含环焊缝圆形气孔缺陷的管道极限承载能力分析

Analysis of Pipeline Ultimate Bearing Capacity of Girth Weld with Round Pores Defects

圆形气孔缺陷在天然气站场管道环焊缺陷中占比最高,严重影响了天然气管道的安全运行及完整性管理。针对中石化川气东送的7个天然气站场中含圆形气孔缺陷较多的几种典型管道,建立有限元模型,分析了基本载荷条件下不同径厚比及不同气孔缺陷位置的管道等效应力分布。研究表明:管道径厚比越大等效应力越大,圆形气孔缺陷越靠近管道内壁等效应力越大,管道越危险。在应力分析的基础上计算了不同影响因素下圆形气孔缺陷管道的极限承载能力,影响管道极限承载能力的因素主要为管径、壁厚及气孔缺陷尺寸,气孔缺陷的位置对极限承载能力的影响很小,并给出了适用天然气站场的含环焊缝圆形气孔缺陷管道的极限内压预测公式。

In general,the round porosity defects account for the highest proportion in the girth welding defects of natural gas station pipeline,which seriously affect the safe operation and integrity management of natural gas pipeline.Aiming at several typical pipelines with many round porosity defects in 7 gas stations of Sinopec Sichuan east gas transmission project,a finite element model was established to analyze the equivalent stress distribution of pipelines with different diameter to thickness ratio and different location of porosity defects under basic load conditions.Results showed that the larger the diameter to thickness ratio,the greater the equivalent stress,the closer the round porosity defect,the greater the equivalent stress of pipe inner wall,and the more dangerous the pipeline was.Based on stress analysis,the ultimate bearing capacity of the pipeline with round porosity defects was calculated under different factors.The main factors affecting the ultimate bearing capacity of pipeline were pipe diameter,wall thickness and the size of porosity defects,while the position of porosity defects had little effect on the ultimate bearing capacity.Furthermore,the prediction formula of the limit internal pressure of the pipeline with girth weld round porosity defect suitable for natural gas station was given.