Many failures of heat exchanger tubes occur within the first six inches. Inlet-end erosion, impingement attack, stress corrosion cracking, pitting and crevice corrosion are typical damage/failure mechanisms encountered in the chemical, petrochemical and oil refining industries.
The presentation will discuss a cost effective, in-situ tube restoration technique, consisting of installing thin-walled metallic inserts or "shields" that are mechanically expanded into the affected tube ends. Since their introduction in 1976, metallic tube shields have successfully restored and protected damaged heat exchanger tubes at a fractional cost of retubing. Materials utilized for I.D. tube shields cover a wide range of copper-base, iron-base, and nickel-base alloys. The technique for affixing tube shields is also being incorporated into the design of new heat exchangers.
This restoration technique and its advantages are compared with traditional tube protection/restoration methods employing thick metal ferrules, ceramic ferrules and epoxy coatings. Unlike any of these, rolled-in metallic shields have the unique capability of restoring perforated tubes to full service.