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1899.] MARINE REV we 21 CAUSES FOR THE ADOPTION OF WATER TUBE BOILERS IN THE UNITED STATES NAVY. BY GEO. W. MELVILLE, ENGINEER-IN-CHIEF, U. S. N. It has been a number of years since I have had the honor and pleasure of addressing this society. Speaking generally, the progress and design of machinery of warships has been, during that time, along such well-devel- oped lines, and so in accordance with the generally accepted theories of designers, that there has been little to say. More recently, however, in order to keep pace with the times and to cope with the necessity we have always before us of securing ships that will be in nowise inferior to those built for any other nations, a change in machinery design has been made that at first glance appears radical--the general adoption of water tube boilers for all new vessels of our navy. Elsewhere violent diatribes have been launched against those responsible for a similar decision, and I am aware that there exists a not inconsiderable sentiment in this country against water tube boilers. I call it a sentiment advisedly, because I be- lieve that much of it is due to the attachment that engineers have for their old and proved friend, the cylindrical boiler. Only a part of the opinions unfavorable to the change arises from the natural and proper conservatism of naval architects and marine engineers, but these demand answer. Flooded always with new devices--or rather by rejuvenated failures in new forms--we find a very small proportion that is even worthy of a trial, and where a new mechanical idea is tried on ship- board so much time is spent in adapting it to naval conditions and in repairing its failures that each of us becomes naturally and properly dubious when any change is suggested. Any important change in design, even of the apparently minor fittings of ships, may involve such risk to vessel and crew as to be unjustifiable, unless the device be thoroughly tried beforehand. Many apparently good ideas have given successful re- sults on shore only to fail dismally at sea. I think that it may be given, as a general rule, that no change in design should be authorized that has not already been successfully made. Of course a strict application of this rule would lead to stagnation. Here, however, enters the designer. His role is an important one. He has to cull the good points from previous work, and, if he be a good de- signer, he must also leave out the bad points: There always are some bad points, but amelioration of conditions should be the aim of naval de- signers. This implies that a good designer must be of vast experience and of extended observation. The larger his field of observation the more valuable his conclusions. It is the details that count. No man can suc- ceed as a designer of warships without the most careful attention to small things. The modern battleship is a monument to the greatness of the minutiz of design. It has been gradually built up from the sailing beauties of a century ago. Steps in advance have been slow, generally speaking. We cannot advance by leaps and bounds in marine work. Here genius is hampered by such conditions as make any step in advance a great achievement. Of course, we have the case of Ericsson and the Monitor, but this was a case not only of special conditions but also of a most exceptional man. Naval architecture is a pyramid, each stone of which is supported by all of the preceding ones. The size of the stone that one man can add to the pile depends, of course, upon his ability, but more especially upon his work. By hard work and by paying attention to what is going on arotind him any man can add his quota, but "those who, having eyes, see not; and who, having ears, hear not,' are worse than useless. NATURAL STEPS TOWARDS THE EVOLUTION OF A PERFECT FIGHTING MACHINE. The task I have set myself to-day is no mean one. I desire to show that the decision to use nothing but water tube boilers in our future war vessels is a step in advance, and that it is a natural step towards the evolu- tion of the perfect fighting machine. I desire to show that it is no radical change, and that it does not involve the use of anything but a tried, successful, and reliable apparatus that gives us positive and great advan- tages over the character of boilers heretofore generally used. I desire not to minimize the disadvantages following this change, but to show that these disadvantages are not only not insurmountable, but, for warships, they have already been overcome. In the first place, I want to state that water tube boilers are bad in principle. They carry the pressure inside their weakest parts--the tubes. A failure in a tube is followed by the opening of a fault, sometimes to a dangerous degree. In a fire-tubular boiler, on the contrary, the pressure would continue to close a split tube. It is true that a failure of a boiler tube generally comes from pitting, where fire tubular boilers generally have such a great advantage as in cases of split tubes. Yet failure of tubes is the most common defect in all boilers, and a proper design would place the pressure on the outside of the tube. Water tube boilers are, from their very definition, designed from a wrong principle, not only because of the direction of application of pressure upon the tubes, but also on account of the decreased amount of water in the boiler, of the increased difficulty of observing a leak, and of the decreased value of heating surface in water tube boilers. For this reason, as an engineer, it is with some misgiving that I state that I con- sider water tube boilers tactical necessities for warships. Builders of | water tube boilers use solid drawn tubes almost exclusively for marine work. This, of course, decreases the danger of split tubes, but it does not change the mechanical principle. Some day, probably not in my time, we may hope to have a boiler having fire tubes and having the advantages of water tube boilers. Such a boiler would force its way at once into all Navies, just as water tube boilers are doing at the present day. : Disbelieving, as I do, in the cardinal principles of water tube boilers, have sturdily opposed their adoption by our navy until now I am con- Vinced that they must be used if we are not going to content ourselves with inferior ships to those built for other nations. Of course, during the Period of development of the design of water tube boilers, that even now continues, I have, in my official capacity, kept track of and taken part in the world-wide experiments with their use. Water tube boilers have ad- vantages and I have never been blind to them. Two years ago I stated that their disadvantages had been sufficiently removed to justify their use On our warships. Now I consider that the value of their advantages has been sufficiently developed to necessitate their use if we do not wish to be left behind in naval design. The principal thing to which I desire to call your attention is the fact that all vessels are essentially compromises. Any ship must be considered in its entirety, and the advisability of a change in design of any part must be determined from its effect upon the ship as a whole. Whether or not water tube boilers are superior to cylindrical boilers as boilers simply, if there be a beneficial effect upon the ship as a whole due to the adoption of water tube boilers, these boilers are essential to the best design. The necessity of compromise in ship design must be self-evident to the members of this society who have the problem before them for solution almost daily. Taking the particular case of warships, the size of our ships is limited by their draught. We are building vessels now that are as large as any that can enter our harbors and docks, and we cannot, therefore, increase their power as fighting ships except by im- provements in design. Any increase in weight allotted to one essential of the efficiency of the ship must be counter-balanced by a decrease in some other perhaps equally essential element. So far, this has most fre- quently been done by robbing the coal pile--an extra gun, a half knot in speed, or an additional inch in armor protection--each means a few tons less coal in the bunkers, I must ex¢ept the more recent designs of battle- ships from the above general rules. The importance of coal endurance has become more and more manifest, and it has been appreciated fully in our recent designs. Incidentally, these last ships are fitted with water tube boilers. Water tube boilers are considerably lighter than those of the old type, and their effect upon ship design may be given as follows: Of two ships, having all other qualities identical, one fitted with cylindrical boilers and the other with water tube boilers, the latter will be somewhat the smaller and handier--will have somewhat less draught, and will cost less. Limited, as we are, in the size of our warships by their draught, I think that the foregoing shows that for a maximum of fighting efficiency we must use water tube boilers. The designing engineers of our naval vessels are limited in weight and space. They save little or nothing in space perhaps, but they save greatly in weight if they adopt water tube boilers. If these can be successfully operated on shipboard they must be used because of their decreased weight. The foregoing is entirely apart from any consideration of the relative merits of water tube and fire tubular boilers, but it is conditional upon the possibility of the successful opera- tion of water tube boilers. HISTORY OF THE WATER TUBE BOILER IN OUR NAVY. Before considering claimed advantages and disadvantages of water tube boilers, I desire to give a few historial facts, most of them already well known to the members of the society. The old Martin boiler was the first water tube boiler ever used in any naval vessel. We had good success with these boilers, but they died out of use with the introduction of high- pressure multiple-expansion engines and the consequent cylindrical boilers. For years none but water tube boilers have been installed in our steam launches. These have always been attended by unskilled labor, yet the results have been very satisfactory. Some accidents have occurred, but they have been very few, probably no greater in number than if fire tubular boilers had been used, and it is to be noted that the results of a boiler explosion would probably have been worse in almost every case if the failure had occurred in a fire tubular boiler. Torpedo boats and de- stroyers in our navy have always, since the time of the Cushing, been equipped with water tube boilers of various types. Small bent tube boilers have generally been used. There have been some cases of sad accidents in the fire-rooms, generally due to carelessness in manufacture, and par- ticularly in tube setting, but not to defective design. The boilers have proved to be quite as reliable as the extremely light engines of these boats. With the small amount of skilled attention it is possible to give torpedo boats, and considering the character of service demanded of these small craft, I think that no engineer will today question that the use of light water tube boilers, with the higher speeds possible as a result, adds to their efficiency and security. I think even Herr Schichau has come to be of this opinion, The first large installation of water tube boilers in our navy was on the Monterey. Indeed, at the time, this was the largest installation of water tube boilers in any navy. In this monitor, as you all know, there are four round Ward water tube boilers, with two cylindrical single-ended fire tubular boilers. The water tube boilers have been satisfactory. It is worthy of note that there has been very little difficulty experienced in maintaining a steady water level, although the boilers have a very small amount of contained water. Tubes have failed by pitting several times, though never with any danger to the firemen. The water tube boilers have been twice retubed by the ship's force without laying the ship up at any navy yard. On one occasion, probably with a view to thoroughly testing the water tube boilers, or to satisfy the unholy desires of some person decrying water tube boilers, the ship made a voyage of about 8,000 knots, largely under forced draft, and, whenever possible, with all boilers in use. There was no resultant injury to the water tube boilers, which performed well throughout the trial. The combustion chambers of the cylindrical boilers came out of the trial badly bulged. The Yarrow boilers of the Nashville have operated fairly successfully, though they cannot be said to be completely satisfactory on account of the amount of trouble given by bulging of drums and by leaky tubes. The first set of copper tubes has been replaced by others of steel to considerable advantage. I believe that the latest designs of this type of boiler provide for the use of slightly curved tubes next the fire. This ought to be advantageous. The Marietta's trip around South America, at the beginning of the war with Spain, was quite as successful as was that of the Oregon. The first ship is fitted with Babcock & Wilcox boilers, the second with cylindrical