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On the other hand, a Piping and Instrument Diagram (P&ID) is more technical, describing mechanical details for piping designers, electrical engineers, instrument engineers and other technical experts who need this detail more than they need process details. The process flow is usually shown from left to right, and arrows show flow direction. A rectangle is usually used to show a piece of equipment and labels illustrate function. Each block can depict a single piece of equipment or a stage in a process. These are also called Block Flow Diagrams and Schematic Flow Diagrams.
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When the diagram needs to show multiple unit processes at a plant, it becomes more of an overview, containing less detail. Typically, these more detailed items are omitted: Values often will include minimum, normal and maximum. Operational data: Such as pressure, temperature, density, mass flow rate and mass-energy balance.Control valves and process-critical valves.Process piping: Moves the product, usually fluids, between equipment pieces.Examples include compressors, mixers, vessels, pumps, boilers and coolers.
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