Abstract
Water hammer in pipelines and pipe networks can result in pipe and equipment failures and economical/environmental losses. The use of a piece of flexible plastic pipe for water hammer control is discussed and experimental data for the use of such a device are presented. The device, referred to as a plastic chamber, reduces pressures resulting from water hammer. The flexibility of the plastic chamber allows radial expansion of its walls under pressure to accommodate the excess fluid and thereby reduce water hammer-induced pressure spikes. To enhance the performance of the plastic chamber, air-filled balls are inserted into the chamber. When a sudden pressure increase takes place, the air-filled balls shrink to reduce the pressure surge. Previous experimental data on the use of the plastic chamber and the air-filled balls (inserted in a rigid chamber) are analyzed. The effect of the plastic chamber on the reduction of water hammer was formulated as a function of a dimensionless parameter related to the plastic chamber and the pipe for which water hammer is to be controlled. Furthermore, the effect of the air-filled balls was formulated and found to be a function of an analogous dimensionless parameter related to the volume/inside pressure of the balls and pipe parameters. The two effects were combined in an empirical formula for the total reduction of water hammer when using a plastic chamber with air-filled balls. The procedure allows the required water hammer reducing device to be sized to achieve a target reduction of water hammer based on the parameters of the pipe, the plastic chamber and the air-filled balls.