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Forum: Reliability & Maintainability Questions and Answers

Topic: Reliability & Maintainability Questions and Answers

Topic Posted by: Reliability & Maintainability Forum ( )
Organization: System Reliability Center
Date Posted: Mon Aug 31 12:47:36 US/Eastern 1998

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Posted by: Ray ( )
Date posted: Fri Aug 13 17:29:06 US/Eastern 1999
Subject: Spurious Trip Rate
I am using Fault-Tree based reliability analysis programs to calculate the Probability of Failure on Demand (PFD) of a process model. I am interested in calculating the spurious trip rate (STR), that is safe trips or false trips. None of the programs I have are able to perform STR. Anyone who knows how to model the voting of redundant devices (especially 2-out-of-2 and 2-out-of-3) to calculate the STR? Any available resources on the internet? Your input is appreciated.


Subject: Spurious Trip Rate
Reply Posted by: Bruce Dudley ( )
Organization: Reliability Analysis Center
Date Posted: Thu Aug 19 9:35:18 US/Eastern 1999
Modeling a voting system for redundant units is a very complex process. The broad range of this application includes hardware, software and clock synchronization fault tolerance situations. I found two informative papers in the IEEE Transactions on Reliability that describe specific algorithms for "majority" voting, "median" voting, "exact" voting, "inexact" voting and "approval" voting. These papers are: "Voting Using Predispositions" by Douglas Blough (Univ of Cal, Irvine) and Gregory Sullivan (John Hopkins, Baltimore) and "Voting Algorithms" by Behrooz Parhami (Univ of Cal, Santa Barbara). Both paper are from the December 1994 issue of the IEEE Reliability Tranactions.

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