The working principle and structural characteristics of the American standard ball valve

The American standard ball valve and the flange 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.

working 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.

B, the closing process

1 When closing, turn the handwheel clockwise, the valve stem begins to lower and the ball moves away from the seat.

2 Continue to rotate the hand wheel. The valve stem is subjected to the guide pin embedded in the upper spiral groove, so that the valve stem and the ball rotate at 90° at the same 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 angular plane at the bottom of the valve stem mechanically wedges against the ball, causing it to press tightly against the valve seat for a complete seal.

Structural features

1. Open and close without friction. This feature completely solves the problem that the traditional [wiki] valve [/wiki] affects the seal due to friction between the sealing faces.

2. Top-loading structure. The valve installed on the pipeline can be directly inspected and repaired online, which can effectively reduce the parking of the device and reduce the cost.

3. Single seat design. It eliminates the problem that the cavity medium in the valve affects the safety of use due to abnormal boosting.

4. Low torque design. The specially designed valve stem can be easily opened and closed with a small handle.

5. Wedge seal structure. The valve is based on the mechanical force provided by the valve stem, and the ball wedge is pressed onto the valve seat to seal, so that the sealing property of the valve is not affected by the change of the pressure difference of the pipeline, and the sealing performance is reliably guaranteed under various working conditions.

6. Self-cleaning structure of the sealing surface. When the ball is tilted away from the valve seat, the fluid in the pipeline passes through the spherical sealing surface at 360°, which not only eliminates the high-speed fluid scouring on the valve seat, but also washes away the accumulation on the sealing surface to achieve self-cleaning. .

In order to reduce the operating torque of the ball valve and increase the reliability of the seal, an oil seal ball valve has appeared, which injects a special lubricating oil between the sealing faces to form an oil film, which enhances the sealing performance and reduces the operating torque. Suitable for high pressure and large diameter ball valves.

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