Flowserve 4 Series Kämmer Pneumatic and Electropneumatic Actuators - Manual (Page 6)

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Flow Control Division
Kammer Control Valves
5.2 I/P Actuator
The I/P transducer, which is an integral part of the actuator, converts the standard electric signal
(0/4 – 20 mA) into a standard pneumatic signal (0.2 – 1.0 bar) by means of a system of light weight moving
parts. This form of signal conversion is extremely insensitive to shocks. The pneumatic signal is supplied to the
integrated pneumatic positioner.
The pneumatic positioner works on the force balance principal, which ensures that the position of the actuator
diaphragm is always directly proportional to the value of the instrument input signal pressure (see figs. 3 and 4).
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
Fig 3: I/P Positioner
Vent
To actuator
Supply