Process & Instrumentation Diagram (P&ID)

A process and instrumentation diagram, also known as a P&ID, is a technical drawing of a process.  It uses graphical symbols for equipment and piping together with graphical symbols for process measurement and control functions.  A P&ID’s information typically spans multiple engineering disciplines and is a pictorial representation of piping and instrument details, safety and regulatory requirements, start-up and operational information, as well as control and shutdown schemes.

P&ID’s include the following information:

• Permanent start-up and flush lines
• Flow directions and interconnection references
• Control inputs, outputs, interlocks and control system input
• Interfaces for class changes
• Identification of components and subsystems
• Instrumentation and designations
• Mechanical equipment with names and numbers
• All valves and identifications
• Process piping, sizes and identifications