When the fluid flows in the pipe, if the valve close suddenly and stop the flow, the kinetic energy will be changed into elastic resilience and create a serial positive and negative pressure wave vibrating back and forth in the pipe until the energy lost by friction. Especially when the pump stop, the fluid still flows by inertia and gravity also cause the fluid to flow back, and these two forces will cause the positive and negative pressure waves. The friction caused by the two waves will make the pipe vibrating and create noise. Hence, the life of the pump and the piping accessories will be affected and, at the same time, cause the uncomfortable noise. under such situation, to set up one or more sets of water hammer arrester will improve the situation.
Our company make use of the airbag principle to design water hammer arresters which will reduce the vibration by pressing air when the in-pipe pressure transfer to air chamber.

The Features of Water Hammer Arresters :
‧the airbag adopts the ball-pressing-type design, which is no friction, less function progresses, prompt and sensitive response and has obvious result. In addition, the life of the arrester will be increased several times.
‧The arrester will absorb water hammer directly and has the functions of water hammer prevention and absorption.
‧Special design of the air diaphragm rubber will not release pressure and its life won't be affected by the bad water quality.
‧To prevent the air leakage, the pressed air chamber is covered by speeding prevention rubber.
‧The design of structure is excellent and easy to maintain.

How big of the fluid pressure of the water hammer will be?
The water hammer effect caused by closing the valve should be added at the largest water head in the pipe to calculate the height of the pressure water head and fluidpressure.

Vensano's formula：

Ho = the pressure water head before closing the valve Vo = the flow speed before closing the valve T = the time needed to close the valve L = the pipe length between the inlet and outlet of free water surface Zo = the largest pressure water head increased by water hammer effect H =full pressure water head after adding water hammer at the end of the pipe Remark: the transferring speed of in-pipe pressure and acceleration 　　　 (about 1000 m / second)

Example：Assume Vo = 5 m/ sec, Ho = 72 m, L = 210 m, if the it takes 3 seconds to close the valve, then, what is the pressure of water hammer?



The full pressure water head including water hammer is： H=Zo+H0=71.35+72=143.35 m
Assume the pressure water head 10 m = 1 kgf/cm²
Then, The fluid pressure including water hammer is ： 143.35 / 10=14.335 kg / fcm²