Fracture failure analysis of heat exchange tube for methanol waste heat boiler
The cracking and leakage of some heat exchange tubes for S32168 methanol waste heat boiler used in one project were observed after use for about one month.The cracking locations were all at the expansion joints of the heat exchange tubes.The macro and micro fracture morphology,microstructure,chemical composition and mechanical properties of the expansion contact of the heat exchange tube were analyzed.It was found that the fracture morphology was the typical mor-phology of stress corrosion fracture and corrosion fatigue fracture.The microstructure was austenite,and other abnormal structures were not found.The composition and mechanical properties could meet the requirements in related standards.By combining with the fracture position,fracture morphology,chemical composition and service environment,the comprehen-sive analysis indicated that the failure of heat exchange tube was mainly due to stress corrosion and corrosion fatigue failure.The reason was that the expansion of the tube during use made its inner diameter larger than other positions in the tube,which was easy to store corrosive medium of H2S aqueous solution at this place,which finally led to cracking and fracture of heat exchange tube here.
heat exchange tube of waste heat boilerfracturestress corrosioncorrosion fatigue
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