Failure analysis of a shell and tube oil cooler R. Taherzadeh Mousavian a,⇑ , E. Hajjari b , D. Ghasemi a , M. Kojouri Manesh c , K. Ranjbar b a Materials Science Department, Shahid Bahonar University of Kerman, Kerman, Iran b Materials Science Department, Shahid Chamran University of Ahvaz, Ahvaz, Iran c Department of Mechanical Engineering, Shiraz University, Shiraz, Iran article info Article history: Received 2 May 2010 Received in revised form 29 August 2010 Accepted 30 August 2010 Available online 20 September 2010 Keywords: Oil cooler Galvanic corrosion Localized corrosion Aluminum gasket Leakage abstract 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 corro- sion 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 cop- per tubes not be used with the carbon steel tube sheet in such heat exchangers. Ó 2010 Elsevier Ltd. All rights reserved. 1. Introduction A shell and tube oil cooler with double tube sheet construction, non-removable baffles and flat aluminum gaskets in con- tact with carbon steel tube sheets is used in the Karkheh dam water power plant in the southwest of Iran. Double tube sheet construction is used in certain services where even minute leakage of one fluid into another cannot be tolerated [1]. The front-end tube sheet is fixed while the rear-end one is floating (see Fig. 1). The cooling medium, which is untreated dam water with an ambient temperature of 24 °C, flows inside the copper tubes and the heat exchanger oil with a higher pressure than the water flows across and along the tubes. The copper and carbon steel that are used as the tube and the tube sheet correspond to ASTM C12200 and ASTM A105, respectively, Tables 1 and 2. After 4 months of service, the oil–water and cooling water–hot water mixing, in addition to gasket failure, were observed in this oil cooler. This eventually led to the oil cooler failure and the oil temperature was found to increase over 45 °C after the heat transfer with the cooling water in three double passes, when it should have been kept constant at about 35–40 °C. Many failures of shell and tube heat exchangers, which occur in power plants, include mechanical failures, chemically induced corrosion failures or both of them together. Corrosion occurrence in real systems such as heat exchangers may cause serious failures, and have been investigated by many authors [2–12]. Scheduled and unscheduled shutdowns for repairing corrosion damage are expensive and anything that can be done to reduce these shutdowns will be of great benefit. The selec- tion of materials for construction also has a significant impact on the efficiency of the plants [4]. 1350-6307/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.engfailanal.2010.08.022 ⇑ Corresponding author. Tel.: +98 9173067320; fax: +98 3412111865. E-mail address: rtaher1898@gmail.com (R.T. Mousavian). Engineering Failure Analysis 18 (2011) 202–211 Contents lists available at ScienceDirect Engineering Failure Analysis journal homepage: www.elsevier.com/locate/engfailanal