Plug valve (plugvalve), a valve with 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. The small unfilled plug valve is also called "Cock". The plug body of the plug valve is mostly a cone (also a cylinder), which cooperates with the cone hole surface of the valve body to form a sealing pair. The plug valve is the earliest valve used, with simple structure, rapid opening and closing, and low fluid resistance. Ordinary plug valves are sealed by the direct contact between the finely machined 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. Generally, it can only be used for low (not higher than 1 MPa) and small Caliber (less than 100 mm) occasions. In order to expand the application range of plug valves, many new structures have been developed. The oil-lubricated plug valve is the most important one. Special grease is injected from the top of the plug body between the cone 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 passage of the plug valve has many forms. The common straight-through type is mainly used to cut off the fluid. Three-way and four-way plug valves are suitable for fluid reversing plug valves. The opening and closing part of the plug valve is a cylindrical body with a hole that rotates around an axis perpendicular to the channel to achieve the purpose of opening and closing the channel. The plug valve is mainly used for opening and closing pipelines and equipment media.
The main advantages of the plug valve are as follows:
1. It is suitable for frequent operation, opening and closing quickly and lightly.
2. The fluid resistance is small.
3. Simple structure, relatively small size, light weight and easy maintenance.
4. Good sealing performance.
5. It is not restricted by the installation direction, and the flow direction of the medium can be arbitrary.
6. No vibration and low noise.
7. According to the structure, the plug valve can be divided into four types: tight plug valve, self-sealing plug valve, packing plug valve and oil injection plug valve. According to the channel form, it can be divided into three types: straight-through, three-way and four-way.