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FMEA 101: How to Build a Failure Mode and Effects Analysis
2025-04-15Vallejo Reliability Group

FMEA 101: How to Build a Failure Mode and Effects Analysis

FMEARisk AnalysisStrategy

What Is FMEA?

Failure Mode and Effects Analysis (FMEA) is a systematic methodology to identify potential failure modes, assess their effects, and prioritize mitigation strategies.

The FMEA Process

Step 1: Define the System

Choose a specific process or equipment. Example: "Cooling system for primary injection molding machine."

Step 2: List Potential Failure Modes

  • Coolant leak
  • Pump cavitation
  • Clogged filter
  • Thermostat failure
  • Contaminated coolant

Step 3: Determine Effects

What happens if this failure occurs?

| Failure Mode | Effect | Severity (1–10) | |---|---|---| | Coolant leak | Machine shuts down; mold temperature uncontrolled | 9 | | Pump cavitation | Reduced cooling; scrap parts | 7 | | Clogged filter | High pressure, pump damage | 8 | | Thermostat failure | Overheating or under-cooling | 6 | | Contaminated coolant | Bacterial growth, odor, corrosion | 4 |

Step 4: Assess Likelihood

How often does this failure occur? Rate 1–10 (1 = rare, 10 = frequent).

Step 5: Assess Detectability

How easy is it to catch before it becomes a problem? Rate 1–10 (1 = easy to detect, 10 = hard to detect).

Step 6: Calculate Risk Priority Number (RPN)

RPN = Severity × Occurrence × Detection

| Failure Mode | Severity | Occurrence | Detection | RPN | |---|---|---|---|---| | Coolant leak | 9 | 3 | 4 | 108 | | Pump cavitation | 7 | 5 | 6 | 210 | | Clogged filter | 8 | 6 | 3 | 144 | | Thermostat failure | 6 | 2 | 5 | 60 | | Contaminated coolant | 4 | 7 | 8 | 224 |

Step 7: Define Mitigation Strategies

Focus on HIGH RPN items first.

  • Contaminated coolant (224): Implement quarterly filter replacement + monthly bacterial testing
  • Pump cavitation (210): Add strainer to suction line + monitor pressure
  • Clogged filter (144): Add pressure gauge with alarm

FMEA Benefits

✓ Prevents high-impact failures ✓ Guides preventive maintenance priorities ✓ Improves equipment design ✓ Reduces emergency repairs ✓ Documents institutional knowledge

🎯 FMEA is most valuable when done as a team exercise with operations, maintenance, and engineering present. The discussion is as valuable as the final document.