The plug valve is a quick-opening straight-through valve. Because the movement between the sealing surfaces has a wiping effect, and when fully opened, it can completely prevent contact with the flowing medium, so it can usually also be used for medium with suspended particles. Another important feature is that it is easy to adapt to multi-channel configurations, so that one valve can obtain two, three, or even four different flow channels. This simplifies the design of the piping system, reduces the amount of valves, and some of the connection fittings required in the equipment. A valve that uses a plug body with a through hole as an opening and closing part. The plug body rotates with the valve stem to realize the opening and closing action. Small unpacked plug valves are also known as 'cocks'. The plug body of the plug valve is mostly a cone (also a cylinder), which cooperates with the conical hole surface of the valve body to form a sealing pair. The plug valve is the earliest valve used, with simple structure, rapid switching and small fluid resistance. Ordinary plug valves are sealed by direct contact between the finished metal plug body and the valve body, so the sealing performance is poor, the opening and closing force is large, and it is easy to wear. Usually, it can only be used for low pressure (not higher than 1 MPa) and small diameter (less than 100mm).