Functional Safety 2014

i) Safety function will not work at all

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Serious breakdown in processes must have occurred

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Many of the errors in this category point to commissioning or brownfield

changes where logic is forced or disabled, probably post validation

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Can indicate techniques to modify logic while plant running

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Forces applied during operation phase

Examples:

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Trip setpoint missing or outside range of transmitter

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Trip function switched off on the software function block.

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Software force applied to I/O driver or communications blocks.

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Temporary logic inserted into the application software to defeat logic.

Neil Wakeling, August 2014