5. Detection and safety barriers

5.1 Detection

Process drifts that could lead to accidents must be contained by means of devices that initially inform operators in the surveillance room (visual and/or audible alarm). Secondly, the operators intervene, or a safety action is triggered to stop the drift. Alarms and safety are major elements of process instrumentation, established during process reviews, also known as "yellow reviews" in the case of new projects, but above all during HAZOP-type safety studies. The result is an instrumental safety matrix defining safety thresholds and actions for each element. It will be kept by the instrumentation department and updated for future installation modifications.

Both the causes and consequences of deviations must be detectable.