1. Used in important regulating systems with high requirements on regulating quality to improve the positioning accuracy and reliability of regulating valves.

2. Used in occasions where the pressure difference between the two ends of the valve is large (△p>1MPa). Increase the output force of the actuator by increasing the pressure of the gas source to overcome the unbalanced force generated by the liquid on the spool and reduce the travel error.

3. When the regulated medium is high temperature, high pressure, low temperature, toxic, flammable, explosive, in order to prevent external leakage, the packing is often pressed very tightly, so the friction between the valve stem and packing is larger, at this time with the positioner can overcome the time lag.

4. When the regulated medium is viscous fluid or contains solid suspension, the positioner can overcome the resistance of the medium to the movement of the valve stem.

5. Used for large caliber (Dg>100mm) regulating valve to increase the output thrust of the actuator.

6. When the distance between the regulator and the actuator is more than 60m, the positioner can be used to overcome the transmission lag of the control signal and improve the reaction speed of the valve action.

7. Used to improve the flow characteristics of the regulator valve.

8. When a regulator controls two actuators to implement split-range control, two positioners can be used, respectively, to accept the low input signal and high input signal, then an actuator low range action, another high range action, that is, constitutes a split-range regulation.