Flowserve 4 Series Kämmer Pneumatic and Electropneumatic Actuators - Manual (Page 4)

4
Flow Control Division
Kammer Control Valves
5 Method of operation (actuators with integral Kämmer positioner)
5.1 P/P Actuator
The actuator with integrated pneumatic positioner works on the force balance principal, which ensures that the
position of the actuator stem is proportional to the value of the input signal (see figs. 1 and 2).
An increased signal to the double diaphragm assembly creates an unbalanced condition. The pilot valve then
moves to cover the vent, increasing the positioner output pressure to the actuator diaphragm until the forces of
the positioner spring and the double diaphragm are equal. The positioner output is then stabilized at an amount
necessary to maintain the desired valve position.
Signal input Supply To actuator
Vent
Fig. 1: P/P - Positioner