Cost optimal reliability based inspection and replacement planning of piping subjected to CO{sub}2 corrosion

摘要

A methodology for cost optimal reliability based inspection and replacement planning of piping subjected to CO{sub}2 corrosion is described. Both initial (design phase) and in-service planning are dealt with. The methodology is based on theapplication of methods for structural reliability analysis within the framework of Bayesian decision theory. The planning problem is formulated as an optimization problem where the expected lifetime costs are minimized with a constraint on the minimumacceptable reliability level. The optimization parameters are the number of inspections in the expected lifetime, the inspection times and methods. In the design phase the nominal design wall thickness is also treated as an optimization parameter. Themost important benefits gained through the application of the methodology are consistent evaluation of the consequences of different inspection and replacement plans, consistent incorporation and handling of uncertainties, and consistent updating ofinspection and replacement plans based on inspection results. The latter is achieved through application of Bayesian statistics for updating in combination with structural reliability methods.