Comparisons Between Dzrerent Tube-to-Tubesheet Expansion Techniques

Abstract

The expanding of tubes in boilers and other types of heat exchangers has evolved considerably since the original methods of tube expanding. First, by driving in tapered expanding pins and then by the conventional roller expanding. SHEREX Industries has been involved and associated with this development through the years of change and advancement of these systems. In this paper various systems used today will be discussed. This will permit a comparison of each system that will point out the capabilities and the advantages or the limitations of these systems. The expanding of tubes into tube plates is a mechanical process that, with a quality approach, will produce reliable mechanical, sealed joints. However, induced stresses and the potential of crevice, intergranular corrosion, etc. are more adequately controlled with use of advanced tube expansion systems. The improvement in tube expanding technology, afforded by more advanced systems, has resulted in a capability to successfully expand specialty high alloy tubes in the higher alloy exchanger designs of today. Like many industrial process, in addition to correct hole tolerance and finish, cleanliness is a prime requirement for fast and easy sealing of these mechanical joint. However, it is not uncommon to find that more care is taken to make a welded seam in an exchanger shell than to properly prepare tube holes for expanded tube joints.