陆上高钢级大口径天然气管道采用等内径技术探讨

Discussion on equal inner diameter technology for onshore high-grade large-diameter natural gas pipelines

陆上高钢级大口径天然气管道采用等外径设计(内锥孔型坡口设计)有效改善了管道不等壁厚处的焊接质量问题,但对于管道内部不等壁厚处的错台及其对通球、管道损耗、管道最大输送能力等的影响并未根本解决。为彻底解决等外径设计的不等壁厚带来的不利影响,分别从国内外标准规范对比、管道环焊缝应力集中数值模拟、钢管生产和现场施工影响、建设成本与运维经济性分析4方面对陆上高钢级大口径天然气管道采用等内径设计方法的可行性进行探讨。结果表明:从设计、材料、施工方面来看,采用等内径设计在技术上是可行的;从建设成本与运维经济性方面来看,通过特定场景模型计算,采用等内径设计与等外径设计在建造成本、全生命周期费用方面基本持平。研究成果可为天然气管道工程采用等内径设计提供借鉴。

The equal outer diameter design(the inner-tapered bevel design) of onshore high-grade large-diameter natural gas pipelines has effectively improved the quality problems of welding at place of pipeline with unequal wall thickness.However, the problems, including the staggered platform at the unequal wall thickness inside the pipeline and its effects on pigging, pipeline loss, and maximum transportation capacity, remain unsolved fundamentally. In order to completely eliminate the adverse effects of unequal wall thickness in equal outer diameter design, the feasibility of equal inner diameter design method for onshore high-grade large-diameter natural gas pipelines were discussed through four aspects, which are the comparison of standards and specifications at home and abroad, the numerical simulation on stress concentration at girth welds of pipelines, the influence of steel pipeline production and onsite construction, and the analysis on the construction cost and the economy of operation and maintenance. According to the results, it is technically feasible to adopt the equal inner diameter design in view of design, material and construction. Besides, in terms of the construction cost and the economy of operation and maintenance, the construction cost and full life cycle cost of equal inner diameter design is basically balanced with that of the equal outer diameter design in the calculation of a specific scenario model.In general, the research results could provide reference to the equal inner diameter design in natural gas pipeline projects.