油气管道环焊缝缺陷检测评价方法研究

Study on Detection and Evaluation Method of Girth Weld Defects in Oil and Gas Pipeline

油气管道环焊缝隐患排查过程中的无损检测方法、无损检测缺陷合格评判尺度、是否需要修复的判定尺度和修复方法的选择等均没有统一的标准。通过对有关无损检测标准的技术内容进行对比,提出应以射线和超声检测作为首选无损检测方法,以SY/T 4109 II级为合格评判标准。对不合格缺陷,建议进行PAUT或TOFD检测确定缺陷自身高度。同时,还应进行缺陷适用性评价,并以评价结果是否可接受作为不合格缺陷修复的依据。缺陷适用性评价应考虑焊缝的断裂韧性、缺陷尺寸、附加载荷、高后果区等安全因素。对适用性评价不可接受但可修复的环焊缝缺陷应采取相应的适当方法进行修复。对于适用性评价可接受但存在附加弯曲载荷的危害性缺陷,可进行环氧套筒或B型套筒补强。

Puzzles such as choice of NDT methods,qualified size of weld flaw,critical flaw size of repair and choice of repair methods,exist in hidden peril identification of oil and gas pipeline girth welds.Against these problems,through comparison of different NDT and pipeline construction acceptance standards,it is believed that RT(Radiographic Testing)and UT(Ultrasonic Testing)are preferred in all NDT methods.And level II of SY/T 4109 should be qualified flaw size in RT and UT.For unqualified flaw,PAUT or TOFD is suggested to determine flaw height.In addition,Fitness for service assessment(FFS)should be performed for unqualified NDT flaws,and the result of FFS should be the criterion of flaw repair.Weld fracture toughness,flaw size,additional load,high consequence areas and other factors should be considered in FFS.For repair of FFS unacceptable girth weld flaw,appropriate methods shall be taken for repair.If a dangerous weld flaw in FFS can be acceptable,but an additional bending load is acting on it,steel epoxy sleeve or B-type sleeve can be used as a reinforcement method.