This paper provides an introduction on carbonate cracking and Los Angeles refinery’s recent experience with this corrosion mechanism. Also included in this paper is the methodology used for developing a risk assessment for equipment and piping susceptible to carbonate stress corrosion cracking in a fluid catalytic cracking unit (FCCU) gas plant.
Cases where alkaline-carbonate stress corrosion cracking (ACSCC) occurred, including a cold wall Fluid Catalytic Cracking (FCC) Unit regenerator and a mercaptan oxidation unit. This paper discusses work done to monitor on-going ACSCC risks through sour water sampling, chemical analysis, and ionic modeling.
Intergranular cracking and faiulure of carbon steel piping and vessels of FCC Main Fraqctionator overhead systems in NH3-H2S-CO2- containing environments is attributed to carbonate stress corrosion cracking. From plant water sampling program, cracking is correlated with water chemistry, open circuit potential and pH.