Root cause analysis and its types

 

 What is Root Cause Analysis (RCA)?

👉 Root Cause Analysis is a structured process to identify the fundamental reason why an incident occurred, so it can be prevented from happening again.

Simple Definition

RCA answers WHY the incident happened, not just WHAT happened.

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 Objectives of RCA

• Prevent recurrence of accidents

• Improve safety systems

• Identify system failures, not blame people

• Improve procedures and training

Example (Simple)

Incident

A worker slipped and fell.

Immediate Cause

Floor was wet.

Root Cause

No housekeeping procedure + no warning signs + poor supervision.

Root Cause Analysis Techniques

1️⃣ 5 Whys Technique (Most Common)

Method

Ask “Why?” five times until you reach the root cause.

Example

1. Why did the worker fall? → Floor was wet

2. Why was floor wet? → Oil leakage

3. Why was oil leaking? → Hose damaged

4. Why was hose damaged? → No inspection

5. Why no inspection? → No maintenance program

👉 Root Cause = Lack of maintenance system

2️⃣ Fishbone Diagram (Ishikawa Diagram)

Used for:

• Complex incidents

• Team brainstorming

Causes are grouped into categories:

• Man

• Machine

• Method

• Material

• Environment

• Management

👉 Helps identify multiple contributing causes.

3️⃣ Fault Tree Analysis (FTA)

Method

• Start with the top event (accident)

• Break down causes using logic gates (AND / OR)

👉 Used in engineering, aviation, oil & gas.

4️⃣ Taproot System

Advanced commercial RCA method

Focus on:

• Human performance

• Equipment reliability

• Organizational issues

👉 Common in oil & gas and nuclear industries.

5️⃣ Bow-Tie Analysis

Method

• Center = Top event

• Left = Causes (Threats)

• Right = Consequences

• Barriers on both sides

👉 Excellent for risk management and HSE.

6️⃣ Event & Causal Factor Charting

Method

• Timeline of events before, during, after incident

• Shows sequence of failures

👉 Used in major accident investigations.

Types of Causes in RCA

1️⃣ Immediate Cause

Unsafe act or unsafe condition

• Example: No PPE, slippery floor

2️⃣ Contributing Cause

System weaknesses

• Example: Poor training, poor maintenance

3️⃣ Root Cause

Management or system failure

• Example: No safety policy, no inspection program

Root Cause Analysis Steps

1. Secure the scene

2. Collect evidence (photos, interviews, documents)

3. Identify immediate causes

4. Use RCA tools (5 Whys, Fishbone, etc.)

5. Identify root causes

6. Recommend corrective actions

7. Follow up and verify effectiveness

RCA in HSE (Common Examples)

Incident	Root Cause
Fire	Poor housekeeping + no hot work permit
Fall	No guardrails + no supervision
Electric shock	No earthing + no LOTO
Explosion	Gas leak + no detection system
Injury	No training + unsafe procedure

Key HSE Principle

Blame systems, not people. Fix the system to prevent accidents.

Summary

• RCA finds the real reason behind incidents

• Common techniques: 5 Whys, Fishbone, FTA, Bow-Tie, TapRooT

• Focus on system failures, not individual mistakes