What Is ISA-88? A Plain-English Guide to Batch Automation Standards
Waleed Khalid
Industrial Automation Specialist
ISA-88 is a framework for organizing batch manufacturing controls. Its central idea is straightforward: describe what the equipment can do separately from the recipe that tells the equipment what product to make. That separation makes applications easier to reuse, test, operate, and extend.
The Physical Model Describes the Plant
The physical model arranges the process from enterprise and site down to areas, process cells, units, equipment modules, and control modules. In practical PLC terms, a unit might be a mixer, an equipment module might manage ingredient transfer, and control modules operate individual valves, motors, or instruments.
The Procedural Model Describes the Work
Procedures, unit procedures, operations, and phases describe how production is carried out. A phase is normally the smallest procedural element that directly commands equipment, such as add water, heat, agitate, or transfer. Higher levels coordinate those phases into a complete batch.
Recipes Supply Product-Specific Instructions
The recipe defines the procedure, formula values, equipment requirements, and other information needed to make a product. Because recipe parameters are separated from equipment logic, the same tested phase can serve many products with different quantities, temperatures, speeds, and timing values.
ISA-88 Is Not a Required Code Template
The standard does not prescribe one PLC language, one vendor platform, or one exact folder structure. A project can claim ISA-88 alignment only when the underlying separation of equipment, procedure, and recipe is meaningful. Renaming ordinary routines as phases without changing architecture does not provide the benefits of the model.
What EPCs Should Ask a Batch Subcontractor
Ask the engineer to explain the proposed physical model, phase interface, state handling, recipe parameters, exception recovery, batch records, and testing strategy. The explanation should connect directly to the process and operator workflow rather than relying on standards terminology alone.
