Appropriate Correlations for Assessing Expanded Tube-to-Tubesheet Joint Strength

Abstract

This paper advocates correlating rolling torque or hydraulic expanding pressure with shear load strength instead of percent wall reduction as the criterion of expanding adequacy for thin-walled tubes. It compares magnitudes of measurements required to estimate wall reduction with cumulative hole-drilling and tube-manufacturing tolerances and graphically illustrates data scatter increase with ratio of tube diameter to wall thickness. As background it discusses expanding theory. It covers hydraulic, roller and hybrid expanding. It describes appropriate annular groove widths for hydraulic and hybrid expanding and concludes with comments on tube rolling procedure specifications and recommendations for two-stage and hybrid expanding.