Failure analysis of heat exchanger tubes of four gas coolers

A Number of leaks occurred on four heat exchangers used on an off-shore platform in the south of Iran. As a result heat exchanger tubes made of Inconel 625 failed after only two years in operation. The failure was caused by pitting corrosion in two contact regions, tubes and baffles as well as in tube sheet and shell contact regions in spite of sufficiently corrosion resistance of Inconel 625 to sea water. X-ray diffraction analysis was conducted on residual corrosion products, while micro structures of propagated pits were studied using scanning electron microscope and also examination of susceptibility of Inconel 625 to crevice corrosion was performed by multiple crevice assembly and anodic polarization in crevice solution. Investigation of failed exchanger tubes revealed that leaks in the tubes were due to the phenomenon of crevice corrosion.