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Functional Safety Standards - IEC 61508 vs. IEC 61511

Functional Safety Standards - IEC 61508 vs. IEC 61511

IEC 61508 is considered a basic or “umbrella” standard for functional safety.  It is generic and sometimes even vague.  IEC 61508 was intended that various industry sectors provide their own specific standards and guidelines as needed.  Here we can see the relationship between 61508 and other standards, such as…

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So what does Interference-Free mean?  And why do we care?

So what does Interference-Free mean?  And why do we care?

An Interference-Free component, either as an interface or a defined functional area, is a system component that is neither safety critical (C3) nor safety relevant (C2), but interfaces with such subsystems. 

If a component has been shown to be interference free (C1), then it has been demonstrated that no…

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Getting Good Proof Test Coverage Numbers

Getting Good Proof Test Coverage Numbers

Several years ago we recognized that proof test coverage was an important variable that must be considered when doing PFDavg calculations. We ran some models and discovered that the difference between “perfect” proof test coverage (100%) and a very good 90% could mean a whole SIL

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IF COMPUTERS RULED THE WORLD…

IF COMPUTERS RULED THE WORLD…

What if the best minds of the world got together to generate the optimum requirements specification for human co-habitation?  And built it into one large decision matrix to run on the best super-computers?

Decisions would be made solely on objective criteria; no mental arbitration, no skipping steps, no checking…

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Conceptual Design and SIL Verification’s Ultimate Resource

Conceptual Design and SIL Verification’s Ultimate Resource

The Importance of Process Safety to the next Generation of Chemical Engineers

The Importance of Process Safety to the next Generation of Chemical Engineers

Realistic Failure Rate Data – Necessary

Realistic Failure Rate Data – Necessary

Reliability engineers have known for decades that realistic data must ultimately come from one source, quality field failure data for devices operating in a similar application. 

Perhaps that is why IEC 61511:2016, Clause 11.9.3 states

“The reliability data used when quantifying the effect of random failures shall…

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Back to the Future?

Back to the Future?

At 7am, my personal robot (I call him ‘Jake’) turns on the bedroom lights to 50% brightness and waits for my body to recognize the onset of morning.  If I take longer than 5 minutes, Jake will begin to play some soft music.  This is usually enough to get…

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Nothing Happens Until Someone Sells Something!

Nothing Happens Until Someone Sells Something!

When I first heard this phrase, I was working in an R&D group developing electronic DCS.  My first interpretation was that until the Sales Department got an order for a new product, new ideas sort of sat on the shelf with low priority… meaning that people were probably working…

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“Never tell me the odds”

“Never tell me the odds”

-Han Solo, Star Wars, Episode V: The Empire Strikes Back, 1980

I have enjoyed watching and reading about the actions of the fictional Star Wars character Han Solo over the years.  I recall hearing the above quotation more than once.  And as much as I enjoyed watching this character,…

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Functional Safety Evolution

Functional Safety Evolution

Protection systems have been around for a long time, going back to having a canary in the mine, and throughout the Industrial Revolution; so they are not a new thing.  Various stakeholders were involved in business enterprises: owners, suppliers, consumers, community members, and workers. Usually the business owners held…

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PRODUCT SPOTLIGHT: Practical SIL Target Selection - Risk Analysis per the IEC 61511 Safety Lifecycle

Let’s Get Personal… with Risk

Let’s Get Personal… with Risk

We recognize that risk is inherent in many aspects of our lives.  And most of us will do what is prudent to avoid unreasonable risk in our activities, such that we are left with some level of tolerable risk.  It may be safer to stay home and not travel…

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Are You Ready For What’s Coming?

Are You Ready For What’s Coming?

If you’re like me then you’ve been waiting for the new draft of IEC 61511 to be officially issued since its release has been delayed for some time.  However, a draft has been released and can help in preparing end users for what’s to come.  The question…

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What Good is a Safety Manual?

What Good is a Safety Manual?

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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