When sudden power cuts happen or valves are closed too fast, water shock waves will be generated like hammers beating against
pipes due to inertia of pressure flows, which is known as
water hammers. The force generated by the water shock wave coming back and forth is great sometimes, which will break the valve and the pump. When the opened valve is suddenly closed, the water flow will generate the pressure on the valve and the pipe's wall. The subsequent water flow's rate will quickly get to the maximum and break the pipe under the effect of the inertia; this is the so called
water hammer in the fluid mechanics. This factor should be taken into account in the construction of the water supply pipeline.
On the contrary, the sudden opening of the closed valve will cause the
water hammer, which also has certain destructive power. Suddenly opening or closing the electric pump unit will also lead to the shock wave and the water hammer. This kind of shock wave moves across the pipe, which will easily cause the breaking of the pipe and the damage to the equipment due to the overpressure of the partial pipeline; therefore, the prevention of the water hammer has become one of the key technologies for the water supply engineering.
Conditions of water hammers
1. Suddenly open or close valves.
2. Suddenly close or open pump units.
3. The single pipe delivers water for the place at higher altitude, and the altitude difference of the terrain is over 20 meters.
4. The total pumping head is high or the operating pressure of the water pump is great.
5. The flow rate in the pipeline is high.
6. The water pipeline is too long, and the terrain changes greatly.
The harm of the water hammer
Intensity of pressure will rise due to
water hammers and can be several times or even dozens of times higher than normal pipelines' intensity of pressure. Main damage to pipeline systems caused by great pressure fluctuations is as the following.
1. The
water hammer will make the pipe strongly shake and the pipe's connection end disconnected.
2. The water hammer will cause the damage to the valve; the high intensity of pressure will cause the pipe burst; the water hammer will reduce the pressure of the water supply pipeline.
3. On the contrary, the high intensity of pressure will cause the collapse of the pipe as well as damage the valve and the fastener.
4. The water hammer will cause the reversal of the water pump and break the pipe or the equipment in the pump room; if the water hammer effect is serious, it will make the pump room submerged, resulting in the major accident like the personal injury, and affecting the production and life.
