Introduction To Print ReadingDOE-HDBK-1016/1-93INTRODUCTION TO THE TYPESOF DRAWINGS, VIEWS, AND PERSPECTIVESAs a rule P&IDs do not have a drawing scale and present only the relationship or sequencebetween components. Just because two pieces of equipment are drawn next to each other doesnot indicate that in the plant the equipment is even in the same building; it is just the next partor piece of the system. These drawings only present information on how a system functions, notthe actual physical relationships.Because P&IDs provide the most concise format for how a system should function, they are usedextensively in the operation, repair, and modification of the plant. ElectricalSingleLinesand SchematicsElectrical single lines andFigure 7 Example of a Single Lineschematics are designed topresent functional informationabout the electrical design of asystem or component. Theyprovide the same types ofinformation about electricalsystems that P&IDs providefor piping and instrumentsystems. Like P&IDs,electrical prints are not usuallydrawn to scale. Examples oftypical single lines are site orbuilding power distribution,system power distribution, andmotor control centers.Figure 7 is an example of anelectrical single line. Electrical schematics provide amore detailed level ofinformation about an electricalsystem or component than thesingle lines. Electricalschematic drawings presentinformation such as the individual relays, relay contacts, fuses, motors, lights, and instrumentsensors. Examples of typical schematics are valve actuating circuits, motor start circuits, andbreaker circuits.Rev. 0PR-01Page 11
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