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P&ID’s

What is a Piping and Instrumentation Diagram – P&ID?

Piping and Instrumentation Diagram – P&ID

What is a Piping and Instrumentation Diagram – P&ID?

A Piping and Instrumentation Diagram – P&ID, is a schematic illustration of functional relationship of piping, instrumentation and system equipment components.

P&ID shows all of piping including the physical sequence of branches, reducers, valves, equipment, instrumentation and control interlocks.

The P&ID are used to operate the process system.

A P&ID should include:

Instrumentation and designations

Mechanical equipment with names and numbers

  • All valves and their identifications
  • Process piping, sizes and identification
  • Miscellaneous – vents, drains, special fittings, sampling lines, reducers / size changes
  • Flow directions
  • Interconnections
  • Control inputs and outputs, interlocks


This figure depicts a very small and simplified P&ID:


Series: Piping Training Sections | Previous: PFD’s | Next: Underground Piping Plans

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