I. floating ball valve ball valve ball valve ball valve ball valve is floating, under the action of medium pressure, the ball can generate a certain displacement and press tightly on the sealing surface of the outlet end to ensure that the outlet end is sealed. The floating ball valve is simple in structure and has good sealing performance. However, the ball bears the load of working medium and all the load of working medium is transferred to the outlet seal ring. This structure is widely used in low and middle pressure ball valves. Fixed ball valve ball valve ball valve ball valves are fixed, after pressure does not move. Fixed ball valve with floating seat, after the medium pressure, the seat moves, so that the sealing ring tightly pressed on the ball to ensure the sealing. Bearings are usually mounted on the upper and lower shafts of the ball with small operating torque for high pressure and large bore valves. In order to reduce the operating torque of ball valve and increase the reliability of sealing, oil seal ball valve has appeared in recent years. It can not only fill special lubricating oil between the sealing cover to form a layer of oil film, which not only enhances the sealing performance, but also reduces the operating torque. It is more suitable for high pressure and large caliber ball valve. The ball of the ball valve is elastic. The ball and seat seal ring are made of metal material, and the sealing pressure is very high. The pressure of the medium itself cannot meet the requirements of sealing, so external force must be applied. This valve is suitable for high temperature and high pressure medium. The elastic sphere is obtained by opening an elastic groove at the lower end of the inner wall of the sphere. When closing the channel, use the wedge of the stem to make the ball open and the seat tight to seal. Before rotating the ball, loosen the wedge head, and the ball will return to its original shape, so that there is a small gap between the ball and the seat, which can reduce the friction and operating torque of the sealing surface. In the closing position, the ball is pressed against the seat by the mechanical /wiki of the stem. When the handwheel is rotated counterclockwise, the stem moves in the opposite direction, and its bottom angular plane disengages the ball from the seat. The stem continues to lift and interact with the guide pin in the screw groove of the stem so that the ball begins to rotate without friction. 4 until fully open, the stem is lifted to the limit position, and the ball rotates to full open position. B. When closing 1, turn the handwheel clockwise, and the stem begins to descend and the ball starts to rotate away from the seat. 2 continue to rotate the handwheel, the valve stem is embedded in the spiral groove on the role of the guide pin, the stem and ball rotate 90 ° at the same time. 3 is close to closing, the sphere has been without contact with the valve seat rotated 90 °. In the last few turns of the handwheel, the angular plane at the bottom of the stem mechanically wedges against the ball, making it tightly pressed against the seat to achieve complete sealing.