The exida Scheme

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Today I was asked: “What is the exida Scheme?”  If one person had this question, it is likely that others may be interested as well.  Therefore, I decided to take a moment and explain the exida structure.  Any Certification Body operates each product certification per a “scheme,” which references standards, notes or describes procedures, and any additional requirements of the standard. 

We at exida have our own Functional Safety Certification scheme to document our procedures which are audited by the American National Standards Institute (ANSI).  We also reference the IEC 61508 standard and document any interpretations of the standard.  Lastly, we take any controversial issues/interpretations before the exida Advisory Board to offer their insight on the issue.  The opinions…

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Root Cause Analysis

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Root Cause Analysis - finding out what happens when a failure occurs, and why it happened in the first place.  There are many reasons for root cause analysis.  The “system” design can be improved to prevent some of the failures from happening again and those who troubleshoot can do so more quickly if this should reoccur. Both improvements can have a significant impact on down time as well as safety.

My home has a fiber optic digital service for internet, television, and telephone.  The internet and television both failed on Friday.  As there is no effective diagnostic and annunciation system, we noticed the failure just before our guests were trying to watch a hockey game on the television.  This was…

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Certificate Forgery!

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exida has discovered yet another forged functional safety certificate.  You can read about another occurrence in a previous blog entry.

The company name on the forged certificate is ISP SA DE CV, Cunduacan, Tab., Mex.  How could someone think this would not be checked?  exida maintains a list of valid certifications on the exida Safety Automation Element List.  This counterfeit certificate is not there.  While I suppose it is a compliment to see that the forgers want to use exida certificates as a base to start from, they should realize that exida’s accredited scheme has a means for anyone to quickly verify the validity of any certificate. 

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Which Edition of IEC 61508 is Relevant to Me?

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Simply stated, the 2nd edition of IEC 61508 is the relevant standard for newly developed products and new certifications.  This represents the current best practices on functional safety techniques and measures, and is what the marketplace expects for today’s products. 

Renewed certifications can use the 1st edition of IEC 61508 if that was the edition used when originally certified.  Certifications can be renewed using the 1st edition for up to nine years post- release of the 2nd edition.  Since the 2nd edition was released in 2010, exida will allow certification renewal under the 1st edition until 2019.  This takes into account the long lifespan of many certified products being used in the field.  Certificate owners may choose to renew…

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Setting the Pace

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Going back in time to the turn of the century (remember 2000?), the amount and quality of failure data threatened to doom the whole probabilistic analysis approach.  I recall a letter in IEEE Spectrum magazine from Patrick D. O’Conner, a well known reliability engineering author, who expressed the opinion that IEC 61508 was a unless burden that would force widespread waste of engineering time. 

We at exida recognized that probabilistic analysis had great potential to allow companies to improve safety while actually lowering cost however more realistic models and failure data were needed.  We have studied hundreds of field failure data sets and incident reports for more than a decade.  The first thing to become clear was that…

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How Do You Certify to IEC 61508?

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As you may already know, when it comes to the certification of equipment according to IEC 61508, there are several 3rd party agencies from which to choose. It is obvious from reviewing different assessments on for example a solenoid, that the interpretation of IEC 61508 and thereby the assessment method, can be quite different from one agency to the next. Why is it that for a specific solenoid one 3rdparty comes up with a failure rate of 0.47 FIT and another 3rd party comes up with a failure rate of 300+ FIT? It’s the same product!!

A few months ago I was at a manufacturer who had an assessment done by exida, as well as another 3rd party. The failure…

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Practice Makes Perfect…Almost

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How often do Managers see training budgets being cut, or personnel becoming blasé about training in general?  Isn’t it the norm that annual performance reviews involve reviewing training requirements?  Realistically, how often do these training requirements get ignored and/or forgotten about during the year?  The answer, I’m afraid, is all too often.

In the world of functional safety it’s essential that any and all personnel involved in safety have appropriate and adequate training, even if it’s just to keep up with the latest changes to the standards or industry trends.  For end users, the IEC 61511 standard is the key driver for process safety.  We at exida are always trying to promote training as a means of informing and educating…

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PHA: A must or a MUST?

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Our thoughts and prayers are with those whose lives were lost, and those injured, as well as their families in last week’s fertilizer plant explosion in West Texas. A few statements made in the press were a bit surprising and I wanted to share those with you. Before I begin, let me be clear that I do not have detailed knowledge of the functional safety culture at the West fertilizer plant nor was anyone from exida involved in any functional safety services for this plant.

• The plant’s June 2011 risk management plan (RMP), filed with the Environmental Protection Agency, identified several potential hazards, … The report asserted that the worst-case scenario for the plant “would be the release of…

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Setting up for FAILURE

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Last week I was part of a conversation that made me really question why people (companies) would set themselves up for failure.  Is it lack of knowledge?  Lack of communication? Or maybe they are simply NEW to the process and don’t know what to expect.

But then I thought about it again and realized that our industry is going through a transition. 

When I go anywhere by car I follow a simple procedure: Ask for the location, get in the car, inform my phone (GPS) where I want to go, and I start driving to the location and never miss a beat.  I can’t even imagine what it was like before we even had road maps…

In today’s…

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The Human Element of Functional Safety (The Challenge)

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The analysis of past safety accidents was conducted primarily regionally, and with companies having an “experienced” workforce. Today the global economy is undergoing major shifts in manufacturing which is making the issue of finding, developing, and retaining experienced people more challenging than in the past. In “Brownfield” (developed) areas, like North America and Europe, it has been estimated that some 30% of the core knowledge staff within the process industries will retire within five years; taking a large amount of engineering and operating experience with them.¹ Additionally, a major petrochemical company expects 50% of its engineering workforce to retire in the next five years.²

Couple the shortage of experienced and knowledgeable workers with the way plants are being designed and…

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A 100% Pass Rate!

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I recently read a blog comment from an instructor in a well-known functional safety personnel certification program.  The instructor bragged that for the last X courses, 100% of the students passed.  In this program a course and an exam are developed by independent consultants who give the course, give the exam, and grade the exam.  The certification agency collects the names and issues a certificate based on the pass/fail information from the instructor.  Is there a real conflict of interest here?  Is the 100% pass rate a metric that one should brag about?

This kind of program violates many of the requirements of ISO 17024, the international standard for personnel certification programs.  These requirements in ISO 17024 exist for good…

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Changing the PVST Interval. Hey, my Architectural Constraints changed!

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Did you see my Changing the PVST Interval. Hey, my failure rates changed! post? There is more…

In addition to impacting the way the Partial Valve Stroke Test (PVST) is addressed in the SIL verification calculation, the PVST frequency can also have a significant impact on the minimum Hardware Fault Tolerance (HFT) requirements or Architectural Constraints. When users adapt the concepts as described in IEC 61508 where HFT requirements are based on equipment type (A or B) and element Safe Failure Fraction (SFF), considering a test automatic or not can easily make a SIL level difference. Consider the SFF formulas below:

If we use the…

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Changing the PVST Interval. Hey, my failure rates changed!

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I’ve been receiving several inquiries lately regarding the impact of the Partial Valve Stroke Test (PVST) interval on the failure rates of a final element. Specifically asking how does exSILentia® deal with this? exSILentia® allows users to specify if partial stroke testing is performed on their final element configuration. In addition to the “yes/no” checkbox, the tool provides some additional features. For example, users can specify the Partial Valve Stroke Test interval, i.e. the frequency at which the partial stroke test is performed.

The frequency of the PVST interval can have an interesting impact on the way the PVST test is implemented in the SIL verification calculations, specifically relating to the…

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That is impossible! It has never happened before…

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A week ago Sunday I was traveling to Baton Rouge, LA. I was flying out of Newark Liberty International Airport (EWR) connecting in Houston (George Bush Intercontinental Airport - IAH) with my final destination as Baton Rouge Metropolitan Airport (BTR). Under normal circumstances I would probably have flown directly to Louis Armstrong New Orleans International Airport (MSY) from either Newark or Philadelphia International Airport (PHL) and driven to Baton Rouge, however all flights for either airport were completely sold out, most likely due to the beginning of Spring Break.

The Newark – Houston flight left on time and I arrived about 30 minutes early in Houston. So far, so good.  However, the flight to Baton Rouge was unfortunately delayed…

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Define the Safety Function for a Better Certification

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When a product is getting certified for functional safety, it is essential to have a clear understanding of the safety function.  First, let’s be clear what is meant by the safety function.  IEC 61508-4 describes a safety function as a “function to be implemented by a safety-related system or other risk reduction measures, that is intended to achieve or maintain a safe state for the equipment under control . . .”

The manufacturer of a product may tend to include all the model variations and configurations. After all, the certification process involves significant resources. They want to be sure not to repeat the effort in 12 months just to include another variation.

But the downside to this is a more…

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