Cause-and-Effect Diagrams in Process Industries: Test Your Knowledge

IEC 61508 is the global standard for functional safety in Safety Instrumented Systems (SIS), guiding C&E Diagrams in safety applications.

ESD overrides allow temporary bypassing of shutdown logic for maintenance or troubleshooting, but must be used cautiously.

Process safety regulations and risk assessments define how C&E logic should be structured to prevent hazardous failures.

Effect delays (T) provide a buffer time for operators to acknowledge or correct issues before automatic shutdown occurs.

C&E Diagrams rely on AND/OR logic to define interlocks and trip conditions for equipment safety.

Rotating equipment (motors, pumps, turbines, compressors) are critical assets that are often tripped by ESD logic to prevent damage.

1oo2 (One out of Two) voting logic ensures that if either of the two input signals is active, the effect will trigger.

Effects are prioritized based on safety criticality, ensuring that high-risk conditions trigger faster protective responses.

A High-High (HH) pressure alarm is a safety-critical condition that triggers emergency shutdown (ESD) or relief actions.

If there is no mark (X, T, or P) at an intersection, it means the cause does not trigger the effect.

Effects trigger specific responses such as tripping pumps, closing valves, or activating alarms.

C&E Diagrams define interlock relationships, while Logic Diagrams show the programming logic.

‘P’ signifies that the effect occurs only when a permissive condition is satisfied.

Permissives (P) allow effect activation only if predefined conditions are met.

IEC 61511 provides guidelines for Safety Instrumented Systems (SIS), including ESD logic implementation via C&E Diagrams.

Fire & Gas (F&G) systems detect fire, smoke, or gas leaks, triggering shutdowns and alarms.

When safety regulations break, ESD systems immediately turn off vital process equipment.

“T” stands for an effect that doesn’t start right away but rather does so after a certain amount of time.

Impacts include alarm activation, valve operation, equipment shutdown, and other preventative measures.

The C&E Diagram contains digital inputs and analog alarms and interlock logic activation among its causes.

A Cause-and-Effect Diagram utilizes the safety information from a SAFE Chart to define safety device actions.

ESD systems use C&E Diagrams to define shutdown sequences triggered by process failures, fire, or gas leaks.

The Cause-and-Effect Diagram is also known as the Ishikawa Diagram or Fishbone Diagram, widely used for root cause analysis.

Any effect which activates in a C&E matrix is indicated with an ‘X.’ This could involve equipment shutdowns or alarm activations or valve closures.

A Cause-and-Effect Diagram (C&E Diagram) helps identify potential failure causes and their consequences in Emergency Shutdown (ESD) and Fire & Gas Systems (FGS).