Vol. Measurement
Chapter Control and Instrumentation Documentation

Instrument and Process Equipment Symbols

This section shows some of the many instrument symbols found in different types of technical diagrams used to document instrument systems.

Line types

Note: the single backslash signifying a “discrete” or “binary” signal type has been removed from the ISA standard as of the 2009 ANSI publication. Regular pneumatic and electrical line symbols may represent either continuous or discrete states. The “triple-slash” alternative linetype for electrical symbols is also absent from the 2009 ANSI/ISA standard.

Process/Instrument line connections

Instrument bubbles

Process valve types

Valve actuator types

Valve failure mode

Liquid level measurement devices

Flow measurement devices (flowing left-to-right)

Process equipment

Functional diagram symbols

Single-line electrical diagram symbols

Fluid power diagram symbols