Large butterfly valves have been supplied for hydropower stations by GE Energy (UK), formerly Kvaerner Boving Ltd, since 1931. For a description of a recent project that incldues the application of large butterfly valves see Jones and Taylor (2000). Some of the most demanding operating conditions for a power station protection valve may be experienced during meergency closing. The high flow rates and large dynamic heads during such conditions can cuase large variations in the static pressure around the valve disc and he resulting loads on valve components can be immense. The prediction of these loads presents the valve designer with a challenging problem, even with modern tools such as finite element analysis and Computational Fluid Dynamics. This paper reports the development of a means of predicting the loads whilst closing on a valve disc rubber seal in a high head power station protection valve. GE Energy performed the research in collaboration ith the University of Oxford to establish the fundamental design parameters and to evalaute seal loads and deflections. The research reported here focused on quantifying the pressure loads on the seal section of a lattice valve during high flow closing. Detailed static pressure measurements were made on a scale model of the valve over the location of the seal. Dimensional analysis allows the real system loads to be predicted from the model tests. The results have shown that the complex separated flow while closing develops unexpectedly high pressure forces on the seal.
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