Instrument issue
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How is the interlocking controlled in the diagram?
Isn’t this just a process flow diagram?
Looking at the circuit diagram, in the flow chart the valves are shown with dashed lines; these dashed lines lead to another measuring instrument, such as FV-2000 or FT-2000. This represents a simple control loop, where the flow control valve FT-2000 adjusts its opening based on the settings of FV-2000. Similarly, PV-4104-1 and PV-4104-2 in the diagram constitute a dual-loop control system, with their dashed lines merging together to lead to a pressure transmitter; thus, the two valves adjust their openings according to the pressure signal from this pressure transmitter. As for interlocking, it refers to these two concepts; one needs to look at the interlocking logic diagram. It mainly involves interconnections with the MCC – generally, it’s about the status signals sent from electrical systems to instruments, as well as the analog control signals sent by instruments to electrical systems. Things like how to achieve variable-frequency control of compressors or how to implement emergency shutdowns of compressors can only be understood by examining the design logic diagram.
It’s not a process flow diagram; it’s a PID diagram.