Evaluation of the efficiency of methods for expanding thick-walled tubes into tube sheets of heat exchangers

The present work is devoted to the experimental study of methods of reaming thick-walled tubes in thick tube grids used in modern heat exchangers. The efficiency of industrial systems largely depends on the reliability of the equipment, the main element of which are heat exchangers. Recently, the use of thick-walled tubes is gaining popularity, which provides higher indicators of strength and tightness of connections. However, the use of such pipes requires the use of methods of pre-deformation of the pipe ends at an angle that corresponds to the conical surface of the holes in the pipe grid. This provides a tighter joint prior to subsequent welding and reaming over the full thickness of the lattice. The main objective of the work was to comparatively analyze stepwise and continuous reaming methods, which are widely used in industry. These methods differ significantly in their productivity, quality and time consumption. The evaluation of these parameters allowed to identify advantages and disadvantages of each of them, which became the basis for the subsequent selection of the optimal method depending on the operating conditions. During the study, special attention was paid to key indicators such as joint strength and tightness, as well as the condition of the surfaces of the flared pipe sections. The research was conducted on the basis of the production unit of Yuzhenergo LLC, Dnipro city. Experimental data were obtained on the basis of studies of pipe joints made of A335 Grade P12 steel with different parameters of diameters and wall thicknesses. In the process of work also quantitative estimation of time spent on execution of reaming operations by each method was carried out. The results of the research have shown that band-screw rolling is a promising direction for fixing small diameter pipes in conditions where high strength of joints is required at minimum time expenditures. The results considered in the work can be useful for improvement of technological processes of production and operation of heat-exchange apparatuses. Application of the obtained data allows to increase not only reliability and durability of the equipment, but also its economic efficiency, which is especially important in the conditions of modern industrial requirements.