The appearance of a ball valve was after the Second World War. Although the invention of a ball valve dates back to the early 20th century, this structural patent failed to complete its commercialization steps due to limitations in the materials industry and the mechanical processing industry. DuPont in the United States invented a high polymer material polytetrafluoroethylene (PTFE) plastic until 1943. This kind of material has advantages of sufficient tensile and compressive strength, certain elastoplasticity, good self-lubricating properties and excellent corrosion resistance, which is very suitable as a sealing material and has very reliable sealing effect. In addition, a ball with high roundness and good surface finish can be manufactured as a closure member of a ball valve due to the development of ball grinding machines. A new type of valve with full bore and 90° rotatory angular travel enters the valve market, drawing much attention. Traditional valve products such as stop valves, gate valves, plug valves and butterfly valves are gradually replaced by ball valves, and ball valves are greatly used, ranging from small diameters to large diameters, low pressure to high pressure, normal temperature to high temperature, high temperature to low temperature. At present, the maximum diameter of the ball valve has reached 60 Inch, and the lowest temperature can reach liquid hydrogen temperature -254℃.The highest temperature can reach from 850 to 900℃. All of these make ball valves suitable for all kinds of media, which become the most promising type of valve.
Ball valves can be divided into floating ball valves and trunnion ball valves based on structure.
Ball valves can be classified into top entry ball valves and side entry ball valves. Side entry ball valves can also be divided into one piece ball valves, two-piece ball valves and three-piece ball valves according to the structure of the valve body. One piece ball valves' valve bodies are integral; two-piece ball valves consist of main valve bodies and auxiliary valve bodies and three-piece ball valves are composed of one main valve body and two auxiliary valve bodies.