Effect of Valve‐Closure Schedule on Water Hammer

The computerized method of chacteristics was used to analyze, for a single pipeline discharging into free air, the effect of valve‐closure schedule on water hammer under turbulent friction conditions. The inherent valve schedule was assumed to be a simple continuous power function of the fraction of the closing time, this function yielding a variety of standard valve configurations. A chart is presented to determine the valve schedule that should be used to yield minimum water hammer pressure. With the exception of the minimum pressure case, the same water hammer strength can be obtained with two different schedules. This follows from the type of schedule function used and from the compatibility equations of unsteady flow through closed conduits. Also, it was found that cavitation is less serious for an inherent valve schedule in which the bulk of the pressure surge occurs during the second part rather than during the first part of valve‐closure.