The first practical firetube superheater was patented in 1912. The intended application was in steam locomotive boilers. Tests proved that thermodynamic efficiency could be improved up to 30%. Fuel consumption could be reduced 30% for the same load, or 30% more tons of freight could be pulled for the same fuel. There was an impediment to its success. In the existing technology of the era, welding was not viable. The return bends were threaded cast steel that were not reliable in rigorous locomotive service. In 1916, a forging process was patented whereby a single return bend was forged from two tubes. This supplied the reliability required. By 1919, three thousand locomotives a year were being manufactured and most locomotives built since 1900 were being retro-fitted with superheaters. Steam was superheated in a firetube boiler by adding larger size firetubes in the tube bundle and populating these “superheater flues” with small diameter tubing elements where the steam flows from the low gas temperature exit end of the firetube toward the high gas temperature furnace end of the firetube. The superheater element tubing has a 180 degree return bend that reverses the flow to send the now superheated steam out of the boiler. Because the traditional firetube superheater requires 2 tubing elements occupying a larger diameter firetube, there are inherent inefficiencies in the heat transfer.  Temperature profile is derived using the methods derived by Lawford Fry.