In brief
Root cause analysis (RCA) is a structured approach to finding the actual cause of a failure and preventing it from recurring.
Contents
What is Root cause analysis?
When faults occur, often only the symptom is eliminated: the defective bearing is replaced and the machine runs again. Root cause analysis goes further and asks why the bearing failed, for example due to misalignment, lack of lubricant or incorrect fitting. Only once this underlying cause has been eliminated does the failure frequency fall permanently.
Common tools are the 5 Whys method, in which the question why is asked repeatedly, the Ishikawa or cause-and-effect diagram with categories such as man, machine, material, method, measurement and environment, fault tree analysis and the evaluation of damage patterns on removed parts. In structured problem-solving processes, root cause analysis is a fixed step. What matters are facts rather than assumptions: measurement data, operating logs, photos and the defective component itself.
The result is corrective actions, such as changed maintenance intervals, better lubrication, training, design changes or the choice of a different material or spare part. For purchasing, the analysis may show that a cheaper part or one not meeting the specification was the actual cause.
In practice: maintenance and procurement
Removed damaged parts should be labelled and kept rather than disposed of immediately, as they are the most important piece of evidence. If a spare part turns out to be the cause, its origin, batch and inspection records belong in the complaint to the supplier.
Synonyms and abbreviations: RCA · failure cause analysis · root cause failure analysis (RCFA) · failure analysis
Frequently asked questions
What is the 5 Whys method?
With the 5 Whys method, starting from the problem, you ask why several times in succession until you reach a cause that can be specifically eliminated. The number five is a guideline; sometimes fewer steps suffice, sometimes more are needed. The method is simple but should be backed up by facts such as measured values or damage patterns.
What root cause analysis methods are there?
Widely used are the 5 Whys method, the Ishikawa diagram, fault tree analysis, Pareto analysis for prioritising frequent causes and damage analysis on components. For complex cases, several methods are combined and embedded in a structured problem-solving process, such as a PDCA cycle.
What is the difference between root cause analysis and FMEA?
Root cause analysis is carried out after a failure has occurred and looks back to find its cause. FMEA is forward-looking: it considers possible failures of a product or process before they occur and assesses their risks. Findings from root cause analyses are frequently fed into updates of existing FMEAs.
When is root cause analysis worthwhile in maintenance?
It is useful for recurring failures, for faults with high downtime costs or safety consequences and for unexpectedly early failures of new parts. Many companies define triggers for it, such as a certain downtime duration or the same fault occurring several times within a given period.