Check valve refers to a valve whose opening and closing part is a circular valve disc, which acts by its own weight and medium pressure to block the backflow of the medium. It is an automatic valve, also known as check valve, one-way valve, return valve or isolation valve. The disc movement mode is divided into lift type and swing type. The lift check valve is similar in structure to the globe valve, except that it lacks the valve stem to drive the disc. The medium flows in from the inlet port (lower side) and flows out from the outlet port (upper side). When the inlet pressure is greater than the sum of disc weight and its flow resistance, the valve is opened. Conversely, the valve is closed when the medium flows backwards. The swing check valve has an oblique disc that can rotate around the axis, and its working principle is similar to that of the lift check valve. The check valve is often used as the bottom valve of the pumping device to prevent the backflow of water. The combination of check valve and globe valve can play the role of safety isolation. Check valves belong to the category of automatic valves, and are mainly used on pipelines with one-way flow of medium, and only allow the medium to flow in one direction to prevent accidents.
Check valves are also used on lines that supply auxiliary systems where the pressure may rise above system pressure. Check valves can be mainly divided into swing check valves (rotating according to the center of gravity) and lifting check valves (moving along the axis).
The function of the check valve is to only allow the medium to flow in one direction and prevent the flow in the opposite direction. Usually this kind of valve works automatically. Under the action of fluid pressure flowing in one direction, the valve disc opens; when the fluid flows in the opposite direction, the valve seat is acted on by the fluid pressure and the self-weight of the valve disc to cut off the flow.
Check valves include swing check valves and lift check valves. The swing check valve has a hinge mechanism, and a door-like disc freely leans on the inclined seat surface. In order to ensure that the valve clack can reach the proper position of the seat surface every time, the valve clack is designed in the hinge mechanism, so that the valve clack has enough swing space, and makes the valve clack truly and comprehensively contact with the valve seat. The disc can be made entirely of metal, or it can be inlaid with leather, rubber, or a synthetic covering on the metal, depending on the requirements of performance. When the swing check valve is fully open, the fluid pressure is almost unimpeded, so the pressure drop through the valve is relatively small. The disc of the lift check valve is located on the sealing surface of the valve seat on the valve body. Except that the valve disc can rise and fall freely, the rest of the valve is like a globe valve. The fluid pressure makes the valve disc lift from the sealing surface of the valve seat, and the backflow of the medium causes the valve disc to fall back to the valve seat and cut off the flow. According to the conditions of use, the disc can be of all-metal structure, or in the form of a rubber pad or rubber ring inlaid on the disc frame. Like the stop valve, the passage of fluid through the lift check valve is also narrow, so the pressure drop through the lift check valve is larger than that of the swing check valve, and the flow rate of the swing check valve is limited. rare.
Classification of Check Valves
According to the structure, the check valve can be divided into lift check valve, swing check valve and butterfly check valve. The connection forms of these check valves can be divided into four types: threaded connection, flange connection, welding connection and wafer connection.
According to the material, the check valve can be divided into cast iron check valve, brass check valve, stainless steel check valve, carbon steel check valve and forged steel check valve.
According to the function, the check valve can be divided into DRVZ silent check valve, DRVG silent check valve, NRVR silent check valve, SFCV rubber disc check valve and DDCV double disc check valve.
Post time: Aug-07-2023