The check valve refers to a valve whose opening and closing part is a circular disc and acts by its own weight and medium pressure to block the backflow of the medium. It is an automatic valve, also known as a check valve, a one-way valve, a return valve, or an isolation valve. The movement mode of the valve disc 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 that drives the valve disc. The medium flows in from the inlet end (lower side) and flows out from the outlet end (upper side). When the inlet pressure is greater than the sum of the weight of the disc and its flow resistance, the valve is opened. Conversely, the valve is closed when the medium flows back. The swing check valve has a disc that is inclined and can rotate around the axis, and the working principle is similar to that of the lift check valve.
It can prevent the flow of many kinds of media such as water and water vapor. The main materials are metal materials such as carbon steel and low-temperature steel. Its main feature is that the valve disc closes quickly, the period of use is relatively long, and the performance is more reliable.
The check valve is often used as the bottom valve of the pumping device, which can prevent the backflow of water. The check valve is used in combination with the globe valve, which can play the role of safety isolation. The disadvantage is that the resistance is large and the sealing is poor when closed
According to the structure, it can be divided into three types: lift check valve, swing check valve, and butterfly check valve. Among them, the lift check valve is divided into two types: vertical and horizontal. The swing check valve is divided into three types: single-lobe type, double-lobe type, and multi-lobe type, while the butterfly check valve is a straight-through type.
The above types of check valves can be divided into four types: threaded connection, flange connection, welded connection, and wafer connection.