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to the furnaces; but the true province of this type of apparatus is in transferring coal (for water shipment) from cars to colliers. In this field they have found
There are in existence many different designs of car-dumping machines; but the most efficient styles are those which pick up and completely overturn the loaded car, transferring its contents to the hold of the vessel to be loaded. The earliest forms of car dumpers, while entirely satisfactory in the rapidity with which they handled material, were corisidered deficient in that they entailed a serious breakage of the coal. This, how
Furnace Hoists The usefulness of new marvels for handling bulk materials is by no means confined to the transfer of coal and iron ore to and from ships, railroad cars, and stock piles, but is demonstrated in scarcely a less striking manner at blast furnaces and iron and steel making plants in general. Foremost among the utilities in this field is the furnace hoist and stock distributer, which has done away entirely with the old-time dangerous and unsatisfactory method of feeding blast furnaces, and, by automatically charging the furnaces, dispenses entirely with the employment of top-fillers.
This hoist consists, in the main, of an inclined steel-trussed bridge starting from a pit and reaching to the top of the shell of the furnace, where it terminates in an extension over the top of the bell and hopper. A skip car with a capacity of from 2,000 to 6,000 pounds is arranged to run on this track, the hoist rope passing over the top sheave and back to the drum of the hoisting engine near the incline. When the skip car, loaded with iron ore, coke, or limestone, as the case may be, arrives at the top of the furnace, the car is automatically tipped, and the load is dumped into the great receptacle, from which the bell has been automatically lifted for the purpose.
At all blast furnaces the transfer of iron ore from stock or storage piles to the furnace as the raw material is required for consumption, constitutes a handling problem of some complexity. In this work there are employed steam shovels, locomotive derricks equipped with grab buckets, and, finally, various modifications of the bridge tramway. Some of the bridges thus employed have a clear span of about 250 feet over storage yard and railroad tracks, thus enabling the ore to be handled directly from railroad cars to furnaces, or from the stock piles where the surplus supply is held.
Car-Dumping Machines Yet another form of apparatus which is being employed in handling both coal and iron ore, is the car-dumping machine. At the furnaces these dumpers are utilized in some instances to transfer the contents of standard-sized railroad cars to smaller cars which carry the material
A Modern Car-Dumping Machine. ever, was finally remedied by modifications whereby the coal is dumped into pans connected with chutes leading to the vessel, which not only enable the fuel to be handled with far less breakage than formerly, but also make it possible to direct the influx to any portion of the hold desired.
The fundamental feature of the average car-dumping machine is a car-tipping device or cradle into which the car is run and then clamped, and which turns over with the car and discharges its contents. In some machines the receiving pan is automatically tilted at an angle proportionate to that of the car-tipping device, so that the coal slides gradually instead of pouring or falling; and in certain machines the coal is not sent into the vessel hold through a chute, but is transferred from the car, as it is dumped, to transfer tubs or to steel buckets arranged on the endless-chain plan, which convey
it to the cargo space by easy stages and per the fuel is delivered to a carrier of with practically no breakage. Some of the continuous type, which hoists it up to these car-dumping machines will handle an incline spout down which it passes upward of 200 loaded cars in an ordinary into a telescope spout and thus directly working day, not only actually transfer- into the boat. This telescope spout is ring the coal, but handling the loaded drawn out to its full length at the comand empty cars to and from the machine, mencement of operations, and is then and obviating all necessity for the em- gradually taken up or shortened as the ployment of a shifting engine and train boat is filled. By this means the spout is crew.
kept constantly full of coal, and the Coal-Loading Machines
breakage of the fuel is reduced to a miniAn ingenious type of coal-loading ma mum. It requires but two men to operchine is found at Fairport on the south ate such a machine, which is driven by a shore of Lake Erie, and at several other 50-horse-power engine. The cost of an points in the United States. By its op- installation of this kind is much less eration the coal to be loaded on a boat than in the case of some of the other is dumped from the hopper-bottomed types of coal-handling machinery, and railroad cars into a large receiving hop- yet such a machine is capable of loading per underneath the car. From this hop- from 600 to 900 tons of coal per hour.
The Marvelously Rapid Progress in Electrical Engineering which has
Revolutionized Industrial Conditions
By R. F. SCHUCHARDT, B. S.
Consolidation of Plants
tem had to be made without sacrificing THE NEXT STEP in the develop- the value of the investment represented ment was one of consolidation. by the generating apparatus and lines
Many cities had been liberal in of the existing stations. Such a change,
granting franchises to lighting naturally, was made step by step, and companies, and as a result there thus required several years. In addition were built within the same city to providing for the existing load, the many systems of various excellence new system had to be designed for the and stability. To the engineers of future; and the probable development in the consolidated company was then the line of various classes of electrical presented the problem of unifying the apparatus had to be considered. systems; but the changes to the new sys- In our larger American cities, the load
ondary pressure ranged from 104 to 125 volts, while some of the earlier systems still maintained a secondary pressure of 50 volts. A few of the later stations had 2,000-volt lines, with a frequency of 60 cycles; and there were also polyphase (generally two-phase) lines for serving a motor load. A view of some of these earlier alternating-current stations is given in Figs. 19 and 20.
30 per cent of the load goes to power users; therefore the system had to be adapted to all classes of motor service, as well as for lighting. For this service in such a district, the Edison direct-current three-wire system is certainly the most satisfactory, and this system has been pretty generally adopted. It permits the use of storage batteries; requires less copper than does the alternating-current system, because in it there is no loss due to inductance; gives better regulation; and is far better for general all-around power service.
To consolidate several systems of this class was a simple matter. It required merely that the separate networks of mains be tied together, and a uniform pressure kept on the system by each station feeding into it. In the outlying districts, however, the problem was more
High-Voltage Polyphase Systems
This conglomerate mass, then, had to be unified. A careful study of various systems showed the four-wire threephase system, with a frequency of 50 to 60 cycles, to be the best suited to the distribution of such a load; and this system is being freely adopted. Good examples of it are found in Chicago, Milwaukee,
St. Paul, and Cincinnati. The generator accomplished by means of the ordinary for this system is star-wound, with the 2,300-volt static transformers. neutral grounded, as explained earlier in In Fig. 22 is seen a 150-light (7.5the paper. The voltage at which this K. W.) transformer hung on a pole. The system is generally operated is 4,000 be- two wires coming down at the right are tween phase wires. This gives a pres- the 2,300-volt primaries; while the threesure of approximately 2,300 volts be- wire secondaries, of 115 volts per side, tween any phase wire and the neutral; are brought up at the left. Fig. 23 is a
FIG. 20. EARLY ALTERNATING-CURRENT STATION and the single-phase lighting feeders are pole line carrying principally alternatingswitched on to this 2,300-volt connection. current primaries. Transmission to subThe various feeders are connected each stations, which in this case are merely to one of the phases and the neutral, so distributing centers, is then done over that the three phases are aproximately the three phases at 4,000 volts, the balanced. For a power load, then, con- neutral preferably being carried along nection is made to all three phases; and also. At the substation, only feeder the motor is usually of the polyphase in regulators are required beside the duction type, of which one is shown in switching apparatus ; and the feeders here Fig. 21. Where the capacity of the also are connected between a phase wire motor is very small—say under 3 H. P.- and the neutral, 2,300 volts. A diagram the single-phase type of induction motor, of a four-wire three-phase distribution equipped with some special starting de- is shown in Fig. 24 (p. 154); and in Fig. vice, is often used. Stepdown of the volt- 25(p. 155) is seen a switchboard installed age to the service pressure is, of course, for such a system.
a neutral conductor is not used and all load is connected between phase wires). Brooklyn has a two-phase 2,300volt 60-cycle system in the residence section; Philadelphia also, though in the latter city the current is generated at 5,500 volts and stepped down to 2,300 volts for alternating-current distribution.
A 500-volt two-phase generator is shown in Fig. 26. For higher voltages the revolving-field type is used, thus avoiding collector rings and brushes for
Fig. 21. POLYPHASE INDUCTION Motor. the high-voltage current. At the South Boston station of the Boston Electric heavy load, would be equally ruinous. Light Company (now part of the Boston Consequently recourse is had to other Edison Illuminating Company), the gen- means of transmission. The success and erators are wound for 2,300-volt three- the comparative copper economy of polyphase 60-cycle currents.
phase transmission lines, already men