Residual ultimate strength investigation of offshore pipeline with pitting corrosion

Pitting corrosion is frequently existed in offshore pipelines adversely influencing the ultimate strength. This paper dealt with the residual ultimate strength of the pipelines with uniform pitting corrosion under external pressure using nonlinear finite element method. Influences of the degree of pit corrosion intensity, relative pitting depth, the length of corrosion region and pitting distribution were analyzed. It was concluded that the degree of pit corrosion intensity relative pitting depth have significant effects on the ultimate strength and they can be attributed to the relative metal loss, whereas the influence of corrosion length is relatively small. Further more, it was also concluded that the random distribution can be simplified to uniform distribution with the same DOP and metal loss Based on the numerical investigation, a mathematical formulation was proposed for predicting the residual ultimate strength of the pipeline.