Abstract: Frequent leakage of the convection section of the raw material preheating section seriously affects the long-term and safe operation of the cracking furnace. Macroscopic inspection, spectral analysis, metallographic analysis, scanning electron microscopy, and energy spectrum analysis were used to detect and analyze the leaking furnace tube. The results showed that the bottom of the leaking furnace tube was densely covered with horseshoe shaped and sponge shaped corrosion pits, which overlapped and connected with each other. Multiple corrosion grooves arranged parallel to the axial direction of the furnace tube were formed, and the maximum corrosion rate at the leakage point of the furnace tube was 0.58mm/a. From the perspective of corrosive media, convection section process flow, coking process flow, and cavitation factors, the corrosion reasons of the preheating section of the raw material furnace tube were analyzed. It was found that the cavitation generated during the execution of the light hydrocarbon process in the convection section of the light hydrocarbon cracking furnace and the dissolved oxygen corrosion generated during coking were the main reasons for the corrosion and leakage of the preheating section of the raw material furnace tube. Under the combined action of both, the inner wall of the furnace tube continuously corroded and thinned. And ultimately, perforation leakage occurred. Finally, the process protection measures of setting a dilution steam blowing line at the inlet of the raw material preheating section were proposed and applied, fundamentally avoiding corrosion and leakage of the furnace tubes.

Key words: light hydrocarbons, cracking furnace, convection section, furnace tube, corrosion, protect