Frequently Asked Question

I am having trouble modelling the final control element of a SIF loop, having a 1oo2 (with 1oo1, and 4oo4) voting logic. The issue is that in the 4oo4 final control element leg, each component is having different failure rates, therefore I cannot select a
Last Updated a year ago

The work around for this scenario would be to assume the worst case failure rates for all four of the devices in your 4oo4 voting configuration. An alternative approach would be to model the 4oo4 voting in a separate SIF, where the final element part has 4 groups voted 4oo4 with each group voted 1oo1. You can then use the calculated PFD/PFH values to determine the equivalent failure rates of the 4oo4 voting in your SIF.

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