Risk Prioritization in FMEA
Abstract
Carl and Fred discuss a question from a reader about risk prioritization in FMEA procedure.
Key Points
Join Carl and Fred as they discuss the role of risk prioritization in FMEA, what is it, and what is the best way to prioritize risk in FMEA.
Topics include:
- Discussion of history of risk prioritization in FMEA procedure
- Discussion of the range of risk assessment in FMEAs, from extreme to inconsequential
- The three elements of risk assessment: severity, occurrence, detection, and how can they be integrated into a risk prioritization method
- Getting to the vital few, not the trivial many
- Risk prioritization, if done properly, identifies the vital few issues
- Pitfalls of RPN: high severity – low RPN can still be high risk
- Avoid a numbers game
- Simplify with 5 point scale, to save time
- Simplify with SOD matrix, not make the risk visible
- Keep FMEA focus on reducing risk, not filling out a form.
- Use strategies such as fail-safe to reduce severity risk
- Management should be involved in reviewing high-risk issues
- When you do FMEA, and when is FTA needed?
- Discussion of case study on a chip socket, and what can be learned?
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Show Notes
In the podcast you asked for comments on thoughts for what we’d done for prioritization. As you discussed, we use a S*O score as our prioritization metric, then bucket those scores into “zones.” This doesn’t completely solve the gamesmanship that comes from RPN, but reduces it. Going with just S and O promotes prevention by either design change or preventative actions rather than relying on detection. I put together a “heat map” just like you described, with severity on one axis and occurrence in on the other. The most severe items are just as you said – in the upper right. We look at all safety items first, regardless of the occurrence. Then we look at zone 1 (the highest risk), then zone 2, then zone 3, then zone 4. RPN is only used to prioritize within a zone. A higher RPN can be “outranked” by something with a lower RPN but in a lower number zone or a safety item (regardless of zone.)
Hi Brian,
Thanks for the comment and description of how you handle prioritization. I do like the built in nudge to improve prevention by design or other steps.
Well done
cheers,
Fred
Hi Brian,
Your use of SO matrix (heat map) is quite good, and it certainly has the advantage of focusing on safety and prevention. I agree on the problems with RPN.
My only comment is that detection risk is real, and there is an alternative method called SOD matrix. I cover this method in my article “Risk Prioritization in FMEA – a Summary” specifically in the section called “Action Priority Method.”
https://accendoreliability.com/prioritizing-risk-in-an-fmea/
This is the method I use in FMEA. You can weight Severity, Occurrence and Detection according to the risk associated with each combination. It’s like a three dimensional heat map.
Carl