Valve refers to a device that controls fluid flow, pressure and flow direction by changing the size of its flow channel. It is a control component in a fluid delivery system. It has diversion, interception, regulation, throttling, prevention of backflow, diversion or overflow discharge Pressure and other functions. The valve relies on a drive or an automatic mechanism to make the opening and closing parts move up and down, sliding, swinging or rotating, thereby changing the size of the flow channel area to achieve its control function. Valves have a relatively high proportion of mechanical products and are indispensable fluid control equipment in various sectors of the national economy such as petroleum, chemical industry, power stations, long-distance pipelines, shipbuilding, nuclear industry, aerospace, and marine oil extraction.

Valves used for fluid control, from the simplest cut-off device to the extremely complex automatic control system, have a wide range of varieties and specifications. The diameter of the valve is as small as a very small instrument valve used in aerospace, as large as a valve for industrial pipelines with a diameter of several meters and weighing more than ten tons; the working pressure can be from vacuum to ultra-high pressure of 1,000Mpa; the working temperature can be From the ultra-low temperature of -269℃ to the high temperature of 1,430℃; the transmission mode can be manual, pneumatic, hydraulic, electric, electric-pneumatic linkage, electric-hydraulic linkage, and even electromagnetic drive, etc.; it can sense in pressure, temperature and other forms Under the action of the signal, it can act according to the predetermined requirements, or simply open or close without relying on the sensor signal; it can be used to control various types of air, water, steam, corrosive chemical media, mud, liquid metal, and radioactive substances. Fluid flow.

My country's valve industry has gone through more than 50 years of development. Before the 1980s, it could only produce more than 600 series of valve products with more than 2,700 specifications. It lacked the ability to design and produce high-parameter, high-tech valves. In order to meet the demand of high-parameter and high-tech valves for the rapid development of industrial and agricultural production in my country, since the early 1980s, my country began to adopt the idea of combining independent development and imported technology to develop valve technology. Some key valve enterprises have increased their technology. With the R&D efforts, there has been a climax of valve introduction technology. Since the 1980s, through the introduction of technology, digestion and absorption combined with independent research and development, my country's valve manufacturing level and product quality have been greatly improved compared with the previous ones. Since the end of the last century, the valve industry has developed faster. Valve manufacturers have grown from small to large. They have made continuous progress in research, development and production. They have produced gate valves, globe valves, throttle valves, ball valves, butterfly valves, and diaphragms. There are 12 categories of valves, plug valves, check valves, safety valves, pressure reducing valves, traps and other valves, with more than 3,000 models and more than 40,000 specifications of valve products. (Test article)