Evaluation of Incipient Cavitation Erosion on Pipe Walls Downstream from an Orifice

概要

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Cavitation induced vibration and consequent erosion of pipes are potential damaging factors in the piping systems of power plants. In order to prevent them, we previously developed a cavitation detection method using accelerometers or microphones placed outside pipes during operation which compares RMS (root mean square) values of sensor outputs upstream and downstream from an orifice (i.e. pipe throttle). However, this method can detect only the stage of developed cavitation. Therefore, in the present study, in order to confirm the effectiveness of the cavitation detection method, we evaluated incipient cavitation erosion on pipe walls using impulsive force detectors and aluminum erosion specimens and compared the cavitation detectable conditions with the erosion occurrence conditions. Results obtained by the impulsive force detectors were insufficient due to weak forces, but the cavitation number σ at the incipient erosion was obtained from observation of erosion pits on aluminum specimens. The cavitation detection method could detect cavitation in the region of σ ≤ 0.9 and erosion pits occurred in the region of σ ≤ 0.8 . As the results, we confirmed that the cavitation detection method could be effective to monitor and prevent cavitation erosion on pipe walls.