In FMEA , for RPN (Risk Priority number)'s threshold value, is there any industry thumb rule or best practice that can be used?

 

RPN number of 100 is the threshold value and you need to derive action plan for reducing the same.But then,RPN is not only the deciding criteria.If your severity is high and occurence and detection are moderate.Still, you need to derive action plans to reduce the severity rating.Example if your S=10, O=3, D=3 RPN will be 90.As your severity is high, you need to derive your action plans.Hope this helps.

Hi,

Further to Gautam's explanation, you can follow 80-20 principle for actionables. As long as I know, there is no industry best practice or thumb rule for threshold limit. Having said that, I must agree that most of the organizations follow 100 or 150 as threshold limit depending on their process maturity.

I always suggest to use 80-20 principle for threshold limit as it will give scope for continuous improvements all the time. Also this will cover all the process steps over a period of time.

Every time you look into FMEA for threshold limit, concentrate on top RPNs which are contributing to 80% of sum of RPNs. Please see below example:

Process Step - B, G, A, C, I, H, D, E, J, F

RPN 504, 432, 280, 240, 210, 180, 120, 27, 4, 2

Cumulative % 25%, 47%, 61%, 73%, 83%, 92%, 98%, 100%, 100%, 100%

here you can consider 210 as threshold and continue on improving process steps with more than 210 RPN (B,G,A and C in this case). once you are done with improvements, you can revise the RPN and calculate the threshold again. You can repeat the cycle till your process reaches the satuaration level.

Hope this helps...

I agree with Suri. Pareto analysis should be used to capture and target top few RPN's.

A caution point here is - If a threshold is fixed, there is tendency of some people manipulating data to keep values within threshold so that no action is needed.

FMEA is a qualitative tool.So there is every likely possibility that the RPN arrived could be debatable.FMEA improvise over a period of time as you collect more data on the defects and analyse them.Cause and effect diagram is a very vital tool for your FMEA.You shall arrive at the best possible things after evaluating them using C&E Matrix.

I agree.

There is no threshold defined for FMEA. For the continuous improvement we need to see Top RPN process through Pareto analysis and analyse that through Fishbone and prepare the action plan. Use Mistake proofing to reduce the S,O & D in FMEA. Revisit the FMEA periodically and do the same for top RPN till you achieve the saturation level.