I get an email that includes a “certificate” of some sort most every week.  The sender asks “Can I accept this certificate?”  Or the sender might ask “Are these failure rates valid for the process industries?” 

At exida we have some specific criteria we use when performing third party independent SIF verification.

1. exida will accept IEC 61508 functional safety certificates from any accredited Certification Body for purposes of Systematic Capability.  Evidence of accreditation shall be the Accreditation Body logo on the certificate.
2. exida will accept data from any source that defines the application and produces results within the SILSafeData Limits (silsafedata.com) which represent statistical limits established by field failure data in the process industries.

The first rule was done because some manufacturers issue their own self-declared “certificates.”  And the IEC 61508 standard allows that.  However, we have had experiences where a manufacturer has been audited by exida and failed.  Rather than improve their design and test processes or improve their safety design some have created their own “certificates.”  There can be exceptions but overall, not good for safety. 

The second rule came about after seeing certificates with published dangerous failure rates 500X lower than process industry field failure data.  Also not good for safety.  To allow all our safety consultants, engineering companies and end users to check the limits, we publish many at www.SILSafeData.com.

exida has some webinars coming up on this topic with detailed examples.  Watch our webinar schedule for details.