PFMEA - RPN - Severity, Occurrence and Detection - Which one does not change?

Paul Simpson

Trusted Information Resource
#41
You study the effects of your process with regard to meeting the specifications. If the DFMEA process has been properly done, if you meet the specifications, the concerns of the DFMEA have been addressed, whether you know specifically what they are or not. This is one reason that I always stress that the PFMEA should address the supplier's process, and its potential failure modes with regard to the specifications.
Then all the severities are the same - Failure to meet specification!You might as well have a PFMA. :)

Going back to how I understand FMEA came about - it was to prioritize actions on the things that have most potential for harm (at NASA) so if you take out the Severity category you loses a lot of the power of the tool.
 
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Helmut Jilling

Auditor / Consultant
#42
You study the effects of your process with regard to meeting the specifications. If the DFMEA process has been properly done, if you meet the specifications, the concerns of the DFMEA have been addressed, whether you know specifically what they are or not. This is one reason that I always stress that the PFMEA should address the supplier's process, and its potential failure modes with regard to the specifications.
I would suggest this is a theoretical position. It does not work this way in the real world.

That is why the PFMEA ranking scale for Severity was changed to a double column scale - one for the effect on the OE customer assembly line, and one for the end user. Neither of those are just meeting the specifications.

The writers of a PFMEA are supposed to determine the level of Severity for both and use the higher of the two. That is difficult to do without seeing the DFMEA, but not impossible to come up with a realistic number.
 

Stijloor

Staff member
Super Moderator
#43
I would suggest this is a theoretical position. It does not work this way in the real world.

That is why the PFMEA ranking scale for Severity was changed to a double column scale - one for the effect on the OE customer assembly line, and one for the end user. Neither of those are just meeting the specifications.

The writers of a PFMEA are supposed to determine the level of Severity for both and use the higher of the two. That is difficult to do without seeing the DFMEA, but not impossible to come up with a realistic number.
Putting this in an automotive context; the effect of failure can also impact dealerships (servicing the vehicle) and even worse: a nonconpliance with a government regulation. All subsequent activities and people affected by the failure mode should be considered.

Stijloor.
 

Jim Wynne

Staff member
Admin
#44
Putting this in an automotive context; the effect of failure can also impact dealerships (servicing the vehicle) and even worse: a nonconpliance with a government regulation. All subsequent activities and people affected by the failure mode should be considered.

Stijloor.
But if a supplier meets the customer's specifications, there should be no worries, right? If a supplier provides a product that is in 100% conformance to the specifications he was given, and something blows up on the OEM assembly line, or in the field, it's a case of "The operation was a success, but the patient died," and none of it is the fault of a supplier who did what he was told to do.

I've been involved in instances where an automotive OEM was warned that what they were asking for was wrong, and the OEM's response was, "Let us worry about that." In other cases, after being supplied with product that conformed to specifications that somehow blew up in the customer's face, the customer made concerted efforts to shift blame to the supplier, saying, "You should have known this was going to happen." The sad fact is that in automotive work, you're often dammed if you do and dammed if you don't, so the best you can do is meet the specifications and cross your fingers.
 

The Taz!

Quite Involved in Discussions
#45
I've been involved in instances where an automotive OEM was warned that what they were asking for was wrong, and the OEM's response was, "Let us worry about that." In other cases, after being supplied with product that conformed to specifications that somehow blew up in the customer's face, the customer made concerted efforts to shift blame to the supplier, saying, "You should have known this was going to happen." The sad fact is that in automotive work, you're often dammed if you do and dammed if you don't, so the best you can do is meet the specifications and cross your fingers.
I think that anyone who has worked in automotive for any length of time has been in similar situations. I remember another supplier once telling me that he actually saw an OEM Work Instruction that actually said that if you have rejects, blame the supplier in all cases.

If a supplier advises a customer that there is a potential safety hazard, and is told basically to ignore it by the customer, the supplier should document the conversation; date, time, who, what, etc. and maintain the record. You may have your customer tap dancing if something "bad" happens, but at least you have some record of the conversation.

We expect to partner with the customer, but partner desks were invented for a reason. You still have to watch out for your company's best interest and do your due diligence.

JMHO

The Taz!
 

Helmut Jilling

Auditor / Consultant
#46
...If a supplier advises a customer that there is a potential safety hazard, and is told basically to ignore it by the customer, the supplier should document the conversation; date, time, who, what, etc. and maintain the record. You may have your customer tap dancing if something "bad" happens, but at least you have some record of the conversation.

We expect to partner with the customer, but partner desks were invented for a reason. You still have to watch out for your company's best interest and do your due diligence.

JMHO

The Taz!
Excellent advice. It is unfortunate that some customers still lean this way, and then they wonder why their business suffers...:confused:

I would remind us that point #8 of the ISO Quality Management Principles is:

Principle 8 - Mutually beneficial supplier relationships.

It states in part,

An organization and its suppliers are interdependent and a mutually beneficial relationship enhances the ability of both to create value.


Key benefits:
  • Increased ability to create value for both parties. Flexibility and speed of joint responses to changing market or customer needs and expectations.
  • Optimization of costs and resources.
Applying the principles of mutually beneficial supplier relationships typically leads to:
  • Establishing relationships that balance short-term gains with long-term considerations.
  • Pooling of expertise and resources with partners.
  • Identifying and selecting key suppliers.
  • Clear and open communication.
  • Sharing information and future plans.
  • Establishing joint development and improvement activities.
And, my favorite -
  • Inspiring, encouraging and recognizing improvements and achievements by suppliers.
I cannot help but wonder how much better the US based auto industry would be, if we simply did these principles which we "claim" to be "committed" to...:agree1:
 

sushant_kulkarni

Involved In Discussions
#47
Sorry Taz but that statement doesn't "ring true" to me. Occurence will change due to better prevention not detection (unless, of course, I completely missed your meaning - which is very possible at this time of the day :rolleyes:)
Whatever u say is correct that the reson now AIAG gives new current control detection & prevention.
 
M

MedQE

#48
Paul,

I am sure Jim will provide an example. I have one that may help.

Let's use a tire (tyre) as an example.

A standard tire is designed to hold air at a certain pressure and resist puncture. The failure mode could be puncturing, losing air pressure. The effect of losing air pressure is a possible roll-over, seriously injuring the passenger(s).

A design change may include filling the tire with a foam-type material in addition to holding air at a certain pressure. When a puncture occurs, the tire may lose pressure, but the foam provides some stability preventing deformation of the tire, thus avoiding a possible roll-over. Now the severity is reduced. The occurrence is reduced as well.

I am sure there are better examples. Thoughts anyone?

Hope this helps (a little).

Stijloor.

In the tire example shown above the severity is not changed despite the design change of adding foam. If I were to evaluate this hazard I would consider the worst possible consequence (severity) as "death" due to a rollover. By adding foam to the tire you have reduced the probability that a rollover or death will occur. But you have not changed the fact that the hazard is being evaluated relative to the worst possible consequence which is death so the severity is unchanged.
 

Stijloor

Staff member
Super Moderator
#49
In the tire example shown above the severity is not changed despite the design change of adding foam. If I were to evaluate this hazard I would consider the worst possible consequence (severity) as "death" due to a rollover. By adding foam to the tire you have reduced the probability that a rollover or death will occur. But you have not changed the fact that the hazard is being evaluated relative to the worst possible consequence which is death so the severity is unchanged.
Hello MedQE,

Have you looked at all the posts in this thread?
Using my tire (tyre) example, can you expand on this?
What would be required to reduce severity?

I am anxious to learn.

Stijloor.
 
R

Redbeard

#50
Severity of a hazard never changes! The design does not have anything to do with the hazard. It has to do with the probaility of occuring and detection to prevent it.
If death is the hazard it does not matter if it was a good design ore not you are still dead.
 
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