Water Hammer and Surge Tanks

This paper discusses certain phases of the general problem of the regulation of long water columns as found in water works practice. This control must be exercised to prevent pressure changes occurring of such a magnitude that there may be danger of rupture of pipes, valves, centrifugal pump casings, etc. The pressure changes that are being considered are ordinarily known as water hammer and result from any rapid variations in the amount of water flowing in a pipe or conduit. Only those pressure changes will be treated that occur either in the delivery pipe from a motor-driven centrifugal pump or in the closed suction pipe to such a pump as the result of a complete stoppage of the power supply. Water hammer has been known for many years. In the ordinary water works distributing system, water hammer pressures, due to any rapid variation in the flow, have been taken care of by the use of pipes of certain sizes and strengths that have been developed as a result of actual practice extending over a number of years. However, where the pumping-station for a large city is remote either from its source of supply or from the distributing system connected with it, conduits of large size must be used, and for economic reasons, velocities must be maintained at a high value. Such conduits must be carefully designed, since the water supply of the community they serve is usually dependent on them. On the other hand, they are likely to be expensive. Therefore any possible measure that may reduce water hammer effects must be carefully investigated so that the amount of material employed in fabricating the pipe may be reduced to the smallest amount consistent with safety. The classic paper in the English language on the subject of water hammer appeared in the Proceedings of the American Water Works Association in the year 1904 and consisted of a digest by Miss O.