Steam:
Its Generation and Use

The steam and water capacity was in- sufficient to secure regularity of action, having no reserve to draw upon when irreguarly fed or fired. The attempt to dry the wet steam, produced by super- heating in the nest of tubes which formed the steam space, was found to be impracticable; the steam delivered was either wet, dry or superheated, accord- ing to the demands upon the boiler. Sediment was found to lodge in the lowest point of the boiler at the rear end, and the exposed portion of the cracked off when subjected to the furnace heat. No. 4.—A plain cylinder carrying the water line at the center, leaving the upper half for steam space, was substituted for the nest of tubes. The sections were made as in No. 3, castings and a mud-drum added to the rear end of the sections at the lowest point farthest removed from the fire; the gases passed off to the stack at one side without coming in contact with it. Dry steam was secured by the great increase of separating surface and steam space, and the added water capacity furnished a storage for heat to tide over the irregularities of and firing. By the addition of the drum it lost a little in safety, but, on the other hand, it became a serviceable and practical design, retaining all the elements of safety except small diame- ter of steam reservoir, which was never large, and was removed from the direct action of the fire, but difficulties were encountered in securing reliable joints between the wrought-iron tubes and the cast-iron headers. No. 5,—Wrought-iron water legs were substituted for the cast-iron headers; the tubes were expanded into the inside sheets, and a large cover placed opposite the front end of the tubes for cleaning. The staggered position of tubes, one above the other, was introduced and found to be more efficient and economical than where the tubes were placed in vertical rows. In other respects it was similar to No. 4, but it had further lost the important element of safety, the sec- tional construction, and a very objectionable feature, that of flat stayed surfaces, had been introduced. The large doors for access to the tubes were also a cause of weakness. A large plant of these boilers was placed in the Calvert Sugar Refinery, Baltimore, and did good work, but they were never duplicated. No. 6.—A modification of No. 5, in which longer tubes were used with three passages of the gases across them, to obtain better economy. Also some of the stayed surfaces were omitted and hand holes were substituted for the large doors. A number of this type _ _L were built, but their excessive first cost, lack of adjustability of the structure under varying temperatures, and the inconvenience of transporting the last two styles together with the difficulty of erecting large plants without enormous cost for brick-work, as well as the “commerical engineering” of several competing firms then in the market, who made a selling point of their ability to add power to any given boiler after it had once been erected, led to : feeding No. 6. No. 7.—In this separate T heads were screwed on to the end of each inclined tube ; their faces milled off, the tubes placed on top of each other, metal to metal, and bolted together by long bolts passed through each vertical section of tube heads, and the connecting boxes on the heads of the drum. A large number of these boilers were put into use, some of which are still at