The Failure Analysis of a Heat Exchanger Condenser Tube of an Oil Refinery

Cupronickel 90-10 is one of the most applicable Cu-based alloys which possess suitable corrosion resistance and strength and is employed extensively in marine industries particularly in the boilers and heat exchangers. Generally, the tubes of water cooling systems especially those use seawater as cooling medium are made of this alloy. In this paper, the causes of premature failure of a cupronickel (90-10) condenser tube used in a cooling system of an oil refinery in the south of Iran have been studied by different microscopical and analytical methods, e.g. X-ray fluorescence spectroscopy (XRF) and X-ray diffraction (XRD). The results showed that pitting corrosion on the internal surface of the tube was the main cause of its failure which was a consequence of the stagnant of the tube by external solids and preparation of an appropriate environment for the activity of microorganisms, hence, microbial corrosion.