The working principle of the three-piece ball valve is as follows:

1. Opening process

•  In the closed position, the ball is pressed against the valve seat by the mechanical pressure of the valve stem.
• When the handwheel is turned counterclockwise, the valve stem moves in the opposite direction, and its bottom angular plane makes the ball free from the valve seat.
• The valve stem continues to lift and interacts with the guide pin in the spiral groove of the valve stem, causing the ball to start rotating without friction.
• Until it reaches the fully open position, the valve stem is raised to the limit position and the ball rotates to the fully open position.

2. Closing process

• When closing, turn the handwheel clockwise, the valve stem begins to drop and the ball leaves the valve seat to start rotating.
• Continue to rotate the hand wheel, the valve stem is acted on by the guide pin embedded in the upper spiral groove, so that the valve stem and the ball rotate 90° at the same time.
• When it is about to close, the ball has rotated 90° without contact with the valve seat.
• In the last few turns of the handwheel, the angular plane at the bottom of the valve stem mechanically wedges and presses the sphere, making it tightly pressed on the valve seat to achieve a complete seal.

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