IEC 61508 Functional Safety Certificates – To Accept or not to Accept?

Aug 10, 2017

[:en][vc_row][vc_column][vc_column_text]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 ( 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

exida has some webinars coming up on this topic with detailed examples.  Watch our webinars for details.[/vc_column_text][/vc_column][/vc_row][:zh][vc_row][vc_column][vc_column_text]No! They are not Inherently Safe!

A collaborative robot is intended to work “collaboratively” with a person. i.e. share a common workspace. It is force and speed limited by design to minimize any potential hazard. Collaborative robots fit the application where the task cannot be easily or cost effectively automated. They are easy to deploy, program and repurpose. Collaborative robots are new to everyone including the standards agencies.

A hazard and risk assessment is required that assesses the robot and the environment that it is deployed in. Just as any other robot, things such as collisions, speed, type of end effector and worksite need to be evaluated. Collaborative robots have their own sorts of collisions and hazards. They may not be as severe, but they still exist.

This all comes down to risk and the amount of risk that you are willing to accept! The diagram below shows the high-level steps for doing a Hazard and Risk Assessment. When following the steps, if you assess the risk and find it to be acceptable (your companies acceptable risk norms) then you are done. No need to add any risk reduction.

The next best approach is to determine if protective measures other than a Safety Function can reduce the risk to an acceptable level. If not, then you must assign a SIL and implement a safety function that will provide the required risk reduction.

exida can effectively train your team to perform machine hazard and risk assessments to identify all possible hazards and estimate the risk for each hazard. Specifically, exida coaches you through the process of evaluating the risk, developing and implementing risk reduction options. exida can also educate your team in multiple approaches to SIL target selection. These are just some of the things exida does to ensure you are on the right path![/vc_column_text][/vc_column][/vc_row] [:]

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