100 Most Important P&ID Symbols Explained | Meanings & Examples
Last reviewed: 2026-10-07. For educational use only; not a substitute for approved site procedures. Table of Contents What Are P&ID Symbols and Why They Matter Before You Start: Standards, Legends and Why Symbols Vary Lines and Connections (Symbols 1–8) Manual and Isolation Valves (9–20) Control Valves and Actuators (21–28) Pumps (29–33) Compressors, Blowers and Drivers (34–38) Vessels, Tanks and Columns (39–45) Heat Transfer Equipment (46–50) Instrument Bubbles (51–56) Instrument Identification: Reading the Tag (57–64) Primary Elements and Sensors (65–70) Control Loop Functions (71–76) Safety and Relief Devices (77–88) Piping Specialties and Drawing Conventions (89–100) How to Read a Simple P&ID Common Mistakes Quick-Reference Cheat Sheet FAQ Key Takeaways References and Source Notes P&ID symbols are the visual language of a piping and instrumentation diagram . They show how process equipment, piping, valves, instruments, control functions, and signal connections r...