Investigation of the Expansion Requirement of Tube to Tubesheet Rolling Fitting

Abstract

Tube Expansion is the process of reducing a tube wall by displacing the outside diameter of the tube against a fixed container such as rolling tubes into tube sheets. To assure a proper tube joint to the tubesheet, the tube wall must be reduced by a predetermined percentage. Different methods have been used to estimate the necessary amount of expansion in tube to tubesheet rolling expansion for strong tubeto-tubesheet joint. The first commonly method depends on torque and pull out strength data collection by experimentation. This method fits with small and large clearance but it suffers from cost of experiments to collect the necessary data. The second method depends on theoretically calculation of the necessary inner radius displacement that to insure proper residual contact stress. That stress gives indication the strength of the joint. This method fits with small clearance as the joint strength decreases until it vanishes as the clearance increases. This paper proposes a new method that depends on the fixed outer tube surface displacement. The finite element analysis results show that, the proposed method provides good results for both low and large clearance.