Greenheck El-O-Matic E and P Series - Manual (Page 4)

Operating Principles
2.
The Posiflex F10 Pneumatic Positioner is a high
gain, motion balance instrument, suitable for use
with a wide variety of single acting and double
acting rotary and linear actuators.
Referring to the diagram below: The positioner is
shown in a mid position with INSTRUMENT and
SUPPLY air connected. The flapper and nozzle (5)
maintains the instrument in it’s “balanced” state
with just enough pilot air pressure being applied to
the spool valve for it to hold the actuator in it’s “set”
position.
When the actuator is required to move to a new
“more open” position, the INSTRUMENT pressure
signal is increased accordingly. This closes the air
gap at the nozzle (5) causing an amplified pressure
increase at the spool valve end, this in turn dis-
places the spool and allowing an increasing air
pressure at the “open” side of the actuator and
exhausting air from the “close” side.
When the actuator moves position it rotates the
cam (6) in a CCW (counter clockwise) direction
and in doing so it progressively opens the air gap
at the nozzle (5). On reaching the new set point the
pilot pressure is reduced to the “balanced” state
and again locks the actuator in new set position.
Similarly a decreasing INSTRUMENT pressure will
cause a CW (clockwise) positioner movement.
The operation for single acting actuators is the
same except that the unused pneumatic connection
OUTPUT 2 is plugged off.
1. Balance assembly.
2. Pneumatic valve block.
3. Actuator.
4. Mechanical feedback.
5. Flapper and nozzle.
6. Cam.
Output
Supply
Instrument 6
1
2
5
3
4
Close
Open