Failure Analysis on Cracking of Finned Tube of High Pressure Evaporator

The cracking of finned tube of a high pressure evaporator appears during shutdown inspection of a non-supplementary combustion waste heat boiler used by a company. The macroscopic observation and SEM observation were carried out on cracked pipe section, and the metallographic structure and chemical composition of the material were analyzed. The results show that there are many corrosion pits and cracks on the inside of the tube wall, and there are large areas of corrosion pits on the cracks. The corrosion products in pits are oxides and chlorides. The metallographic shows that the cracks originate from the pits, and there is no bifurcation during the propagation process, the cracks are transgranular crack. The cracking of the finned tube is corrosion fatigue.