In the closed position, the ball is pressed tightly on the valve seat by the mechanical pressure of the valve stem. When the hand wheel is turned counterclockwise, the valve rod moves in the opposite direction, and the angular plane at the bottom makes the ball disengage from the valve seat. The valve rod continues to lift and interacts with the guide pin in the spiral groove of the valve rod, so that the ball begins to rotate without friction. Until it reaches the full open position, the valve rod is lifted to the limit position, and the ball rotates to the full open position.
When closing, rotate the hand wheel clockwise, and the valve rod begins to drop and make the ball leave the valve seat and start to rotate. Continue to rotate the handwheel, and the valve rod is affected by the guide pin embedded in the spiral groove on it, so that the valve rod and the ball rotate 90 ° at the same time. When it was about to close, the ball had rotated 90 ° without contact with the valve seat.
During the last few turns of the hand wheel, the angular plane at the bottom of the valve rod mechanically wedges the ball to make it tightly press on the valve seat to achieve complete sealing.