Vibration signal characteristics of centrifugal pumps with cavitation erosion impellers

Cavitation erosion is a phenomenon that surface material damages by the crumbling and failing of cavity. In order to investigate the vibration characteristics of a centrifugal pump after cavitation erosion, a single-stage single-suction centrifugal pump (type IS-50-160-00) was selected as the research object. A testing rig was built with the utilization of virtual instrument. The vibration signal of the centrifugal pump was measured. Statistical indicators of RMS and kurtosis were taken to analyze the average energy and shock wave energy of vibration signals. STFT was used to characterize vibration signals in time-frequency domain. The results show that there is a large extent variation of vibration amplitude in the direction of base and axis, and weak variation of vibration amplitude in the direction of radial and vertical. With the increasing of flow rate, the RMS of vibration signal falls at first, then keeps steady, and mounts at last when the flow rate is over the design point. The phenomenon of cavitation erosion causes the increasing of RMS and kurtosis value of vibration signal of the centrifugal pump. When the kurtosis value of vibration signal in the direction of base is over 3, it can be judged that the phenomenon of cavitation erosion occurs. It can be shown from the time-frequency spectrum that there is a shock wave and pause signals caused by the shock wave, which are reflected by the higher frequency band components of the vibration signal that can provide a reference to the diagnosis of the occurrence of cavitation erosion. Analyzing the vibration signal characteristics of centrifugal pumps with cavitation erosion impellers is of great significance to find out the cavitation erosion failure of the centrifugal pumps in time, and adjust the operating parameters to avoid serious consequences. © 2020, Editorial Office of Journal of Vibration and Shock. All right reserved.