A check valve is a valve in which the switch is a circular valve that prevents the backflow of the medium by producing movement through its own weight and medium pressure. Automatic valves, also known as check valves, return valves, or isolation valves. A typical check valve is as follows.
Both vertical and horizontal. Because the valve shape of the lift check valve is the same as that of the globe valve, the fluid resistance is large. The valve slides along the vertical centerline of the valve body. When the medium is downstream, the valve is opened by the medium thrust, and when the medium stops, the valve falls vertically on the valve.
(1) Vertical lift non return check valve: its medium inlet and outlet channels are in the same direction as the valve channel, and its flow resistance is smaller than that of the straight-through. Vertical lift check valves are installed on vertical pipes.
(2) Linear lift non return check valve: can only be installed on horizontal pipes. Depending on the installation requirements, for small diameters, DN less than 50 is often used.
The valve of the rotary check valve is in the shape of a disc, which rotates around the hinge of the valve channel. Because the passages inside the valve are flow lines, the flow resistance is less than that of lift check valves. It is suitable for small and medium-diameter, low-pressure large-diameter pipelines (low flow rate and large-diameter conditions with infrequent changes in flow). The sealing performance is not as good as the rising type.
(1) Rotary check valves are divided into three types: single, double and half types. These three forms are mainly divided according to the valve diameter, and the purpose is to reduce the hydraulic impact when the medium flows or reverses. Swing check valves are generally suitable for medium-bore situations. When selecting a single rotary check valve for large-diameter pipelines, in order to reduce the hammer pressure, it is recommended to use a slow check valve that can reduce the hammer pressure. Double swing check valve is suitable for medium and large pipelines.
(2) The installation position of the rotary check valve is not limited, and it can be installed on horizontal, vertical or inclined pipelines.
The structure of the butterfly valve is similar to that of the butterfly valve. The structure is simple, the flow resistance is small, and the water hammer pressure is small. A check valve in which the valve rotates around a pin within the valve. The disc check valve has a simple structure and can only be installed on horizontal pipelines with poor sealing performance.
Diaphragm check valves have various structural forms, all of which use diaphragms as switches. Due to its excellent performance, simple structure and low cost, the waterproof hammer has developed rapidly in recent years. However, the operating temperature and pressure of the diaphragm type China check valve are limited by the diaphragm material. Diaphragm check valve is suitable for pipelines that are prone to water hammer. The diaphragm can well eliminate the water hammer that occurs when the medium returns. Generally, low pressure and normal temperature pipelines, especially tap water pipelines, generally have a medium working temperature between -12-120℃. The working pressure is less than 1.6MPa, but the diaphragm check valve can be large in diameter and large in DN.