The Precision Model FPS Vertical Firetube Steam Boiler features the traditional firetube design in the vertical configuration with an underfired power burner. In additon to the simplicity of the 4-piece design, the Model FPS includes many advantages over other vertical configured boilers such as larger water volume and steam chest which reduce cycling and improve overall efficiency, easier sludge cleanout, standard "off the shelf" burners, and the proven firetube reliability. An integral feedwater preheater eliminates "cold water shock" problems characteristic of some fixed tubesheet designs.