Laboratory Measurement of Tube-to-Tubesheet Joint Strength at Temperature

Abstract

The strength and leak-tight integrity of expanded tube-to-tubesheet joint is dependent on a residual interfacial pressure between the outer surface of the tube and the tubesheet hole. This interfacial pressure is induced during the manufacturing process at room temperature and is affected by operating temperatures as well as creep and fatigue cycling during service. This experiment will deal with the effect of operating temperature on rolled tube-to-tubesheet joint behavior. Much theoretical and experimental work has been accomplished on tube-to-tubesheet joints at room temperature but data at elevated temperature is sparse. Indeed, the ASME Boiler and Pressure Vessel Code's Appendix A to Section VIII Division 1 states the "---procedures for establishing allowable operating temperatures applicable to joint types i, j, and k as listed in Table A-2 relative to joint strength are in the process of development---". This paper describes a test program, complete with detailed test results, where the strength of rolled tube-to-tubesheet joints has been evaluated at various elevated tubesheet temperatures for different tube and tubesheet material combinations. Consideration is made for situations where the tube expands more quickly with temperature than the tubesheet and where the tube sheet expands more quickly with temperature than the tube. Test results are compared with theoretical calculations and a basis is established for possible use by the ASME Code in Appendix A. Future experimental work is also identified.