Plug valve is one of the earliest used valves with simple structure, fast opening and closing and low fluid resistance. Ordinary plug valves are sealed by the direct contact between the finished metal plug body and the valve body, which has the disadvantages of poor sealing, large opening and closing force and easy wear. They can only be used in low (not higher than 1 MPa) and small diameter (less than 100 mm).

In order to expand the application range of plug valve, many new structures have been developed. Oil seal plug valve is the most important one. 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 opening and closing torque and improve the sealing performance and service life. Its working pressure can reach 64 MPa, the maximum working temperature can reach 325℃, and the maximum diameter can reach 600 mm.

The closing part of the plug valve is a cylinder with holes, which rotates around the axis perpendicular to the channel, so as to open and close the channel.

Advantages of plug valve:

1. Easy for frequent operation, quick opening and closing;

2. Low fluid resistance;

3. Simple structure, relatively small volume, light weight and easy maintenance;

4. Good sealing performance;

5. The installation direction is unrestricted, the flow direction of media can be arbitrary;

6. No vibration and low noise.

Classification of plug valves:

1. By structure: tight set plug valve, self-sealing plug valve, pressure balance plug valve and oil seal plug valve;

2. By channel: straight plug valve, three-way plug valve and four-way plug valve.

The channel of plug valve has many forms. The common straight through type is mainly used to cut off the fluid; Three-way and four-way plug valve are suitable for fluid reversing.