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Fishbone Diagram

Risk & Failure Analysis
mechanicalprocesselectrical

Definition

A cause-and-effect analysis tool (also called Ishikawa diagram or cause-and-effect diagram) that visually organizes potential causes of a problem into major categories branching from a central spine. Standard categories for manufacturing/maintenance include: Man (People), Machine (Equipment), Method (Procedure), Material, Measurement, and Mother Nature (Environment). Each category is explored for contributing causes.

Context

Used in RCA workshops for complex events with multiple potential contributing causes. The fishbone diagram provides structure for brainstorming sessions and ensures that all categories of potential causes are considered. It complements the 5-Why technique by providing breadth where 5-Why provides depth.

Examples

  1. A fishbone diagram for a heat exchanger tube failure explores causes across six categories, identifying that the combination of Material (wrong alloy specified), Method (no pre-commissioning cleaning), and Mother Nature (higher-than-design chloride content in cooling water) together caused the premature SCC failure.
  2. An RCA team uses a fishbone diagram to identify 23 potential contributing causes for a compressor trip, then narrows to 3 most likely causes for detailed investigation.

Applicable Standards

  • IEC 62740:2015
  • ISO 9001:2015

Related Terms

Root Cause Analysis(RCA)

A systematic investigation methodology used to identify the fundamental underlying cause(s) of a failure, incident, or undesired outcome. RCA goes beyond the immediate or proximate cause to uncover the latent organizational, procedural, or design factors that created the conditions for the event. Common RCA techniques include 5-Why analysis, fishbone (Ishikawa) diagrams, fault tree analysis, and barrier analysis.

5-Why Analysis

An iterative root cause analysis technique that repeatedly asks 'Why?' (typically five times, though the actual number varies) to peel away successive layers of symptoms and intermediate causes until the fundamental root cause is identified. Each answer forms the basis of the next question. The method is effective for straightforward cause-and-effect chains but may need supplementing with other techniques for complex multi-causal events.

Corrective Action

An action taken to eliminate the root cause of a detected nonconformity, failure, or undesirable situation to prevent its recurrence. Corrective actions address why something went wrong, not just the immediate symptoms. They are distinguished from immediate actions (containment) and preventive actions (proactive measures for potential future problems).

Where this appears in Reliatic

This concept is used in the FMEA & Risk module.