Glossary · Batch and process operations
ISA-88 procedural model
Also known as: Procedural control model
German: Prozedurmodell nach ISA-88
In ISA-88 batch control, the procedural control model is the hierarchy of procedural elements used to describe how a batch is made: procedure, unit procedure, operation and phase.
- Batch control
- Process industry
- Standards
In one sentence
The ISA-88 procedural model describes how a batch is made as a hierarchy of procedure, unit procedure, operation and phase.
Example
The procedure for producing a coating consists of the unit procedures "premix" and "disperse", each broken down into operations and phases such as "charge solvent".
How it applies
- Engineering: The procedural model separates recipe knowledge (what to do) from equipment control (how the equipment does it), so recipes can change without reprogramming equipment.
- Operation: Batch systems show progress through the hierarchy, and operators can hold, restart or abort at defined levels.
- Recipe management: Recipes use the same levels, as Recipe procedure, Recipe unit procedure, Recipe operation and Recipe phase.
- Documentation: The documentation team can mirror the hierarchy in process descriptions and SOPs. Using the ISA-88 terms consistently avoids confusion between "operation" in the ISA-88 sense and everyday language.
Procedural model vs. physical model
The procedural model describes actions; the ISA-88 physical model describes equipment. A unit procedure runs on one unit, and a phase is carried out by an equipment entity such as an Equipment module (ISA-88).