The operating logic may be diagrammed to different levels of completeness of information. Whatever the level of completeness, the diagram communicates functional information explicitly to the degree of completeness intended by the diagrammer. The diagram may serve, for example, to improve the interface coordination between a designer of pneumatic circuits, or may simply provide a symbolic functional system description to a plant manager.


To provide a method of logic diagramming of binary interlock and sequencing systems for the start-up, operation, alarm, and shutdown of equipment in the chemical, petroleum, power generation, air conditioning, metal refining, and numerous other industries.

The standard is intended to symbolize the binary control functions of a system in a manner that can be applied to any class of hardware, whether it be electronic, electrical, fluidic, pneumatic, hydraulic, mechanical, manual, optical, or other.


For information about ISA5.2, contact Charley Robinson, ISA Standards.