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Ⅰ. Introduction of plug valves

Plug valve is a quick opening and closing through the valve. Because the movement between the rotary sealing surfaces has the function of wiping, it can completely prevent contact with the flowing medium when fully opened, so it can also be used for the medium with suspended particles. Another important feature is that it is easy to adapt to multi-channel structure, so that one valve can obtain two, three or even four different flow channels. This can simplify the design of the piping system, reduce the consumption of valves and some connecting accessories required in the equipment.

Ⅱ. Classification of plug valves

According to the structural form, it can be divided into four types including tight plug valve, self-sealing plug valve, plug valve and oil filling plug valve. According to the channel form, it can be divided into straight plug valve, three-way plug valve and four-way plug valve. There are also ferrule plug valves. Plug valves are classified by purpose including soft seal plug valve, oil lubricated hard seal plug valve, lifting plug valve, three-way and four-way plug valve.

1. Soft seal plug valves

Soft seal plug valves are often used in harsh environments such as corrosive, highly toxic and high hazard media, where leakage is strictly prohibited, and where valve materials will not pollute the media. According to the working medium, the valve body can be made of carbon steel, alloy steel and stainless steel.

2. Oil lubricated hard seal plug valves

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 conical hole of the valve body and the plug body, then an oil film is formed to reduce the opening and closing torque of the valve, to improve sealing performance and service life. The working pressure can reach 64mpa, the maximum working temperature can reach 325 degrees, and the maximum diameter can reach 600mm.

3. Lifting plug valves

There are many structural forms of lifting plug valve. According to the materials of sealing surface, lifting plug valve is divided into soft seal and hard seal. The basic principle is to raise the cock when it is opened. The friction between the cock and the sealing surface of the valve body can be reduced when the cock rotates 90 degrees to the full opening of the valve; When closing the valve, turn the cock 90 degrees to the closed position and then lower it to contact the sealing surface of the valve body to achieve sealing.

4. Three-way and four-way plug valves

Three-way and four-way plug valves are suitable for fluid reversing, changing medium flow direction or medium distribution. According to the requirements of service conditions, soft seal bushing or soft seal and hard seal lifting plug valve can be selected.

Ⅲ. Advantages of plug valves

1. The plug valve is used for daily operation, which can be opened and closed quickly and easily.

2. The plug valve has small fluid resistance.

3. The plug valve has the advantages of simple structure, small relative volume, light weight and easy maintenance.

4. The plug valve has good sealing performance.

5. The plug valve is not limited by the installation direction and the flow direction of medium can be arbitrary.

6.The plug valve has no vibration and low noise.