The opening and closing parts of the stop valve are plug-shaped disc, the sealing surface is flat or conical, and the disc moves in a straight line along the center line of the fluid. The movement form of the valve rod includes the lifting rod type (the valve rod is lifted and the handwheel is not lifted) and the lifting rotating rod type (the handwheel is rotated and lifted together with the valve rod, and the nut is set on the valve body). The function of stop valve is only applicable to full open and full close, and it is not allowed to regulate and throttle. This is mainly determined by the characteristics of the stop valve, as follows: