关键词: 加氢反应器, 法兰密封槽, 失效原因, 扫描电镜(SEM), 堆焊层, 应力腐蚀开裂

Abstract:

In order to prevent accidents caused by the failure of the flange sealing groove in the hydrogenation reactor, failure analysis methods such as macroscopic inspection, fracture analysis, ferrite detection, chemical composition analysis, hardness detection, metallographic detection, SEM analysis and operation process analysis were adopted. The influencing factors of damage mode, start-stop operation process, ferrite content in the weld overlay layer, material properties, and abnormal elements were studied, and the reasons for the failure of the flange sealing groove at the outlet of the hydrogenation reactor were analyzed. The results indicate that the failure of the sealing groove is mainly due to the high stress between the weld overlay layer and base metal of the sealing groove, which produces stress corrosion cracking under the action of a corrosive medium containing F, S and other elements. There is no weld overlay layer on the bottom surface of the cracked flange sealing groove, and the transgranular cracks started at the junction of the surface weld overlay layer and the non-weld overlay layer, mainly on the surface of the non-weld overlay layer side. According to the failure causes, the corresponding improvement measures are put forward from the aspects of manufacturing, material selection and maintenance.

Key words: hydrogenation reactor, flange sealing groove, failure causes, scanning electron microscope(SEM), weld overlay layer, stress corrosion cracking