The Study Of Loading Capacity On Corroded Oil Pipelines

All the time, the oil and gas' transportation is suffering restriction for further development because of the pipe incident, and the great losses it brings to national economy and ecological environment. Under certain conditions, the safety incident easily occurs on corroded long-distance pipelines. Therefore, the accurate assessment of residual strength for corroded pipelines is very important.In this paper, a brief introduction to ANSI/ASME B31 G evaluation criterion and FEA(finite element analysis) method is provided, and verifying the FEA method is more accurate than the B31 G evaluation criterion by analysing the adaptabilities of them.Combining the mechanical principle and the FEA method, effects on pipes of pressure from internal fluid and external earth are discusse d.It is proved that the static pressure affects pipe stress mostly, and the earth pressure has little effect on loading and deformation capacity.Using the FEA software ANSYS, the FEA models of corroded pipeline are established, effects from pipe models on the FEA results are studied, especially the ones from corrosion shape on stress distribution and residual strength. The result shows that the shape of surface projection of corrosion has little influence on stress distribution but much influence on residual strength, for which the angle than the arc, the arc with small curvature than the one with big curvature are more likely to reduce the residual strength, and the shape of depth transition of corrosion affects both elastic stress distribution and residual strength, depth along the arc transition can make the stress distribution more uniform and the residual strength closer to the experimental value. Comparing to the pressure blasting test results, the correctness of the FEA model is proved.