Valve Accessories & Controls' Fail-Freeze Positioner
VAC D400 digital positioner is available with a fail-freeze operation option. This means that, on loss of signal, the unit will freeze the actuator/valve/damper in the last known input signal. Normal positioner operation would be for the positioner to return to its zero position on loss of signal, probably driving the valve/damper open or closed. HART, Foundation fieldbus and Profibus communications protocols are supported.