Experimental Study on Impact/Fretting Wear in Heat Exchanger Tubes

The objective of this study is to provide qualitative impact/fretting wear information for heat exchanger tubes through the performance of a series of tests involving the pertinent parameters: force between the tube and its support; tube to support plate hole clearance; tube support plate thickness; preload; and tube vibration frequency. The characteristics of impact/fretting wear relative to material combinations and fluid environment were also investigated. The test apparatus consists of a cantilevered tube with a simulated tube support plate at the “free end.” Tube vibration is induced by an electromagnetic exciter to simulate the flow-induced tube motion occurring in a real heat exchanger at the tube/tube support plate interface. Tests are conducted in air, water, and oil, all at room temperature. Removable wear rings are attached to the tube free end and simulated support fixture. Wear ring materials include carbon steel, 304 stainless steel, Inconel 600 and brass. Wear is measured by a weight loss technique and wear rates are calculated and reported as functions of the various pertinent parameters. Based on the test results, general conclusions are drawn.