exida explains Blog

One of the objectives of new performance based standards like IEC 61508 is to allow performance metrics (like PFDavg for low demand systems) to identify the weak links in any proposed design.  Obviously, it is not necessary to put effort into design and spend money on areas…

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A.K.A You’re About to Severely Under-Design your SIF and Put your People at Risk. Twice this week alone, and much more often than I like to remember, I’ve had safety system designers blindly follow certificates that contain data that simply cannot be true. They get a certificate from…

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When building a product such as an anti-lock braking system for an automobile, or a railroad, or process control safety system, making sure that the product works as specified is a big part of functional safety. When it is time for the system to engage to prevent an accident,…

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Please see the first entry of the Requirements Management blog series here

Please see the second entry of the Requirements Management blog series here

So, you have a set of detailed safety requirements.  You have derived them down to a level of detail you feel spells out…

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Sure, you might think I’ve got it made… sitting here on my perch telling you what you need to do to meet IEC 61508, while you sit there with all the work to do.  Well, it wasn’t always that way.  I was in your shoes, responsible for achieving functional…

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Traceability is about connecting the dots to determine that the web of activities for a functional safety project have followed the proper paths.  Think of it like cheating at hide-n-seek; it provides a shortcut to find all those requirements and design parts that are hidden in your specification documents. …

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Many products have options and features that are valuable to users.  But not all these features should be permitted while the product is performing a safety function.  For example, HART communications should not be permitted to write data to a transmitter while it’s performing the safety function.  If you…

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exida was recently auditing a systems level project per IEC 61511.  During such audits we check to verify that all equipment used in a safety instrumented function meets systematic capability by either IEC 61508 certification OR justification per reasonable IEC 61511 “prior use” criteria.  Most engineers at…

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In the 1980’s, there was a raging debate in the functional safety committee about redundancy versus diagnostics. Some said functional safety could only be achieved with redundant systems. This was strongly supported by Triple Modular Redundant (2oo3) safety PLC vendors. 

Others argued that diagnostics would be an equal or…

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I’ve been following some discussions from one of the online forums regarding competency and it’s clear from the correspondence that the issue of competency is still very subjective.  It made me think about “what is competency?” To me it’s a blend of knowledge and experience and just how well…

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The term SIL is rapidly spreading to Request for Proposals (RFP) and purchase requirements in many industries.  But in many of those industries, few have heard about SIL and fewer have a grasp of the fundamental concepts of SIL.  SIL is a term that means Safety Integrity Level. It is used…

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It used to be that a pump would operate at a single speed dictated by a motor, thus fixing the pump curve. As the discharge flow decreased due to a restriction downstream, the pump outlet pressure would increase reaching its deadhead pressure. If the downstream piping and vessels were…

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This year, make your New Year’s resolution safety! 

Take a moment this year and think about where you currently stand with functional safety. And actually, be honest with yourself. REALLY honest. Do you proof test on time, or does it sometimes get pushed out? Do you pull your devices…

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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…

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I’ve heard this phrase so many times in my life… “<Something> is the best thing since sliced bread.” I personally can’t remember a time when sliced bread was not available, but I certainly remember going to the deli and having them use the slicing machine before handing me a bag…

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When I start working with new customers for IEC 61508 certification projects, it’s easy to understand why they might not have a compliant development process for functional safety:  they’ve never done it before!  They understand their market and their products, but they need help to understand the…

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Many will agree that exida's Safety Equipment Reliability Handbook (SERH) and the Safety Automation Equipment List (SAEL) are very useful tools for choosing products to use in safety instrumented systems. The SAEL shows a product’s IEC 61508 and cyber security…

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This was a question posed to me by an engineering contractor the other day.  Although I found the question quite strange, it made me think “okay, why do they need us?”  I suppose there are a few answers:

1. Regarding the end user perspective, we exist to provide an independent third-party…

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If you find yourself faced with this question you might be wondering why it is that having successfully used risk assessments without FMEDA your team are suddenly faced with the complexity of executing FMEDAs.

Maybe us safety people answer with a follow…

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Some organizations complain about the ‘high bar’ to comply with 61508.  They complain that there is too much overhead in documentation and testing, and it all costs too much.  Other organizations actually benefit from this ‘high bar’ as a barrier to entry for competitors.  This is a differentiation factor…

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