The plug valve is a kind of quick-switch straight-through valve. Because the movement between the sealing surfaces has a wiping effect, and can completely prevent the contact with the flowing medium when it is fully opened, it can usually also be used for the 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. According to the structure, it can be divided into four types: tight plug valve, self-sealing plug valve, plug valve and oil-filled plug valve. According to the channel form, it can be divided into three types: straight-through plug valve, three-way plug valve and four-way plug valve. There are also cartridge-type plug valves. The plug valves are classified according to their uses: soft sealing plug valves, oil lubricated hard sealing plug valves, poppet plug valves, three-way and four-way plug valves. Soft seal Soft seal plug valve is often used in harsh environments such as corrosive, highly toxic and highly hazardous media, where leakage is strictly prohibited, and where the valve material will not pollute the medium. The valve body can be made of carbon steel, alloy steel and stainless steel according to the working medium. Oil-lubricated hard-seal oil-lubricated hard-seal plug valves can be divided into conventional oil-lubricated plug valves and pressure-balanced plug valves. Special grease is injected from the top of the plug body between the taper hole of the valve body and the plug body to form an oil film to reduce the valve opening and closing torque and improve the sealing performance and service life. Its working pressure can reach 64MPa, the maximum working temperature can reach 325 degrees, and the maximum diameter can reach 600mm. Lifting type Lifting plug valve has various structural forms. Lifting plug valve is divided into soft seal and hard seal according to the material of the sealing surface. The basic principle is to make the cock rise when it is opened, and then turn the cock 90 degrees until the valve is fully opened, which can reduce the friction with the sealing surface of the valve body; when the valve is closed, turn the cock 90 degrees to the closed position and then descend to seal with the valve body. Face contact to achieve sealing. Three-way and four-way type The three-way and four-way plug valve are suitable for the occasion of changing the flow direction of the medium or distributing the medium in the Shanghai plant. According to the requirements of the working conditions, you can choose a soft-seal bushing or a soft-seal, hard-seal poppet valve.