EFFECT OF VALVE LOCATION AND ITS CLOSURE SCHEDULE ON WATERHAMMER PRESSURES.

Abstract

The present investigation concerns the effect of valve location in a pipeline connecting two reservoirs and its closure schedule on the resulting waterhammer pressures. The exact method of characteristics is employed for the solution of the unsteady flow problem to obtain the variation of the pressure heads and velocities in the pipeline. Various valve closure schedules are proposed, to simulate real valve operations, together with the linear (uniform) valve closure schedule. The effect of the valve location along the pipeline on the extreme maximum and minimum pressure heads is studied. Comparisons between the respective results are made for three selected locations at the upstream, the middle, and the downstream of the pipeline. Extreme maximum pressures decrease considerably when the valve is located at the upstream while the safest minimum pressures to avoid cavitation are obtained when the valve is at downstream. The results for valve closure schedules simulating real valve operations show considerable decrease in maximum pressures. Also, the respective extreme minimum pressures show improvement as they rise well above cavitation limit. Extreme maximum and minimum pressures occur at the valve when it is located at the middle of the pipeline compared with the respective results when the valve is at the other two locations.