Rolling-Element Bearing Fault Detection (Sound and Vibration Measurement Suite)
December 2007
NI Part Number:
372416A-01
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You can use the envelope detection technique to perform machine fault detection on a rolling-element bearing. Faults on a rolling-element bearing exhibit peaks of characteristic frequencies or orders in the power spectrum of the envelope signal. You can calculate the characteristic frequencies or orders of a bearing and compare them with the peaks in the power spectrum of the envelope signal to identify the bearing faults.
Use the OAT Envelope Detection VI to calculate the envelope signal of the vibration signal of a bearing. You first must specify the center frequency and span of the frequency or order band to use. If you want to identify the location of a fault, specify one of the resonant frequencies in the high frequency band as the center frequency. Resonant frequencies in the high frequency band provide the highest signal-to-noise ratio. If you want to perform machine condition monitoring, set the center frequency away from the resonant frequencies. The vibration level at the resonant frequencies is sensitive to the placement of the accelerometer and to other mechanical changes, and changes in the vibration level might prevent you from performing fault trend analysis. Set the span of the frequency or order band that you want to use to several tens of orders. You also can specify the frequency span in hertz by multiplying the value of the order by the rotational frequency.
Use the Waveform Output instances of the OAT Envelope Detection VI to perform envelope detection when the rotational speed of the bearing is constant. Use the Even-Angle Signal Output instances of the OAT Envelope Detection VI when the rotational speed of the bearing is variable. You must manually select whether to use the 1 Channel or the N Channels instance of the OAT Envelope Detection VI.
The output of the OAT Envelope Detection VI is an envelope signal. You can use the SVFA Power Spectrum VI to display the frequency power spectrum and the OAT Order Power Spectrum VI to display the order power spectrum of the envelope signal.