Failure analysis of a shell and tube oil cooler

Failure analysis was carried out on aluminum gaskets in both sides of a shell and tube oil cooler and the causes of oil–water and hot water–cooling water mixing were investigated. The cooling water (as it enters into the oil cooler) and hot water (as it leaves the oil cooler) were chemically analyzed. Galvanic corrosion was evaluated using the immersion corrosion test under weightlessness and Tafel potentiodynamic polarization curves, and both results were compared. The morphology and corrosion products components of corroded aluminum gaskets were studied using SEM and EDS, respectively. The results indicated that the aluminum gaskets were corroded as a result of chemically induced corrosion leading to hot water–cooling water mixing in both sides of the oil cooler, while the failure of the rear-end aluminum gasket led to oil–water mixing in the rear side of the oil cooler. Also, it was demonstrated that leakage from tubes–tube sheets joints in both sides due to chemically induced corrosion has taken place. Finally, the relationship between corrosion occurrence and the oil cooler failure was discussed. It is recommended that aluminum gasket and copper tubes not be used with the carbon steel tube sheet in such heat exchangers.