Comparison of cavitation erosion rate with liquid impingement erosion rate.

Abstract

Both cavitation erosion and liquid impingement erosion are phenomena that can cause pipe wall thinning in power plants. The Code for Power Generation Facilities, Rules on Pipe Wall Thinning Management, was published by the JSME (Japan Society of Mechanical Engineers) in 2005. The code says that cavitation erosion shall be prevented either in the design stage or by daily inspection. On the other hand, liquid impingement erosion can occur in any location where a working fluid attacks a pipe wall at high flow velocities. Therefore, it is very important to evaluate the amount of erosion by liquid impingement for pipe steels quantitatively from the viewpoint of aging management. In this study, we carried out both cavitation erosion and liquid impingement erosion tests, and clarified the relation between the two erosion rates. As a result, we found that the erosion rate by cavitation increases in proportion with the 5.2th to 6.8th power of the flow velocity and that by liquid impingement with the 6.0th to 7.4th power. Moreover, a good correlation was obtained between erosion rates by cavitation and by liquid impingement. We also discussed the erosion mechanism with SEM photography, and proposed an erosion model.