complicated as it grew, before the primal theories of the heat motor assumed corporate, practical form. It is true that later knowledge of materials, and how to work them, has made the way clearer; and the wider use of the steam turbine has in a measure depended upon the development of electrical practice, with which latter it is now so intimately identified. Much interest has for some time been centered in this type of prime mover and the possibilities of its application. The history of its development is quite generally known, and up to this time attention has been more particularly directed to its engineering and mechanical characteristics. It now seems appropriate to inquire into the controlling features of its commercial utility, and determine, if we may, whether the steam turbine, subjected to a somewhat careful analysis, is a machine still to be developed, though of ultimate promise, or whether it has been well tried and its advantages proved. What has it accomplished? What justifies its use? What otherwise unattainable results will it produce? What are its limitations? It is this aspect of the case on which the light is needed. It is of little moment what the direct or contingent advantages of the turbine may be, if its reliability remain in doubt. Offered, as it is, in large units, and being apparently more related to the classes of service which impose the most exacting requirements, the demand is imperative that in this one vital respect there be little left to chance. Before recurring to actual experience, it may be instructive to consider for a moment the general character of the turbine as a type of motor, contrasted with the piston engine. Fig. 1 shows the longitudinal section of the Westinghouse turbine. The steam entering the governor valve arrives at the chamber “A," then turns to the right, passing first a set of stationary blades, then impinging on the moving blades, driving them around, and so on, until it arrives at exhaust chamber "B." And here is an interesting lesson in physics—a demonstration of the conversion of heat into energy; for while the temperature of the inlet end is that of the entering live steam, the exhaust end, but three or four feet distant, is not so hot (about 126 degrees F.) but that one may bear the hand. The cut will show that the only real moving part is the spindle, revolving in its bearings, the governor mechanism and oiling arrangement being comparatively insignificant. The blades do not wear, as the steam velocity-some five or six hundred feet per second-is not sufficient to affect them. The blades are made of a special material, and are calked in such manner that the force required to pull them out would exceed the elastic limit of the material in the blades. They are subjected in regular practice to a strain of about one-fortieth of this amount. The actual pressure exerted on each blade is about one ounce. A complete description of the mechanism is not needed here.* It is sufficient to note its general character and to contrast its obvious simplicity and freedom from complication, with the recognized complexity of the piston engine. The inference is clear that in constructive opportunity, at least, the turbine should be the more reliable. The steam turbine, before it had obtained any considerable recognition here, was not entirely without success abroad. Parsons and others had done much to prove its reliability. For instance, in 1897 the Newcastle & District Electric Lighting Co., operating eleven turbines of 75 to 150 K. W. each, showed their cost of repairs and renewals on their entire plant, including turbines, generatórs, boilers, condensers, pumps, fittings, cables, etc., to be 26-100 of a cent per K. W. per annum. In this country the steam turbine is now operating in several plants. The first prominent installation was at the Westinghouse Air Brake Company's works, at Wilmerding, Pa., where the first unit was started in August, 1899, two more shortly after, and the fourth unit in April, 1901. Thus, the plant has been in service, for the most part, more than three years, and the fourth unit about eighteen months. The plant operates regularly eleven hours per day, the service being electric power and lighting. With the iron foundry running at night. one turbine is run 22 to 23 hours per day. In general, the units have run quite to their rated capacity-perhaps within twenty per cent of it. as a minimum. An interesting comparison has been made elsewhere of the efficiency of this turbine plant with the installation it supplanted, the latter comprising simple and compound engines, scattered about the works. After the three turbine units had been placed in operation, they were shut down and the steam engines previously in use (not yet disconnected from service) were again started up and a test made. A test was then made of the turbine plant. These were based upon a week's run, careful measurements being taken of fuel and water. The saving of coal in favor of the turbine plant averaged 35.7 per cent during the day, and 36.4 per cent during the night. The saving in feed water averaged 29.8 per cent during the day and 41.4 per cent during the night. In round numbers, this meant a saving of about 40,000 lbs. of coal per 24 hours. This improvement, of course, was attributable not entirely to the turbine itself, but also to the more efficient method of electric power transmission in comparison with the previous scattered arrangement of steam engines, with long runs of steam piping, use of belts, etc. It is, however, instructive *See paper read by Mr. Francis Hodgkinson before Engineers' Society of Western Pennsylvania, November, 1900. as indicating the results accomplished in a specific and prominent case, as between an old and still commonly used system of power transmission, and a modern method. This plant at Wilmerding was the first of its kind. It naturally was not without its minor difficulties. The turbines themselves from the time of starting have been practically free from trouble of any kind. Some armature difficulties were at first experienced-not of enough moment to interfere with operation-and were readily corrected. Summing up the experience had with this first installation, undertaken somewhat experimentally at the time, the net result is that the plant has operated about three years in heavy daily service; that the work has not suffered interruption, and that the plant is to-day running with sustained satisfaction and with no visible signs of wear in any of its parts. Fig. 2 shows this installation, comprising four 400 K. W. units located within a space 45 by 61 feet, the height of the engine-room being 20 feet 6 inches. The Yale & Towne Manufacturing Co., at Stamford, Conn., have a 400 K. W. steam turbine furnishing 240 volt, 2-phase current at 7,200 alternations. This outfit was started in operation February 1st, 1902. Since that time it has been in regular daily service, carrying about its rated load, operating 10 hours per day, furnishing current for electric motors and some lighting. Up to this time, therefore, it has been in service some eight months, and its mechanical operation has been most satisfactory. No quantitative tests have yet been made of steam performance, but there is general evidence of its economical operation. Fig. 3 shows the appearance of this outfit. The Hartford Electric Light Co., at Hartford, Conn., have a 1,500 K. W., 2-phase, 2,400 volt, 60 cycle, turbo-generator outfit, which was started in April, 1901. This, at present, is the largest turbine yet installed in this country. Put in, as it was, to relay their water power, it has not been in constant service, but has usually been required but one or two days a week. At such times, however, it has carried the full station load of some eighteen or nineteen hundred kilowatts. Reference will hereafter be made to its striking economy. A great deal of interest has centered in this early installation of a good-sized outfit in a prominent location, and its excellent performance is now generally well known. Some difficulties were at first experienced; nor were they entirely unexpected, for there had been no facilities, as there now are, for testing the outfit before shipment, and it was merely run at the shop without load. Before the machine was successfully in operation, one trouble that developed was with lubrication. The packing glands around the turbine shaft leaked somewhat, and the construction of the oil passages with reference to these glands enabled the oil to come into contact with the steam, im |