A check valve is a special type of valve designed to ensure that a medium flows in only one direction and prevents reverse flow. These valves typically operate automatically. When pressure is applied to the fluid in one direction, the valve disc opens; when the fluid flows in the opposite direction, the disc, relying on fluid pressure and its own weight, locks tightly against the valve seat, thus cutting off the flow.
A swing check valve is a common type, characterized by a hinged mechanism and a door-like valve disc that rests freely against an inclined valve seat. Its ingenious design ensures sufficient space for the disc to fully contact the valve seat when swinging. Furthermore, the disc material can be selected based on performance requirements, such as metal, leather, rubber, or synthetic materials. In the fully open state, a swing check valve offers very little resistance to fluid pressure, resulting in a relatively low pressure drop across the valve.
Another type is the lift check valve, where the disc is located on the valve seat sealing surface on the valve body. When fluid pressure acts on the valve disc, it rises from the valve seat; conversely, when the medium flows back, the valve disc returns to the valve seat due to its own weight, cutting off the flow. Similarly, the valve disc can be made of all-metal or materials with embedded rubber gaskets. Because the passage of fluid through a lift check valve is relatively narrow, the pressure drop when passing through the valve is slightly greater than that of a swing check valve.
Furthermore, check valves have the characteristic of automatic opening and closing, relying on the force generated by the flow of the medium itself in the pipeline to operate. This type of valve plays a crucial role in piping systems, including preventing backflow, protecting pumps and their drive motors from reverse rotation, and providing supplies to auxiliary systems. It is widely applicable and can be used in pipelines carrying various media, depending on the materials used. At the same time, the installation and use of check valves also have a significant impact on the fluid flow state.
