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NOVEMBER 28, Igo. THE MARINE. RECORD. THE SELECTION OF A STEAM BOILER.* BY W. E. SNYDER, M. E. The series of physical and chemical tests prescribed by. the U. S. government for marine biolers is a good guide as to the quality of the material and strength of tubes, the size and distribution of stay bolts and braces and the man- ner of their connection; the kind of tubes and their proper expansion in ‘the tube sheet or header. As regards the kind of tube, Mr. Seaton, in The Engineer of June 20, 1900, Says solid drawn steel is better than lap-welded iron and much better than lap-welded steel, while a series of tests made by the British Naval Architects and reported in Zeitschrift des Vereins Deutscher Ingenieure of June 23, 1900, shows that tubes made from steel containing from 20. , per cent to 2’ per cent nickel are much superior to oe common iron or steel tubes. The design of the ‘joints demands special attention... One point which deserves particular mention is the thickness oi the plate as specified, compared with its actual thickness. The plates are sometimes rolled much thinner on the edge than the nominal thickness, owing to the wear and spring of the rolls. The vice president of one of the principal boiler insurance companies gave the writer data which he had obtained by actual measurement of plates, and. which showed from 10 per cent to 30 per cent less on the edge than the nominal thickness of the plate. A joint made with the worst of the above plates would have only 70 per cent of the effective metal which the designer intended it should have. On most of the plates, however, the reduc- tion of the edges will not be so great as this, but the best way to get the proper thickness is to insert in the specifi- cations, after the nominal thickness, the words “measured on its thinnest edge.” This will prevent any possible mis- understanding. In water tube boilers the tube caps and bolts and nuts by which they are fastened deserve attention. The stripping of. the threads or breaking of these bolts has cost more than one man his life. In water tube boilers the sweeping effect of circulation manifests itself in very curious ways. In some horizontal water tube boilers the mud and sedi- ment will be swept up into the back ends of the upper rows of tubes, often closing them completely while the hottest part of the boiler will be comparatively clean. In other cases: this dirt will deposit in the nipples connecting the back headers with the drums, thus restricting circulation, which in turn causes overheating of the upper rows of tubes with serious results in consequence. The writer has seen in ordinary two-flue and-return tubular boilers de- posits of loosé scale and sediment directly over the bridge wall, varying in quantity from a peck to two or three bush- els, while the remainder of the surface would be practically clean. The circulation in this case would be sweeping the entire boiler with the exception of directly over the hottest part of the fire, where the current would be directly up- ward, while the scale would be deposited in a heap, its presence frequently not being suspected until a large bag appeared in. the shell. In considering the importance of the Prcalenon both for promoting evaporation and for preserving the heating sur- face it would seem essential that this particular feature be one for special investigation in choosing a boiler. The boiler ought to be of. such design that circulation is free and unrestricted. Unfortunately this is a special defect in some common water tube boilers. The connections. be- tween the generating tubes in which most of the evapora- tion takes place, and the drums in: which. the liberating occurs, are'so restricted in area that the circulation is throt- tled and:the tubes become overheated and blistered very easily. This trouble is: far more prevalent in some cases than in others. If the furnace is directly under the front eds of the tubes, so that the hot flame from the fine im- pinges directly against the tubes. or if férced blast be used or blast furnace gas—which sometimes produces the sharp effect of forced blast—the conditions are. especially favor-. ‘able to blistered tubes due to restricted circulation. . ~+ Another matter which merits discussion when considering the boiler as a steam generator, is that of moisture in. the ‘steam. No particular type may be designated as one which makes wet steam, though many practical men assert the contrary. Conditions of operation and not features of de- ge ‘produce wet steam. In some I, 200 tests of the quality _*Extracts from a paper presented before the Engineers’ Society of Western Pensylvania, June 18, 1900. of steam made by different types of boilers, the writer has found in nearly ‘all cases the steam commercially dry or containing less than 2 per cent moisture. This will usually be found in practice, though some boilers run as high as between 2 per cent’ and 3 per cent: The, writer has seen trials’ of ‘boilers in Which'over' 8 per cent ‘moisture in the steam was ‘reported, and has then tested these same boilers ‘and found’ less*'than 14 ‘of ¥ per: cent moisture present. This tends‘to verify thé statement made above that exces- sive moisttire is due rather to some condition of practice than désign of ‘boiler. such an abnormally high percentage ofwater present .un- ‘less we conclude that the engineer reporting such results Was incompetent. To illustrate the cumulative saving of a good boiler plant as compared to a poor one when they are run side by side for a number of years, suppose we make the following as- sumptions : Suppose a plant of 7,000 h. p. capacity, good boilers and furnaces, properly designed and erected, be operated an average of.275 days a year for 20 years; the coal consump- tion being 4 pounds per boiler. horse-power hour, and the cost of the coal $1.50 per net ton, delivered at the boilers. ‘Now suppose a plant of equal capacity, but of such poor type, wrong proportions and bad designs, that 5 pounds of coal are burned per boiler horse-power hour, for the same period of time and that the coal costs the same per ton. The value of the fuel wasted by the poorer boiler plant in ‘the 20 years is $693,000—a sum sufficient to command the respect of the average business man, even at the present time. The poorer boiler plant might be installed for about $100,000, while the better: one might cost about $130,000. Now, suppose an expert engineer had had charge of the installation of the better plant and received $10,000 for his services. What does the total difference in first cost amount to when compared to total saving effected? ‘There is simply no comparison, as the difference in first cost would be saved in little more than a year. In addition, in the poorer plant, cost for cleaning and repairs would be great- er, as well as for the removal of the greater amount of waste from the furnaces. : The figures given are in round numbers and the condi- tions are assumed, but neither is by any means the result of guesswork. The writer has tested, and has in mind, plants where more than 5 pounds of coal per boiler horse- power hour were burned, as well as plants where less than 4 pounds per boiler horse-power hour were burned. While the boiler plant may not run.275 days every year for 20 years, yet its lifetimes will certainly be equivalent to that running time, and the total amount wasted would be the same. Seven thousand horse power ‘is not an especially large plant. Many plants are much larger, and the waste will’be in proportion to the size of plant as well as to time of operation. So that there are really no unusual condi- tions in the above comparison, which serve as some illus- tration of what the aggregate waste from a boiler plant ‘may mean when considered for a number of years. $$ LAKE FREIGHTS. Grain rates have not changed. ‘The shippers are still offering 334 cents from Duluth and 4 cents from Fort William, and these rates are being accepted. It is now apparent that the grain movement is to be the source of employment for the boats’ after the ist of December. Rates are weak and dropping, as 3 cents was accepted on one Buffalo charter and 2% cents is offered at Chicago, a drop of % cent from last week’s figures. Vessels are more plentiful than cargoes at the upper lake ports, and the market is easier. The boom in grain freights that was looked for has flattened out, and carry- ine charges are lower than they were a week ago. A number of charters have been made at 90 cents from Escanaba to Ohio ports, and at $1.05 to Buffalo. Shippers tried,.to charter on Monday at 75 cents, Escanaba with no takers, _—_-< A SURVEY BOAT. Major J. G. Warren, United States Engineer in charge of the improvment of ‘rivers and harbors on the west shore of Lake Michigan, has made a recommendation in his an- nual report. that a steamer be provided for. inspection and-survey-work. ‘The cost of the boat is given as $30,000, and it is hoped to have the boat built next year. There is no other explanation of. DISCREPANCY IN FIGURES. ~ The Duluth coal men have expressed some surprise at the figures furnished.by the local United. States Engineer's. office ‘on the receipts of the anthracite’ variety. of coal for the sea- “son of 1991 to: November 1, and it has Jed to/an investiga, tion which discloses that an’ important error has* been. thade either by the Sault officials or by the compiler in the local United States office, says the Duluth News Tribune. The local engineer’s office has figures showing that to November 1, this year, the receipts of anthracite coal were 748,254. tons,.awhile, ‘according to the Sault officials, the total was only 657,147 tons. more remarkable when it is considered that the head ‘of the - lakes receives only 81 per cent., or thereabouts, of all the hard.coal coming to Lake Superior. : Assuming that the head of the lakes has received this The discrepancy will be found all the. fe ay per cent., and that the Sault figures are right, the Duluth- ~ Superior harbor would have received to November 1 about §32,289 tons, according to the figures of the local U. S. en- . gineer for 1900. Still further, with the Sault figures as a basis those of the local U. S. Engineers are found to be ant 215,965 tons in excess of the actual. On the other hand assuming that the figures on stint : receipts at Duluth-Superior to November 1 are correct as reported by the local United States Engineer’s office, and therefore represent about 81 per cent, of all the coal re- ceived on Lake Superior, the Sault figures for this com-~ modity must have been in the neighborhood of 925,600 tons, ‘whereas they are given as 657,147 tons. The attention of Capt. D. D. Gaillard, U. S. Engineer i in charge at Duluth, was called to the apparent discrepancy. He said, when the coal figures were first given out that his. figures had not been checked over and he would not-vouch ~ for them absolutely until such precaution had been taken. . When these statistics are finally completed it is after they, Tt is have been proved and there is no chance for mistake. a big task and cannot be completed for some time. The Duluth coal men have been much mystified and sur- prised at the aggregate size of the receipts, and their inves- Ae resulted in the discovery of the discrepancy. ae ee A SUBMARINE TEST. In the presence of a number of people which assembled! to witness the emerging of the submarine boat Fulton on ° Sunday last, that craft rose from the bottom of ‘Peconic’ bay, which is at the eastern end of Long’ Island, with-all. well and greatly surprised to find there was a storm raging. The test of the Fulton’s staying powers was highly satis- - factory, not only to the officers of the company that built: her and the naval officers present, but to those who went to the bottom in the boat. They report there was not the slightest discomfort to them during theif more than 15 hours of submersion beneath the surface. : Captain Cable, of the Holland Company,’ who was. in command, said the boat could have remained down for three months if there was food enough on board. Although there was but six feet of water over the top of the turret, those on board felt nothing of the storm.’ Throtgh ‘the night there was a light rolling motion to the craft, but this was ascribed to the regular motion of the water and not to. the disturbance which was rolling the: waves high on the’ shore. Rear Admiral Lowe, U. S. N., and Lieut. Arthur Mae- Arthur refused to go into any discussion of the perform- ance of the boat, except to say that they would be’satisfied tc stay down longer. Members of the crew say they expe- rienced no difficulty in breathing, and: that the air was ail that could be desired, and much purer and better than “in an ordinary closed room in which are several persons. Every piece of machinery worked to perfection during the night. The men ate two meals while under w ater and most of them obtained three or four hours’ sleep. oe oo THE marine insurance companiés carrying risks on’ the lakes have been in correspondence over a request from Canadian western shippers that the period ‘of insurance should be extended from December 5 to 12, so that the sea- son of navigation could be lengthened and exporters be en- abled to get their grain out of the Canadian northwest: The companies have decided to extend the season in individual cases, where exporters asking are their regular custoniers, and where the vessels are considered in the first class. After December 5 a higher rate will be charged: The:best class of Canadian boats will have no difficulty in obtaining the extex- sion,