Selection and analysis of pneumatic actuator for ball valve

Ball valve has the advantages of small flow resistance, quick opening and closing and easy pigging, which makes it widely used in oil, natural gas and other industries. When the ball valve is closed, it is completely sealed by the medium force without the forced sealing force exerted by the driving mechanism. However, the operating torque of the ball valve is large, especially when the valve is opened under full differential pressure. For ball valves ≥ DN 100, worm gear transmission device is generally used, and intelligent control is widely used in modern factories.

Pneumatic transmission has the characteristics of fast action, simple control and reliable operation, so pneumatic ball valve is widely used by piping engineers in process industry. The pneumatic actuator used in ball valve has a variety of structures. The selection of pneumatic actuator is mainly based on the matching principle of dynamic torque characteristics of ball valve and output torque characteristics of pneumatic actuator.

According to the analysis, the operation torque of the ball valve at the starting point and closing point is the maximum. Through the comparison between the opening and closing torque of a certain type of ball valve and the output torque of various pneumatic actuators, it can be seen that when the fork type pneumatic actuator acts, the output torque can change with the change of angle, and the maximum torque value can be obtained at the opening and closing position of the valve, which is consistent with the dynamic torque characteristics of the ball valve, so the fork type pneumatic actuator is the most ideal Pneumatic driving device for ball valve. For small diameter and low pressure ball valves, the built-in fork type pneumatic actuator can be selected, while for large diameter and high pressure ball valves, the external fork type pneumatic actuator can be selected.