LIBRARY NOTES. The Library Committee wishes to express thanks for donations to the library. Back numbers of periodicals are desirable for exchange and aid in completing valuable volumes for our files. Since the last issue of the Journal, we have received the following as gifts from the donors named: Transactions of New England Cotton Ass'n.-Oct. 27-28, 1897. U. S. Treas. Dept.--Statistical Abstract of the United States, 1897. Board of R. R. Com'rs of Mass.-29th Annual Report, January, 1898. B. F. Sturtevant Co.-Mechanical Draft. American Society of Heating & Ventilating Engineers.-Transactions of, 3d Annual Meeting, January 26-28, 1897. Sewerage Com'n. of Baltimore, Md., 1897, Report of. U. S. Treas. Dept.-The Foreign Commerce & Navigation of the U. S. for year ending 30th June, '97. U. S. Bureau of Foreign Commerce.-Consular Reports, March, 1898. Exports declared January, 1898. Robert A. Smart, M. E.-The Performance of a Four-cylinder Compound Deeper Water Ways from the Great Lakes to the Atlantic.-Reports of the Canadian Members of the International Commission. Proceedings of the 7th Annual Convention of the Ass'n of Railway Superintendents of Bridges and Buildings. Oct. 19, 20, 21, 1897. Locomotive. Smithsonian Institution.-Proceedings & Trans. of the Nova Scotia Institute of Science. Session 1896-7. Almon D. Thompson.-6th Annual Report of the Dept. of Public Works, Peoria, Ill. Cement & Engineering.-The Constitution of Hydraulic Cements. Chicago Electrical Association.-Standard Diagrams for Uniformity in Electrical Engineering & Patent Office Drawings, February, 1898. Institution of Civil Engineers of Ireland.-Transactions. 63d Session, to May, 1897. Chief of Engineers, U. S. A.-Monograph upon Reservoirs and their Effects upon Floods of the Mississippi River, by James A. Sheldon, Asst. Eng'r. L. G. Carpenter.-10th Annual Report Agricultural Experiment Station of Colorado, for 1897. Mass. Institute of Technology.-In Memory of Francis Amasa Walker, President of the Institute. Annual Catalogue, 1897-8. Annual Report of President and Treasurer, December, 1897. PERIODICALS. New Exchanges on file in the Library: The Electrical Review, London, England. Railroad Men, New York City. Thonindustrie-Zeitung, Berlin, Germany. The library and reading rooms are open from 9 A. M. to 5 P. M., on week days, except Saturday, until noon. Journal of the Western Society of Engineers. The Society, as a body, is not responsible for the statements and opinions advocated in its publications. VOL. III. JUNE, 1898. XXXIV No. 3. "A TOPICAL DISCUSSION UPON ELECTRICAL, PNEUMATIC AND MECHANICAL POWER TRANSMISSION IN MANUFACTURING ESTABLISHMENTS." Held April 20, 1898, before the Western Society of Engineers. Prof. D. C. Jackson: I have no set speech for this evening. This society has heard from me within eighteen months upon this subject, and as the paper I read at that time was practically repeated at a meeting of the American Society of Mechanical Engineers, it is doubtless more or less well known to you from the journals of both societies. In the way of opening the discussion, I will repeat two or three of the remarks made in my former paper. It will give a foundation for discussion and give the men who have had large experience with compressed air and with ropes and shafts and belts a foundation for argument-give them a hook upon which to hang their facts. The question of power transmission in manufacturing establishments may be stated thus: What can be installed to do the work in manufacturing establishments in transmitting power from the prime mover to the machines, with (1) the least cost for the plant and with (2) assurance of the least operating costs and the best satisfaction in operation? We all must admit that for general purposes electric transmission is likely to cost materially more than shafts and belts, or shafts and ropes. While I have had no experience with compressed air, I am inclined to the belief that pneumatic plant installed for general transmission purposes would be much more costly than electric plant. On the other hand, for many special purposes the first cost of electricity is no greater than the first cost of other transmitting agents which will do the work. There are many places in which shafts and belts, or shafts and ropes, cannot serve satisfactorily. In the latter places electricity has often displaced other means of transmission; and we now have ELECTRIC POWER IN ROLLING MILLS. Mr. Eugene B. Clark, of the Illinois Steel Company, read the following: The conditions existing in a large rolling mill are particularly advantageous to the use of electric power for operating many of the auxiliary machines which are scattered through such a plant. The large area, compared with the average manufacturing plant, which is covered by a steel mill, necessitates either a large number of small complete steam units or else a large amount of piping. The economy of either method is so low as to be prohibitive in many cases, consequently we must either bring the outlying machines into a small radius at the sacrifice of convenience and economy of operation, or we must adopt some cheap method of power transmission. Both pneumatic and hydraulic transmission has each its own particular field in which it possesses superior advantages, but when the field of each has been covered there still remain a large number of places to which power can be conveyed by electric means far more cheaply and far more conveniently than by any other method. Of course, the question of economy is the prime consideration, but the word "economy" to the manager of a rolling mill has a somewhat broader meaning than it does to the average station manager. The question of convenience of operating a mill is oftentimes so important that an apparently wasteful method is frequently preferable to one which is more economical from the steam producer's standpoint. A highly efficient motor may be, and generally is, much inferior to one whose mechanical excellence and high insulation reduces its liability to break down to a minimum. Of course, what we want is a combination of all these qualities, but it is not always possible to obtain it. The uses to which electric power is put in a steel plant are numerous and diversified. Among them may be mentioned: (1) Lighting, both arc and incandescent. Much of the arc lighting is preferably of the series kind, by reason of the considerable territory to be covered, and as yet the open arc lamp. has not been displaced to any considerable extent for series work, though the enclosed lamp is making inroads upon its field. For inside lighting, however, meaning the lighting of the interior of the mills, constant potential enclosed lamps possess advantages, which are even more marked than in many of the stores and halls where they have superseded the open arc. The trimming of an arc lamp in a mill during a week day nearly always seriously interferes with the operation of a part of the work being done there, so the installation of long burning enclosed lamps saves more money than is represented by the decreased cost of carbons, the decreased labor of trimming, the decreased repairs and attendance on series arc machines, and the decreased fuel consumption attendant upon running small units instead of large ones, as usual in such comparatively small lighting plants. Incandescent lighting may be of two kinds also with advantage. Such as is necessarily far distant from the source of generation should be alternating, from considerations of economy of transmission, while . such as is close at hand may be direct, operated directly from the constant potential mains. (2) Series motor operation: This covers the use of motors on traveling cranes, electric hoists and conveyors, charging and drawing machines, table rolls, transfer cars, etc. All such motors are operated intermittently, and therefore make demands upon the steam plant only at the times and in the proportions that work is demanded of the motor. This means, of course, that no losses occur in the transmission lines except when power is being used. (3) Shunt motors operated intermittently. This covers the use of electric power to drive lathes, shears, pumps, fans, crushers, drills, punches, etc. Such motors operate rather more steadily than series motors, but still their demands upon the generator are decidedly uneven. (4) Shunt motors operated continually. There are always some such motors distributed through a large plant to operate grinding machines, crushers, pumps, fans and similar devices. Some of these operate all the time, some only during the week days, some at night, and some in the day and so on. (5) Incidental uses. By these may be covered the use of electric current in lifting magnets, signals, testing devices, etc. The power used in this way is considerable. Upon a careful consideration of the relative value of each of the above classes of loads depends the intelligent design and location of the generating plant. For rolling mill work at present, direct-current apparatus seems much better suited than alternating, on account of the difficulty of properly controlling alter-' nating current motors under such conditions as exist on travelling cranes and similar machines operated each by a number of motors. However, it is the controlling device which gives the trouble with direct-current apparatus now, and not the motor, if it is a good one, and if an entirely new plant were being built, it would be a question to be very carefully investigated whether the advantages of transmission by an alternating system would warrant its installation as against a direct-current system. The most suitable voltage is between 220 and 250, the former being preferable for smaller plants, and the latter for larger ones. The units should be chosen of as large a size as is compatible with a sufficient allowance for reserve power, without too high an investment for machinery. The load curve on the generating plant should be carefully plotted from readings on such motors as are already installed (if the question is one of increase), and from careful consideration of the probable character of the increase of load. A study of the probable load curve gives opportunity for intelligent selection of units. The accompanying figures show such a load curve plotted from the conditions existing at the south works of the Illinois Steel Co. Three figures are rep resented. Fig. 377 shows the actual variation of the load on our present power station, each small horizontal line being the plotted average of ninety readings, extending over a period of fifteen minutes 1000 900 800 700 600 500 400 300 200 100 0 6am7 8 9 10 11 12 1pm2 3 4 5 6 7 8 y 10 11 12 lam2 3 4 Each plotted reading FIG. 377. CHART SHOWING ACTUAL LOAD ON PRESENT POWER STATION with ten seconds intervals. The form of this diagram will vary from day to day, the one given being a representative day's run. A number of such diagrams superimposed upon each other will give an average line such as shown in the next figure. Fig. 378. The line marked "Average Load Without Battery,' is a representave curve of the average fluctuation of load during twenty-four hours under present conditions. Beginning at 6 A. M. the load is about 400 amperes, from which it increases rapidly to about 700 at 7 o'clock. Then just before noon it runs up about 100 or 200 amperes, but drops off to about 400 again between noon and I P. M. It runs up a little before 6 P. M., more or less, according to how dark it is, and then drops off again, somewhat, after 6. This cycle is repeated again during the night, the load being a little heavier, however, on account of the lights. The sharp peaks on Fig. 378 show how the load actually varies. Of course, if a high peak should occur between 12 and 1 o'clock, due to a heat in the open hearth, or some similar cause, this Fig. would be changed somewhat. The straight line marked "Average Load With Battery," is the line to which the load curve would closely approximate if an accumulator plant were installed. This Fig. was plotted upon the average of a great number of readings, taken under average conditions. |