EDC Cracking Furnace Tubes Failure: External CLSCC Cracking in Alloy 800 Tubes

Abstract Corrosion management in petrochemical complexes, particularly those handling chlorinated hydrocarbons, poses a significant challenge in the downstream industry. These hydrocarbons tend to hydrolyze, producing hydrochloric acid (HCl), which is highly corrosive. Additionally, incineration of chlorinated hydrocarbons releases airborne chlorides, increasing the risk of external chloride stress corrosion cracking (Cl SCC) in stainless steel and nickel-based alloys. An integrated chlor-vinyl complex has been operating Chlor-Alkali, Ethylene Dichloride (EDC), and Vinyl Chloride Monomer (VCM) manufacturing facilities for the past 16 years where two EDC cracking furnaces are being used to convert 1,2-Dichloroethane into VCM and anhydrous HCl at operating temperature of 510°C. These furnaces are comprised of two sections i.e., radiant and convection, with SS347H and Alloy 800 as construction material for tubes. However, in one of the EDC cracking furnaces, eight Alloy 800 coils in the convection zone failed due to external Cl SCC caused by airborne chlorides. Fortunately, these failures were detected through annual pressure testing thus preventing a catastrophic event. This paper presents a case study demonstrating how even corrosion-resistant alloys like Alloy 800 can suffer from external Cl SCC under extreme conditions, emphasizing the importance of thorough risk assessment in corrosion management.