Severity, Occurrence and Detection FMEA Ranking Tables - Guidelines?

[YKT]

A question which has been bothering me for some times...
The Severity, Occurence and DEtection ranking tables given in the FMEA manual is just a guideline (suggestions).

My question is that can I change the criterias of the ranking up to my liking? Say for instance, if I'm in an industry of non-automotive, and where the process will not likely to endanger someone's life, can I change the ranking 10 to the criteria that suit my industry ?

Also another related question is that can I not follow the 1-10 ranking ? What I mean is can I have a Severity ranking, for instance, of 1 - 8 only ?

 

[Duke Okes]

Re: FMEA Ranking Tables

Yes, unless you are bound by regulatory or customer requirements you should use your own ranking system.

 

[prototyper]

Re: FMEA Ranking Tables

FMEA is a tool to predict what can go wrong with a process, the consequences of that failure and the effectiveness of your controls to detect that failure in your process. It is used to ensure you have considered proper controls in the pre-production phases of a project and to drive improvement. The only reason for the scoring is that you have a comparative measure of your risks.

As you are non automotive, you are not bound contractually to the AIAG guidelines so, in theory, you can change the scoring method to whatever you wish.

That said, if you do change the scoring or criteria you may well have to start justifying your decisions to your CB every time you are audited! Changing the scoring could lead to long discussions as a 1 to 10 scale is most common practice. You would also have to identify and justify your action limit for your RPN. (I am aware of the opinion that an action limit is not always relevant!)
Also consider, do your customers have any specific requirements for the format of your FMEA?

The answer is, it is up to you to decide, but beware of the pitfalls!

 

[SteelMaiden]

jmho, 1) why reinvent the wheel, 2) wouldn't it be easier to just use what the standard is and lower your max RPN for triggering action, 3) why do FMEA if your process is such a low severity rating that you are thinking of redefining the FMEA?

As stated previously, I would think that you would end up justifying your changes to your registrar, your customers, any interested parties.

the opinions expressed are mine and mine alone.

 

[D.Scott]

the opinions expressed are mine and mine alone.

No they aren't. I agree with them.

Dave

 

[Jen Kirley]

Applying industry guidelines is helpful for the sake of continuity. For this reason I would avoid doing thinks like use a 1-8 scale, no matter how much I liked it. Since many things in our society are done on a scale of 1 to 10, this seems sensible.

But, there's no law that I know of. Guidelines means just that, a guide. What really matters is that all the needed elements are there, and are being consistently and effectively used. There are some things I won't compromise with, like how to derive RPN and that changign Severity requires a design change.

 

[Stijloor]

A question which has been bothering me for some times...
The Severity, Occurrence and Detection ranking tables given in the FMEA manual is just a guideline (suggestions).

My question is that can I change the criterias of the ranking up to my liking? Say for instance, if I'm in an industry of non-automotive, and where the process will not likely to endanger someone's life, can I change the ranking 10 to the criteria that suit my industry ?

Also another related question is that can I not follow the 1-10 ranking ? What I mean is can I have a Severity ranking, for instance, of 1 - 8 only ?

You can adjust/change the ranking descriptions if that would better fit the terminology in your industry.

I would not change the 1-10 scale. It's an accepted practice, and it allows for comparisons and measuring with the same yard (meter) stick.

Having said this, please keep in mind the ultimate goal of the FMEA process: The prevention of problems in designs and processes. How you get there is less important.

Good luck.

Stijloor.

 

[harry]

A good example of how it had been adapted is that for determining the severity of impacts in ISO 14001. Look at the relevant sections (keyword - impact or aspect) in our 'file attachments list' to see how different people/organization adapt them for their own use.

 

[Roger Thorpe - 2008]

Hi all,

I've read all the comments above and as an FMEA consultant to the automotive sector for the last 13 years what I have found is that the standard ranking tables, usually occurrence don't suit all companies in automotive especially when they make either 10 a week or 600 a minute, because there is no resolution.
I also work in industrial, healthcare, railway, motorsport and banking sectors, in short you can do what you like.

I also would recommend you maintain the 1 - 10 approach for resolution.

The resulting numbers don't matter, the order does and as long as you are consistant the answer will always be the same regardless of value.
One last thing don't use a threashold they're not allowed!

Hope this helps,

Roger