Evaluation of Likelihood of Failure of Topsides Piping on an Offshore Drilling Installation Due to Corrosion–Erosion Using Fuzzy Logic–Possibilistic Approach

Abstract

Corrosion and erosion are common degradation mechanisms associated with offshore drilling installations. These degradation mechanisms lead to failures in piping and other equipments resulting in loss of containment. In order to develop inspection–maintenance programs for these installations, engineers need to estimate rates of associated degradation mechanisms. Unfortunately, due to the complexities involved, it is often difficult to develop models that can accurately predict the rates of degradation mechanisms in operational installations. Luckily, development of risk-based inspection programs does not require accurate prediction models. It often suffices to have models that can give approximate predictions, but models should be robust enough to be applicable for analysis under different operating conditions of the plants, and can incorporate subjective knowledge available with inspection engineers. This paper presents a methodology to estimate likelihood of failure of a pressurized mud system piping subjected to internal corrosion and erosion. The methodology consists of two parts (a) fuzzy logic approach for estimating the rate of degradation of equipment walls subjected to corrosion and erosion; and (b) possibilistic approach for calculating possibility of failure and necessity of failure.