Study On Burst Pressure Of Steel Pipeline With Colonies Of Corrosion Defects

Submarine pipelines, which serve as the arteries of the oil and gas industry, are the most efficient and safe ways to transport fluids and gases over long distances. The damage of submarine pipelines could cause not only economical loss but also severely environmental pollution especially in the harsh marine environment. Corrosion is one of the major factors which result in pipeline failure.Since corrosion defects are often displayed as colonies due to their randomness, It is of necessity to figure out interacting mechanism between the interacting corrosion defects in order to evaluate residual strength of corroded pipelines correctly.The research of interacting mechanism in this paper includes the following parts.Firstly, the results of full-size burst tests on pipelines containing interacting corrosion defects or complex shaped corrosion defects are collected. For the pipelines containing interacting corrosion defects, failure modes are illustrated and factors that affect burst pressure are described.Secondly, using ANSYS, three-dimensional finite element model of pipelines containing interacting corrosion defects are established. The FE model is validated with comparisons of the analysis results with the experimental results. Based on FE analysis, the effects of corrosion length, depth, longitudinal and circumferential spacing between corrosion defects on failure pressure of the pipelines are studied.Thirdly, according to the FE results, the limit interaction spacings between corrosion defects along longitudinal and circumferential directions are obtained, and a new interaction rule is proposed. Comparisons of the new interacting rule with the existing ones show that the new one is more accurate to identify whether or not the corrosion defects interact. Then, a new burst pressure assessment method of pipelines containing interacting corrosion defects is suggested and verified with FE results.Finally, three-dimensional FE model of pipeline containing complex shaped corrosion defects is established and validated. Based on FE analysis, the factors on failure pressure of pipeline with complex shaped corrosion defects are researched.