Patent ID: 6901887

Claim:
A package, two-drum, water tube boiler comprising: (a) a first side wall, a second side wall, and two end walls disposed in a rectangular configuration, the side walls being substantially longer than the end walls; (b) a cylindrical, lower, water drum adjacent to, and having its longitudinal axis parallel to, the bottom of the first side wall; (c) a cylindrical upper, steam drum adjacent to, and having its longitudinal axis parallel to, the top of the second side wall; (d) a combustion chamber located generally between the drums, for containing a flame extending parallel to the axes of the drums; (e) riser tubes connecting the lower drum to the upper drum so as to permit water, saturated steam, and mixtures thereof to flow from the lower drum to the upper drum, which riser tubes comprise (i) first, inboard radiant tubes extending from exits in the lower drum, upward in a vertical run along the side of the combustion chamber which is closer to the first side wall, then laterally toward the second side wall in a generally horizontal run along the top of the combustion chamber at a height below the upper drum and passing through a vertical plane which includes the upper drum's longitudinal axis, and then to entrances in the upper drum; (ii) second, outboard radiant tubes extending from exits in the lower drum, laterally toward the second side wall in a generally horizontal run along the bottom of the combustion chamber, then upward in a vertical run along the other side of the combustion chamber, and then to entrances in the upper drum; (iii) a bank of convection tubes extending from exits in the lower drum, upward in a vertical run adjacent the vertical run of the inboard radiant tubes, then laterally in a generally horizontal run above the generally horizontal run of the inboard radiant tubes, and then to entrances in the upper drum; (f) wherein the inboard radiant tubes in their generally horizontal run extend past said vertical plane by a distance equal to at least 60% of the radius of the upper drum and then bend upward and away from the second side wall before entering the upper drum.