Functional Safety 2014

Learning points from real plant data

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The undetected failure rate is similar to the spurious trip / detected failure rate

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For every fault you know about, there’s one you don’t

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And it means your Safety Function will never work

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Beta factor = 25%

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Probably not, as could be Systematic, but it’s not 1%

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Proof testing interval is set by PFD (Random + Common Cause)

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But it catches Systematic too

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Here Systematic was 20% of all failures

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And maybe higher if Common Cause failures actually Systematic