Abstract
In modern pumping installations it is generally considered that the most common cause of water hammer is that due to inadvertent stoppage of the prime mover. However, mal-operation of pipeline valves is a further common source, and if danger from such units is to be avoided a knowledge of their operating characteristics is essential.
Valve characteristics can determine, to a great extent, the magnitude of the surges which will be initiated following opening or closing of a valve. By graphical representation it is shown how important proper valve selection and operation can become, when related to the system characteristics.
Terminal float valves, pressure reducing valves, etc., are prone to oscillation or ‘hunting’ and, if the valve movement enters into phase with certain multiples of the pipeline period (2l/a), resonance occurs. The effect of such continuing valve oscillation is illustrated graphically.
Check valves are primarily installed in pumping systems to prevent the establishment of the reverse flow which could damage both pump and prime mover. For trouble-free operation it is important that the valve possesses inherent non-slam closing features. The effect of check valve operation with respect to surge is illustrated graphically.
If certain basic system parameters are known it is possible to predict how a check valve will perform in a given installation. The results of the application of one such analytical approach are presented, together with full experimental verification.
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