An analysis to minimize the amount of spring back after coiling of helical steam generator tubes

The spring back phenomena occurring in the coiling process of a steam generator tube induce dimensional inaccuracy and make the coiling procedure difficult. In this research, an analytical approach has been carried out to evaluate the amount of spring back for helical steam generator tubes. The model was developed on the basis of beam theory and elastic-perfectly plastic material properties. This model was extended to consider the effect of plastic hardening and the effect of the tensile force on the spring back phenomena. Parametric studies were performed for various design variables of steam generator tubes in order to minimize the spring back in the design stage. A sensitivity analysis has shown that low yield strength, high elastic modulus, small helix diameter, and large tube diameter result in a small amount of spring back. The amount of spring back can be controlled by the selection of adequate design values in the basic design stage and reduced to an allowable limit by application of a tensile force to the tube during the coiling process. (C) 2001 Published by Elsevier Science Ltd.