Failure Analysis of the Heat Exchanger Tubes Exposed to High Temperature Environment

摘要

This paper has investigated the failure of a vertical heat exchanger used in processingrnboiler feed water. The bundle of the heat exchanger was removed from service after 8 years forrnmetallurgical investigation. The tube side contains boiler feed water at 622°F and 1800 psig; thernprocess gas heats the shell at 1836oF and 565psia.rnThe tubes failed to provide expected performance due to restriction caused by thernpresence of tightly adhered deposits on the internal surface of the tube. The samples exhibitedrnextensive coverage of iron oxide deposits (hematite, Fe_2O_3 and magnetite, Fe_3O_4).rnMicrostructures on the outer surface of the tubes were more homogenized when compared to thernmicrostructures on the internal surface which contains predominantly segregated and bandedrnstructures. Both microstructure variation on the tube surfaces and the nature of the deposits couldrnhave severely influenced the general performance of the tubes of the heat exchanger.