Sensitivity Analysis of Fitness-For-Service Assessment Based on Reliability for Cylindrical Pressure Vessels With Local Metal Loss

Abstract

The concern with Fitness-For-Service (FFS) assessment using stochastic analysis for aged pressure equipments with local metal loss has been growing for the last several years. The structural integrity assessment based on reliability helps to make a decision as to whether to run or repair the equipments with local metal loss. As for analysis of failure probability, it is important to clear which variables affect highly the structural integrity. The stochastic property of the influential parameter needs to be clarified. There has, however, been little study to analyze quantitatively the sensitivity of the parameters for the FFS assessment of the components with local metal loss. In this study, the effects of parameters on plastic collapse of the damaged component were evaluated utilizing parameter sensitivity study. Additionally, sensitivity indices for the component with several shapes of local metal loss were analyzed. It was found from the results that the corrosion rate has much influence on probability of failure. Finally, practical stochastic analysis procedure for the component with local metal loss was proposed. In the proposed procedure, the parameter which has consistently low sensitivity to limit state was used as constant value.