The externally threaded ball valve and the flanged gate valve are the same type of valve. The difference is that the closing member is a ball, and the ball rotates around the center line of the valve body to open and close a valve. The ball valve is mainly used in the pipeline to cut, distribute and change the flow direction of the medium. Two-piece ball valve, three-piece ball valve, is a new type of valve that has been widely used in recent years. This valve is generally installed horizontally.
advantage
1. The fluid resistance is small, and its resistance coefficient is equal to the pipe length of the same length.
2. The structure is simple, small in size and light in weight.
3. It is compact and reliable. At present, the sealing surface material of the ball valve is widely used in plastic and has good sealing performance. It has also been widely used in vacuum systems.
4. The operation is convenient, the opening and closing is rapid, and the rotation is 90° from full opening to full closing, which is convenient for long-distance control.
5. The maintenance is convenient, the ball valve has a simple structure, and the sealing ring is generally movable, and the disassembly and replacement are relatively convenient.
6. When fully open or fully closed, the sealing surface of the ball and the valve seat is isolated from the medium, and the medium does not cause erosion of the sealing surface of the valve.
7. Wide range of applications, from small to a few millimeters, up to a few meters, from high vacuum to high pressure can be applied.
Externally threaded ball valves can be divided into straight-through, three-way and right-angle types according to their channel positions. The latter two ball valves are used to distribute the medium and change the direction of the medium.
principle
A, the opening process
1 In the closed position, the ball is pressed by the [wiki] mechanical [/wiki] of the valve stem and pressed against the seat.
2 When the handwheel is turned counterclockwise, the valve stem moves in the opposite direction, and the bottom angular plane causes the ball to disengage from the valve seat.
3 The valve stem continues to lift and interacts with the guide pin in the screw groove of the valve stem, causing the ball to start rotating without friction.
4 Until the fully open position, the stem is raised to the extreme position and the ball is rotated to the fully open position.
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