3 Torque of pneumatic ball valve The friction force of pneumatic ball valve depends not only on the working pressure of the medium and the diameter of the valve, but also on the form of the pneumatic ball valve, the structure of the sealing and supporting parts, and the nature of the sealing materials. In addition, in each specific structure, the friction force on the seal seat also depends on the rotation angle of the pneumatic ball valve. Torque acting under normal differential pressure: when the pneumatic ball valve is turned to 30, the maximum value appears, and when it is fully opened, it is zero. In fact, when the pneumatic ball valve is turned to 80, the pressure difference is usually much less than the maximum value. When the pneumatic ball valve is closed, the pressure difference is the largest, which gradually decreases with the increase of its opening degree. Therefore, under the condition of constant pressure, the maximum torque generation turns to 30~40; When. The work of pneumatic ball valve can be divided into two main stages.
(1) From the start of the ball to the opening of the pneumatic ball valve, the ball only acts on the friction force generated by the preload in the sealing element and the static pressure of the working medium.
(2) From the beginning of opening the valve to the stage when the ball hole completely coincides with the valve channel, the friction force generated by the static pressure difference in this stage should be added with the force caused by the liquid or gas medium. With the closing of the valve, the ball will block the through hole, so that the fluid action force on the ball will decrease and the differential pressure will increase.

In addition, when the elbow is installed at the inlet side of the pneumatic butterfly valve, bias flow will be formed, resulting in an increase in torque. When the valve is in the middle opening, the operating mechanism needs to be self-locking due to the action of the hydrodynamic moment.