The plug valve is a rotary valve in the shape of a closing member or a plunger. By rotating 90 degrees, the channel port on the valve plug is the same as or separated from the channel port on the valve body, so as to realize the opening or closing of a valve. The shape of the plug of the plug valve can be cylindrical or conical. In cylindrical valve plugs, the passages are generally rectangular; in conical valve plugs, the passages are trapezoidal. These shapes make the structure of the plug valve light, but at the same time, it also produces a certain loss. Plug valves are best suited for shut-off and on-media and diverting applications, but may also be used for throttling depending on the nature of the application and the erosion resistance of the sealing surface. Turn the plug clockwise to make the groove parallel to the pipe to open, and turn the plug 90 degrees counterclockwise to make the groove perpendicular to the pipe to close.
Main classification of plug valve
1. Tightened plug valve
Tight-type plug valves are usually used for low-pressure straight-through pipelines. The sealing performance depends entirely on the fit between the plug and the plug body. The compression of the sealing surface is achieved by tightening the lower nut. Generally used for PN≤0.6Mpa.
2. Packing plug valve
The packing type plug valve is sealed by the plug and the plug body by compressing the packing. Due to the packing, the sealing performance is better. Usually this kind of plug valve has a packing gland, and the plug does not need to protrude from the valve body, thus reducing a leakage path of the working medium. This kind of plug valve is widely used for the pressure of PN≤1Mpa.
3. Self-sealing plug valve
The self-sealing plug valve realizes the compression seal between the plug and the plug body through the pressure of the medium itself. The small head of the plug protrudes upwards from the body, and the medium enters the large head of the plug through the small hole at the inlet, and the plug is pressed upwards. This structure is generally used for air media.
4. Oil-sealed plug valve
In recent years, the application range of plug valves has been continuously expanded, and oil-sealed plug valves with forced lubrication have appeared. Due to the forced lubrication, an oil film is formed between the sealing surface of the plug and the plug body. In this way, the sealing performance is better, the opening and closing is labor-saving, and the sealing surface is prevented from being damaged.