Working principles of different types of valves

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Valves are control components in fluid transportation systems, with functions such as shutting off flow, regulating it, directing it, preventing backflow, stabilizing pressure, and splitting flow. Valves used in fluid control systems range from the simplest globe valves to a wide variety of valves employed in highly complex automated systems; there is a great diversity in terms of types and specifications. Different types of valves have significant differences in their working principles. The ball valve was invented in the 1950s. With the rapid advancement of science and technology and continuous improvements in manufacturing processes and product design, it has rapidly developed into a major type of valve within just 40 years. Ball valves are primarily used in pipelines to shut off flow, distribute fluid, and change the direction of flow; they can be closed tightly with just a 90-degree rotation and a very small torque. A globe valve controls the degree of opening by the upward and downward movement of a circular valve core. A globe valve, also known as a stop valve, is one of the most widely used types of valves; therefore, when the valve is closed, pressure must be applied to the valve disc in order to ensure that the sealing surfaces do not leak. When the medium enters the valve from below the valve disc, the resistance that the operating force must overcome consists of the friction between the valve stem and the packing, as well as the thrust generated by the pressure of the medium. The force required to close the valve is greater than that needed to open it; therefore, the diameter of the valve stem must be large, otherwise the valve stem may bend. A butterfly valve, also known as a flap valve, is a type of regulation valve with a simple structure. It can be used for controlling the flow of media in low-pressure pipelines. In this type of valve, the closing element is a disc that rotates around the valve shaft to enable opening and closing. Such valves can be used to control the flow of various types of fluids, including air, water, steam, various corrosive substances, mud, oils, liquid metals, and radioactive materials. It mainly serves to cut off and throttle flow in pipelines. The operating element of a butterfly valve is a disc-shaped butterfly plate that rotates around its own axis within the valve body, thereby achieving the purpose of opening, closing, or regulating flow. The butterfly plate is driven by the valve stem; turning it 90° completes one cycle of opening and closing. By changing the deflection angle of the butterfly valve, the flow rate of the medium can be controlled