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% SIL for final elements?
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Brian kennedy
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Tuesday 24 July 2007 9:47:06 am
% SIL for final elements?
Does either IEC 61508 or 61511 confirm what % of the SIL can be allocated to final elements. Does it further suggest how much should be allotted specifically to the valve, actuator, etc
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Michel Houtermans
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Monday 26 November 2007 9:58:46 pm
Re: %SIL for final elements
There is a golden rule about this that is applied in industry for a long time. 35% for the sensor section, 15% for the logic solver, and 50% for the actuating section.
But I think it is outdated. The distribution can be very different. I have also seen 15% for the sensors, 5% for the logic solver and 85% for the actuating section.
Just remember it is only a guideline and can different significantly per loop
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