Detection of Cavitation with Accelerometer Mounted on Outer Surface of Piping

Abstract

Cavitation induced vibration and erosion of pipes are the potential damaging factor in a piping system. To prevent such trouble, it is necessary to develop the detection method of cavitation phenomena. Especially, in power plants, it is preferred to detect them from the outside of piping during operation. In this paper, detection of cavitation phenomena was experimentally investigated using accelerometers mounted on the outer surface of piping at upstream and downstream of an orifice. As the results : (1) According to the progress of cavitation, output voltage of the accelerometer varied, and the amplitude and number of the pulse-shaped signals increased. However, it might be difficult to distinguish them from noises in an operating plant. (2) It was difficult to recognize the characteristic frequency of cavitation, because the power spectrum density was broad up to the accelerometer limit of 45 kHz. (3) The flow directional distribution of RMS (root mean square) values of accelerometer outputs varied greatly according to the progress of cavitation. Therefore, comparison of RMS values at upstream and downstream of the orifice might be possible to detect cavitation phenomena in a piping system of operating plants.