Prediction of the internal corrosion remaining life of a gas pipeline made of highstrength steel

Hui-qing Lan

Abstract


During the operation of a high-strength steel compressible gas pipeline, the corrosion rates in the strong turbulence position near the inner-wall of the pipe are higher than the average corrosion rates. These changes lead to internal corrosion defects of the pipeline. In this work, a finite-element pipe model was built based on the working conditions of an X70 pipeline in the West-to-East Natural Gas Transmission Project. The stress distributions in the inner-wall of the pipe under different parameters of semiellipse defects were calculated by a time domain method with fluid-structure interaction. In the stress distributions simulation, the failure pressure formula of the high-strength steel pipe with semi-ellipse defects under the influence of the flow field was fitted based on Marquardt method. The prediction formula of the internal corrosion
remaining life of the high-strength steel gas pipe was established according to the deWaard corrosion model modified by the flow field. The prediction for the semi-ellipse defect parameters shows that depth has the strongest effect on the failure pressure of the pipe, whereas width has the least effect. Based on the obtained formula, the failure pressure prediction of the pipe with defects under the influence of the flow field was slightly lower than the experiment data under a simple internal pressure load. Under stable operating conditions, inclination angle had the largest effect on the internal corrosion and remaining life of the high-strength steel gas pipeline. This prediction method provides a more targeted on-site inspection of long-distance gas pipelines made of high-strength steel.


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