 The rapid passage of gas was indicated by too high a temperature in the smokebox, and the choking of the smokebox by excessive char carried through from the firebox.The boiler was re-tubed with 180 smaller tubes 1⅞ inches diameter, and with superheater elements 1¼ inch diameter.The single blastpipe was replaced with a double blastpipe and chimney to provide adequate gas velocity in the smokebox.