Research On The Tightness Of The Hydraulically Expanded Tube-To-Tubesheet Joint

Many investigations and practical experience show that the leakage failure of the tube-to-tubesheet joints is a common failure mechanism for the shell and tube heat exchangers. To systematically research the tightness of the hydraulically expanded tube-to-tubesheet joints, a three-dimensional finite element model was developed to consider the influence of such factors as the hydraulic expansion pressure, operating temperature and multi-tubes expansion. on the residual contact pressure between the tube and tubesheet-hole of the joints. The analytical results show that the hydraulic expansion can improve the tightness of the joints significantly. The leakage pressure of the joint first increases and then decreases with the increase of the expansion pressure, thus, an optimal expansion pressure exists. The leakage pressure improves at the beginning and lowers gradually with an increase in the temperature. The tightness of the joint is reduced very little after the temperature cycle. The optimized expansion pressures are quite different between the single-tube expansion model and multi-tithe expansion model. Thus, the influence of expanded tubes on the expanding tube should be taken into consideration in the research of the tightness of the joints.