When speaking with several manufacturers’ sales teams recently, it became very evident that some of these sales people, selling into the Industrial Safety and Controls markets, had little or no knowledge of how their products’ failure rate data compared to their competitors and/or another industry benchmark (such as DOW or OREDA).  Indeed, most of them had never seen their safety manual, let alone know of its existence.  Some of the companies I spoke with were experiencing a problem competing with their competitors who were using lower, more favorable failure rates.  However, these failure rates being offered by the competitors for similar devices were outside process industry realistic ranges and dangerously optimistic.  For example, a manufacturer of an actuator (let’s say Company A) has a certificate from a well-known certification body stating that it’s dangerous failure rate (λd) was 41.2 FITs or put another way it will fail dangerously once every 2,770 years!  The certificate went on to list it as SIL 3 capable with a hardware fault tolerance (HFT) = 0.  Those of you reading this in the know will understand what this means and will immediately scoff at this.  If you compared this result to DOW plant study data, you will see that similar devices come out to be 210 FITs, or 5 times higher.  Now of course, the certificate for Company A doesn’t list the assessment method, the assumptions made or how these numbers were derived.  If the manufacturer’s field failure data has been used then you cannot know what the percentage of actual failures are recorded and whether these were just during the warranty period.  Furthermore, the definition of “failure” can be different because what happens when “no fault is found” when the unit is returned and tested?  Is this classified as a failure?

Increasingly, we at exida are seeing certificates for field devices with highly optimistic and dangerously low failure rates.  An educated customer will see through this and will not accept these optimistic failure rates.  If you are a member of a sales team, working for a manufacturer selling certified safety-rated equipment, competing with some of these manufacturers using optimistic failure rate data, then these are some of the questions you should be asking your customers when he or she compares your product to these competitors:

  • Has the customer seen the assessment report for the device from the certification agency?
  • Regarding final elements, has B10 cycle test data been used? And if so, is the device in question being used in continuous or demand mode?  If used in demand mode then B10 data isn’t relevant because the predominant failure mode being tested is premature wear-out, whereas in demand mode cold-fusion and sticktion are the key failure modes of concern
  • Was the analysis done using manufacturers’ field warranty returns?
  • Has the customer compared these failure rates to industry benchmarks?  In which case you need to have the information to hand to be able to show where your product sits relative to industry benchmarks for similar products

There are of course more questions that can be asked but essentially you need to know your product’s safety manual and what your failure rates are.

Tagged as:     Steve Gandy     Failure Rate Data  

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