Analysis of failure cause of leakage of ammonia supply pipeline in urea hydrolysis reactor of an ultra-supercritical unit

In response to the leakage of the ammonia supply pipeline in the urea hydrolysis reactor of a certain thermal power plant’s ultra-supercritical unit, the leakage mechanism of the ammonia supply pipeline was studied through methods such as macroscopic analysis, material composition, metallographic examination, mechanical performance testing, and scanning electron microscopy inspection. The results show that there are a large number of strips like chromium rich phase segregation structures in the microstructure of the leaked ammonia supply pipeline base material, and the tensile strength and elongation after fracture are lower than the lower limit values required by relevant standards. Therefore, it can be determined that the main reason for the leakage of the ammonia supply pipeline is the obvious tissue and component segregation of the raw materials, which leads to the deterioration of the mechanical and corrosion resistance properties of the pipes, thereby exacerbating the initiation and propagation of cracks.