再沸器换热管U形段失效原因分析OA

A 2507 duplex steel(S25073)U-shaped tube reboiler in a chemical plant experienced a leakage during operation.After disassembly,it was discovered that the U-shaped bend exhibited severe corrosion and perforation,resulting in the failure of the reboiler.To address the above issues,various methods such as macroscopic inspection,microscopic morphology analysis,chemical composition analysis,metallographic analysis,mechanical property analysis,residual stress analysis,and heat exchange vibration analysis were employed to investigate the causes of failure.The results show that inadequate circulation of the liquid phase material at the U-shaped bend causes the corrosive medium to evaporate and concentrate,thereby increasing the risk of corrosion.Meanwhile,residual stress in the U-shaped bend region reaches up to 231 MPa.Under the combined effect of these two factors,the heat exchange tube corrodes and failes at the U-shaped bend.The straight pipe section do not experience significant corrosion because the concentration effect of the liquid phase material is not obvious and the residual stress is low,ensuring that the corrosion resistance still met the requirements.Based on the analysis of the failure causes,suggestions for improving the selection of the reboiler under this operating condition are proposed.After the actual operation under the working conditions,it has been verified that the reboiler with the improved selection performes well under the same conditions.This case shows that in the design of heat exchange with corrosion tendency,apart from the conventional calculation of heat transfer,vibration analysis and strength calculation,the corrosion problem caused by local concentration should be paid more attention.