Three-piece Ball Valve
Working Principle:
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 flat disengages the ball from the valve seat.
The stem continues to lift and interacts with the guide pins in the helical grooves of the stem, preventing the ball from rotating frictionally.
Until it reaches the fully open position, the valve stem is lifted to the limit position, and the ball rotates to the fully open position.
2. Shutdown Process
To close, turn the handwheel clockwise, the stem begins to descend and the ball leaves the seat to begin to rotate.
Continue to turn the handwheel, the valve stem receives the action of the guide pin embedded in the spiral groove, so that the valve stem and the ball rotate 90° at the same time.
Just before closing, the ball has rotated 90° without making contact with the valve seat.
During the last few turns of the handwheel, the angular flat at the bottom of the valve stem mechanically wedges the ball to press it tightly against the valve seat to achieve a complete seal.
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