高圧調節弁プラグに生じるキャビテーション壊食の形成と進展(流体工学,流体機械)

概要

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In control valve technology, life time due to cavitation erosion is one of the most important items to be predicted. As the erosion develops, the throttle characteristics deviates from the original, and the seat leakage at the shut-down position increases. Even a rough estimation of the life-time in relation with on-cite history is necessary for a reliable operation of respective fluid system. In the present study, a contoured plug of stainless steel inserted in a globe valve has been subjected to erosion tests using a 20 MPa water test bench. Numerical analysis of cavitation-free flow and cavitation observation in a low differential pressure range were also made to obtain a fundamental insight of the valve flow structure. The erosion initiates from a stage of pit formation on the seat-joint-taper of the plug surface. Then, as the second stage, the weight loss increases rapidy with time as a process in which the erosion extends inward from the surface. The duration of the initial stage becomes short as the plug lift increases. The weight loss rate, which takes the highest at the full lift, is correlated by the kinetic energy of the valve throat flow. The weight loss in the second stage of erosion is also correlated by a power law to the working duration. The valve life time may be predicted by the correlation relationships based on the seat-leakage flow rate which is related to the erosion weight loss.
2002-06-25