The meaning of valve markings
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Hello, experts. In the PID diagram, I see the letters I, S, A, and 22 marked next to the valve, as shown in the image below. What do these mean? ? Anyone who knows something about this, please give some advice! ! ! Thank you! ! My understanding is that I,S,A mean the valve should have display, position feedback, and alarm functions; I’m not sure if this is correct. As for 22, I’m not aware of what it means.
I indicates or interlocks with alarm A; S relates to interlocks or solenoids – check the legends in the earlier diagrams of the design process
Your understanding is basically correct: I stands for Indicator, S stands for Switch (usually referring to a position feedback switch), and A stands for Alarm. As for \"22\", this number may be a specific identifier corresponding to a particular item or drawing; its exact meaning needs to be understood in light of the standards applicable to your project or the annotations provided in the drawings. .
There is no legend; it can be referred to together with the data table and interlock diagram