Cyclic Spectral Analysis of Vibration Signals for Centrifugal Pump Fault Characterization

Abstract

Seal damage and cavitation are common faults during centrifugal pump operation. The characterization and recognition of these faults are investigated in this paper to improve the efficiency and reliability of pumps. A time-frequency signal analysis method based on the cyclostationary theory is adopted to extract the frequency characteristic components from non-stationary vibration signals under cavitation and seal damage conditions. Specifically, the signal analysis was conducted preliminarily based on the calculation of cyclic autocorrelation functions (CAFs) for various signals. Corresponding slices are extracted from the CAFs and processed by fast Fourier transform (FFT) method. Consequently from the FFT spectra, indicators for characterization are extracted to demonstrate the occurrence and severity of faults. Results show that the indicators for seal damage characterization are 100 and 600-Hz frequency components in slice $\alpha =600$ Hz of CAF corresponding to shaft and blade passing frequency in the frequency domain of vibration signals. Meanwhile, the occurrence and development status of cavitation are indicated by the frequency component of 200 Hz in slice $\alpha =600$ Hz of CAF. Additionally, the effect of instability caused by off-design, seal damage, and cavitation operation conditions are distinguished by cyclic spectra analysis. Characteristic components are innovatively extracted at specific frequencies to avoid the effect from modulated and noise components in vibration signals. And the results about recognition of different types of faults could provide important evidences for fault detection during pump operation.