“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.

The air flow for pressurizing or depressurizing the actuator is

continuously adjusted. As a result, excellent control is

achieved. When reaching the setpoint, the 3/3-way valve is

closed in center position to minimize the air consumption.

Four different pneumatics versions are available: for single

acting or double-acting actuators, each with “fail-safe” or “fail freeze” function.