TJ ' w NRLF GIFT OF Arthur E. Moncaster Small Turbines for Electric Drive A description with suggestions and instructions for their INSTALLATION CARE AND OPERATION ENGINEER'S REFERENCE BOOK Please keep this book where your engineer can refer to it readily m. \ Instruction Book WM 105 Jan. 1913 The Westi n^house Small Turbines for Electric Drive A description with suggestions and instructions for their INSTALLATION CARE AND OPERATION AST PITTSBUR.G.RA. er d d Q < w C/2 w O o PQ o o Q Q M M O iC R. W. INTRODUCTORY The following pages describe the small turbines manu- factured by The Westinghouse Machine Co., and are in- tended as a guide for those who have occasion to erect and operate them. The matter herein is confined to a detailed description of the construction together with illustrations. It is believed that a better knowledge of the operation of the machines may be imparted in this way than by a lengthy series of instructions. The particular type of turbines herein described, is intended for direct connection to small direct current or alternating current generators, in sizes from one to 300 kilo- watts. The smaller sizes are designed for non-condensing service only, while the larger units are built for either con- densing or non-condensing 'operation. Full instructions covering the direct and alternating current generators connected to these turbines may be found in the following publications of The Westinghouse Electric &Mfg. Co.: D. C. turbo generators, Instruction Book 5107. A. C. turbo generators, Instruction Book 5024. FUNDAMENTAL PRINCIPLES OF SMALL WESTING- HOUSE STEAM TURBINES. As in all steam turbines, the operation depends upon the expansion of steam in suitably formed nozzles so that the potential energy given up during the expansion causes the velocity of the expanded steam to increase the velocity at the outlet from the nozzle or nozzles being such that the kinetic energy (velocity energy) is substantially equal to the energy given up during the expansion in the nozzles. After the expansion in the nozzles, and having converted the poten- tial energy in the steam into kinetic energy, means must be provided for converting the energy of motion into mechanical work at the shaft. This may be done in a number of different ways, and the method employed in the small turbines under discussion depends almost wholly upon the operating condi- tions, though it is also governed partly by the size of the turbine and the shaft speed. To show more clearly the differences found in the working parts of the smaller turbines, the diagrammatic sketches Figs. I, 2, 3, 4 and 5 are presented. The principle involved in all of these is the same, differing only in degree of elaboration as higher powers and higher pressure ranges are reached. The arrangement of Fig. i is the simplest, consisting of only the nozzle "A," a single row of rotating blades "F," and the reversing chamber U B," which parts are common to all small turbines. Steam is admitted to the nozzle "A" through the governor valve, and expands to approximately atmos- pheric pressure, thereby attaining a velocity which is about four times the velocity of the moving blades in Fig. I . Now since the blades move with about % the velocity of the steam leaving the nozzle "A," the steam after having passed through the moving blades, enters the reversing chamber "B," with approximately half the nozzle velocity. The reversing chamber "B," as the name suggests, reverses the direction of the steam, and causes it to again im- pinge on the same row of moving blades, further reducing the velocity of the steam, and thus absorbing the energy remain- ing after the first passage through the blades. In the arrangements Figures 2, 3 and 4, the principle of operation is the same as for Fig. I, except that instead of completing the expansion in the first nozzle, the expansion is carried down only sufficiently far to give the steam the desired velocity, i. e., approximately four times the blade velocity. O Cn The expansion is then completed in a second nozzle "C" (Fig. 2) after which the steam passes through the blades a third time, enters the reversing chamber "D," passes through the same row of blades a fourth time and thence to the ex- haust. This may be regarded as a combination of two of the elementary units shown in Fig. i, in the same manner as two cylinders of different sizes are put in series to form a compound engine. Thus, by a proper selection of one of these arrange- ments, the turbine can be adapted to any steam pressure and blade speed. Fig. 3 shows a nozzle arrangement for a condition intermediary between Figures I and 2, in which the steam makes one passage through the blades after passing the second nozzle. Fig. 4 is a combination occasionally used, in which the element in Fig. i is followed by two nozzle elements, each dis- charging steam once through the blade passages. Fig. 5 shows the scheme used in some of the larger turbines to permit carrying heavy overloads, or temporary operation with low steam pressure. Steam from the governor valve is admitted to the nozzle "A" same as in Fig. i, but in addition a secondary hand operated valve admits steam to the nozzle "E," which is also under the control of the governor when in operation. It will be noted that the nozzles "A" and "E" each have an independent reversing chamber, that for the nozzle "E" being located within that for the nozzle "A," thus utilizing the energy in the steam with equal economy at heavy overload, as well as at normal rating. The overload valve "E" should not be used, however, except when necessary to prevent the speed from falling and lowering the voltage, as then the economy will not be so good at fractional loads. General Features of Design. All the turbines, ex- cepting the 10 and 15 Kw. sizes, and smaller, are equipped with a vertical geared governor of generous design, having great power, operating at the best speed for efficient and close regulation. An extension of the governor spindle downwards, operates an oil pump of simple design, for supplying the bear- ings with an ample flood of oil. Fig. 6 is a typical cross section of a small turbine, and shows also on the end elevation, the automatic stop and governor valves. It will be noted that the rotor carries but a single row of blades, which revolves between the nozzle blocks and reversing chamber, as previously described. These are plainly indicated in the lower portion of the machine. C/2 W n All the working parts of the turbine are in the lower half of the cylinder or casing, thus making it unnecessary to disconnect the steam and exhaust pipes when the turbine is opened for inspection. Also, it permits the spindle to be removed from the casing without removing the turbine rotor from the shaft. Furthermore the governor (shown in greater detail in Fig. 15) may be removed from the turbine without the necessity of taking it apart, beyond disconnecting the link attached to the governor valve stem. The governor shown in Fig. 6 is driven by means of a worm and wheel, although in some cases bevel gears are used. The oil pump, which is located under the oil reservoir, is driven by the governor spindle. This particular design of governor may be removed from the turbine by simply removing the bolts on the horizon- tal joints and upper half of the vertical joint. However, some governors have the union type coupling and cannot be removed until the union coupling has been disconnected, the latter being accessible through the hand-hole shown in the cross section, Fig. 6. In the majority of small turbines there are but two bearings, both of which are part of the generator, the turbine rotor being carried on the end of the generator shaft. In some of the larger sizes, three bearings are employed, as also in the case of small turbines for driving alternators. Rotor. In smaller sizes up to 25 Kw., the turbine rotor is integral with the hub, but in the larger sizes the rotor consists of a hub to which the turbine disc is bolted, the disc being doweled into the hub to insure its running true. The blades, as will be seen from the cross section of the rotor, are held in place by means of rivets which go through the shanks of the blades inserted in the periphery of the turbine disc. The hubs of all rotors are fitted on to the shaft with a considerable taper, so that if necessary they can be easily removed by loosening the nut on the shaft and tapping the latter lightly with a babbit hammer. The extension shaft for driving the governor is bolted to the rotor hub and carries the outboard turbine gland sleeve and also the automatic stop, which will later be taken up in detail. In 'the case of alternating current units, it is, for elec- trical reasons practically impossible to split the armature horizontally, and therefore it is necessary to withdraw the re- volving field from the armature endwise. For this reason, bO Oi w o r > U D I- I- O O t- O < CO CO O O CO o O o o o o o cr cc a: o: cc r r r r r CO I I 6 >' >* >' >' >' >' >' >' >' >" >' ooooooooooo ooooooooooo 26 latch is released by the tripping of the automatic stop, the pressure of the throttle valve spring on the throttle valve stem nut forces the latter downward, closing the valve, providing the latter has been opened. From the construction, it will be evident that the throttle cannot be opened after it has been tripped by the automatic stop, until the throttle valve hand wheel has been turned around in the direction required to close the valve, and until the throttle valve stem nut is brought to its upper posi- tion, and has caused the throttle valve latch guide rod to en- gage with the throttle valve latch, and hold it in the position shown in Fig. 16. Furthermore, it will be evident that the automatic releasing of the throttle valve is possible in any position, whether wide open, or only partially open. The steam after passing through the automatic throttle valve, enters the space above and below the governor valve. The latter is of the double disc poppet construction, thus being entirely balanced for steam pressure. The only force required to move it, is that necessary to overcome a slight friction of the valve stem in the valve stem bushing and valve cage guides. As will be noted, from the cross section, the valve cage is not bolted into the steam chest body but is held on its seat by means of a spring which permits it to expand and con- tract without warping the valve seats. The lower end of the valve cage is free to expand and contract without resistance, steam tightness being obtained by the valve body being ground into the steam chest, and the governor valve cage spring seat and governor valve cage spring seat ring, shown in the draw- ing. The valve is so constructed that it has to be moved about 1/32 " before steam begins to pass, thus preventing cutting of the valve and valve seats when steam is being throttled through the valve at light load. Steam tightness, where the valve passes through the valve bonnet is obtained by a plain bronze bushing and a small soft packing washer, which need not be made very tight, however, as any steam leaking past the bushing will escape through the drain port "O." A more elaborate metallic packing of well known type is employed in the larger sizes. 27 The Westinghouse Machine Company Designers and Builders of Steam Turbines Stokers Steam Engines Gas Producers Gas Engines Pumps Condensers Blowers Turbo Compressors SALES OFFICES New York 165 Broadway Chicago 39 South La Salte Street Pittsburgh Westinghouse Building Philadelphia 1003 North American Building Boston 201 Devonshire Street Atlanta Candler Building Denver Gas & Electric Building Detroit 27 Woodward Avenue Cleveland 1117 Swetland Building Cincinnati 1 102 Traction Building San Francisco Hunt Mirk & Co., 141 Second St. City of Mexico Cia Ingeniera, Importadora y Contratista, S. A. Havana, Cuba Galban & Company San Juan. Porto Rico Porto Rico Construction Co. Iquique, Chile J. K. Robinson & Co. Tokio, Japan Takata & Company Caracas. Venezuela. . . H. I. Skilton GENERAL OFFICES AND WORKS EAST PITTSBURGH, PA. 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