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Functional Safety Play Book
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1 contribution to Functional Safety Play Book
Jan 8 •
Mission Time
Hi all, thanks for accepting. First of all, I am new in functional safety and sorry for my bad english😊. Actually I have some doubt about one of variable in PFDavg calculation namely mission time, couple of question to all: 1. What will happen in the end of mission time?should end user decommissioned the plant?or just replace everything and the mission time will get restarted? 2. If it depend on end user, than based on what consideration usually for them to determine the correct mission time?and what is the reason behind that? 3. Since by the time PFDavg will get derated, and SIL claimed may decreased over the time, shouldn't end user decide to set the mission time before the SIL/RRF drops beyond the rating it should be? Hope you guys can share your knowledge. Thanks,
1 like • 9d
@Tomasz Barnert Hi Tomasz, that is a very good insight, totally agree, To my knowledge, this mission time decision should not come from system integrator or engineering CPY, the one that should define is the asset owner. Unfortunately, here many asset owner especially power generation (not nuclear), they don't really follow and concern about IEC61511.
0 likes • 10h
@Harvey Dearden hi harvey, thanks for the comment, i think realistically PFDavg will never return to zero as Proof test coverage will never have 100% coverage. PFDavg will then accumulated over the mission time. Just wondering what to do in the end of mission time, should we refurbish everything or replace with new equipment? And can it returned the PFDavg value to zero. Or basically the plant will be decommissioned in the end of mission time.
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