Note: The following article on "Central Air Plant at a Georgia Quarry," is taken from "Mine and Quarry" Magazine, Sullivan Machinery Co., Publisher, Chicago, Illinois, Vol. IX. No. 3 - October 1916, pages 924 - 929, Whole No. 31.
Central Air Plant At A Georgia Quarry(Lithonia Gneiss District in Georgia)
By J. E. M. Schultz
Houston Bldg., Knoxville, Tenn.
An industry of considerable importance to the State of Georgia is the quarrying of granite for paving blocks and curbing. The center of the activity is at Lithonia, in the north central portion of the state and about 30 miles east of Atlanta.
In close proximity to Lithonia, about 8 miles to the west, are the well known Stone Mountain quarries, but the main product in that district is dimension stone for building and monumental purposes, the stone being a true granite and not a gneiss, so that less attention is paid to the curbing and paving block industry than at the first named point.
Within a radius of four miles from Lithonia are some twelve actively operating quarries, chiefly engaged in the quarrying of curbing and paving blocks, with rubble and crushed stone as more or less byproducts. The granite, which is more accurately described as a gneiss, outcrops over a wide area, sometimes in flat ledges, at other times in broad dome-like structures. Two of the largest properties are of the latter character, namely, the Arabia Granite Co. and the Pine Mountain Granite Company.
Conditions are favorable for the economical production of stone. The climate is exceedingly mild; and with the possible exception of two months in the year, no discomfort or handicap is attendant on quarrying in the winter. Railroad facilities are ample, the Georgia Railroad serving the district, with but a short freight run to Atlanta, from which point, truck lines radiate in all directions. In addition, an interurban is projected from Atlanta into Lithonia. However, the main asset is the character of the stone itself. As it is gneiss, it splits readily, a particularly desirable feature, when the rapid production of curbing and paving blocks is to be considered. As a consequence of the ease with which the stone is worked, the operating companies are able to keep their costs down to a point where they can actively and successfully compete for granite business in the Mississippi Valley and with quarries more closely situated to the large centers of consumption, such as St. Louis and Chicago.
While most recently organized, the Arabia Granite Co. is the largest in the Lithonia district. The quarries are situated about four miles from the town; a standard gauge railroad, owned and operated by the company, serving as the connecting link with the Central of Georgia Railroad. Some 200 acres of land are owned by the Arabia Granite Company, on the site of Arabia Mountain, from which the company takes its name. However, "Mountain" is a misnomer, being simply a popular application to the low-lying, dome-like mass of granite, which is high enough to slightly dominate the surrounding country. All of this acreage is almost entirely clear of overburden, and the outcrop is sufficient to last for many years to come without contending with problems of quarry drainage or removal of soil and vegetation.
Possessing such large and valuable natural resources, the organizers of the company decided to purchase the required equipment on a basis commensurate with their holdings. The most vital piece of machinery in a granite quarry is the air compressor. Upon it all the operations depend. It must produce air economically and it must be reliable in its service, ready at all times and for all demands. The Arabia Granite Company, with this in mind, purchased a Sullivan Class WC Tandem Compound Corliss Steam-driven Two-stage Air Compressor, having a rated displacement of 2450 feet of free air per minute at 100 R. P. M. The dimensions of this machine are, high pressure steam cylinder, 20 x 30 inches; discharge air cylinder, 18 x 30 inches. This Sullivan design represents the highest development of steam-driven air compressor construction. With full Corliss valve gear on the steam end, the best of steam economy is represented; while on the air end, two-stage cylinders with minimum clearance losses and liberate intercooler area insure usually high volumetric efficiency.
The tandem design also possesses the great advantage of occupying a minimum amount of floor space. The compressor in question is 33 feet 6 inches long by 7 feet 7 inches in width, or of approximately half the floor area needed for a cross compound compressor of the same capacity. Steam for the compressor is supplied by two 175 H. P. tubular boilers manufactured by the Casey-Hedges Boiler Company of Chattanooga.
These boilers also supply steam to a vertical, Type A. American blower engine, which is belted to a 30 KVA Westinghouse generator, which in turn provides power for driving the machine shop equipment of lathes, drill presses, etc., for pumping water required for the boilers and air compressor and for lighting the power house. The latter building is 50 feet by 65 feet in size.
Five-inch air mains are carried out from the power plant to the surrounding quarry. Nearly a mile and a quarter of five-inch main and three quarters of three-, two-, and one-inch pipe lines connect directly with the ledges and cutting sheds. The use of a large feed line results in a minimum drop in the air pressure. A pressure gauge one half mile from the compressor plant shows less than five pounds loss. An air pressure of ninety pounds at the power plant is found to be ample.
The Arabia Granite Company employs some 200 men, including 40 block makers and 38 curb cutters. In addition, it leases out portions of the quarry to small operators on subcontracts. There are at the present time, eight such farms engaged in quarrying out stone for curbing and paving blocks and finishing them ready for delivery. These operators, including W. R. Watson, W. D. Abbott, E. O. Reagan & Co., Powell & Wright, J. W. Haygood, E. C. Powell, and Francis Jones Co., employ 165 men. Another Leaser, though independent as far as handling output is concerned, is the Arabia Mt. Stone Crushing Co., with W. S. Dallas as manager. This latter company operates a stone crushing plant equipped with No. 4 and No. 5 Gates gyratory crushers. All the above operators are supplied with Sullivan DA-15 and DF-3 Plug Drills, which are standard throughout the Lithonia district. This standardization has resulted from the common experience that the Sullivan plug drill maintains its efficiency over a longer period of time at a lower cost of upkeep than other makes of drills tested in the district.
Air for these drills is supplied from the Sullivan corliss compressor at a stated price per day per drill.
Arabia Granite Company keeps its quarries clean by crushing all the waste stone that accumulates in getting out curbing and paving blocks. This is handling in two crushing plants equipped with No. 5 and No. 4 Champion jaw crushers, driven by slide-valve engines operated on compressed air. The capacity of these two plants together is in the neighborhood of 300 tons per day.
In addition to supplying air for the drills and crushers, the Sullivan compressor supplies motive power for one 35 H. P. double cylinder hoisting engine and three 25 H. P., and supplies the blast for six blacksmith forges, the operation of the crane surfacing machine, and five tripod rock drills, ranging in size from 2 ½ to 3 ¼ inches. With the exception of the electric-driven pump and the machine shop equipment, every bit of machinery on the premises is driven by compressed air from the central air plant. The crushing plants were formerly operated by steam, but this has been abandoned in favor of compressed air, as being more satisfactory.
At this time the coal consumption at the power house averages three tons per day, and all this, of course, should not be indebted against the air compressor, inasmuch as the engine-generator set is also supplied with steam from the same set of boilers. The fuel cost of supplying compressed air for all these varying quarrying operations is thus less than three tons per day, which will be still further reduced when the compressor is run condensing, as is intended. All coal is weighed carefully so that an accurate daily cost sheet as to fuel consumed can be readily secured.
The present wage scale provides $4.00 for an eight-hour day for curb cutters, $20.00 per thousand blocks for paving block makers, with minimum wage of $4.50 for an eight-hour day. The general run of quarry hands average $1.50 for a nine-hour day, while the plug drill operators, who are on piece work, receive $3.00 to $4.00 for drilling sufficient stone to make 1000 blocks. The skilled laborers are all white, negroes predominating as general quarry hands and plug drill operators.
There is a constantly increasing demand for granite curb and block from this district. Its durability, as compared with substitutes, is more and more generally realized, and, as a consequence, new territory is opening up each year. During the past year the Arabia Granite Company has shipped its products to Columbus, Cincinnati, Ohio, St. Louis, New Orleans, Savannah, Springfield, Ohio, Louisville, Nashville, and Indianapolis, in addition to various other cities in Florida and Georgia. The rubble makes an attractive building stone and is being used largely in the Atlanta residence district.