A company’s heat exchanger began operation in mid-July 2022. Heat exchanger tube medium for river water, the design pressure is 1.0MPa, working pressure is 0.4MPa; The inlet temperature is 34°C, and the outlet temperature is 40°C. The material of pipe path is S31603(GB/T 13296-2013), and the specification is φ16*1.5mm. The shell medium of the heat exchanger is syngas (hydrogen, methane, nitrogen, ammonia, etc.), the design pressure is 8.0MPa, the working pressure is 7.5MPa, the inlet temperature is 156.6°C, the outlet temperature is 42°C. In February 2023, a large amount of pungent gas was discharged when the return water of the heat exchanger pipe was drained. The sample was analyzed for syngas composition. On February 10, 2023, Quansheng planned to shut down the system to eliminate defects. After opening the heat exchanger, serious scaling was found. The failure analysis of the heat exchanger tube was carried out, and it was found that the physicochemical and mechanical properties of the heat exchanger tube (S31603 material, φ16*1.5mm) were qualified and in line with the material standard GB/T 13296-2013. The main reason for the heat exchanger pipe cracking is that the running medium uses river water, river water contains more impurities and high sulfur oxygen content, in the inner wall of the pipe scaling generation of polysulfuric acid; There is a certain residual stress in pipe manufacture, which results in stress corrosion of polysulphuric acid.