What is a P&ID and how does it differ from a PFD?

A Piping and Instrumentation Diagram (P&ID) is a detailed engineering drawing showing all piping, equipment, instrumentation, and control systems. Key differences from PFD: includes all piping (process and utility), shows all valves (manual, control, safety), displays complete instrumentation with tag numbers, includes equipment details (nozzles, internals), shows electrical/signal connections, and uses standardized symbols (ISA). P&IDs are used for construction, operation, and maintenance. They are the primary documents for plant detailed engineering, providing information needed for procurement, installation, and commissioning.