Glossary · Engineering, integration and validation
Cause-and-effect matrix
Also known as: C&E matrix, Cause and effect chart
German: Ursache-Wirkungs-Matrix
In process automation, a cause-and-effect matrix is a tabular specification that lists initiating conditions (causes, such as trip signals from transmitters) in rows and the resulting actions (effects, such as closing valves or stopping pumps) in columns. Marked cells define which causes trigger which effects.
- Validation
- Functional safety
- Process industry
In one sentence
A cause-and-effect matrix maps initiating signals to the actions they trigger, a compact way to specify interlocks and trips in process plants.
Example
In the cause-and-effect matrix of a tank farm, the cell linking LSHH-101 (high-high level) to XV-101 (inlet valve) specifies that the inlet valve closes on high-high level.
How it applies
- Engineering: Process and control engineers derive the matrix from the Hazard and Operability Study (HAZOP) and the process design, then use it as the basis for programming interlocks and trips in the control or safety system.
- Commissioning: Each marked cell becomes a test step during the Factory acceptance test (FAT) and Site acceptance test (SAT); testers force the cause and confirm every effect.
- Maintenance: Changes to trip logic are made in the matrix first and handled through Management of change (MOC), so the matrix and the program stay consistent.
- Documentation: The documentation team keeps the matrix as a controlled document, uses the same tag numbers as the I/O list and the Piping and instrumentation diagram (P&ID), and records the revision that was tested.
Cause-and-effect matrix vs. control narrative
A Control narrative describes control behavior in prose, including sequences and operator interaction. A cause-and-effect matrix captures discrete trip and interlock logic in a table. Many projects use both: the narrative for sequences, the matrix for interlocks. A matrix entry describes intended logic; on its own it does not demonstrate that a Safety function meets its required integrity.