PFMEA Assumption to Exclude Latent Failures

S

sjqlty

#1
Hello-
Can anyone provide me some insight as to whether it makes sense and is common to exclude latent failures (failures that occur past the point of final manufacturing) as part of a manufacturing PFMEA for a medical device? And why or why not?

It seems to me that while this is drawing a clear line in the sand, it may not address all the risks that the product could experience that we'd want to assess and possibly mitigate.

Other options would be:
1. to exclude latent failures that occur after a short time past the point of sale (to include any shipping and handling related causes past manufacturing).
2. to include latent failures

Thanks!
 
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somashekar

Staff member
Super Moderator
#2
When that latent failure is assessed to be effecting to the risk of patient or user of the medical device, it needs to be included and suitably mitigated based on the risk evaluation.
The focus is risk to patient / user.
 

Helmut Jilling

Auditor / Consultant
#3
Can anyone provide me some insight as to whether it makes sense and is common to exclude latent failures (failures that occur past the point of final manufacturing) as part of a manufacturing PFMEA for a medical device? And why or why not?

It seems to me that while this is drawing a clear line in the sand, it may not address all the risks that the product could experience that we'd want to assess and possibly mitigate.

Other options would be:
1. to exclude latent failures that occur after a short time past the point of sale (to include any shipping and handling related causes past manufacturing).
2. to include latent failures
For comparison, in Automotive, the Severity evaluation requires us to consider the severity on the final assembly and on the end user, and take the higher of the two. Thus, an impact on the end user could cause a high Severity, even if iit does not become a problem during manufacturing.
 
S

sjqlty

#4
Thanks Helmut-
Please help me understand- I'm a little confused by your response. For a manufacturing PFMEA, isn't the severity always considered from the device end user's perspective (with exception to the case in which there is a risk to an operator of the process for example)? I don't understand what the impact would have on the final assembly, if the product isn't used.

What I was getting at in my question was to include both the effects that occur immediately upon use (or even occur in testing during manufacturing) and those effects that occur later due to some use condition being applied to the device.

For example- a non latent failure would be that an operator forgets to connect a cable (completely unconnected) and the device fails to power ON during testing.

A latent failure example would be that a manufacturing operator only partially connects a connector (it is electrically connected, but not fully latched) and through either vibration during shipping or during early use by an end user, the connector becomes loose and the device won't continue to power ON. I'm curious if this type of failure could be excluded from the PFMEA for any good reason?
 

Helmut Jilling

Auditor / Consultant
#5
Thanks Helmut-
Please help me understand- I'm a little confused by your response. For a manufacturing PFMEA, isn't the severity always considered from the device end user's perspective (with exception to the case in which there is a risk to an operator of the process for example)? I don't understand what the impact would have on the final assembly, if the product isn't used.

What I was getting at in my question was to include both the effects that occur immediately upon use (or even occur in testing during manufacturing) and those effects that occur later due to some use condition being applied to the device.

For example- a non latent failure would be that an operator forgets to connect a cable (completely unconnected) and the device fails to power ON during testing.


A latent failure example would be that a manufacturing operator only partially connects a connector (it is electrically connected, but not fully latched) and through either vibration during shipping or during early use by an end user, the connector becomes loose and the device won't continue to power ON. I'm curious if this type of failure could be excluded from the PFMEA for any good reason?

In Automotive, we apply it pretty much as you described, but we consider Severity of failure at Manufacturing, at Assembly, and at the end user. Examples:

The connector is not attached, Failure Effect is the unit will fail final test. Severity might be a 6.

The connector is not fully attached, Failure Effect is the unit will pass the final inspection, but fail in the coming months in the hands of the end user. Severity might be a 7 or 8.

The connector is not fully attached, Failure Effect is the unit could short out and shock the holder, either in final inspection, or in the hands of the end user. Severity might be a 9 or 10 in this case.

The position of Automotive approach, is to consider who could be affected by each Failure Mode, and determine the max Severity on that situation. In other words, it is seeking the "worst case" scenario.
 
M

MIREGMGR

#6
Sure, you can include an issue from one section of the overall risk analysis, as long as it's included in another section of that analysis. So, if you want to analyze issues that arise or are fixable during manufacturing in a separate section from those that arise during distribution or use, OK.

Just as long as all patient risk issues are addressed, all the way through use and even beyond use if there are identified risks there.
 
S

sjqlty

#7
Ah, gotcha. That clarifies your situation. The bottom line is that you include those failures that occur past manufacturing. I don't see any reason why we wouldn't want to do that, but wanted to throw it out there.
 
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