“Fail-safe” function

If the electrical supply power fails, the positioner output 1 is

depressurized, and the pneumatic actuator’s return spring

moves the valve to the defined safe position. In case of a

double-acting actuator the second output 2 is additionally pressurized.

Change from two to one column

“Fail-freeze” function

If the electrical supply power fails, the positioner output 1 (and

2. if applicable) is closed and the pneumatic actuator stops

(“freezes”) the valve in the current position. If the compressed

air supply power fails, the positioner depressurizes the actuator.