Silent check valves are automatic valves that open and close their valve discs based on the medium's own flow, used to prevent the medium from flowing back. Also known as non-return valves, one-way valves, backflow valves, and back-pressure valves. Check valves are a type of automatic valve, primarily used to prevent backflow of the medium, prevent pumps and driving motors from reversing, and to release the contents of containers. They can also be used on piping in auxiliary systems where the pressure may rise above the system pressure. Check valves are mainly categorized into swing check valves (rotating around the center of gravity) and lift check valves.

The check valve functions to allow fluid flow in only one direction and prevent reverse flow. Typically, such valves operate automatically. When fluid flows in one direction, the valve disc opens under the pressure of the flowing fluid; when fluid reverses direction, the pressure of the fluid and the weight of the valve disc close the valve disc against the seat, thus stopping the flow. Not suitable for use with media containing solid particles and high viscosity.

Type

It includes swing-check valves and lift-check valves. The swing-check valve features a hinge mechanism and a valve disc that freely rests against the inclined valve seat surface like a door. To ensure the valve disc reaches the appropriate position on the valve seat each time, the valve disc is designed within the hinge mechanism to provide sufficient swing space and to ensure a true, contacting fit with the valve seat. The valve disc can be made entirely of metal, or it can have leather, rubber, or synthetic overlays inlaid onto the metal, depending on the required performance characteristics. In the fully open condition, the swing-check valve allows fluid pressure to flow almost unhindered, resulting in relatively low pressure drop through the valve.

The swing check valve's disc seat is located on the sealing surface of the valve body's seat. Besides the disc, which can freely rise and fall, the rest of the valve operates like a gate valve; fluid pressure lifts the disc off the seat's sealing surface, and the medium's backflow causes the disc to drop back onto the seat, thus stopping the flow. Depending on operating conditions, the disc can be a full metal structure or incorporate a rubber pad or ring embedded in the disc bracket, similar to a gate valve. Like a gate valve, the passage through the swing check valve is narrow, resulting in a higher pressure drop compared to a butterfly check valve, and the butterfly check valve experiences minimal flow restriction. Such valves are generally installed horizontally in pipelines.