VALVE CLOSURE - METHOD FOR CONTROLLING TRANSIENTS

One of the objectives of this study was to reduce the undesirable dyna mic pressure oscillation that occurs in a simple pipeline due to valve closure and to prevent the occurrence of column separation. This is a ccomplished by maximizing the minimum pressure in the pipeline. The se cond objective was to minimize the maximum dynamic pressure, and the t hird objective was to estimate the best (minimum) time of closure, T(C ) that results in a pipe stress equal to the maximum allowable stress . The method of characteristics with the time-line interpolation techn ique was used to solve the transient stresses and pressures in a liqui d-filled piping system. Frequency-dependent friction was used in the e quation of motion for the fluid and the pipe wall. A nonlinear optimiz ation technique was utilized to generate the optimum valve closure pol icy. Maximum and minimum pressure heads resulting from a uniform valve closure. Plots of pressure variation at the valve for these two valve closure policies were also generated. Examples are presented to demon strate the advantage of the optimum valve closure policy over the unif orm valve closure policy. The reduction in the maximum dynamic pressur e and stress at the valve for different T(c) is also presented.