L360QS管道环焊缝泄漏失效分析

Failure Analysis of Leakage for the Girth Weld of L360QS Pipeline

利用力学性能分析、X射线探伤和微观组织分析等研究方法对L360QS管道环焊缝的泄漏原因进行了系统研究和分析。射线检测结果表明相邻未失效环焊缝未发现有超标缺陷;失效环焊缝除开裂部分外,未发现有超标缺陷。理化性能检测结果表明母材及环焊缝符合标准要求。裂纹从环焊缝根焊部位起裂,沿着靠近直管一侧的熔合线扩展,焊缝根焊部位附近有氧化物存在。裂纹由环焊缝根焊部位起裂,向外壁辐射扩展,属于脆性断裂,断口处存在硫化物和氧化物,为H2S应力腐蚀开裂所引起的管道失效。

The leakage reasons for the girth weld of L360 QS pipeline was investigated through mechanical properties test,X-ray inspection and microstructure analysis by scanning electron microscope. The results show that the exceeding defects in the girth weld cannot be found by X-ray inspection without the cracking part,but the results of tests for base metal and weld conform to the standard. The crack initiation is in the root weld of the pipe,propagates along fusion line which is close to the straight pipe,and the oxides are found in the root weld.The crack starts from the root weld,propagates to the surface,the oxides and sulfides exist in the brittle fracture,so the reason for the failure is the hydrogen sulfide stress corrosion cracking.