Air on/off valve
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How to determine the forward and reverse effects of fault open/fault close based on process drawings
Determine the forward and reverse action sequence of the regulator: first, determine whether the control valve should operate in an air-open or air-close mode based on principles such as process safety; then, determine its forward and reverse action according to the characteristics of the process being controlled； Finally, the positive or negative action mode of the regulator is determined based on the principle that the product of the polarities of the static gain coefficients of the various components that make up the system must be positive. Generally speaking: for positive action, the set value is higher than a certain threshold; under normal conditions the output is 0, which means that the valve is usually closed (or open), while reverse action is the opposite of positive action
We use the two brands, Yamaki and Xuzhou Aka
Generally, the drawings indicate this as follows: FO stands for \"open in an emergency situation\", that is, it is a wind-shut valve which closes when there is wind and opens when there is no wind； FC means shut in an accident condition, that is, the wind-operated valve opens when there is wind and closes when there is no wind.
How can I tell on the DCS panel whether the valve is open or closed?
It is mainly determined based on the interlock logic