Three-piece ball valve works as follows: First, the opening process 1 In the closed position, the ball by the stem of the [wiki] mechanical pressure, squeezed on the seat. 2 When turning the handwheel counterclockwise, the stem moves backwards and the bottom angled plane disengages the ball from the seat. 3 The stem continues to lift and interact with the guide pin in the helical groove of the stem to allow the ball to start spinning without friction. 4 until it reaches the fully open position, the stem lifted to the limit position, the ball rotates to the fully open position. Second, the closure process 1 When closed, clockwise hand wheel, stem began to decline and the ball left the seat began to rotate. 2 Continue to rotate the handwheel. The stem is guided by the guide pin embedded in the spiral groove on it, causing the stem and sphere to rotate 90 ° at a time. 3 When it is about to close, the ball has rotated 90 ° without contact with the seat. 4 In the last few turns of the handwheel, the angled plane at the bottom of the stem mechanically wedges the ball to press it tightly against the seat to achieve a complete seal. More Search Keywords: Ball Valve