What is the function and principle of a check valve?

What is the function and principle of a check valve?

Check valve, also known as non return valve or non check valve, is a device that prevents fluid backflow. Its main function is to prevent fluid backflow in the pipeline, thereby ensuring the normal operation and safety of production equipment. Check valves are widely used in various fields such as chemical, petrochemical, metallurgical, power, tap water, and domestic water supply and drainage.

The principle of check valve is based on the principle of Fluid mechanics. In a fluid, as the velocity of the fluid increases, the kinetic energy of the fluid increases and the pressure decreases. If the flow rate is fast, the pressure can drop below the pressure of the surrounding medium, and a negative pressure area will appear. If the pipeline system is momentarily interrupted due to various reasons, backflow phenomenon will occur. The appearance of check valves is to solve this problem. The main principle is to use a certain mechanism to allow the flow of liquid to pass through under a certain pressure, while being blocked in the other direction.

Generally speaking, the structure of a check valve is divided into the following four parts: main body, piston, spring, and sealing ring.

The main body is equipped with an inlet and an outlet, through which fluid is transmitted. The piston is the core component of a check valve, and there is a sealing device between it and the inlet of the main body. This sealing device can be divided into two types: one-way sealing device and two-way sealing device. The bidirectional sealing device can prevent the medium inside the main body from being extracted by suction, while preventing external impurities from entering the main body, protecting and extending the service life of the piston. Springs are another important part, and common types of springs are tension and compression. The function of a stretching spring is to bear the gravity of the piston and provide it with sufficient rebound force; Compression springs are mainly used to close liquids when they recoil. The sealing ring is one of the simple components in a check valve, which ensures sealing, reduces the flow area, increases sealing effectiveness, and avoids the risk of leakage.

Taking a one-way gate valve as an example, it is a check valve that controls flow through a one-way piston. Its working principle is to control the opening and closing of the valve by utilizing the gravity of the piston itself, as well as the hydrostatic pressure on the inlet pressure, and the difference in pressure between the end and bottom of the piston surface caused by spring force. When the inlet pressure inside the gate valve body is greater than the pressure of the outer fluid, the piston will open and allow the fluid to flow. When the outer pressure is greater than the pressure inside the body, the gate valve will close to prevent reverse flow.

In summary, a check valve is an important pipeline valve that utilizes mechanical principles to achieve the function of fluid flowing only in one direction. Its function is to protect the normal operation of the pipeline system and prevent equipment damage or safety accidents caused by backflow. Its working principle is based on the principle of Fluid mechanics, mainly through the piston, spring, seal ring and other components. The structure of different types of check valves varies, but their working principles are very similar.