The Effect of Water Hammer on Pressure Increases in Pipelines Protected by an Air Vessel

Original scientific paper In the pipelines of water supply systems, the water hammer phenomenon often arises during rapid unsteady developments. Pipelines are mostly protected using an air vessel, which is designed by means of equations for oscillations of water mass. In this study, an analysis is made of the impact of pressure increases caused by water hammer on pressure variations in pipelines protected by an air vessel. The analysed unsteady (transient) developments occurred in a pressure system between the Ravnik pumping station and the Veliko Brdo reservoir, and thereby the measured pressure values were compared with values calculated with a numerical model. It was observed that although the air vessel converts kinetic energy into oscillations of water mass, part of the energy is transformed into elastic deformations of pipelines and into water compression. This study assesses the relationship of the conversion of kinetic energy into significant changes in pressure (phenomenon called water hammer), depending on the extent of the velocity change in time.