Estudio de trabajo a fatiga en ductos marinos para una unidad flotante de producción, almacenamiento y descarga (FPSO) usando un sistema pasivo de compensación de rolido : evaluación de daño por fatiga en ductos marinos.

Abstract

Offshore hydrocarbon extraction uses flexible pipelines (risers) attached to the balcony of an oil production, storage, and offloading (FPSO) vessel. These risers are subjected to cyclic loads caused by wave impacts. This project deals with a methodology to assess fatigue damage in the upper attachment point of a riser. This analysis was performed for different wave heights (Hs) a peak period (Tp), with and without a roll compensation system on the FPSO. The Rain Flow Counting (RFC) method and the Palmgren Miner rule were used to evaluate fatigue damage in the riser using of MATLAB functions. The application of the RFC method starts from a stress time history. Then, it is converted into a histogram of cycles as a function of stress ranges. The Wöhler curve of the API 5L X65 material and the Palmgren Miner rule, allows to compute the fatigue damage of the riser in the upper section. The results indicate that for the most critical cases when Hs = 5 [m] and the period Tp = 14[s], there is a stress range of ∆σ = 63.27 [MPa] y ∆σ = 103.84 [MPa] with and without a roll compensation system, respectively. The stress ranges mentioned above are below the fatigue strength limit of the material σe = 150 [MPa]. For the pipeline studied in this work, it is concluded that there will be no fatigue damage at the riser attachment point