Knowledge
ISA-88 batch control, explained
ISA-88 (also IEC 61512) is the standard for structuring batch process control. Products that fit existing equipment capabilities can be added as new recipes rather than new control code.
The core idea: separate the recipe from the equipment
In many plants, the "recipe" is buried in PLC code: timers, setpoints and sequence steps written for one product on one vessel. Every new product means new code, new testing and new risk.
ISA-88 separates two things:
- What the equipment can do: fill, heat, agitate, transfer, clean. These are programmed once as tested phases.
- What the product needs: which phases, in what order, with which parameters. That is the recipe, and it is data.
The physical model
| Level | Example in a cheese plant |
|---|---|
| Process cell | Cheese make room |
| Unit | Cheese vat 3 |
| Equipment module | Vat 3 milk-fill assembly coordinating valves and flow measurement to perform a defined filling activity |
| Control module | A single valve, motor or temperature loop |
The procedural model
The procedural control hierarchy is procedure, unit procedure, operation and phase. A unit procedure is a production sequence carried out within a unit; operations organize related processing activities (for example "set and cut"), and phases are the lowest procedural elements (for example "add rennet"). Recipe procedural elements invoke the appropriate equipment procedural control.
Recipe types
- General recipe: an equipment-independent product definition. Site recipe: adapts that definition to a site's conditions and constraints, without specifying the particular process-cell equipment.
- Master recipe: defines how to make a product in a specified process cell, including its formula, procedure and equipment requirements. Approved and version-controlled.
- Control recipe: the batch-specific recipe derived from a master recipe and adjusted as needed for that batch's execution. The batch production record documents what actually occurred.
What it means in practice
- Faster recipe changes. Products that fit existing equipment capabilities can reuse tested phases; new capabilities may still require engineering and testing.
- Consistency. The same phase code runs every product, so a fix or improvement applies everywhere.
- Better records. Batch reports record what ran, when, and with which parameters and materials. Traceability →
- Equipment flexibility. Recipes can run on any suitable unit, so scheduling around maintenance or capacity is easier.
- Cleaner integration. OEM skids built with ISA-88 structure plug into a plant batch system as well-defined units. OEM skids →
ISA-88 in ABB Freelance
Freelance supports controller sequencing and offers Freelance Formulation for recipe parameter management and reporting. More extensive batch applications require a defined batch-management architecture. We confirm software compatibility, equipment allocation, recipe execution and reporting capabilities before specifying the system, and design the unit and phase structure with your process and quality teams. Freelance DCS systems →