In the world of industrial pipelines, valves are like the "throat" that controls the flow of the medium. And gate valves, as the most classic type of shut-off valves among them, with their unique structural design and reliable performance, play a significant role in various fields such as petroleum, chemical industry, power, water supply and drainage. 

Its core function is to achieve "full opening and full closing" of the medium. When the gate plate is completely separated from the valve seat, the medium can pass through without any obstruction; when the gate plate is tightly in contact with the valve seat, a reliable seal can be formed, blocking the flow of the medium. This characteristic of "fully open when open, fully closed when closed" makes it the preferred choice in working conditions where the medium needs to be completely cut off. 

Its working principle is also quite interesting. The opening and closing process is more similar to our intuitive "opening" and "closing" actions. The design philosophy is to use the simplest mechanical movements to achieve the most thorough control of the medium. 

A highly coordinated mechanical system, which is mainly composed of these core components: 

Valve body and valve cover 

This is the main framework of the entire valve. It is usually made of cast steel, stainless steel or alloy steel and is required to withstand the working pressure and temperature of the pipeline system. The interior of the valve body is designed with flow channels, whose diameters are consistent with those of the pipelines, ensuring the minimum resistance for the flow of the medium. 

Blade plate

This is the core component of the opening and closing mechanism, which is divided into two major types: wedge type and parallel type: 

Triangular gate plate: The single gate plate is in the shape of a triangle, while the double gate plates are composed of two symmetrical triangular plates. The sealing performance is enhanced by the wedge angle pressure, and it is suitable for high-temperature and high-pressure working conditions. 

Parallel type gate valve: The gate plate makes parallel contact with the valve seat, achieving sealing by relying on the medium pressure or spring force. It is commonly used in low-pressure large-diameter pipelines. 

Valve stem

This is the transmission component that connects the gate plate with the driving device. It must have sufficient strength and corrosion resistance. At the top of the valve stem, there is a trapezoidal thread which meshes with the handwheel or actuator, converting the rotational motion into the linear up-and-down movement of the gate plate. 

Sealing device 

It consists of two parts: the valve seat sealing ring and the packing chamber. The valve seat sealing ring is usually made of metal hard seal or rubber soft seal to ensure zero leakage during closure; the packing chamber is filled around the valve stem with materials such as graphite and polytetrafluoroethylene to prevent the leakage of the medium along the valve stem. 

Drive device 

When operated manually, it is a handwheel. When controlled automatically, it is an air, electric or hydraulic actuator. The actuator precisely controls the opening degree of the gate by receiving control signals (such as 4-20mA current or air pressure signals).