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FMEA Risk Priority Number (RPN) - what is the minimum threshold to rank the RPN as "High Risk&q2

FMEA Risk Priority Number (RPN) - what is the minimum threshold to rank the RPN as "High Risk&q

(OP)
Hi All,

I am currently working on pilot FMEA program for one of the critical assets in our plant. There has been a debate on the RPN minimum number, where the failure mode is defined as "high risk" and "need immediate attention" at the number of 120. Any RPN above or equal to 120 is HIGH RISK. Below 120, considered as LOW. Let's take below matrix as an example:

Case A:
Severity = 10
Occurrence = 4
Detectability = 3
RPN = 120

Case B:
Severity = 5
Occurrence = 4
Detectability = 6
RPN = 120

Based on the above examples, both with same RON of 120, Case A warrants us to define it as "Need Immediate Attention - because of its inherent severity", while Case B is "risk may be acceptable, but let's work on enhancing its detectability".

I attended a Quality Course recently and 120 was being mentioned by the instructor as "Best Practice". Not sure if there is ever a minimum threshold number for RPN to define it as "need immediate attention" in the industry standard (MIL-STD-1629 et al). But I would really appreciate of any of you in this Forum have your "standard" or best practices on FMEA RPN definition or classification.

Thank you.

RE: FMEA Risk Priority Number (RPN) - what is the minimum threshold to rank the RPN as "High Risk&q

I've seen 100-150 determined as being the threshold at various places; but it's all hand waving. I've had FMEAs throw an 80 that I wasn't happy with and wasn't a challenge to reduce, so it got reduced.

RPN is a tool to rank things against each-other, not to determine what you need to work on and what you can ignore.

RE: FMEA Risk Priority Number (RPN) - what is the minimum threshold to rank the RPN as "High Risk&q

(OP)
Many thanks both Greg & Ted for your inputs.

I share similar views as well that there shouldn't be a magic number to restrict what failure modes should be prioritized based on its RPN, but to focus on the inherent or un-mitigated risks (S x O) as the FMEA workshop concludes the RPNs.

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