Tube Expansion Guidelines

Improperly rolled joints require additional expense to correct, whether they are under-rolled and can be corrected merely by rerolling, or over-rolled and require removal and replacement. The optimal joint is one that develops a leaktight joint with adequate strength for the service intended with the minimum amount of cold working or reduction of the tube wall. Experience indicates that joints of this type are obtainable with non-ferrous tubes in surface condensers by expanding to a wall reduction of 3 percent to 4 percent after metal-to-metal contact of the tube Outer Diameter with the tubesheet hole. Steel tubes in heat exchangers may require wall reductions of 5 percent to 10 percent; soft copper and aluminum tubes in heat exchangers also require larger wall reductions in the area of 8 percent to 12 percent. Boiler tubes requiring development of optimum joint strength require wall reductions of 12 percent to 14 percent.

A typical example of the application of this method is indicated for a 3/4" x 18" Gauge tube in a condenser.