Corrosion Failure Analysis of the Vacuum Tower at the LVC Draw Piping Line

Abstract The corrosion failure of the Light Vacuum Condensate (LVC) draw piping line in a vacuum tower was investigated to identify the damage mechanism. The failure was localized at the LVC draw elbow near the tower's draw nozzle, with significant corrosion observed in the outlet straight piping up to the first elbow. Visual Inspection and RT inspection showed a corrosion damage morphology named “wolverine claws”. Metallurgical analysis revealed smooth pits and grooves, with corrosion products consisting of iron sulfides, and other oxides containing chlorides. The study explored the potential role of nitrogen-based compounds, particularly amine-hydrochloride oil-soluble salts formed from the interaction of crude feed nitrogen and amine-based chemical injections, as key contributors to the corrosion process. These salts, trapped in the LVC circuit, can enhance and accelerate organic corrosion, especially at lower temperatures (<400F) where Naphthenic Acid Corrosion is not expected. The paper explores possible sources of chloride in the LVC system and describes the morphology of the damage mechanisms