Check valve

A check valve refers to a type of valve with a circular valve disc as the opening and closing component, which acts to block the backflow of the medium by its own weight and medium pressure. It belongs to the category of automatic valves, also known as check valves, one-way valves, reflux valves, or isolation valves. The valve disc movement modes are divided into lifting and swing types. The lifting check valve has a similar structure to a globe valve, except for the valve stem that drives the valve disc. The medium flows in from the incoming end (lower side) and out from the outgoing end (upper side). When the purchase pressure is greater than the sum of the weight of the valve disc and its flow resistance, the valve is opened. On the contrary, when the medium flows back, the valve closes. A swing check valve has a disc that is inclined and can rotate around the shaft, and its working principle is similar to that of a lift check valve. Check valves are commonly used as bottom valves in pumping devices to prevent water backflow. The combination of check valve and globe valve can provide safe isolation. The disadvantage is high resistance and poor sealing when closed

Working principle:

Check valves can also be used to supply pipelines to auxiliary systems whose pressure may rise above the system pressure.

. Check valves can be mainly divided into swing check valves (rotating according to the center of gravity) and lift check valves (moving along the axis)The function of check valves of this type is to only allow the medium to flow in one direction and prevent flow in the opposite direction. Usually, this type of valve operates automatically, and under the pressure of fluid flowing in one direction, the valve disc opens; When the fluid flows in the opposite direction, the valve seat is cut off by the fluid pressure and the self weight of the valve disc, which acts on the valve seatAmong them, check valves belong to this type of valve, which includes swing check valves and lift check valves. The swing check valve has a hinge mechanism and a valve disc that is like a door, freely leaning against the inclined valve seat surface. In order to ensure that the valve disc can reach the appropriate position on the valve seat surface every time, the valve disc is designed in a hinge mechanism, so that the valve disc has sufficient swing space and makes good and complete contact with the valve seat. The valve disc can be made entirely of metal, or it can be embedded with leather, rubber, or synthetic covering on the metal, depending on the performance requirements. When the swing check valve is fully open, the fluid pressure is almost unobstructed, 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 for the valve disc, which can be freely raised and lowered, the rest of the valve is like a globe valve. Fluid pressure lifts the valve disc from the sealing surface of the valve seat, and the medium reflux causes the valve disc to fall back onto the valve seat, cutting off flow. According to the usage conditions, the valve disc can be an all metal structure, or it can be in the form of a rubber pad or rubber ring embedded on the valve disc holder. Like globe valves, the passage of fluid through lift check valves is also narrow, so the pressure drop through lift check valves is greater than that of swing check valves, and the flow rate of swing check valves is limited very little