Abstract
Dent is a common form of defect on oil and gas pipeline. Some dents will undergo elastic or plastic recovery due to changes in internal pressure, also known as springback. To analyze the springback law of an API X60 pipeline with a dent defect, the secondary development technology of finite element software ABAQUS was used for parametric modeling of a dented pipeline. Using this model, the effects of various factors (wall thickness, internal pressure, indenter size, dent location, and dent depth) on the springback coefficient of a dented pipeline were analyzed. The significance of each factor was analyzed by combining an orthogonal experimental design with the Grey correlation degree. Finally, nonlinear regression analysis was used to obtain formulas for the springback coefficient as a function of the influential factors. The results show that the springback coefficient of the dented pipeline after pressurization was between 0.15 and 0.65, and the factor that had the largest effect on the springback coefficient was the dent location. The springback coefficient of the dented pipeline after de-pressurization was between 1.1 and 1.5, and the factor that had the largest effect on the springback coefficient was the internal pressure. The formulas that relate the springback coefficient and various influential factors can be used as a reference for estimating the springback of dented pipelines.
Highlights
Since the beginning of the 21st century, the oil and gas industry in China has been developing rapidly
About 20–40% of pipeline accidents are related to mechanical damage, most commonly in the form of dents [3]
The stress concentration coefficient of the dented pipeline depends on the dent depth, which is affected by the springback behavior of the dent [6,7]
Summary
Since the beginning of the 21st century, the oil and gas industry in China has been developing rapidly. The European Gas. Pipeline Accident Data Organization [11] defined the springback coefficient of a plain dented pipeline after the internal pressure was unloaded to be 1.43. Yang et al [14] established a finite element model of a dented pipeline and qualitatively studied the relationship between the dent depth, internal pressure, and springback. W Hanif et al [15] adopted a finite element method to investigate the springback of a pipeline with a dent-corrosion defect and to calculate the stress concentration factors of the pipeline. Various factors (dent size, pipe size, and internal pressure) were considered to develop a springback coefficient formula. This research was focused on the springback behavior of an API 5L X60 dented pipeline under different parameters using finite element analysis. Nonlinear regression analysis was carried out to fit the relationship between the springback coefficient and parameters
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