An Analytical Method to Predict Fretting-Wear Damage in the Double 90° U-Bend Tubes

Abstract

When the flow velocity exceeds a critical value, fluid-elastic instability is believed to be a factor of the large-amplitude vibration and results in the rapid wear of heat exchanger tubes. For sub-critical flow velocities, however, the random turbulence excitation is considered the main mechanism to cause the long-term wear on steam generator tubes. Since flow-induced interactions between the tube and tube supports in the sub-critical flow velocity can cause a localized tube wear, tube movement in the clearance between the tube and tube support, as well as the normal contact force on the tubes by fluid should be maintained as low as possible. An analytical method is proposed for predicting fretting-wear damage of the double 90° U-bend tubes. This approach is based on Archard’s equation for adhesive wear with both the straight single-span tube analytical model proposed by Connors and the linear structural dynamic theory of ASME Section III, Appendix N-1300. The results from the presented method show good trend compared with the field data. It is expected that this method can be utilized to predict the fretting-wear of the double 90° U-bend tubes in steam generators.