Instrument and Process Equipment Symbols

Chapter 9 - Control and Instrumentation Documentation

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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