冷低分安全阀接管断裂失效分析

Rupture Failure Analysis of Safety Valve Connecting Pipe in Cold Low-pressure Separator

介绍了加氢裂化装置冷低分罐安全阀前接管断裂失效情况,从外观形貌分析发现接管断口没有塑性变形和颈缩,属于脆性开裂。能谱分析显示接管断口有大量的硫,证明焊缝断裂失效是由于H_2S引起的应力腐蚀开裂。化学成分分析结果认定现场所用材料与设计选用材料一致,另外金相组织分析表明焊缝过渡层中高硬度马氏体组织使焊缝脆性增加。根据上述原因分析从设计规范、焊接施工和工艺操作等方面提出了建议。

Rupture failure was introduced of the front connecting pipe of safety valve in cold low-pressure separator of hydrogenation cracking unit, and the rupture is of brittle fracture for that there was no plastic deformation and neck shrinkage in the fracture through the appearance analysis. Spectrum analysis shows that there are a large number of S ions in the fracture surface, proving that fracture failure of the weld is due to the stress corrosion cracking caused by H2S. The results of chemical composition analysis found that the materials used in the field are consistent with the materials selected in the design, besides, analysis of metallographie structure discovered that high hardness martensite in the transition layer increases the brittleness of the weld. Suggestions were proposed in terms of design specification, welding construction and process operation, according to the above analysis.