液化天然气气化站集合管三通断裂失效分析

Fracture Failure Analysis on Tee in LNG Regasification Manifold

某液化天然气气化站天然气集合管三通发生断裂失效,导致大量天然气泄漏。为分析失效原因,采用宏观形貌分析、扫描电镜分析、化学成分分析、显微组织检查、力学性能检验和应力水平校核等系列方法对该失效三通进行了分析。结果表明,集合管三通存在较严重魏氏组织及较严重的焊接缺陷,并由于两端固定的支承条件和较高的轴向温差应力水平,导致裂纹在支座焊接部位产生并扩展,最终发生脆性解理断裂。最后提出了预防同类事故发生的措施及建议。

Tee in LNG regasification manifold of LNG vaporizing station breaks, which can lead to large amount of LNG leakage. The failure causes were investigated by visual examination, SEM observation, chemical composition analysis, metallographic examination, mechanical properties testing and stress verification calculation. The results show that the cause for the failure of the Tee is due to Widmannstatten structure and weld defects, as well as the conditions of fixed supports and the high axial thermal stress, which can result in the crack formation and propagation at the welding HAZ of the pipe, and finally lead to brittle cleavage fracture. The prevention measures and recommendations were proposed to prevent the similar failures.