Full definition
A structured problem-solving methodology that investigates beyond the symptoms of a failure to identify the fundamental (root) cause — the specific condition that, if eliminated, would prevent recurrence. RCA distinguishes between: physical cause (the mechanical or material reason — e.g., bearing fatigue), human cause (the action or inaction — e.g., missed lubrication), and latent/systemic cause (the organizational factor — e.g., no lubrication schedule in CMMS). Key RCA methods: (1) 5 Whys — iteratively asking "why?" until the root cause is reached (simple, effective for straightforward failures). (2) Ishikawa/fishbone diagram — categorizes possible causes under Man, Machine, Material, Method, Measurement, Environment. (3) Fault tree analysis — Boolean logic diagram tracing from top event to basic causes (for complex, safety-critical systems). (4) Pareto analysis — identifies the 20% of causes responsible for 80% of failures. (5) Failure mode and effects analysis (FMEA) — proactive identification of potential failures. Per ANSI/API 689 (recommended practice for RCA) and DOE-NE-STD-1004-92 (nuclear). The RCA report must include: problem statement, timeline, evidence, root cause(s), and corrective actions with assigned owners and deadlines. Without RCA, maintenance teams repeatedly fix symptoms while the root cause continues generating failures.