SafetyandReliabilityAnalysisLecture3Yiliu LiuDepartment of Production and Quality EngineeringNorwegian Universityof ScienceandTechnologyyiliu.liu@ntnu.noNTNU- TrondheimNorwegian University ofScience and Technologywww.ntnu.edu
1 Safety and Reliability Analysis Lecture 3 Yiliu Liu Department of Production and Quality Engineering Norwegian University of Science and Technology yiliu.liu@ntnu.no
COMPONENTIMPORTANCENTNU-TrondheimNorwegian University ofScienceandTechnologywww.ntnu.edu
2 COMPONENT IMPORTANCE
3ComponentimportanceThecomponentimportancemaybeusedtoProvideacoarserankingofthecomponentswithrespecttotheirinfluenceonthesystemreliability (ortopeventprobability inafaulttree)HelpfocusingonthetopcontributorstosystemunreliabilityHelprelaxforthelowestcontributorstosystemunreliabilityFocusonimprovementswiththegreatestreliabilityeffectIndicatesensitivityformodelparametersHelpfocusingreviewsandsensitivitystudiesGiveprioritiesforfault-findingincomplexsystemNTNU-TrondheimNorwegian UniversityofScienceand Technologywww.ntnu.edu
3 The component importance may be used to: • Provide a coarse ranking of the components with respect to their influence on the system reliability (or top event probability in a fault tree) • Help focusing on the top contributors to system unreliability • Help relax for the lowest contributors to system unreliability • Focus on improvements with the greatest reliability effect • Indicate sensitivity for model parameters • Help focusing reviews and sensitivity studies • Give priorities for fault‐finding in complex system Component importance
ImportancemeasuresThe following component importance measures are definedand discussed in this courseBirnbaum'smeasureTheimprovementpotentialmeasureRiskachievementworthRisk reductionworthThecriticalityimportancemeasureThe importance measures arenot always consistently defined in the literature.NTNU-Trondheim莎NorwegianLniversityofScience and Technologywww.ntnu.edu
4 The following component importance measures are defined and discussed in this course: – Birnbaum’s measure – The improvement potential measure – Risk achievement worth – Risk reduction worth – The criticality importance measure The importance measures are not always consistently defined in the literature. Importance measures
5ImportancemeasuresThevariousmeasuresarebased onslightlydifferent interpretationsoftheconceptcomponentimportance.Intuitively,theimportanceofacomponentshould dependontwofactors:ThelocationofthecomponentinthesystemThereliabilityofthecomponentinquestionand,perhaps,alsotheuncertaintyinourestimateofthecomponentreliabilityNTNU-TrondheimNorwegian University ofScience and Technologywww.ntnu.edu
5 The various measures are based on slightly different interpretations of the concept component importance. Intuitively, the importance of a component should depend on two factors: – The location of the component in the system – The reliability of the component in question and, perhaps, also the uncertainty in our estimate of the component reliability. Importance measures