Glossary · Batch and process operations
Phase (ISA-88)
Also known as: Equipment phase
German: Phase
In ISA-88 batch control, a phase is the lowest level of procedural element in the procedural control model. It carries out a process-oriented action, such as dosing, heating or agitating, and may be subdivided into steps and transitions.
- Batch control
- Process industry
- Standards
In one sentence
In ISA-88, a phase is the lowest procedural element and carries out one process-oriented action, such as dosing, heating or agitating.
Example
The phase "heat" receives the target temperature and ramp rate as parameters and reports the reached temperature and duration back to the batch system.
How it applies
- Engineering: Equipment phases are implemented in the controller with a standard state model and commands (start, hold, restart, abort, stop) so the batch system can run them uniformly.
- Operation: Phase states are visible to operators, who can hold or abort a phase under defined conditions.
- Recipe management: A Recipe phase in the recipe references an equipment phase and passes parameters such as quantities or temperatures.
- Documentation: Each equipment phase should be documented with its function, parameters, reports, states, failure behavior and alarms. A consistent template across phases helps operators and validation teams.
Phase vs. step
A phase is an ISA-88 procedural element. A step in a sequential function chart is a programming construct inside a phase. Several steps usually implement one phase. In electrical engineering, "phase" also means a conductor of a polyphase system, which is unrelated.