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trated in Fig. 145, and a fairly good conception of the assembling of the various members, and especially the reducing gears, may be had by reference to Fig. 146,
which shows a 110 H. P. turbine and rotary pump with the upper half of the gear case and field frame removed for purposes of inspection. The slender shaft is seen projecting from the center of the turbine case, and upon this shaft are shown the small pinions meshing into the large spiral gears upon the two pump shafts.
Referring to Fig. 145, A is the turbine shaft, B is the turbine wheel, and C is the pinion. As the turbine wheel is by far the most important element, it will be taken up first. It is made of forged nickel steel, and it is claimed by the builders, the De Laval Steam Turbine Co. of Trenton, New Jersey, that it will withstand more than double the normal speed before showing any signs of distress. A clear idea of the construction of the wheel and buckets may be had by reference to Fig. 143. The number of buckets varies according to the capacity of the machine. There are about 350 buckets on a 300 H. P. wheel. The buckets are drop forged and made with a bulb shank fitted in slots milled in the rim of the wheel.
Fig. 147 is a sectional plan of a 30 H. P. turbine connected to a single dynamo, and Fig. 148 is a sectional elevation of the same.
The steam, after passing the governor valve C, Fig. 148, enters the steam chamber D, Fig. 147, from whence it is distributed to the various nozzles. The number of these nozzles depends upon the size of the machine, ranging from one to fifteen. They are generally fitted with shut-off valves (see Fig. 144) by which one or more nozzles can be cut out when the load is light. This renders it possible to use steam at boiler pressure, no matter how small the volume required for the load. This is a matter of great importance, especially where the load varies con
siderably, as, for instance, there are plants in which during certain hours of the day a 300 H. P. machine may be taxed to its utmost capacity and during certain
otner hours the load on the same machine may drop to 50 H. P. In such cases the number of nozzles in action may be reduced by closing the shut-off valves until the required volume of steam is admitted to the wheel. This adds to the economy of the machine. After passing through the nozzles, the steam, as elsewhere explained, is now completely expanded, and in impinging on the buckets its kinetic energy is transferred to the turbine wheel. Leaving the buckets, the steam now passes into the exhaust chamber G, Fig. 147, ani out through the exhaust opening H, Fig. 148, to the condenser or atmosphere as the case may be.
The gear is mounted and enclosed in the gear case I, Fig. 147. J is the pinion made solid with the flexible shaft and engaging the gear wheel K. This latter is forced upon the shaft L, which, with couplings M, connects to the dynamo or is extended for other transmission,
O, Fig. 148, is the governor held with a taper shank in the end of the shaft L, and by means of the bell crank P operates the governor valve C. The flexible shaft is supported in three bearings, Fig. 147. Q and R are the pinion bearings and S is the main shaft bearing which carries the greater part of the weight of the wheel. This bearing is self-aligning, being held to its seat by the spring and cap shown.
T, Fig. 147, is the flexible bearing, being entirely free to oscillate with the shaft. Its only purpose is prevent the escape of steam when running non-cca densing, or the admission of air to the wheel case when running condensing. The flexible shaft is made very slender, as will be observed by comparing its size with that of the rotary pump shaft in Fig. 146. It is by means of this slender, flexible shaft that the dangerous feature