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8 MARINE REVIEW. Compound Marine Boilers. Col. N. Soliani, director of naval construction in Italy, is prominent among the great naval authorities who are not of the opinion that water tube boilers are soon to replace entirely the old style of cylindrical boiler. A paper on " Compound Marine Boilers," which he presented at the last mzeting of the Institution of Naval Architects, is attracting a great deal of attention. It deals with boilers having the heating surface made up both of water and fire tubes. After dealing with the prominent features of the modern marine cylindrical boiler, developed during an experience of two generations at sea, Col. Soliani says it is worthy of note that only in one country, France, are water tube boilers in general use both for merchant and war ships. The navies, now drifting to the water tube boiler, began really to feel the want of a change only when the cylindrical boilers appeared unsuitable to forced draft. He does not admit, however, that this unsuitableness exists, and points tothe favorable results ob- tained with Serve tubes and with the Howden and Brown systems of of combustion, by which the steaming power of marine cylindrical boilers) per unit area of wetted heating surface has been brought up to limits which were lately deemed dangerous. But apart from these arrangements, SINGLE ENDED' DOUBLE ENDED a 0 9 hate fe tiodo Fig. 1.--Longitudinal Vertical Section.. 1% aa Doors FOR VISIT AND i / @ \\ REPAIR OF FIRE TUBES water spaces around the ordinary combustion chambers, and substituting for them water tubes, some of which would be properly arranged as q protecting screen in front of the tubes and tube plates, '"' My meaning will perhaps be clearer by reference to Figures 1 to 4, in which the proposed alteration is sketched as applied both to single and double ended cylindrical boilers. Such boilers, if successful would be lighter, simpler, less sensitive to differenee of temperature and to rapid changes of fire; while the screen of water tubes in front of the tube plates would protect toa great extent plates and tubes from damage un. der forced draft. In other words, these boilers would fulfill most of the requirements of modern steaming at sea, and exert, if adopted, a usefy] -- function in the present period of transition, which, by them, would become longer and smoother. 'The benefit would be mainly felt by the mercantile marine, on account of thelarger interests involved, and because of its requirements, to which the ordinary marine boilers appear on the whole so well suited. : "Another advantage of the arrangement I propose would be the facility of admitting air under the back end of the fire grate, in a proper measure, to improve the efficiency of combustion, through a regulating DOUBLE ENDED Fig. 5.--Longitudinal Vertical Section. SN 4 ">. aa DOORS FOR VISIT AND a : mes i. REPAIR OF FIRE TUBES 'a » u a . YS NS N hod SSE Soe l fh NS x 4 nd i ae SS Si ~/ ° go g0 ° ° 3° Re oe 0? ° ° ° ° ) ° °8 o5 95 ° On °° ° o8 oe ©5 SSS BE LOIG OLR SAO Ea ste Ole ees == Fig 2--Horizontal Section Fig. 1. Fig. 4.--Transverse Vertical Section Fig. 3., Fig. 6.--Horizontal Section Fig. 5. COMPOUND MARINE BOILER. which, if efficient in increasing the specific power of the boilers, have not improved them in respect to lightness and suitableness for rapid steam- ing, there are, in the opinion of Col. Soliani, other stages for the develop- ment of the cylindrical boiler. "Cylindrical boilers not only have, as yet," he says, "a great power of endurance in the mercantile competition, but there is still room on their side for further improvement, by which their vitality may be in- creased and the struggle prolonged, even for navy purposes, with ad- vantage to the great interests involved. This new vitality may, I think, be conferred on cylindrical boilers by compounding them with water tubes in such a way as to make them partake, toacertain extent, of the good features of the water tube boilers, without .detracting much from their own valuable characteristics. There are several compound boilers in the market. I do not wish to disparage any of these boilers, but they are not the kind of boiler I mean, viz.,a marine cylindrical boiler com- pounded with water tubes to the extent that is necessary to give protec- tion to the tubes and tube plates, and improve the boiler also in other respects (such as economy of weight, fitness to rapid changes of temper- ature, etc.), but without altering its main characters. Such a result may in my opinion, be achieved simply by doing away altogether with the door fitted under the bridge and underneath the casing of water tubes forming the combustion chambers. My suggestions may be briefly sum- marized as follows, with a view to meet discussion: "1. For swift vsssels of small dimensions, designed for the use of torpedoes or special services, water tube boilers are a necessity. "2. For certain classes of war ships of large size, water tube boilers are distinctly advantageous. "3. For mercantile purposes and many classes of war ships, the water tube boilers are not yet perfectly suitable, and the cylindrical type of mariue boiler is still to be preferred, and its continued employ- ment is probable for some considerable time. "4. Thereisa possibility of retaining the most valuable characteristics of the cylindrical type, while securing increased efficiency and fitness to meet the exigencies of modern steaming, by means of arrangements of water tubes somewhat of the character illustrated by figures 1 to 6. Lieut. J. B. Cavanaugh of Detroit, who isin charge of the 20-foot -- channel work, is of the opinion that within a week or ten days the entire width of 800 feet in the channel at the foot of Lake St. Clair will be com- pleted to 20 feet.