关键词: 不等壁厚焊口, 失效分析, 试压开裂, 应力集中, 内部目视检查

Abstract: Aiming at the problem of weld cracking during hydrotesting of the equipment at a natural gas station, failure analysis of the welds was carried out by macro-morphological and physicochemical tests.The results show that there are such quality problems as root overlap and root incomplete fusion in the girth weldwith unequal wall thickness, and under the combination of hydrotest stress and residual stress, the weld defect starts to crack from the internal surface and extends to the outer wall. According to the causes leading to weld cracking, suggestions including optimizing the groove design, strengthening quality control during construction, and carrying out internal visual inspection and surface non-destructive testing of key welds were put forward, which can provide reference for preventing the failure of welds with unequal wall thicknesses.

Key words: weld junction with unequal wall thickness, failure analysis, crack due to hydrotest, stress concentration, internal visual inspection