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By J. F. Myers

AT the Regional meeting in Columbus, Ohio, in September 1949, the authors presented a progress report of the first year's operation with a Hardinge tricone mill in closed circuit with a Dorr hydroscillator. The present report covers our findings on this grinding circuit to January, 1950. In order to clarify our position, the authors wish to state that no invention or discovery is claimed. The Tennessee grinding circuit is simply an engineered arrangement of known equipment arranged to incorporate all of the recognized efficiency factors of comminution as they are known today. As we concluded our first report, it was not clear how effective the Tennessee mode of operation would be on harder ores. The only information we had at that time was that the Bond grindability test at 48-mesh gave 6.04 g of undersize per revolution. A later test on the same sample at 100-mesh reduced this to 2.04 g, which is definitely in the harder ore class, and which makes the reported 8.80 kw-hr per ton of -200-mesh produced a very creditable figure.

Jan 1, 1950

By S. H. Williston

IT is not often that bore hole surveys can be checked by actual civil engineering methods. A recent Arizona survey was checked by normal surveying methods and the comparison of the results should be of value to both oil and mining men. During the summer of 1948 the Phelps-Dodge Corporation, at its Copper Queen property near Bisbee, Ariz., drilled a 1245 ft, 8 in. diam, churn drill- hole in a mineralized area and cased part of it, intending to use it to transfer mill tailings for stope fill. The hole, as frequently occurs, was not straight, and, in endeavoring to locate the bottom in- the underground workings, they found no evidence of the hole at the underground coordinates directly below the surface location. The noise of the drilling tools was reasonably clear, but the direction of sound was uncertain. Preliminary tests with available equipment were not successful in locating the bottom of the hole. Be- cause of the mineralized character of the area and the fact there was some casing in the hole, any magnetic method of well surveying would give results ' of doubtful value.

Jan 1, 1950

By M. R. Geer, H. F. Yancey

Four coals were treated in the Humphreys spiral concentrator, and the products were examined by float-and-sink and screen-sizing tests to determine fundamental performance characteristics. The efficiency of the separation between coal and impurity was shown to be influenced greatly by particle size.

Jan 1, 1950

By E. O. Wagner, V. F. Parry

This paper summarizes investigations during 1949 on three pilot plants for drying low-rank fine cool by entrainment in hot gases. Detailed operating results on processing seven coals having moisture ranging from 24 to 62 pct, formulas and data for calculating performance of large units, and general conclusions on the problem of drying fine coal are presented.

Jan 1, 1950

By Rclssell Gibson, F. S. Turneaure

The tin deposit of Monserrat; Bolivia, consists of one major vein 1600 m in length. The ore is unusual because of the notable quantity of teallite, even though cassiterite is the principal tin mineral. The deposit, formed at shallow depth under a wide range in temperature, may be classed as xenothermal. Polished sections reveal a complex history of replacement, with low-temperature minerals deposited before high-temperature minerals.

Jan 1, 1950

By Brahm Prakash, R. Schuhmann

Chemical conditions for flotation and nonflotation of quartz with oleic acid as collector and barium, calcium, aluminum, iron, and tin as activators were studied using a simple vacuum-flotation technique in glass-stoppered graduates. The detailed study of barium activation led to an interpretation based on ideal Langmuirian chemisorption.

Jan 1, 1950

By C. M. Marquardt

Tramp iron and steel moving on a conveyor belt cause small currents to be generated in a coil situated in a strong magnetic field, which are converted to an alternating current and are amplified. The output voltage from the amplifier fires a thyratron with a relay in its anode circuit, which actuates a howler and simultaneously drops a spot of marker material on the belt.

Jan 1, 1950

By Leslie C. Richards

The competitive position of producers of industrial minerals depends upon the delivered price of their product. Freight charges are a major factor in the sales to consumers. A comparison of freight rates on movements of limestone and silica rock in the Pacific Northwest shows a wide variance in mills per ton mile for like hauls, thereby favoring some localities over others.

Jan 1, 1950

By Elmer A. Jones

Development work in mines of St. Joseph Lead Co., Southeast Missouri, using trackless loading equipment shows definite advantages: Speed of cleaning, ability to work on steep grades and sharp crosscuts, good later tracking conditions, and possibility of wasting rock in old abandoned stopes.

Jan 1, 1950

By J. R. Guard

Development of electrical power in coal mining has been an outstanding example of adaptability. It has accommodated itself to new inventions, changing mining methods, increasing demands, increasing safety requirements and many other new conditions. With the appearance of the continuous miner in the mining machinery picture, those engineers interested in the application of electricity to mining have been thinking about what new combination of electrical apparatus will best suit this newcomer. It is the purpose of this paper to discuss the relative costs of supplying d-c versus a-c power to mining equipment with particular reference to continuous miner setups. Assume that a-c power will be delivered to the mine at some high voltage suitable for transmission to the various substation locations. Typical voltage for this purpose is 4000 volts. The problem then is to change the power to some kind of power suitable for driving the motors of mining equipment. For safety and other reasons the voltage to be delivered to the motor terminals must be under 600 volts.

Jan 1, 1950

By W. B. Plank

THE figures on enrollment in the engineering schools of the United States and Canada indicate that the total number of students in these schools for the current year, 1949-50, is about 10% less than it was a year ago. This year, 226 - 533 undergraduates and graduate students are studying engineering in the United States and Canada as compared with. 249,913 students last year. These figures are taken from advance data in the Journal of Engineering Education for February 1950.

Jan 1, 1950

By Howard H. Fields

Any mining engineer with a desire to operate independently, with some financial backing, and with no fear of heavy responsibility and long hours, should be able to make a comfortable living in Mexico. Barring a few inconveniences such as a lack of satisfactory liability or accident insurance, the difficulty of obtaining repair parts or vehicles, and the length of time required to receive returns from shipments, the operation of small mine is not at all difficult. It is, in fact, a little easier to find a good prospect in Mexico than in the U.S.

Jan 1, 1950

By William S. Springer

A NEW preparation plant has been put in - operation to treat coal from the recently opened Concord mine, located about 15 miles west of Birmingham, Ala., by the Tennessee Coal, Iron & Railroad Co., a U. S. Steel subsidiary. The mine produces metallurgical grade coking coal from the American seam for use as coke in the company's blast furnaces at the Fairfield and Enseley works. The capacity of the operation is 1000 tons of run-of-mine per hr, approximately half of which is delivered to the by-product coke plant at Fairfield after beneficiation to metallurgical grade. The remaining portion of the mine run is rock and refuse removed during preparation. No boiler coal or other fuels are produced by this mine. Preparation of the coal is done both under- ground and on the surface. The underground primary crushing station removes some tramp iron, and screens and crushes the oversize, most of which is rock, to protect the main slope conveyor. The surface plant consists of a crushing and screening plant, large blending bins, a two- process washing plant, a water clarification and

Jan 1, 1950

By S. R. Zimmerley, S. F. Ravitz

High-grade cobalt concentrates were produced from the complex Blackbird ore with very good recovery in continuous pilot-plant operations in which a low-grade bulk cobaltite-pyrite flotation concentrate was roasted in a multiple-hearth furnace to oxidize the pyrite selectively. The cobaltite was floated from the resulting calcine.

Jan 1, 1950

By Kefton H. Teague

Attempts to locate domestic supplies of sillimanite have been unsuccessful until recently. This paper describes recent discoveries of sillimanite-bearing schists in the Southeastern States, with emphasis on geology of the deposits, mineral composition, origin, and reserves. Statements concerning possible methods of mining, milling, and utilization of sillimanite are given. Results from refractory tests on a laboratory scale are summarized.

Jan 1, 1950

By Harlowe Hardinge, R. C. Ferguson

Laboratory and plant data covering 12 different operations show that lower than "standard" ball mill speeds increase grinding efficiency. In the case of high pulp-level mills, the gain is so great that the increase in capital cost of the larger lower speed mill will pay for itself in less than a year's time.

Jan 1, 1950

By Paul M. Tyler

HISTORICAL concepts of the economics of the glass-sand industry are changing rapidly. The greatly expanded demand for glass containers combined with higher freight rates on raw materials and manufactured products have induced a migration of glass factories toward densely populated centers and the creation of new standards of place value for sub- standard sand deposits. This migration has been facilitated by the construction of pipelines to bring cheaper natural gas and liquid fuel to large cities and may be further speeded by the adoption of modern mineral dressing methods to permit economical utilization of local raw materials. Our national resources of naturally high-grade 1 silica sand are abundant, but most of the best de- posits are situated so far from large centers of population that it now costs $3.00 to $5.00 a ton to carry the sand from the mine to the optimum site for a 1 factory making beverage bottles, scientific and electrical glassware, and miscellaneous blown and pressed ware for local markets. It follows that on the basis of freight savings alone it may be economical to use material from inferior deposits closer to the factory even though the f.o.b. cost of mining and treatment may be much high

Jan 1, 1950

By John G. Hall

The unstable metal market during 1949, with resulting lower metal prices, has focused every mine operator's attention on the problem of reducing operating costs. Improvement in mining, methods, use of modern mechanical mining equipment, and increasing the efficiency of the labor force are the tools with which we will have to work. Careful planning is necessary to coordinate all phases so that no one phase is overdone. A mine may become over-mechanized if, for instance, capital charges against new equipment exceed the savings in labor costs, or where a large enough tonnage is not produced. The cooperation, of labor is essential to any mechanization program. There have been too many instances where mechanization and improvements have done nothing more than make up for a decrease in labor efficiency, thus bringing the production of labor back to its old standard. The operator has gained little and labor has gained only a "softer job." In any mechanization program there are gains to be had by both the operator and labor. By the efficient application of modern equipment and improved mining methods the operator should gain by decreased costs, and labor may profit by receiving a share of these decreased costs.

Jan 1, 1950

By H. Merton Ruth

THE northern anthracite fields, although facing the same economic problems as the southern fields, are confronted with the additional problem of fast dwindling reserves of anthracite which can be conventionally and economically won. The mining of coal which remains in thin beds and the recovery of pillars from areas heretofore considered unrecoverable, either by reason of cost or surface restriction, pose problems of in- creasing importance to the economic life of the northern field operations. Successful approaches have Been made to this problem and other work is being performed that holds promise. There exists in the northern anthracite field millions of tons of solid coal, the recovery of which has not been too successful due to the following inherent operating faults: inability to concentrate producing areas; the great quantities of rock to be cut and handled, lack of consideration of proper sequence and speed of second mining, and the continued use of the mine car as the basis of payment. A mining system that has successfully solved these major problems has been in operation in the Scranton area since 1944. Over 1% million tons have been produced from veins varying from 3 to 4% ft thick by this method, which is known as the multiple panel-triangular system-conveyor mining.

Jan 1, 1950

By George T. Bator

If confronted with the problem of pumping a mixture of slime-free sand, gravel and boulders up to six in. in diameter, at the rate of 175 tons per hr in one single-stage pump against a static head of 90 ft and a total head of 140 ft, of which 20 is on the suction side, an engineer might be forgiven for backing away from the job, especially if he were also told that the pump wearing parts must have a minimum hardness of 550 Brinell for the sake of abrasion resistance.

Jan 1, 1950