加氢换热器管束腐蚀断裂分析及改进措施

Analysis and improvement measures of tube bundle corrosion in hydrogenation heat exchanger

在某加氢裂化装置一台反应产物/低分油换热器管束中,有两根换热管发生断裂、脱出问题。经换热管断口宏观分析、材料成分分析、断口扫描电镜观察及能谱分析、金相分析、介质分析和交变载荷等综合分析,结果表明:换热器的换热管断裂失效是由点蚀和腐蚀疲劳引起的,点蚀是由氯等腐蚀性元素造成的,且管程受壳程介质冲击载荷影响,在近管板处产生一定的循环应力促进了腐蚀坑处疲劳裂纹的产生和扩展。

Two heat exchange tubes were broken and detached in a heat exchanger of hydrocracking unit.Comprehensive research was conducted by means of fracture macro analysis,material composition analysis,fracture scanning electron microscope and energy spectrum analysis,metallographic analysis,medium analysis and alternating load analysis,it was concluded that the failure comes from pitting corrosion and corrosion fatigue.The main cause of fracture is pitting corrosion caused by Cl-and other corrosive elements in shell side medium.Under the influence of shell side medium impact load,a certain cycle stress was generated near tube sheet,which promotes the growth of fatigue cracks in corrosion pit.