Equipment and Instrumentation Codes

P 1 diagrams contain four important pieces of information, namely, all vessels, valves and piping, along with a brief description and identifying specifications of each all sensors, instruments and control devices, along with a brief description of each the control logic used in the process and, finally, additional references where more detailed information can be obtained. 

Information normally excluded from P I diagrams includes electrical wiring (normally separate electrical diagrams must be consulted), nonprocess equipment (e.g., hoist, support structures, foundations, etc.) and scale drawings of individual components. 

Shown on vessel with power pack and control signal 

Wlien denoting instrumentation it is important that definitions be understood clearly. Terms for instruments and controls most often included on P 1 diagrams are given below  

Instrument Loop-A combination of one or more interconnected instruments arranged to measure or control a process variable. 

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