Patent ID: 7819302

Claim:
A method for forming a substantially leak-tight aluminum tubular unit used for long-term storage of fluids, the method comprising: providing a hollow cylindrical tubular unit having a cylindrically shaped exterior, an end, and a hollow central region; providing an end cap having a cylindrically shaped inner region, a shoulder region, and a cylindrically shaped outer region, said cylindrically shaped outer region shaped substantially similar to said cylindrically shaped exterior of the hollow cylindrical tubular unit; introducing a cylindrically shaped inner region of the end cap within said hollow central region such that a shoulder region of the end cap abuts said end; introducing a quantity of a fluid into the hollow region of said tubular unit prior to sealingly coupling said end cap to said tube; ultrasonically forming a cylindrically shaped solid state weld directly between said end and said shoulder region to sealingly couple the end cap to the hollow cylindrical tubular unit; providing at least one fin; and ultrasonically welding said one of said at least one fin directly to said cylindrically shaped exterior, whereby as the ultrasonic welding does not generate significant heat highly volatile and flammable liquids can be present and as no significant heat buildup occurs, the melting temperature of the aluminum is not reached so that substantially no microstructural changes to the end cap, the tubular unit, the cylindrically shaped exterior and said fin occur.