Do you have World Cup Fever? Well I do. Especially after the Netherlands (Holland) beat Spain 5-1 on Friday. I wished that was the score last time they played. So what does this have to do with failure rates? Sometimes my mind works in odd ways. While driving home from work Friday afternoon I was listening to an interview with the Dutch coach on Dutch radio (where would we be without internet radio?). The first thing being discussed was the penalty that was awarded to Spain. The Dutch opinion was very clear: that was a gift, there was no foul. I bet that the Spanish opinion was that it was a clear foul, and a neutral viewer may have gone either way. In the end it didn’t matter, as with Robin van Persie’s first goal (the diving header which most likely will end up being the most beautiful goal of the tournament) the flow of the match changed.

The foul or no foul discussion lead me to think about the “Schwalbe” or as some of you may know it the dive that some football (soccer) players take to trick the referee in awarding them a penalty. You can argue that this is not fair play, but it really is providing incorrect information to observers. And here is the link to failure rates.


When you get a set of failure rates from a manufacturer/third party you really need to make sure that you have all information you need to determine if the failure rates are realistic.

Safe failures for a ball valve: a Schwalbe

No safe failures for a spring return actuator: a Schwalbe

Solenoid failure rates that are lower than the failure rate of a single resistor: a Schwalbe

Unfortunately we see the trend continue. There are third party assessment agencies’ subsidiary divisions that are responsible for the assessment of washing machines and dishwashers that are getting into the functional safety certification for equipment used in the process industries. That is quite a different environment and operating profile. It may sound too crazy to be true but unfortunately it is; as a result more Schwalbes. We are now seeing the same thing happening in the actuator market. Manufacturers are losing jobs because their competitors show up with Schwalbe certificates. That is not a fair playing field. Field failure studies, detailed analysis of the products however show that the Schwalbe certificates are 2 orders of magnitude off reality.

Now you may not be too concerned which manufacturer gets the order, but you should be very concerned when using unrealistic data in your SIL verifications. You will end up with SIF designs that are not achieving the risk reduction that you think they will achieve. You are exposing your colleagues/personnel to higher risks than they can reasonably expect.

So enjoy the World Cup and watch out for Schwalbes!

Tagged as:     SIL Verification     SIF designs     SIF     Safety Integrity Level     Safety Instrumented Functions     Iwan van Beurden     functional safety certification     failure rates  

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