Abstract: In recent years, with the crude oil processed by domestic refineries has gradually deteriorated, and the content of corrosive elements such as Cl, N and S in the feedstocks used in the hydrogenation system has gradually increased, which has led to an increase in the number of corrosion failures caused by ammonium salts in hydrogenation units.Based on the historical failure cases of hydrogenation systems, the corrosion locations and corrosion mechanisms, and formulates the risk level of the equipment under different operating conditions were summarized using risk based inspection(RBI) technology.Then, the gas oil hydrogenation system of a factory was taken as the research object, and the corrosion circuit division and risk assessment of the equipment and pipelines prone to ammonium salt (NH₄Cl, NH₄HS) corrosion were carried out. At the same time, ideal control ranges are set for various indicators of different corrosion unit circuits in the system to control or slow down the occurrence of ammonium salt corrosion.

Key words: hydrogenation system, ammonium salt corrosion, RBI, risk assessment