油气管道环焊缝面临的主要问题及应对措施

1.中国石油渤海装备巨龙钢管公司；2.国家管网集团科技部；3.中国石油集团渤海石油装备制造有限公司

1.CNPC Bohai Equipment Julong Steel Pipe Co.Ltd.; 2.PipeChina Headquarter of Science and Technology; 3.CNPC Bohai Equipment Manufacturing Co.Ltd.

为解决高钢级管道环焊缝失效难题，提升中国油气管道安全性，系统分析了管道环焊缝失效的影响因素，发现管道环焊缝失效是附加载荷、缺陷、性能劣化以及应变集中综合作用的结果。引起环焊缝应变集中的最关键原因是不等壁厚（包括钢管几何尺寸问题导致的错边），以及焊缝或热影响区软化导致的低强匹配问题。从提高环焊缝承载能力、降低环焊缝应变集中角度，提出一种新型管材设计思路，该管材管端具有极高的几何尺寸精度，不圆度、周长差等接近于0，对接时环焊缝错边和对口间隙接近0，解决了当前因管端几何尺寸导致的错边、不等壁厚等问题；通过增加管端厚度，利用结构补强原理，可大幅提升环焊接头的应力承载能力，解决环焊缝低强匹配以及焊接热影响区软化导致的低强匹配难题，实现管道受力变形时环焊接头不发生或少发生塑形变形，显著提升管道环焊缝安全。（图7，表5，参22）

In order to solve the problem of girth weld failure of high-grade pipelines and improve the safety of oil and gas pipelines in China, the influencing factors of girth weld failure of pipelines were systematically analyzed. It was found that the girth weld failure of pipelines was resulted from the combined action of the additional loads, defects, performance degradation and strain concentration. Meanwhile, the strain concentration in girth welds was mainly led to by the unequal wall thickness, including the misalignment caused by the geometric dimension of steel pipelines, and the low strength matching due to the welds or softening of the heat affected zones. In order to improve the bearing capacity of girth welds and reduce their strain concentration, a new type of pipe design idea was put forward, with the high dimension accuracy, out-of-roundness and circumference difference at the end of the pipes, as well as the misalignment of girth welds and the joint clearance during butting, close to zero, solving the current problems of misalignment and unequal thickness caused by the geometric dimensions at the end. In addition, by increasing the end thickness of pipes and using the principle of structural reinforcement, the stress bearing capacity of girth welding joints can be greatly improved, and thus the problem of low strength matching caused by the girth welds or softening of the heat affected zone could be solved, so that no or little plastic deformation occurs at the girth welding joints and the safety of the girth welds of pipes is improved significantly. (7 Figures, 5 Tables, 22 References)