While discussing functional safety certification of an integrated valve assembly with a manufacturer, exida stated that all devices (actuator, pneumatic parts, valve, etc.) must be IEC 61508 certified. The manufacturer said this was no problem, and provided a set of exida and TÜV certificates. 

Of course, we need good failure rate data for each device, so each certificate was reviewed. One of the actuators had numbers that were far below www.SILSafeData.com. That is a red flag. 

I recalled a conversation with one of the TÜV auditors about these low numbers. He explained that no one really used the failure rates for anything, and therefore they are not important. Ouch! 

It is understandable that those who think these failure rate numbers are a waste of time would not work too hard to predict realistic results. In this case, for the devices chosen, exida did a Calibrated FMEDATM to predict realistic failure rates based on the component failure data derived from field failure data. These results meet the requirements of IEC 61511:2017 Ed 2.1. 

This is important for any manufacturer who wants to sell an offering in the process industries. An integrated final element assembly clearly fits into this process industry category. 

Stay on the lookout for this new product category: integrated final element. The whole idea looks good.  And the devices done by some certification bodies will come with realistic field failure-based failure rate data.

Tagged as:     william goble     IEC 61511     FMEDA     final elements     failure rates     dr. william goble     Calibrated FMEDA  

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