Batch Control.

Batch control is the automation of production that runs as a sequence of phases rather than at a steady state. Charge, mix, react, hold, transfer, clean, each with its own setpoints, alarms, and exit criteria, repeated run after run with the recipe changing between them. It is far broader than its pharma reputation suggests, fermentation, infant formula, brewing, paint and adhesive mixing, polymer reactor cycles, and lubricant blending all fit the pattern and even continuous plants run batch logic during startup, shutdown, and grade transitions. The modern practice is built on ISA-88, which separates the recipe from the equipment so the same recipe runs on different trains and the same train runs different recipes, with the phase logic living in the controller and the recipe living in a batch manager above it. The controller handles the phase execution well. The harder problems sit in the layer above, where recipe authoring, equipment qualification across trains, material genealogy, exception handling, and the operator-action audit trail are what a batch MES is bought to manage. The drawing helps identify which units are batch. They are often explicitly labelled and carry the inventory instrumentation, level, weight, charge metering that steady-flow units do not, and the unit boundaries that ISA-88 turns into equipment modules are frequently drawn on the P&ID. Reading those tags and boundaries cleanly off the set is what gives the batch configuration a correct starting inventory of instruments per unit.