Maintenance

Root Cause Analysis

Structured methods: 5 Whys, fishbone, and evidence preservation.

Overview

Root cause analysis pursues the systemic cause behind a failure — the conditions that made it possible — rather than the broken part that made it visible.

Engineering purpose

Prevent recurrence: replacing the failed component without RCA simply schedules the same failure.

How it works

Evidence is preserved before cleanup (photos, parameter dumps, alarm history, the component itself); 5-Whys chains advance only on verified answers; fishbone categories ensure systemic factors get examined; the proposed cause must reproduce or fully explain the event.

• RCA targets the systemic cause; replacing the failed part treats a symptom and schedules a repeat.
• 5 Whys works when each answer is verified with evidence — unverified chains produce confident fiction.
• Preserve evidence before cleanup: photos, parameter dumps, alarm history, and the failed component itself.

Common faults

Unverified why-chains producing confident fiction; evidence destroyed by eager cleanup; analysis stopping at the first human error found; corrective actions never tracked to completion.

Diagnostic checks

1. 1Check whether the same failure mode occurred before and what was concluded then.
2. 2Validate the proposed root cause by demonstrating it reproduces (or fully explains) the failure.
3. 3Search the failure history first — if this mode occurred before, the prior conclusion is your most important piece of evidence.

Safety notes

Incident scenes involving injury or near-miss have preservation and reporting obligations that precede any engineering analysis — secure first, analyze second.

Commissioning notes

Make RCA a standing process: trigger criteria, evidence kit, template, and corrective-action tracking owned by someone with authority to close loops.

Related concepts

Evidence preservation, verified 5-Whys, fishbone analysis, failure history, corrective-action tracking.

root cause · 5 why · five whys · fishbone · ishikawa · علت ریشه‌ای · پنج چرا · استخوان ماهی

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When Hermes Brain uses this article

Cited for repeated failures, post-incident investigation structure, and converting a fixed symptom into a prevented recurrence.