Glossary · Engineering, integration and validation
Piping and instrumentation diagram (P&ID)
Also known as: P&ID, Process and instrumentation diagram
German: Rohrleitungs- und Instrumentierungsfließschema (R&I-Fließschema)
In process engineering, a piping and instrumentation diagram (P&ID) shows the equipment, piping, valves, instruments and control functions of a process plant with standardized symbols and tag numbers. It is the central engineering document linking process design, instrumentation and automation.
- Validation
- Process industry
- Technical documentation
In one sentence
A P&ID shows the equipment, piping, valves, instruments and control functions of a process plant with standard symbols and tag numbers.
Example
On the P&ID, the level transmitter LT-101 on tank T-100 is connected to the level controller LIC-101, which acts on the control valve LV-101.
How it applies
- Engineering: Instrument and control engineers derive the I/O list, instrument data sheets and control functions from the P&ID. ISO 10628 covers diagrams for the process industry; ANSI/ISA-5.1 defines instrumentation symbols and identification.
- Safety: HAZOP teams review the plant node by node on the P&ID; see Hazard and Operability Study (HAZOP).
- Operation and maintenance: Operators and technicians use P&IDs to understand the process and to plan isolations; the P&ID must reflect the as-built plant.
- Documentation: The documentation team uses P&ID tag numbers consistently in operating instructions and keeps track of the P&ID revision the instructions are based on.
P&ID vs. process flow diagram
A process flow diagram (PFD) shows the main process steps, streams and equipment. The P&ID adds all piping details, valves, instruments and control loops. Data-centric P&IDs stored in an Engineering information model make these links machine-readable.