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380 TAE Marine REVIEW Fic. 2--LOoNGITUDINAL SECTION OF THE \ perimentation with water tube boil- ers, has been thoroughly tested in actual service and thas proven _ its claim to consideration. Fig. 1 shows a cross 'section of the boiler, which, it will be seen, consists of a lower central drum, two 'banks of vertical tubes arranged on either side of a central combustion cham- ber and a cylindrical steam drum at the top. The lower central drum is connected to the pipe sections «by slightly bent vertical feeder pipes. Each top header is 'connected to the steam drum 'by a short nipple. Each section is complete in 'itself, As steam will naturally rise vertic- ally, vertical tubes will offer the least impediment to its escape as soon as it is generated. It will be noted that in the Ballin boiler the feed or riser pipes from the lower center drum and the tubes immediately above them, will receive the impact of the hottest gases. An upward current is imme- diately set up in these generating tubes next to the combustion cham- ber. As the nipple or steam outlet from the section to the steam drum is not large enough to let this current pass freely, the water thus set in mo- tion is deflected in the top headers away from the steam drum and re- turns to the bottom header through the generating tubes further removed from the combustion chamber. Tests have shown that when such circulation iS once set up it will remain con- Battin WaAtTeER-TuBE Bol!cer. stant. While this circulation inside of each section is taking place, steam generated in the bottom headers and tubes escapes. vertically with and against the circulation, collecting in the top headers and finding its escape through the top nipples into the steam drum, carrying. along very little water. The great heat applied to the inside bent riser pipes causes them to act as generating tubes and in- duces a very strong upflow of water, October, 1909 more than can be evaporated by the whole section. The surplus water thus entering the section is taken care of by the tube connecting the seciion to the side lower drums, which thus acts as a downflow pipe. The heated water thus returned meets in these downflow pipes the new entering feed water from the heater, causing it to precipitate any impurities it may con- tain. It is evident from the above de- scribed internal action, which is not a hypothesis but observed by actual demonstration, that each section in itself represents a boiler in miniature, having its fecd and downflow pipes and generating tubes, each one inde- pendent of its neighbor and each one with a steam connection discharging into the common steam drum _ only steam with very slight admixture of water. Understanding this action will explain the fact that this boiler gives almost perfectly dry steam even when forced or when the vessel is rolling in heavy seas. Fears were expressed by engineers that the evaporation might leave deposits in the bottom headers, since they are exposed to the hottest direct fire. To guard against such possibility, the 'cross section of these headers is made D shaped and is as small as_ possible. Inspection after five months contin- uous steaming has proved them to be perfectly clean and without a vestige of deposit. This shows that the cir- culation in the headers is almost per- fect. The sections are so arranged that they can be withdrawn from the top through openings left inthe casing 'Ic 2 tak : Fis, 3--InTer1onk View Turoucu THE Frue Door, SHowrinc OF THE SECTIONS IN PLACE, SoME