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a2 x MARINE REVIEW. [November 23, boilers. No repairs were required to either set of boilers after the com- pletion of the trip. The Annapolis is also equipped with Babcock & Wilcox boilers, and here, as on the Marietta, these boilers have been thoroughly successful. Indeed, a former chief engineer of the Annapolis has stated to me that the boilers of that ship were easier to manage in use and easier to maintain in a state of high efficiency than are cylindrical boilers. The Chicago has several Babcock & Wilcox boilers, and these have so far worked in a thoroughly satisfactory manner, no failure being reported under any circumstances. - The foregoing represents the tried installations of water tube boilers in ships larger than torpedo boats and destroyers in the United States navy. Babcock & Wilcox boilers of the shore or stationary type were in- stalled in the old monitors Canonicus, Mahopac and Manhattan, the old rectangular boilers being entirely worn out and it being deemed advisable to fit these old boats for whatever service they could do. The change was commenced at the beginning of the Spanish war. Before its close the change was complete and a somewhat greater speed was attained than with the original boilers. This change was made without injuring the decks of the monitors. The old boilers were cut up and passed out through the smokestack, down which the parts of the new boilers were passed, the latter being assembled in the engine-room space. This is an instance where none but water tube boilers could have been used, and where every facility of repair and installation was of enormous advantage. For naval vessels with their protective decks the facility with which water tube boilers can be removed or completely renewed without disturbing the decks may, of itself, justify us in adopting water tube boilers. There are building and: repairing several other ships of our navy to be. fitted with partial or complete outfits of water tube boilers. These include the Alert, Atlanta, Cincinnati, Wyoming (Babcock & Wilcox), Maine and Connecti- cut (Niclausse), Missouri, Wisconsin and Arkansas (Thornycroft), and Florida (modified Normand). The foregoing gives the installation of water tube boilers in our navy from which data has been obtained. So far as tried the boilers have in- variably been easy of operation, though I have found more skill required to obtain the best results from these boilers than would have been neces- sary if cylindrical boilers had been used. 'Particular attention has been given, in all. cases, to the feed arrangements. Water tube boilers must have ample feed pumps, and the regulation of the feed must be easy. At. first the heating surface of water tube boilers was made 3 square feet per horse power against 2 square feet necessary with cylindrical boilers. This figure has been gradually reduced until now we are down to 2.4 square feet of heating surface per horse power, about as low as I think it is yet safe to go with water tube boilers. The economical results from water tube boilers were at first not particularly good. At present we get quite as good results from water tube boilers of the latest design as from the best cylindrical boilers, The ratio of heating surface to grate surface has been kept up to at least 40, although we do not yet feel warranted in allow- ing as small grate surfaces in water tube boilers as in cylindrical boilers. Water tube boilers lose in efficiency when forced, especially those of the straight tube type. Of course, this is not of very great moment to us ina naval vessel which is under forced draft only at maximum speed, but it is nevertheless a disadvantage. The following table shows the relative economy of cylindrical and water tube boilers: RELATIVE ECONOMY OF CYLINDRICAL AND WATER TUBE BOILERS. Annap-| Mari- | New- | Prince-| Vicks- | Wheel- olis. etta. port. ton. | burg. | ing. Type and number of boilers................. (2B. &W.) | (2 single-ended cylindrical.) MDisplacemie nGehOnMS has ere se take ssces, 1,000 1,000 1,000. 1,000 1,000 | 1,000 Knots per ton of coal at most eco. : FOOTE NL (Sy OXELEXC Ls arepocnniadesos abso ponoceee os 2 22.27 18 19.6 21.25 16.6 Number Of SCLEWS. ...).:.:...2005:.0-. alge a 2 1 1 1 2 Grate surface, square feet .......... i 8 94 78 78 | 78 60 Heating surface, square feet 8,66 2,524 2,524 | 2,524 | 2,508 'The increased grate surface we have required with water tube boilers will be a positive advantage to our ships' steaming qualities. I consider that sustained sea speed depends largely upon the grate surface. Heating surface, of course, must be provided, but I should prefer an excess of grate surface to an exceedingly high ratio of heating surface to grate. Up to this time we have had no trouble from salt water or grease in water tube boilers. Indeed, we could hardly be more troubled by salt water with this type of boiler than we have been with cylindrical boilers. We suffered severely in our short war with Spain from dropped furnaces in cylindrical boilers. I do not think that a properly designed water tube boiler will give more trouble from the use of impure feed water, such as sometimes we have at sea, than any other boiler. I do not think tubes more liable than furnaces to fail from a deposit of scale. In any event, the evaporating plants of all our ships are being made adequate to give fresh feed water. The only danger of salt water in the future should come from leaky condensers. Glancing abroad, for a moment, we find every modern naval power, from England to Japan, committed to the use of water tube boilers on the largest scale. Each of these countries has had its experience, and each has decided not only that water tube boilers can be worked, but also that they work well and that they must be used in naval vessels. I will give a few observations on the working of various types of water tube boilers abroad. The result of a first glance would seem to be that anything would do to make steam, from Watt's tea-kettle to the most complicated of modern steam generators. I know of one French boiler (you know what ingenious mechanics the French are) composed equally of water and fire tubes. The tubes were concentric and the distance between them but one millimeter. Of course the amount of water is very small--so small as to put this boiler in the class called by their originators "inexplosible." This boiler was tried at the works of the maker with good results. It was next tried in a torpedo boat with equally remarkable results--seven men killed, I believe. We have read of explosions, however, of really well- designed water tube boilers. Generally it is found that a tube had failed and that the furnace door was open--the result, more or less fatal burns to all in the fire-room. We hear of all the failures but the successes are never mentioned. It is not difficult to foresee the failure of a boiler plant designed to furnish 120,000 pounds of steam_ per hour but regularly required to furnish 160,000 pounds per hour. If nothing else fails the feed pumps will not do the work and the tubes will, of course, be burnt out. This would happen with any type of boiler. You see, I harp on the fail- ures, for I find I can glean the most information from them. Many of the - failures have come from the use of boilers that were inaccessible for clean- ing and repairs; others from faulty design; others from poor workman- ship; others, again, from neglect. Water tube boiles require © skilled attendance. Other boilers have failed from poor material; others from failure of the feed pumps; but there is not one, so far as I know, that can properly be said to have failed purely as a result of being a water tube boiler. Failures may come from misusing water tube boilers but not from using them. I consider that the experience of the last ten years or more in our own and foreign navies justifies me in stating that water tube boilers, when proper precautions are used, can be successfully adopted for the steam generating plant of ocean-going vessels. They are necessities to the best design of warships. ae OLAIMS FOR AND AGAINST WATER TUBE BOILERS. I would naturally come now to a discussion of the claims of the ad- herents and opponents of water tube boilers. You have all heard these arguments and it seems almost useless to go over them. I shall simply state what I believe to be the advantages and disadvantages of water tube boilers compared with cylindrical boilers: Advantages--Less weight of water; quicker steamers; quicker response to change in amount of steam required; greater freedom of expansion; higher cruising speed; more per- fect circulation; adaptability to high pressures; smaller steam pipes and fittings; greater ease of repair; greater ease of installation; greater elas- ticity of design; less danger from explosion. Disadvantages--Greater danger from failure of tubes; better feed arrangements necessary; greater skill required in management; units too small; greater grate surface and heating surface required; less reserve in form of water in boiler; large number of parts; tubes difficult of access; large number of joints; more danger of priming. A saving in space has been claimed for water tube boilers, but I do not find this claim sound when account is taken of the increase in grate and heating surface necessary in water tube boilers to ensure satisfactory working, and because of small units the space for accessibility is increased rather than diminished. The fact that water tube boilers raise steam quickly is of the greatest advantage. I have stated elsewhere that I con- sider the battle of Santiago to have developed the necessity of the use of water tube boilers whether it taught us anything else or not. It would have been of the greatest advantage to have had, during the blockade of Santiago, boilers capable of raising steam in less than half an hour. Coal need not have been used to keep all the boilers under steam all the time. The Massachusetts might have shared in the glories of the fight if she had been fitted with water tubes boilers. The Indiana would have kept up with the Oregon and the Texas. The New York would have developed at least three knots more speed and the navy would have been spared a controversy. I think the Colon would not have gotten as far away as she did. But we did not have the water tube boilers. The higher pressures possible with water tube boilers give us smaller and safer steam pipes and better valves. It decreases the size of the fit- tings and the difficulty of tracing the labyrinth of a ship's piping. It in- creases the efficiency of the engines. The introduction of compound en- gines forced us to use cylindrical boilers. In the same way the use of quadruple expansion engines necessitates, for economy, the use of water tube boilers. But the quick steam raiser is, because of that very fact, not so safe as its predecessor. Of course, nothing on a man-of-war is very safe in war time, but we want things as safe as possible, and the boilers are the keys to the situation in the modern battleship. I think that safety in handling water tube boilers may be assured by using skill in the fire- rooms. I have more than ten years' successful experience with water tube boilers on which to found this opinion, and I submit that the boilers, placed as they are behind the heaviest armor and below the thick pro- tective deck, are, at the worst, the safest apparatus on a battleship. If we can make them work well we would do wrong to refuse to use water tube boilers on our ships. For merchant and for yacht practice it is a different question. I was recently asked what boilers to use in a large steam yacht. I recommended cylindrical boilers. For merchant work the boilers are always in use de- veloping a fixed power. Weight is not there so important as in warships, and I think it is at best a moot question whether cylindrical boilers are not still the best that can be fitted in ocean-going merchantmen. In some cases where there are short trips and the opportunities for repair must be gotten during the very short lay-ups at the end of the route, the quick steam raising qualities of water tube boilers, with their freedom of expan- sion, enables blowing down the boiler immediately on arrival in port and still having steam at an hour's notice on all boilers. Such cases as this seem to me to demand water tube boilers. As to the type of boiler to be used there are as many to choose from as there are fleas on a dog. Someone has said that a certain amount of fleas keep a dog from brooding over being a dog. So the number of varieties we have to choose from may be a good thing for all. I have always opposed the use of boilers containing screw joints in contact with the fire, and have attempted to secure boilers laaving no cast metal in the pressure parts. Cast steel is not yet good enough to put be- tween 300 pounds of steam and our firemen. I believe in straight tube boilers as being easier of examination and repair than bent tube boilers. I believe in large tube boilers for the same reason and because the tubes are thicker and have more margin for corrosion. I believe in boilers hav- ing as few joints as possible. Water tube boilers must have freedom of expansion of the various parts, and the simpler the boiler the better. It should not be necessary to introduce reducing valves between the boilers and the engines to secure a steady steam pressure at the latter, nor should it be necessary to have automatic feed arrangements to ensure steady water level in the boilers. To be successful a boiler must be easy of repair. Lightness is a natural attribute of all water tube boilers. but it is not wise to go too far in this direction. The ratio of grate surface to fire