Glossary · Batch and process operations
Control module (ISA-88)
Also known as: CM
German: Control Module
In ISA-88 batch control, a control module is the lowest level grouping of equipment in the physical model that can carry out basic control, such as a single valve with its limit switches, a motor with its starter or a regulating loop.
- Batch control
- Process industry
- Standards
In one sentence
In ISA-88, a control module is the lowest physical-model grouping of equipment that carries out basic control, such as a valve or motor.
Example
The inlet valve XV-101 with its open and closed feedbacks is engineered as one control module that the equipment module commands.
How it applies
- Engineering: Control modules are usually implemented as reusable function blocks for device types (valve, motor, analog input, PID loop), with modes, interlocks and alarms.
- Operation: Operators can often operate control modules manually, for example opening a valve in manual mode, within the limits of interlocks.
- Maintenance: A consistent control module library means that faults, alarms and diagnostics look the same for every device of a type.
- Documentation: Documenting each control module type once, including modes, states, alarms and interlock behavior, and referencing it from the unit descriptions avoids repetition. Tag names in documentation must match the P&ID and the HMI.
Control module vs. equipment module
A control module performs basic control of individual devices. An Equipment module (ISA-88) coordinates several control modules to carry out a minor processing activity, such as dosing or heating. A control module does not execute procedural control.