Glossary · Batch and process operations
Unit (ISA-88)
Also known as: Batch unit
German: Teilanlage
In ISA-88 batch control, a unit is a collection of associated control modules, equipment modules and other process equipment in which one or more major processing activities, such as reacting, crystallizing or mixing, can be conducted. A unit typically operates on only one batch at a time.
- Batch control
- Process industry
- Standards
In one sentence
In ISA-88, a unit is equipment in which major processing activities such as reacting or mixing are carried out, usually on one batch at a time.
Example
Reactor R-201 with its agitator, jacket heating and dosing equipment forms one unit; the batch system allocates it to one batch at a time.
How it applies
- Engineering: The unit is the central object of batch control: unit procedures run on units, and equipment and control modules are organized under them.
- Operation: Units are allocated to batches; a unit's state (available, in use, being cleaned) matters for scheduling.
- Maintenance: Maintenance work is often planned per unit, fitting into gaps between batches.
- Documentation: Plant manuals usually describe each unit with its purpose, equipment, capacities, phases offered and operating limits. Because "unit" is ambiguous, documentation should make the ISA-88 meaning clear and never mix it with Engineering units or units of measure.
Unit vs. equipment module
A unit carries out major processing activities and holds the batch. An Equipment module (ISA-88) performs minor activities, such as dosing, within or shared among units.