Water hammer caused by a change (or sudden) in the velocity of fluid flow in a conduit (network) is created. In other words, while the phenomenon of water hammer kinetic energy to the elastic energy becomes.

It flows under pressure in pipelines pumping happen and obviously the laws of gravity or pressure, flow rate variations, or changes in flow rate and fluid motion is based on circumstances of time and place. In some hydraulic systems under pressure, such as water transmission lines, oil or water pipelines and distribution networks, water tunnels, pumping systems and gravity flow, water hammer phenomenon by creating waves, fast, transient and mortal would be various risks . Sometimes the destructive power of the waves to the extent that brings serious consequences. The bursting of pipelines in the transmission system and distribution network, downtime and broken valves, control valves and pumps are obvious examples of this phenomenon.

Despite the gravity and pumping lines for steady current, viable and sustainable (Steady State) are always designed and calculated to achieve this type of process does not happen. Sudden changes in transmission line system on unsteady flows and unsteady fluid flow may be happening.

Because the pressure to change the speed depends on water hammer to avoid undesirable pressures must prevent the sudden change of pace. So often control methods and equipment hammer, in fact controllers are sudden changes in speed