When choosing and using check valve products, it is necessary to have a clear understanding of the principle of the check valve in order to select the appropriate check valve and extend its service life. The working principle of the check valve is as follows: the check valve allows fluid to flow in a specific direction and prevents fluid from flowing back or in the opposite direction. Ideal check valves should start closing when pressure drops in the pipe and fluid kinetic energy slows down. When the direction of fluid flow reverses, the check valve should be completely closed.
Check valves are characterized by large load variation and small opening and closing frequency. Once they are in the closed or open state, their service life is very long, and the moving parts are not required to rotate. But once there is a switching requirement, it must be flexible, which is more stringent than the common mechanical movement. In most practical applications, the check valve is qualitatively determined to be used for quick closure, while in the instant of the check valve closing, the medium flows backward. With the closing of the valve disc, the medium rapidly drops from the maximum reverse flow velocity to zero, while the pressure rises rapidly, that is to say, the phenomenon of “water hammer” which may destroy the pipeline system occurs. The water hammer problem of check valve is more prominent for the high-pressure pipeline system with multiple pumps in parallel. Water hammer is a kind of pressure wave of transient flow in pressure pipeline. It is a hydraulic shock phenomenon caused by the change of fluid velocity in pressure pipeline. The physical principle is the result of the combination of the incompressibility of liquid, the inertia of fluid motion and the elasticity of pipe. In order to prevent the hidden danger of water hammer in pipeline, people have adopted some new structures in the design of check valves for many years. While guaranteeing the performance of check valves, encouraging progress has been made in minimizing the impact force of water hammer.
Post time: Sep-28-2019