Abstract

Cavitation is a common fault in centrifugal pumps. The detection and diagnosis of the onset and severity of the cavitation provide the means of preventing the cavitation from causing harmful effects such as deterioration of the hydraulic performance, damage to pump components and the pollution by vibration and noise. This paper presents a new approach to monitoring cavitation based on the measurement of instantaneous angular speed (IAS) of the pump. IAS is measured using a cheap shaft encoder and processed using order spectrum analysis. It has been found that the normalised amplitude at the third order of the rotational speed can be used as a primary monitoring feature to detect the onset of the cavitation and to quantify the severity of the cavitation. A secondary detection feature is also defined in the high frequency range. This makes the detection results more reliable.