Three girth weld cracking events were found by X-ray inspection in one natural gas station. To determine the failure cause, one of the three failure events was studied by visual inspection, nondestructive testing, microstructure examination, scanning electronic microscopy (SEM) coupled with energy dispersive spectrometry (EDS), blasting tests, finite element simulations and a series physical and chemical tests. The results revealed that the welding defects were original failure factor, and these welding defects led to crack initiation and propagation through the wall thickness under three aspects of stress concentration effects with internal pressure. The stress concentration effects were originated from the unqualified inner chamfering angle, unequal wall thickness, and inherent shape of tee pipe. The reason causing welding defects of girth weld is that the slag inclusions were not cleaned up timely, and then the slag inclusions led to the existence of welding defects.

通过X射线检查在一个天然气站中发现了三个环缝焊缝开裂事件。为了确定故障原因，通过视觉检查，无损检测，微结构检查，扫描电子显微镜（SEM）结合能量色散光谱（EDS），爆破测试，有限元模拟以及一系列物理和物理方法研究了三种故障事件之一。化学测试。结果表明，焊接缺陷是原始的破坏因素，这些焊接缺陷在内部压力引起的应力集中效应的三个方面导致了裂纹的萌生和在壁厚上的扩展。应力集中的影响源于不合格的内倒角，不相等的壁厚和三通管的固有形状。