What are the working characteristics of the check valve?

The working characteristics of the check valve are large load changes and small opening and closing frequency. Once in the closed or open state, the service cycle is very long and does not require the rotation of moving parts. But once there is a switching requirement, it must be flexible. This requirement is more demanding than common mechanical movements. Since the check valve is qualitatively determined to be used for fast closing in most practical use, and the moment the check valve is closed, the medium flows in the reverse direction. As the valve flap is closed, the medium rapidly drops from the maximum backflow speed to zero, and the pressure rises rapidly, that is, the phenomenon of "water hammer" that may have a destructive effect on the piping system is generated.

For high-pressure piping systems where multiple pumps are used in parallel, the water hammer problem of the check valve is even more prominent. Water hammer is a kind of pressure wave of transient flow in pressure pipes. It is a hydraulic shock phenomenon in which the pressure rises or falls due to changes in the flow rate of the fluid in the pressure pipes. The physical principle is the result of the combined effect of the incompressibility of the liquid, the inertia of the fluid motion and the elasticity of the pipe. In order to prevent the hidden danger of water hammer in the pipeline, for many years, people have adopted some new structures in the design of the check valve, such as the check valve with lever&weight (As shown below), ensuring the performance of the check valve and minimize the impact of water hammer.

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