The opening and closing part of the valve is a sphere, and in the closed state of a one-piece ball valve, the sphere is pressed on the valve seat by the pressure exerted by the valve stem. When turning the handwheel counterclockwise to open the valve, the valve stem moves in the opposite direction, the ball leaves the valve seat, and starts to rotate under the combined action of the valve stem and the guide pin, until the valve stem rises to the highest position, the valve All open. The principle of closing the valve is the opposite of the principle of opening the valve, which is to turn the handwheel clockwise.