The function of hand wheel of pneumatic control valve is relatively large. The handwheel mechanism is used together with the regulating valve, and its main uses are as follows:

1. In case of failure of air source signal or electric signal, or damage of main components of actuator, such as diaphragm, spring, seal, transmission parts, etc., automatic operation shall be changed to manual operation, and handwheel mechanism can be used to maintain the regulating function of regulating valve.

2. The handwheel mechanism can also be used as a limiter for regulating valve travel.

3. The handwheel mechanism can improve the operation reliability of the control valve. If a bypass is added to the regulating valve, the investment cost is large, the floor area is large, and the cost is higher when the caliber is large or precious metal is used. It is cost-effective to use the handwheel mechanism in consideration of investment cost or floor area.