How are loop identifiers numbered in a P&ID?
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In ANSI∕ISA-5.1-1984(R1992) Instrument Symbols and Labels, 4.3.1 states that each instrument in a circuit is assigned the same circuit number, and when numbering them sequentially, the first letter is also the same. I would like to ask everyone how to understand this sentence? In a cascade control system, for example, the temperature of the reaction tank controls the flow rate, the flow rate is controlled by a regulating valve – is the temperature identifier TIC001, the flow rate identifier FIC001, and the valve identifier TCV001? But the description states that when using parallel numbering, the first letter is the same; should the flow rate identifier then also be TIC001? Wouldn’t that cause a conflict with the temperature identifier for the reaction tank? I would appreciate it if you could give me some advice. Thank you
In a cascade control system, the flow control loop of the secondary circuit is one identifier, while the temperature control loop of the primary circuit is another loop; the identifiers of these two loops are independent of each other. Take a look at HG/T 20505-2014 \"Functional Indicators and Graphic Symbols for Process Measurement and Control Instruments\".