Enhancing Heat Exchanger Reliability with Tube Inserts and End Techniques When tubes in a shell-and-tube heat exchanger corrode or crack, thin metallic inserts (#sleeves or ferrules) can be installed to restore performance. Technicians insert a snug, thin-walled liner into the damaged tube and expand it at each end, creating a tight metal-to-metal seal. This simple fix stops leaks and lets the tube carry fluid again without the need for full retubing. In fact, thin metallic tube liners have been