The working principle of a check valve

A check valve is a type of automatic valve that controls the one-way flow of a medium by relying on the pressure of the medium itself and the weight of the valve disc, thereby preventing backflow. Its core working principles can be categorized into the following two types: 1. Lift-type check valves: The valve disc moves in a direction perpendicular or parallel to the axis of the valve body. Its structure is similar to that of a globe valve, but it does not have a valve stem. When the medium flows in from the inlet, the pressure opens the valve disc, allowing the flow to proceed; when the flow reverses, the valve disc closes under the combined effect of its own weight and the reverse pressure. These valves are suitable for use in small-diameter pipelines with clean media, but they tend to generate higher fluid resistance.2. Swing-type check valves: The valve disc rotates around a pivot axis to open and close the valve. Their streamlined design reduces fluid resistance. When the medium flows in the forward direction, it causes the valve disc to rotate; when the flow reverses, the valve disc returns to its original position under the force of gravity, thus sealing the valve. Depending on the diameter, these valves can be single-disc, double-disc, or multi-disc types. They are ideal for applications involving high flow rates and pulsating flows. 3. Special types of check valves: – Butterfly check valves: The disc-shaped valve disc rotates around an axis and are suitable for use in medium and low-pressure systems. – Slow-closing check valves: These valves use springs or hydraulic mechanisms to slow down their closing process, thereby reducing the risk of water hammer effects. When installing check valves, it is important to follow the following guidelines: Use straight-through types for horizontal pipelines and vertical types for vertical pipelines. Additionally, the valves should not be subjected to any additional loads.

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