Failure Analysis and RCA Flashcards

Which tool uses top-down Boolean logic (AND/OR gates) to model how combinations of basic events lead to an undesired top event?

Answer: Fault Tree Analysis (FTA)

FTA is a deductive, top-down method that uses logic gates to connect basic events to a top event.

In a fault tree, an AND gate means the output event occurs when:

Answer: All input events occur together

An AND gate requires all inputs to occur at once, which is why redundancy is modeled with AND gates.

A fracture surface on a steel bolt shows a dull, fibrous appearance with shear lips and visible necking. This indicates:

Answer: Ductile overload

Necking, a fibrous texture, and shear lips are classic signs of ductile overload.

Which RCA approach is most effective at preventing hindsight bias during interviews?

Answer: Asking open-ended questions about what people knew and saw at the time

Open-ended questions about what was known at the time capture real decision context without biasing recall.

A Pareto analysis of 12 months of downtime shows that 3 of 40 failure modes cause 75% of lost production. What should the reliability leader do next?

Answer: Prioritize RCA and defect elimination on the top 3 failure modes

Pareto analysis points effort at the vital few causes that drive most of the loss.

What does a 'cut set' represent in Fault Tree Analysis?

Answer: A combination of basic events that together cause the top event

A cut set is a combination of basic events whose joint occurrence causes the top event; minimal cut sets are the smallest such combinations.

Corrective actions from an RCA are most robust when they:

Answer: Change the design or system so the failure cannot recur

Following the hierarchy of controls, engineering and system changes beat administrative fixes like training or signs.