A C&E diagram (Cause & Effect diagram) is used to determine how and when actions are performed in a safety system. The Cause Effect Diagram is usually displayed in a matrix showing which activation of a SIF or DCS leads to which action.
- Cause - This is the process deviation that you represent in the C&E matrix in the rows. When the process deviation is above or below the conditions defined in the design, it becomes active.
- Effect - This is the action that the security system performs and that you show in the columns of the Cause Effect Diagram matrix. For example: stop the gas supply to the burner.
- Intersection - Here you can see which effect responds to which cause. If the intersection is empty, the cause will not affect the effect. If the intersection does contain an action, an active cause will activate the corresponding effect.
For example, for low gas flow protection to a burner:
Cause: The gas flow gets below 10m3/h, then FSLL-1234 becomes active
Consequence: The gas flow to the burner is stopped, which affects AOV-1234 and FIC-1234
Crossroads: Valve AOV-1234 is closed and regulator FIC-1234 switches from automatic to manual and the output of the regulator goes to 0%.
C&E diagrams are conceived by a process engineer and are elaborated on the basis of information from the SIF design. If during the design process or during the life span of the plant, changes to the SIF design occur, you will need to check whether this also affects the cause and effect diagram.
To ensure that the latest changes made to the SIF architecture are immediately implemented in the C&E diagrams, we use advanced safety lifecycle software aeShield®. With this we turn static Cause Effect Diagrams into dynamic C&E diagrams, which are always the same as the SIF design.