大管径、高钢级天然气管道环焊缝焊接技术

唐山LNG外输管道是与规划建设中的中俄东线天然气管道、涿州—永清天然气管道等项目的互联互通工程，管道沿线主要地貌为沿海滩涂、连片鱼塘、水网、软土地基、果园和农田等，该工程采用了单管自重超过10 t、外径1 422 mm、X80钢级管道，焊接施工难度大、质量要求高，以往的半自动、手工焊等环焊工艺不能完全满足工程的需要。为此，基于X80钢管的环焊接头技术要求，结合该工程地貌特点和施工人力资源情况，提出了以管道环焊缝自动焊为主要焊接方法的环焊缝焊接工艺方案，并设计、确定了焊接坡口形式，优选了焊接材料和焊接设备，拟定了焊接施工管理措施。焊接工艺评定结果表明：所提出环焊缝焊接工艺获得的焊接接头、强度、韧性、硬度、低倍金相等理化性能试验结果均满足相关标准和设计的要求。该工程项目现场焊接实践证明，采用所提出的环焊缝焊接工艺进行焊接施工，焊接质量优良、施工效率高，从施工质量管控过程中总结出的质量管控关键点，可以为后续油气管道工程建设的焊接施工管理提供借鉴。

Girth welding technology for large-diameter high steel grade gas line pipes

The Tangshan LNG Pipeline is interconnected with Russia-China Eastern Route Pipeline and Zhuozhou-Yongqing Gas Pipeline, which are in planning and construction. The landforms along the Tangshan LNG Pipeline are mainly coastal tidal flats, continuous fish ponds, water networks, soft soil foundations, orchards and farmlands, and D1422 X80 pipes with the single-pipe weight over 10 t are adopted in this project, which increases the welding construction difficulty and quality requirement. The previous girth welding procedures (e.g. semi-automatic welding and manual welding) cannot completely meet the engineering need. Based on the technical requirements of X80 girth welding joint, combined with the landform characteristics and construction human resources of the Tangshan LNG Pipeline project, this paper put forward a girth welding procedure with automatic girth welding as the main welding method. Then, the form of welding groove was designed and determined, and welding materials and welding equipment were selected. Finally, welding construction management measures were worked out. The results of welding procedure qualification show that the tested physical and chemical properties of the girth welding joints made through the proposed girth welding procedure meet the relevant standards and design requirements, such as strength, toughness, hardness and low-power metallographic phase. The welding practice in the field of the engineering project proves that the welding quality is excellent and the construction efficiency is high when the proposed girth welding procedure is adopted. The key quality control points summarized in the process of construction quality control can provide reference forwelding construction management in the subsequent construction of oil and gas pipelines.