The turnnion mounted ball valve has a floating valve seat. After being pressurized by the medium, the valve seat moves, so that the sealing ring is tightly pressed on the ball to ensure the sealing. Bearings are usually installed on the upper and lower shafts with the ball, and the operating torque is small, which is suitable for high-pressure and large-diameter valves.

The turnnion mounted ball valve has a floating valve seat. After being pressurized by the medium, the valve seat moves, so that the sealing ring is tightly pressed on the ball to ensure the sealing. Bearings are usually installed on the upper and lower shafts with the ball, and the operating torque is small, which is suitable for high-pressure and large-diameter valves. In order to reduce the operating torque of the ball valve and increase the reliability of the seal, oil-sealed ball valves have appeared in recent years. Special lubricating oil is injected between the sealing surfaces to form an oil film, which not only enhances the sealing performance, but also reduces the operating torque. , more suitable for high-pressure and large-diameter ball valves.
1. Opening process
1. In the closed position, the ball is pressed against the valve seat by the mechanical pressure of the valve stem.

2. When the handwheel is turned counterclockwise, the valve stem moves in the opposite direction, and the angular plane at the bottom makes the ball disengage from the valve seat. 3. The valve stem continues to lift, and interacts with the guide pin in the helical groove of the valve stem, so that the ball starts to rotate without friction. 4. 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. .

Second, the closing process
1. When closing, rotate the handwheel clockwise, the valve stem starts to descend and the ball leaves the valve seat and starts to rotate.
2. Continue to rotate the handwheel, the valve stem is acted by the guide pin embedded in the upper spiral groove, so that the valve stem and the ball rotate 90° at the same time.

3. When it is about to close, the ball has rotated 90° without contacting the valve seat.
4. In the last few laps of the handwheel rotation, the angular plane at the bottom of the valve stem mechanically wedges the ball to press it tightly on the valve seat to achieve complete sealing.