Lockup valves are used as an accessory to modulating pneumatic actuators when it is functionally desirable for them to “fail in place” or “fail last POSTTTION”. They function in response to a pneumatic control signal. When the signal is present, the lockup valve is open and allows the free flow of compressed air from the POSTTTIONer to the pneumatic actuator. When the lockup valve loses its signal (or it drops below an adjustable set point), the lockup valve closes and prevents the flow of air into or out of the actuator, thereby “locking” the actuated valve assembly in place. When the control signal returns, the valve will reopen. With the use of accessory solenoid valves the system can be configured to lock in POSTTTION on loss of electrical power as well.
Lockup Valves
