Plug valve, a valve that uses a plug body with a through hole as the opening and closing component. The plug body rotates with the valve stem to achieve opening and closing action. A small plug valve without packing is also known as a "cock". The plug body of the plug valve is mostly a conical body (also known as a cylinder), which forms a sealing pair in conjunction with the conical hole surface of the valve body. Plug valve is the earliest type of valve used, with a simple structure, fast opening and closing, and low fluid resistance. Ordinary plug valves rely on direct contact between the precision machined metal plug body and the valve body to seal, resulting in poor sealing performance, high opening and closing force, and easy wear. They are usually only used in low (not higher than 1 MPa) and small diameter (less than 100 mm) applications. In order to expand the application range of plug valves, many new structures have been developed. Oil lubricated plug valves are the most important type. Specially made lubricating grease is injected from the top of the plug body into the conical hole between the valve body and the plug body, forming an oil film to reduce the opening and closing torque, improve 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 millimeters. There are various forms of channels for plug valves. The common through type is mainly used to cut off fluids. Three way and four way plug valves are suitable for fluid reversing. The opening and closing parts of the plug valve are a cylindrical body with holes that rotate around an axis perpendicular to the channel, thus achieving the purpose of opening and closing the channel. Plug valves are mainly used for opening and closing pipelines and equipment media.
The main advantages of plug valves are as follows:
1. Suitable for frequent operation, quick and lightweight opening and closing.
2. Low fluid resistance.
3. Simple structure, relatively small size, light weight, and easy maintenance.
4. Good sealing performance.
5. The flow direction of the medium can be arbitrary without being limited by the installation direction.
6. No vibration, low noise.
7. Plug valves can be divided into four types according to their structural form: tightly set plug valves, self sealing plug valves, packing plug valves, and oil injection plug valves. According to the channel form, it can be divided into three types: straight type, three-way type, and four-way type.
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