FMEA RPN Calculations
FMEA RPN Calculations
(OP)
On FMEA's, I have concerns about the validity of the Risk Priority Number, determined by multiplying the Severity, Occurrence, and Detection (1-10) numbers. On http://www.quality-one.com/services/fmea.php a problem is presented:
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Determine the order of need for change in the following three examples:
#1 - severity ( 5 ) , Occurrence ( 4 ) , Detection ( 2 ) = 40
#2 - severity ( 9 ) , Occurrence ( 2 ) , Detection ( 2 ) = 36
#3 - severity ( 8 ) , Occurrence ( 1 ) , Detection ( 8 ) = 64
The correct order for action is #2, #1, #3.
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They make a good point that Severity should be given more weight than Occurrence, which should be given more weight than Detection. I find that if I raise Occurrence to the 0.8 power and Detection to the 0.4 power, and then multiply them, I get an RPN that reflects their priority for this particular case. Does anyone have anything further on this, or any recommendations? I have a sprreadsheet that demonstrates this and can be used to play around with it.
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Determine the order of need for change in the following three examples:
#1 - severity ( 5 ) , Occurrence ( 4 ) , Detection ( 2 ) = 40
#2 - severity ( 9 ) , Occurrence ( 2 ) , Detection ( 2 ) = 36
#3 - severity ( 8 ) , Occurrence ( 1 ) , Detection ( 8 ) = 64
The correct order for action is #2, #1, #3.
*************************
They make a good point that Severity should be given more weight than Occurrence, which should be given more weight than Detection. I find that if I raise Occurrence to the 0.8 power and Detection to the 0.4 power, and then multiply them, I get an RPN that reflects their priority for this particular case. Does anyone have anything further on this, or any recommendations? I have a sprreadsheet that demonstrates this and can be used to play around with it.





RE: FMEA RPN Calculations
Some would argue that it's better to pick the low hanging fruit first, to get the biggest bang for your buck....
RE: FMEA RPN Calculations
RE: FMEA RPN Calculations
Detection of 2 means it's VERY difficult to catch it if it does occur.
Seems like a lot of effort to solve a problem that doesn't occur very often, without a method of detecting it if it does fail.
RE: FMEA RPN Calculations
Regards,