Instrument power off, self-regulating valve position
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If the DCS loses power, it is merely impossible to see the operation screen in the control room; however, the set point of the on-site automatic control valve should remain at its original value. If the power to the on-site distribution cabinet is cut off, what valve position will some of the on-site self-acting valves (pneumatic valves) maintain? Is it open? Is it closed? Keep the original opening? Is the valve position displayed on the DCS screen identical to the actual position of the control valve? This post was last edited by daigf on 2009-2-12 13:25]
The valve shutdown position for FO is OPEN, while the valve shutdown position for FC is CLOSE
Is the self-control regulating valve electric or pneumatic? If it is pneumatic, a dual-pneumatic double-acting actuator can be used to maintain the valve position in the event of a power loss.