Since the preheating furnace has been put into use, a total of 8 equipment abnormal accidents have occurred during the operation period, as follows. (1) The outlet flange of the radiant section of the preheating furnace leaks, and the gaskets and bolts are replaced when the vehicle is stopped. Reason analysis: The installation quality is the problem, the bolt selection is wrong. (2) Cracks appear in the welding seam of the header header at the outlet of the radiant section, stop for repair welding. Reason analysis: The welding quality of the header manufacturing is unqualified. (3) The boiler water heat exchange tube in the convection section of the preheating furnace leaked. Due to the difficulty of repair and construction, it was decided to short-circuit the boiler feed water pipe from the outside of the furnace after research at the special meeting, and the inlet and outlet headers of the boiler feed water were blocked. Reason analysis: The manufacturing quality of the boiler water heat exchange tube in the convection section is poor. (4) Leakage occurs in the fillet weld between the outlet header of the radiant section and the coil, and the system is shut down to repair the leak. Reason analysis: The original design and welding process of the welding structure of the outlet pipe of the radiant coil and the header are not perfect; the fillet weld has the problem of insufficient fillet height and incomplete penetration. (5) Leakage occurred again at the fillet weld between the outlet header of the radiant section and the coil, and the header was stopped for renovation and replacement, which completely solved the defects in the design. (6) Crack leakage of the paired flange at the outlet of the radiation section header. Reason analysis: There is a misalignment between the matching flange and the pipeline in the original installation process, and the thermal expansion stress of the pipeline is concentrated in the transition area of ​​the high neck of the flange, and cracks are generated due to excessive stress during operation. Further inspection found that there was a crack at the high neck of the header flange, and the header flange and mating flange were replaced.