油气管道内外壁腐蚀缺陷干涉作用影响因素研究

目的研究油气管道内外壁腐蚀缺陷干涉作用机理及影响因素,为管道安全运行提供依据和保障。方法采用ABAQUS有限元分析软件,结合二倍弹性斜率法和控制变量法,改变内外壁腐蚀缺陷尺寸(相对深度、相对长度、相对宽度)和缺陷轴向表面间距,求解含内外腐蚀缺陷管道极限载荷,以极限载荷的变化为依据,通过5%极限影响判定标准,求得内外腐蚀缺陷干涉作用极限影响距离,同时利用MATLAB软件建立管道内外腐蚀缺陷-干涉极限影响距离函数关系,拟合得到公式。结果当外缺陷深度a1/t、内缺陷深度a2/t在0.1~0.3变化时,双缺陷干涉极限距离从46 mm增大到193 mm,且变化速率越来越大;当外缺陷长度b1/1/2Rt、内缺陷长度b2/1/2Rt在0.5~2.5变化时,双缺陷干涉极限距离从71 mm增大到219 mm,但变化速率越来越小。随着内外缺陷宽度c1、c2的增大,管道极限载荷几乎不减小,双缺陷干涉极限影响距离基本不变。构建的四元三次多项式拟合公式R2=0.9898、SSE=0.5361、RMSE=7.3219,离散性低,精度较高。结论缺陷深度是影响干涉极限距离的最主要因素,缺陷长度次之,缺陷宽度基本不影响。

Influencing Factors of Interference between Corrosion Defects in the Inner and Outer Wall of Oil & Gas Transportation Pipelines

In this paper, the interference mechanism and influencing factors of corrosion defects in oil and gas pipelines were studied to provide guarantee for the safety of pipelines. By using ABAQUS and the double elastic slope method and the control variable method, the ultimate load of the pipelines with internal and external corrosion defects were solved when the sizes of internal and external corrosion defects (relative depth, relative length, relative width) and the axial distance of the defect are changed. The influence criterion was determined by the limit of 5% interference effect, and the limit influence distance of internal and external corrosion defects were obtained. At the same time, MATLAB was used to establish the relationship between the corrosion defects with the interference effect limit distance. Also, the formula was obtained by fitting. The constructed quaternary cubic polynomial fitting formula R2=0.9898, SSE=0.5361, RMSE=7.3219, showing low dispersion and high precision. The results show that: With the increase of depths of internal and external defects a1/t and a2/t from 0.1 to 0.3, the influence distance of the interference increases significantly from 46 mm to 193 mm, and the rate of change becomes larger and larger. With the increase of the lengths of internal and external defects and from 0.5 to 2.5, the influence distance of the interference increases continuously from 71 mm to 219 mm, but the rate of change becomes smaller and smaller. With the increase of the internal and external defect widths c1 and c2, the influence distance of the interference is unchanged. Defect depth is the most important factor affecting the interference distance, the defect length is second, and the defect width is not affected.