Fatigue analysis and Risk Based Inspection planning for life extension of fixed offshore platforms

The present paper reports on the application of Risk Based Inspection (RBI) planning as conducted on a recent project for Pemex Exploration y Production. The project considers the engineering assessments required for a possible service life extension of 23 fixed steel jacket structures located in the Bay of Campeche. In the project RBI plays an important role as this quantifies the relation between the overall performances of the platforms in their present condition with their future deterioration and facilitates the identification of strategies for cost efficient condition control by means of targeted inspection and maintenance activities and if necessary repair and strengthening. For the purpose of facilitating efficient RBI for larger number of structures of more or less similar characteristics, a generic scheme for RBI is pursued. The specific aspects of the generic RBI for the considered group of structures in regard to risk acceptance criteria, modeling of inspection qualities and the probabilistic fatigue and fracture mechanical modeling are outlined. Finally also a study is reported whereby the benefit of the RBI approach is assessed as a means of risk control in comparison to standard code based requirement for inspection planning.