Electric control valve, normally open type and status indication
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What are the definitions of electric open and electric close types for electric control valves? What are their respective characteristics? How to display the valve stroke in an electric on/off valve control room?
The electric open-type electric control valve means that once the control signal is received, the actuator activates to open the valve; the greater the signal, the wider the opening degree, and the valve remains closed in the absence of a signal； Conversely, it is of the electric-off type, with the valve at its maximum opening when there is no signal. The valve closes when the signal is at its maximum. By connecting the position feedback signal from the control valve to the control room, the valve opening degree can be displayed. The same is true for electric on-off valves.
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Electric control valve: \"Electrically open\" means it is in the closed position when there is no power supply； An electrically closed state means it is in the open position when there is no power ； Choosing which type is more appropriate from a security perspective. It’s just a simple display, which can be achieved using the DI card in the DCS.
For electric actuation structures, when the motor power is lost, the valve remains in its preset position, as the motor on the electric actuator cannot operate without power. Electric actuators generally have valve position feedback contacts, which can be connected to the control room. For other details, see the reply on floor 2; no repetition is needed.