The plug body rotates with the valve stem to achieve the opening and closing action. Small plug valves without fillers are also called plug valves "cocks". The plug body of the plug valve is mostly a cone (also a cylinder), which cooperates with the conical hole surface of the valve body to form a sealing pair. The plug valve is the earliest type of valve used, with a simple structure, fast switching, and low fluid resistance. Ordinary plug valves rely on the direct contact between the precision-machined metal plug body and the valve body to seal, so the sealing performance is poor, the opening and closing force is large, and it is easy to wear. It can usually only be used in low (not higher than 1 MPa) and small-caliber (less than 100 mm) occasions.
