Good Envelope / Demodulation Setup is a Perfect Tool for Fault Diagnosis
Envelope/Demodulation is a useful tool for diagnosing faults in rotating equipment, but incorrect selection of Filter Central Frequency and BandPass Filter width can lead to data loss. A better approach is to collect vibration measurements across a wide frequency range and then select the appropriate FCF and BPF based on the energy concentration in the spectrum.
Good Envelope / Demodulation Setup is a Perfect Tool for Fault Diagnosis
There is no question that the Envelope / Demodulation is one of the employed tool to diagnose the faults in rotating equipment specifically in early fault detection. Unfortunately, the incorrect selection for Filter Central Frequency (FCF) and BandPass Filter (BPF) width to construct the Envelope Spectrum losses important data in the frequency spectrum which are difficult to interpret.
The shown example was performed on compressor in York Chiller. It was found that there is some vibration energy concentrated in the range of (1500 – 3500) Hz which is so difficult to interpret. Two Envelope setup were implemented; the first one by selecting FCF and BPF in the range of interest (around 2000 Hz) and the second one was away of any vibration energy (around 7500 Hz). Good results were investigated from the former one and displayed readable peaks.
Furthermore, the competitive solution for this issue is to collect firstly the vibration measurement in the range 0 – 20KHz without collecting Envelope spectrum. After that, the selection of FCF and BPF is based on where the energy is concentrated in the spectrum.
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