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Title: |
1893 Article-Southwark Foundry, Triple Expansion Engine |
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Source: |
Cassier's Magazine May 1893, pgs. 111-113 |
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Insert Date: |
11/13/2012 10:37:18 AM |
Beside the numerous steam engines belted to dynamos, there are various examples of electric generators directly connected and one of these, which attracts much attention, is exhibited by the General Electric Company of New York and Boston. The engine, which was designed under the supervision of J. C. Henderson, the engineer-in-chief of the company, is of triple expansion, direct acting, vertical condensing type, similar to others installed during the last two years by the General Electric Company, with the exception that, instead of piston valves, Corliss valves are used, which are equally, if not more, suitable, as the speed is but 100 revolutions per minute.
The high-pressure cylinder is 22½ inches in diameter. The intermediate cylinder measures 33 1/8 inches, and the low pressure cylinder 55 3/8 inches. The stroke of all is thirty-six inches, which, with the stated speed of 100 revolutions per minute, gives a piston speed of 600 feet per minute. At maximum efficiency the number of expansions is 12½, and at maximum power 7½. The initial pressure of steam carried is 160 pounds per square inch, and the condenser maintains a twenty-four inch vacuum.
The chief novelties in the design are, to begin with, found in the fact that the valves are arranged in the top and bottom cylinder heads, thus reducing the percentage of clearance to a minimum. Steam dash - pots are used, located in the heads and easily accessible, and the whole arrangement relieves the front of the engine of the appearance of complication. In the governor is found quite a departure from general practice, this part being made much smaller than is usual and running at a considerably higher speed than is customary, so that a finer adjustment is possible.
The design was principally intended for operation in stations using the three-wire system with the two dynamos placed on each end of the shaft, thus keeping a constant balance, never allowing the full power of the engine to be transmitted on one side alone. The end bearings are water-jacketed. The armatures are overhung, thus doing away with unnecessary extension of the bed-plate, liability of breaking shaft, besides making it more easily renewable and reducing the floor space required. The normal output of the generator is 800 kilo-watts, or 5,333 amperes at 150 volts, and the maximum output is 920 kilo-watts, or 6,133 amperes at 150 volts. The maximum efficiency is 700 kilowatts, that being the load decided upon as the load of longest duration in actual practice.
The calculated efficiency was eighty six per cent., but as the smaller generator (the 2 x 200 K. W.), fitted with piston valves did considerably better than figured, it is quite likely that this type will exceed the calculated efficiency in the same ratio. Steadiness of motion is insured by the three-throw crank design and the weight of the armature, which amounts to 39,000 pounds. The surface condenser specially designed for the engine is contained in the foundation box, which carries the bed plate as well as the feet of the dynamos. The air and circulating pumps can be worked either direct from the crossheads on the back of the columns, or independent, as in the present instance. The engine is fitted throughout with steam jackets around all cylinders, and outside, between that and the lagging, with magnesia blocks and cement. Katzenstein's metallic packing is used. The total weight of the engine, including that of the condenser and foundation box, is 320,000 pounds. The weight of the two dynamos is 165,200 pounds, bringing the total weight of the whole outfit up to 485,000 pounds. This gives a weight of about 0.6 pounds per watt.
The whole design, working drawings, etc., were prepared by the engineering department of the General Electric Company, the builders being the Southwark Foundry and Machine Company of Philadelphia, Pa. |
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1893 Southwark Foundry, Triple Expansion Engine
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