Silent check valves are valves that automatically open and close their disc based on the flow of the medium itself, used to prevent backflow of the medium. 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 prevent the release of medium in containers. They can also be used on pipelines that supply auxiliary systems where the pressure may rise above the system pressure. Check valves are mainly divided into swing check valves (rotating around a center of gravity) and lift check valves.

The check valve's function is to allow flow in only one direction and prevent reverse flow. Typically, such valves operate automatically, opening the valve plate under the pressure of fluid flowing in one direction; when the fluid flows in the opposite direction, the valve plate is closed by the combined force of the fluid pressure and the weight of the valve plate, thereby 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, like a door, rests freely against the sloped valve seat surface. 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 ensure a true, contacting fit with the valve seat. The valve disc can be entirely made of metal, or it can have leather, rubber, or synthetic coatings 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 across the valve.

The swing check valve's disc seat is located on the valve body's seat sealing surface. This valve, in addition to the disc being freely swingable, the rest operates like a gate valve, with fluid pressure lifting the disc off the seat sealing surface. Medium backflow causes the disc to fall back onto the seat, thereby cutting off the flow. Depending on operating conditions, the disc can be a full metal structure or have a rubber pad or ring embedded in the disc frame. Like a gate valve, the flow channel through the swing check valve is narrow, resulting in a higher pressure drop compared to a lift check valve, and the lift check valve experiences minimal flow restriction. This type of valve should generally be installed horizontally in the pipeline.