What is the primary purpose of P&ID?

• A. Measures flow rates
• B. Provides scale drawings of piping and instrumentation control systems
• C. List of equipment vendors
• D. A 3D model viewer

Answer: (B)

P&ID is a schematic map of how a process plant’s piping and control elements are connected. It shows the pipes, valves, pumps, tanks, exchangers, and the instruments and control devices that monitor and regulate the process, along with the lines that tie them together. This diagram communicates the design intent for material flow and how the control system interacts with each piece of equipment, so engineers, operators, and maintenance teams can understand interlocks, sequence of operation, and safety requirements. It serves as the primary reference during design, construction, commissioning, and daily operation because it captures where things are located, how they connect, and how the control loops should function. It’s not primarily about measuring flow rates, listing vendors, or presenting a 3D model; those roles belong to other documents or tools.