400,000 bearing models. The selected bearing frequeinces can be shown on the spectral plot for comparision.
Benstone Instruments offers the envelope spectrum in our FFT analysis program and the data collector program. The Impaq Elite, Impaq and Fieldpaq have this software program available.
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