What Is FMEA?
Key Terms
- FMEA (Failure Modes and Effects Analysis)
- A structured, proactive risk analysis technique used to identify potential failure modes in a product, process, or system before they occur — and to prioritise preventive actions based on the severity, likelihood, and detectability of each potential failure. Originally developed by the US military (MIL-P-1629, 1949) and widely adopted in aerospace, automotive, and manufacturing industries.
The FMEA Risk Priority Number (RPN)
Each potential failure mode is scored on three dimensions, each rated 1–10:
| Dimension | Definition | Scale |
|---|---|---|
| Severity (S) | Impact on the customer or process if the failure occurs | 1 (negligible) → 10 (safety/regulatory) |
| Occurrence (O) | Likelihood that the failure will occur | 1 (extremely unlikely) → 10 (almost certain) |
| Detection (D) | Likelihood that current controls will detect the failure before it reaches the customer | 1 (certain to detect) → 10 (undetectable) |
RPN = Severity × Occurrence × Detection
Failure modes with the highest RPN scores are prioritised for preventive action. Actions that reduce Severity (by design change) or Detection (by improved testing) are typically higher leverage than those that reduce Occurrence alone.
Related Quality Prevention Resources
- ►TQM Tools: The Quality Management Toolkit
- ►Quality Management Tools: 13 Techniques Explained
- ►PDCA: Building Prevention Into the Improvement Cycle
- ►Lean Manufacturing Tools: Poka-Yoke Error Prevention
The following section contains our original guide to the FMEA tool.
Failure Modes Effects Analysis or FMEA tool is a powerful method for understanding potential issues and problems to processes, before they happen. Think of it as being a forecasting tool, to allow the team using it, to design quality and safety into a product and process, by eliminating the possible problems that could happen, before they happen!
It has been used extensively in safety critical industries like aerospace businesses, and has become popular in the automotive industry due to the same requirements.
FMEA Benefits:
The benefits of an effective and systematic use of the FMEA tool are vast. Notwithstanding the obvious benefits above, FMEAs can create smooth production processes first time, reduced development costs, increased profit margins in production and the ability to successfully win more business, supplying competitive and long lasting product.
Additional benefits are:– Minimize product failures
– Early risk identification
– Track process improvements
– Documented evaluation
– Develop efficient test plans
The FMEA tool is a means of identifying failures before they happen by providing a ‘check list’ procedure that is built around three key questions.
1. What is the likelihood that failure will occur?
2. What would the consequence of that failure be?
3. How likely is such a failure to be detected before it affects the customer?
How to Create an FMEA
- ► Review the Process – Map the process in question, step-by-step, capturing every value added activity.
- ► Identify Failure Modes – For each process step, brainstorm all potential failure modes (things that could go wrong with that particular activity).
- ► List the effects and causes – For each failure mode, list its effect on the output of that process step, and also the real root cause.
- ► Give each item a severity score – Rank each failure mode as to how severe the failure mode could be (scoring 1 to 10).
- ► Give each item an occurrence score – Rank each failure mode as to how often it will / does occur (scoring 1 to 10).
- ► Give each item a detection score – Rank each failure mode as to how easy the failure mode can be detected by the next customer or next internal customer in the process. (Again, scoring 1 to 10).
- ► Calculate RPN numbers – For each failure mode, give it a Risk priority number (RPN) by multiplying the severity score x occurrence score x detection score. This now allows you to focus on the highest scoring, higher risk problems first.
- ► Develop an action plan – For each high scoring RPN, note who is doing what by when to close eliminate the failure modes.
- ► Take action!
- ► Recalculate new RPNs – Once action has been taken, recalculate the new RPN numbers. Repeat the steps if further action is needed (if the RPN number is still too high)
You can use an FMEA tool template by clicking here. There are numbered steps at the top of each column, which guides you through the typical sequence of completing a Failure Mode Affects Analysis.
How to Conduct an FMEA: A Step-by-Step Guide
FMEA is most powerful when applied before a problem occurs — during the design or planning phase of a process, product, or system. The objective is to systematically identify every possible way a process can fail, assess the consequences of each failure, and prioritise preventive action based on risk.
Step 1 — Define the scope. Identify the process, product, or system to be analysed. Break it down into its individual components or process steps. Each step or component will be analysed separately. The more granular the breakdown, the more thorough the analysis.
Step 2 — Identify potential failure modes. For each process step or component, ask: “In what ways could this step fail to perform its intended function?” Document every plausible failure mode, not just the ones that seem most likely. Incomplete failure mode identification is the most common weakness in FMEA practice.
Step 3 — Determine effects and severity (S). For each failure mode, identify the potential effect on the customer or downstream process. Rate the severity of that effect on a scale of 1 (negligible) to 10 (catastrophic or safety-critical). Severity ratings should be defined by a consistent organisational standard, not left to individual judgment.
Step 4 — Identify causes and rate occurrence (O). Identify the root causes that could trigger each failure mode. Rate the likelihood of occurrence on a scale of 1 (extremely unlikely) to 10 (almost certain). Use historical data where available; expert judgment where data is limited.
Step 5 — Assess current controls and rate detection (D). Identify what controls currently exist to detect each failure mode before it reaches the customer. Rate the effectiveness of detection on a scale of 1 (detection is almost certain) to 10 (no detection capability exists).
Step 6 — Calculate the Risk Priority Number (RPN). RPN = Severity × Occurrence × Detection. The RPN ranks failure modes by risk priority. High RPN items — particularly those with high Severity scores — are the highest priority for preventive action. A failure mode with Severity = 10 should be addressed regardless of its RPN, because the consequence of that failure is unacceptable even if it occurs rarely.
Step 7 — Develop and implement actions. For each high-priority failure mode, define specific actions to reduce severity, occurrence, or improve detection. Assign owners and deadlines. Recalculate the RPN after actions are implemented to confirm risk reduction.