Search Documents

By AIME AIME

THE STANDARD herewith submitted is the result of several years of research and consideration by the A.I.M.E. Technical Committee on Milling Methods. In the early work of this committee it was found necessary to undertake the development of a standard laboratory method for screen testing of ores. During the research stages the desirability of having this standard, when completed, approved as American Standard was brought out. In accordance with this idea, its initiation as a project of the American Standards Association (then the American Engineering Standards Committee) was approved by the latter body and the A.I.M.E. designated as sponsor. In 1929, the A.S.A., on recommendations of its advisory committee, the Mining Standardization Correlating Committee), authorized the A.I.M.E. to be sole sponsor for this project. The personnel of the Institute's Committee on Milling Methods was then increased to make it thoroughly representative of all diversified interests in the mining field. Two years ago the standard was circulated and has been given wide distribution. Early in 1932 the committee voted unanimously, with 38 affirmative votes, that the standard be recommended to the Board of Directors of the Institute for submission to the American Standards Association for approval as American Recommended Practice. This was accordingly done, at the Feb. 1.6, 1932, meeting of the directors, and the American Standards Association approved the standard on July 6; 1.932, designating it as ASA M5-1932.

Jan 1, 1932

By J. F. K. Brown

ANTHRACITE?S satisfactory showing in 1942 was accomplished in the face of adverse conditions, such as the loss of man power to the active services and to other industries, and the difficulty and delay in obtaining the necessary materials and equipment required in mining operations. Although the in- creased output was stimulated by the war, and thus does not impress one as contributing to continuing improvement in the industry, nevertheless the year witnessed several efforts ant1 consideration of others that have the appearance of permanent progress.

Jan 1, 1943

By Rudolf Gahl

SOME time ago the Detroit Copper Mining Co. had to decide the question whether it would pay to re-treat slime-tailings, and several machines were tested in order to ascertain the type of construction which would give the greatest saving. In previous tests on the ore of this company, several tables proved far inferior to the Frue vanner, and for this reason they did not receive any serious consideration. In the late tests, however, one table was found to surpass the vanner in the percentage of saving made. The Frue vanner used in these tests had been adjusted approximately to the slope which the slime-vanuers in the concentrator of the Detroit Copper Co. had at that time, about 2 in. between the inside of the wooden posts, or 0.272 in. per ft. It had not been determined, however, if this slope was the most economical one for treating the slime-feed in the mill, or for re-treating the tailings from the slime-vanners, and I was instructed to ascertain by test-runs, under different conditions, the best adjustments for the work to. be done. In order to determine if a change in the adjustments of the machines would improve the results, it seemed sufficient to continue running the tests between the vanner and the table before mentioned, keeping the feed and all other conditions the same, but. varying the adjustments of the vanner .from run to run. I employed a vanner-man of long experience to operate these machines, who expressed the opinion that a slope between 2 3/8 and 2.5 in. between the posts (0.323 and 0.340 in. per ft.) would give the best results. Some runs made this way gave a considerable improvement. While for a slope of 2 in. (0.272 in. per ft.) the saving had been only 40.5 per cent. of that of the table, it .was 49.2 per cent. for 2.5 in. (0.340 in. per ft.) slope. A decrease of

Sep 1, 1909

By Charles E. Lundin, Albert S. Yamamoto

The phase eqrtilibria of the binavy system, Nb-Al, weye established by metallographic, X-ray diffraction, hardness, and thermal-analysis techniques. Three intermediate phases were identijied, Nb3.41, Nb2Al, and NbAl,. The N6,Al and NbAl phases have extensiue ranges of solubility. The maximum solubility of aluminum in niobiuitz is 23.0 i0.5 at. pct (8.0 wt pct) A1 clt 1960" i 10°C. The maximumt solinbility oj niobiunz in alunzinutz is less than 0.3 i0.1 at. pct (1.0 tut pct) fib. The A'h,Al and Nbgl interinediate phases forr peritectically at 1960° 1UcC and 1870" i 1U9C, respectively, zuhereas the NbAl, phase fornts congvuently fio11t the melt at 1605" 10°C. A eutectic reaction oc- The intent of an over-all research program was to develop niobium-aluminide-base coatings for refractory metals since these coatings exhibit useful high- curs at 57.8 i 0.5 at. pct (28.5 wt pet) A1 and 1500" 10°C between NbAl and NbAl3. The aluminum-rich region of the system has a peritectic reaction where liquid reacts with NbAL, to form aluminum solid solution. Structural and lattice -pavarneter data /or the intermediate phases were determined by X-ray diffraction analyses. An unusual transfov?nation having charactevistics of nucleation-growth and martensitic nleclanisils occurs on cooling the niobium solid solution in the region from 18 at. pct (6 wt pct) Al to 23 at. pct (8 wt pct) Al. The transfornzed product on rapid quenchirzg is an acicular NhAl. temperature resistance to oxidation. As a prerequisite, the phase equilibria of the system, Nb-A1, were necessary. A literature survey revealed that the phase-equilibria data reported by various investigators were rather incomplete and conflicting. Therefore a complete determination of the system was undertaken by the authors from 0 to 100 pct of solute addition.' In 1959 Savitskiyz presented a tentative diagram which

Jan 1, 1967

By Arthur F. Daily

8.5-1. Bucket Line Dredge. INTRODUCTION. The modern bucket-line dredge for mining placer deposits is a combined floating excavating machine and a gravity concentration system. Material is excavated at the forward end by the buckets, elevated, washed and screened, concentrated for recovery of valuable mineral, and discharged off the stern as coarse and small fractions. The end product is a concentrate consisting either of the valuable mineral(s) and associated heavy minerals, which are taken to a treatment plant on shore; or in the case of gold, a clean amalgam ready for retorting. The bucket-line dredge may be adapted for purposes other than mining for valuable mineral by installing, in lieu of a concentrating system, machinery for pumping all of the solids ashore in a pulp, or for producing washed gravel in selected size fractions of which all or a selected fraction is pumped to disposal areas on shore or into side barges. The two principal types of bucket-line dredges designed for mining are: 1) those having an inclined belt conveyor stacker to discharge the coarse fraction of washed tailing well astern of the hull, and sluices to discharge the sand fraction (Fig. 8.5-1), and 2) those having only sluices for discharge of all tailing astern. Use of the latter type has been confined, with few exceptions, to mining cassiterite-bearing deposits in Malaysia and at sea off Indonesia. Small dredges having only flumes for washing and concentrating all material dug by the buckets have been used for mining shallow stream valley deposits. GENERAL ARRANGEMENT. The general arrangement of a modern bucket-line dredge for mining tin, with a primary concentrating plant on board, is shown in Fig. 8.5-2. The hull and superstructure of most dredges are fabricated of structural steel; wood also has been used for both small and large dredges with complete satisfaction. All-riveted or partially welded unit hulls have been widely used and are desirable for exceptionally severe service. The hull

Jan 1, 1968

By Robert Ammon

THE milling practice at Mascot, at present, consists of dry crushing to 5/8 in., jigging, fine grinding, and flotation. The ore arrives at the mill from two mines, No. 1 mine shaft being located in the mill proper, and No. 2 mine shaft being situated about 2000 ft. east of the mill. No. 2 mine is served by a coarse-crushing plant and aerial tramway to the mill bins. In jigging the No. 2 mine ore, 50 per cent. of the mill feed is rejected by the jigs as a jig tailing ranging from 5/8 in. to 10 mesh; the balance of this ore, after removing a jig concentrate, is ground to flotation feed. In jigging No. 1 mine ore, approximately 80 per. cent. of the mill feed is rejected as a coarse jig tailing, and the balance is ground to flotation feed without the removal of a jig concentrate. The difference in the treatment is due to the fact that No. 2 mine ore carries a higher content of zinc than that from No. 1 mine. Of the total concentrates produced, 30 per cent. are made on jigs and 70 per cent. by flotation. At present, 1350 tons of No. 2 ore and 800 tons of No. 1 ore are treated each 24 hours. The recoveries for a typical week are as follows: Heads 3.55 Jig concentrates 61.30 Jig tails 0.80 Flotation concentrates 60.60 Flotation tails 0.09 Extraction 86.50 The associated minerals are a straw-colored sphalerite, dolomite, calcite, pyrite, quartz, and a small amount of greenockite, which occurs as a stain and sometimes small crystals along with sphalerite, but is comparatively rare. Pyrite is present in small quantities, usually less than 0.5 per cent.; quartz occurs in bands a few inches thick. A complete analysis of the ore is as follows:

Jan 9, 1924

By John S. Marshall

The purpose of this paper is to present to the profession data and experience obtained over a period of 5 years in the operation of 87 shaker-conveyor units, and the production of 2,169,638 tons of run-of-mine anthracite coal. The data are not generally available and should be of interest to those concerned with the operation of anthracite and bituminous mines. To simplify comparison, a ton of 2000 lb. of raw run-of-mine coal has been used as the production unit throughout this paper. Mining Methods and Equipment The mine is in the vicinity of Wilkes-Barre, Pa., in the Buried Valley area of the Susquehanna River. Seven veins were mined, varying in thickness from 18 in. to 8 ft. The cover overlying the veins varied from 200 to 800 ft. Three-fourths of the 1200 acres of property was covered with from 100 to 200 ft. of water-bearing gravels and clays, which prevented first mining under rock cover less than 50 ft. and pillar removal under rock cover less than 100 ft. The property was opened by two shafts sunk on the mountainside to avoid the sand and gravel present in the river valley. The veins dipped an average of 5" from the shafts. In certain areas the veins were practically flat and in some places a reverse pitch as high as 5" was encountered for short distances. A daily output of 3800 tons was hoisted on a two-shifi; hoisting operation. The mining consisted of 75 per cent pillar removal, and of the total production in the later years of operation 80 per cent was loaded by shaker conveyors, chain conveyors and scraper loaders. Shaker conveyors accounted for 70 per cent of the total output; chain conveyors and scraper loaders for 10 per cent. All conveyor work was double-shifted and 25 per cent was triple-shifted. A total of 87 shaker-conveyor units were on the property, of which 75 were kept in operation at all times.

Jan 1, 1940

By John S. Marshall

The purpose of this paper is to present to the profession data and experience obtained over a period of 5 years in the operation of 87 shaker-conveyor units, and the production of 2,169,638 tons of run-of-mine anthracite coal. The data are not generally available and should be of interest to those concerned with the operation of anthracite and bituminous mines. To simplify comparison, a ton of 2000 lb. of raw run-of-mine coal has been used as the production unit throughout this paper. Mining Methods and Equipment The mine is in the vicinity of Wilkes-Barre, Pa., in the Buried Valley area of the Susquehanna River. Seven veins were mined, varying in thickness from 18 in. to 8 ft. The cover overlying the veins varied from 200 to 800 ft. Three-fourths of the 1200 acres of property was covered with from 100 to 200 ft. of water-bearing gravels and clays, which prevented first mining under rock cover less than 50 ft. and pillar removal under rock cover less than 100 ft. The property was opened by two shafts sunk on the mountainside to avoid the sand and gravel present in the river valley. The veins dipped an average of 5" from the shafts. In certain areas the veins were practically flat and in some places a reverse pitch as high as 5" was encountered for short distances. A daily output of 3800 tons was hoisted on a two-shifi; hoisting operation. The mining consisted of 75 per cent pillar removal, and of the total production in the later years of operation 80 per cent was loaded by shaker conveyors, chain conveyors and scraper loaders. Shaker conveyors accounted for 70 per cent of the total output; chain conveyors and scraper loaders for 10 per cent. All conveyor work was double-shifted and 25 per cent was triple-shifted. A total of 87 shaker-conveyor units were on the property, of which 75 were kept in operation at all times.

Jan 1, 1940

By H. l. Burghoff, D. E. Lawson

The presence of tellurium in copper and, by inference, in copper alloys, has been considered seriously detrimental and has been avoided. In particular, very small amounts of tellurium have been found to produce red-shortness, although the effects on cold-working and ordinary physical and mechanical properties have not been known so definitely. References in the literature are few, but as long ago as 1881, Eglestonl reported that 0.083 per cent tellurium in fire-refined copper rendered the copper red-short and therefore worthless for hot-rolling. In hot-rolling copper cakes containing this amount of tellurium, he found that fine cracks appeared in the cakes on the first pass through the rolls, the cracks opening further in successive passes. When cold, the metal was said to be tough and malleable. A few years ago, during the course of an investigation in our laboratory on copper-base alloys, it was found that tellurium-bearing alloys could be machined much more freely than similar alloys not containing tellurium. The study was pursued further in this direction, and considerable data were obtained, which indicated that certain tellurium-bearing alloys might have properties of commercial interest. The work eventually led to patent protection,2 a wide range of tellurium-bearing copper-base alloys being covered. This article presents results obtained on the effect of tellurium on the mechanical properties of three copper-base alloys: commercial bronze (90 Cu, 10 Zn), 1.5 per cent tin bronze (98.5 Cu, 1.5 Sn), and silicon bronze (96 Cu, 3Si, 1 Zn). Several alloys were cast in each series, with tellurium content ranging from 0 up to about 1 per cent. The alloys were melted under charcoal in a clay-graphite crucible, using a high-frequency induction furnace, and were cast without undue difficulty in rod form, 15/8 in. in diameter. Charges for the zinc and tin series were made up from the following materials: cathode copper, electrolytic zinc, tin, and tellurium in slab

Jan 1, 1938

By R. P. Rothwell

The milling of silver ores has arrived at a great degree of perfection in the mining districts of our Western States and Territories, and I hare thought the record of the practical results obtained at the present time, in a few of the principal districts, would prove of value arid interest to many of our members, both at home and abroad. An American silver mill is composed, in descending order from where the ore is dumped, of: 1st. A rock-breaker, usually of the Blake or Alden pattern; 2d. The battery of stamps, the number of which varies from 5 to 120, generally in batteries of 5 or 10 heads, so arranged that a single battery may stand while the others are running; 3d. The tanks where the crushed ore settles (if it is a met stamping-mill), or of a drying-floor if the crushing is done dry; 4th. Amalgamating pans ; 5th. Settling pans ; 6th. Agitators or pans in which mercury escaping in the tailings is caught; 7th. Blanket sluices, over which the tailings run, and where mercury and unamalgamated sulplides are saved. A reference to the engravings (see plate), which show one of the latest forms of an 80stamp silver-mill run by a turbine water-wheel, will show clearly the arrangement of the several parts. THE ONTARIO, UTAH, SILVER MILL. One of the best examples of a silver-mill, and at the same time one of the most successful concerns in the West, is the mill of the Ontario Silver Mining Company, near Salt Lake, in Utah. This mill treats the ore from the Ontario mine, ore which at present is very base, being composed of zinc, lead, and silver sulphides and silver chloride in a quartz gangue. This ore has become baser as the mine attained greater depth, though the vein holds its own, or rather increases, both in thickness and richness. The mill is managed in a skilful and economical manner, though the necessity for

Jan 1, 1880

By Robert Franke

(Butte Meeting, August, 1913.) IN view of the prominence which the conical mill has attained in the fine-crushing field .within the few years since its introduction, the following comparison with its more mature forerunner, the Chilean mill, based on extensive tests, is submitted in the interest of the milling profession. Soon after designing the concentrating plant of the Miami Copper Co. in 1909, the Hardinge conical mill made its appearance in the milling forum. . Its possibility as a suitable crushing device for the plant was well recognized, but in view of the lack of commercial demonstration, at the time, as to capacity, efficiency for desired product, and the still more uncertain factors of cost of maintenance and power consumption, it was deemed that the immediate adoption of this machine throughout the plant would be a hazardous undertaking. For these reasons it was decided to equip the majority of the immediately required units of the plant with Chilean mills, the fine-crushing proficiencies of which were better known, and one section with Hardinge mills, to serve as a test unit for the guidance of future installations and replacements. Thereby, after 1.5 years' operation with both types of mills, a thorough test as to metallurgical efficiency and cost economy has been obtained. The conical mill used in these tests is the 8-ft. Hardinge pebble mill, having a cylinder 22 in. in length. The cylindrical portion of this mill is lined with cast-iron liner plates, and the conical extensions with silex bricks bound together by cement. Each. liner plate carries a projecting lifter, the function of which is to increase the height of drop of the lifted material. Danish No. 5 pebbles, obtained from the coast deposits of Denmark, are used for the grinding charge. The Chilean mill used is a fast-running, 3-roller, 6-ft. Saturn mill, with screens of 0.037-in. opening. The feed to these mills is the oversize of Callow screens having 0.029-in. openings, which. follow rolls crushing to 0.5 in.

Jan 7, 1913

By H. l. Burghoff, D. E. Lawson

The presence of tellurium in copper and, by inference, in copper alloys, has been considered seriously detrimental and has been avoided. In particular, very small amounts of tellurium have been found to produce red-shortness, although the effects on cold-working and ordinary physical and mechanical properties have not been known so definitely. References in the literature are few, but as long ago as 1881, Eglestonl reported that 0.083 per cent tellurium in fire-refined copper rendered the copper red-short and therefore worthless for hot-rolling. In hot-rolling copper cakes containing this amount of tellurium, he found that fine cracks appeared in the cakes on the first pass through the rolls, the cracks opening further in successive passes. When cold, the metal was said to be tough and malleable. A few years ago, during the course of an investigation in our laboratory on copper-base alloys, it was found that tellurium-bearing alloys could be machined much more freely than similar alloys not containing tellurium. The study was pursued further in this direction, and considerable data were obtained, which indicated that certain tellurium-bearing alloys might have properties of commercial interest. The work eventually led to patent protection,2 a wide range of tellurium-bearing copper-base alloys being covered. This article presents results obtained on the effect of tellurium on the mechanical properties of three copper-base alloys: commercial bronze (90 Cu, 10 Zn), 1.5 per cent tin bronze (98.5 Cu, 1.5 Sn), and silicon bronze (96 Cu, 3Si, 1 Zn). Several alloys were cast in each series, with tellurium content ranging from 0 up to about 1 per cent. The alloys were melted under charcoal in a clay-graphite crucible, using a high-frequency induction furnace, and were cast without undue difficulty in rod form, 15/8 in. in diameter. Charges for the zinc and tin series were made up from the following materials: cathode copper, electrolytic zinc, tin, and tellurium in slab

Jan 1, 1938

By Milo W. Krejci

(Butte Meeting, August, 1913.) THE plant and quarries of the Inland d Portland Cement Co.. are located- at Metaline Falls, Wash, about 128 miles north of Spokane, on the Fend Oreille river, and 10 miles, of the Canadian border. The plant is one of a chain of cement plants controlled by the Lehigh Portland Cement Co., of Allentown, Pa. Work on this plant was commenced in June, 1910, and was completed in April, 1911, but on account of some delays in the construction of the power plant, the works were not put into operation until August., 1911. Since then it has been in continuous operation and has furnished the Inland Empire with a high grade of cement. Fig. 1 is a, view and Fig. 2 is a plan of the works. Water Power Development.-The source of the water supply for the hydro-electric plant of the Inland Portland Cement Co. is Sullivan lake, a body of water approximately 5.5 miles long and 0.5 mile wide, situated in the Kanisku Forest Reserve. A wooden crib dam was installed so as to raise the elevation of the lake 25 f and the additional storage capacity was taken up by the diversion of Sullivan creek into the lake by means of a wooden flume, 0.25 mile long, 6 by 8 ft. in crosssection, and a ditch 1,200 ft. long. The water from the lake follows the natural water course to an intermediate storage reservoir, which was created by the construction of an earthen dam. This pond was used in connection with the saw mill which was installed at this point. Besides the earth dam, there was also built a crib, at the point shown in the sketch map, Fig. 3. This crib dam is 35 ft. high. From this point the excess water follows the natural -course of Sullivan creek to the Pend Oreille river.

Jan 7, 1913

By A. U. Seybolt

A. U. Seybolt (General Electric Research Laboratory)— As pointed out in an earlier paper,41 it appears to be very difficult to nucleate Si3N4 in Si-Fe of silicon content up to around 5 pet. Therefore, one observes, as did Pearce, that equilibrations with nitrogen gas yield only nitrogen in solid solution at temperatures above about 700°C, or, as Pearce found, 770°C. Evidently, the free energy of formation of Si3N4 only becomes high enough at -770°C to overcome the reluctance of Si3N4 to nucleate. However, as mentioned in Ref. 41, if some Si3N4 is first formed by a mixture of ammonia and hydrogen, one can then replace this gas mixture by nitrogen gas, and either increase or decrease the amount of Si3N4 present at any temperature by suitable adjustment of nitrogen pressure: that is, to equilibrate with Si3N4. In the equilibration experiments cited in Ref. 41, equilibrium was approached from both sides, and it was found that samples up to 944oC, at least, were in equilibrium with Si3N4. Higher temperatures were not employed, as this would have necessitated a redesign of the apparatus for using nitrogen pressures in excess of 1 atm. To summarize, the results of Pearce's experiments and those of Ref. 41 cannot be directly compared because two quite different equilibria were studied. Therefore, the statement by Pearce on p. 1398 indicating apparent error in Ref. 41 is unjustified. M. L. Pearce (author's reply)— There was limited evidence obtained in the current investigation which would indicate that excessive "supercooling" did not occur. A small piece of the same resulting from heat treatment No. 5 in Table III was subsequently held at 800°C for 16 hr in 95 pet N-5 pet H. Isotope-

Jan 1, 1964

THE CHALRYAN.--I think that we have set the stage for the balance of the sym- posium. Most of the emphasis has been placed on the immediate value of every- thing we can do and everything we can learn for the furtherance of the war effort. I believe that ought to be first, but I also believe that this is the time for us to con- sider very seriously not only what these improved methods and techniques do to form a closer approach to ideal segregation but what effect these great quantities of scrap metals and alloys that are going to be produced this year and next, are going to have-what their impact will be-on post- war industry in general and in particular ,, on the primary metals fields. In some cases we have been hearing in the last month or two of the law of diminishing returns coming to the fore. We find alloy simplification growing and certain alloys being produced in great quantities, which will perhaps drop out of the picture some- what as the war ends but never to the lower ( stage they had before. We have I think a pretty good cross- section of the producers, the refiners, the reclaimers and ingot makers, the ultimate users here, and there ought to be some good and helpful discussion. The papers are open for discussion. Mr. Beattie, do you want to make any 1 comment? H. J. BEATTIE.*-To start the discussion I might ask Mr. Deitz what they do with manganese bronze turnings? We segregate the manganese bronze turnings from the other bronze turnings. The value of it seems to be much out of line with the price of ingot, that is, as compared to some of the other alloys like 88-10-2 or 85-5-5-5. I assume it is because they can only use a

Jan 1, 1943

By Glenn A. Keep

THIS paper is not an announcement of the successful conclusion of the Cerro de Pasco Copper Corporation's pacos-pyrite problems, but merely a description of the commercial-scale, intermittent-roasting operations conducted by the writer, J. H. Lucas and others of the staff. It was prepared by request, for presentation at the February meeting of the Institute. The results obtained in Peru confirm the 1-ton-a-day experiments completed about three years ago at Kearny, N. J. by C. C. Gordon and Mr. Lucas, where it was first demonstrated that a mixture of about 80 per cent. pacos ore with 10 per cent. pyrite ore and 10 per cent. salt could be roasted intermittently in a small 1-ton-a-day Holt-Dern furnace without extraneous fuel, producing porous calcine that could be leached rapidly. Mr. Keep and his staff, by successfully introducing improvements in the construction of the commercial furnace and in their handling of material, have established beyond doubt a low cost for roasting. The other steps in the process of treating pacos and pyrite ores have not as yet been demonstrated as sufficiently conclusive to warrant their acceptance for a permanent plant. Cerro de Pasco Ores The ores of the Cerro de Pasco Copper Corpn. at Cerro de Pasco, Peru, are situated at an altitude of 14,000 ft. The town and mines are served by the Cerro de Pasco Railroad, which operates between Cerro de Pasco and Oroya, the site of the company's copper and lead smelters. Table 1.—Average Analysis of Cerro de Pasco Ores Pacos Ore Pykite Ore Silver, oz............................................... 10.3 12.0 Gold, oz................................................ 0.007 0.01 Lead, per cent........................................... 1.7 1.8 Copper, per cent......................................... 0.19 0.27 Zinc, per. cent........................................... 1.4 1.02 Iron, per cent........................................... 13.4 34.45 Silica, percent.......................................... 61.8 24.5 Alumina, per cent....................................... 2.5 0.62 Lime, per cent........................................... 1.5 0.20 Manganese, per cent..................................... 0.42 0.09 Sulfur, per cent,.......................................... 1.1 34.2

Jan 1, 1929

By Alexander L. Holley

The 400-ton testing machine, ordered in June, 1875, by the United States Board appointed to test "iron, steel, and other metals," has lately been completed at the Watertown Arsenal, thoroughly proved and accepted by the Board. The excellence of the machine in every respect is more than satisfactory, and its accuracy is at first sight astonishing, although an investigation of its principles must show that if the weighing apparatus will weigh at all, it must do so with perfect accuracy, because all its movements are absolutely without friction. The proof experiments were numerous, and the effects of recoil after sudden ruptures at maximum loads, were watched with great care, but without much anxiety, because the weighing parts affected are by no means delicate in structure, and their motion is almost infinitely small. Among the tests were the following : A forged link of hard, wrought iron, 5 inches in diameter between the eyes, was slowly strained in tension, and broke short off with a loud report at 722,800 pounds. The diameter before breaking at the point of fracture was 5.04 inches; after breaking, 4.98 inches. In order to see if the weighing parts had been disturbed by the recoil, which was obviously near the greatest recoil the machine will ever suffer, a horse-hair was next tested; it was 7-1000ths of an inch in diameter; it stretched 30 per cent., and broke at 1 pound. Other horse-hairs vary in tenacity between 1 and 2 pounds. Of course, the accuracy of the machine on such delicate specimens, and indeed on specimens having some hundreds of pounds tenacity, has been checked and proved by other weighing machines. A 5-inch round bar, turned down to 38 inches diameter along the centre, was pulled apart at 430,200 pounds tension. Then some more horse-hairs were tested ; also copper wires 191/2-1000ths of an inch in diameter, which averaged 25 pounds tenacity..

Jan 1, 1879

By T. D. Yensen

Discussion of the paper of T. D. YENSEN, presented at the New York meeting, February, 1916, and printed in Bulletin No. 110, February, 1916, pp. 483 to 512. JOHN A. MATHEWS, Syracuse, N. Y.-Concerning the critical composition of the steel containing 2.50 per cent. of silicon, I may say that 12 or 13 years ago we made some of these alloys. They. were not as pure as the alloys made by Mr. Yensen, nor were they melted in vacuo, but one of them contained exactly 2.50 per cent. silicon, and about 0.25 per cent. carbon. It gave us no trouble whatever in hammering to a billet or rolling into bars, nor even when rolling into ¼ -in. wire rods. The steel in question was practically free from everything except carbon or silicon and contained no manganese sulphur or phosphorus worth mention. The alloy containing 2.50 per cent. of silicon worked perfectly well, as well as one containing 0.5 per cent. silicon, and it seems to me that further work should be done by Mr. Yensen on the physical properties of alloys at this seemingly critical change point. W. E. -RUDER, Schenectady, N. Y.-We -have made silicon steels of practically every composition and have never obtained any material under 5 or 6 per cent. of silicon which was brittle. This may be due, of course, to the presence of carbon, in some of the 'commercial materials, and I presume that Mr. Yensen would argue that the: presence of this carbon might prevent inter-granular brittleness. However, all of our silicon steels, up to 5 per cent. of silicon, by treatment in hydrogen at temperatures near the melting point, can be made to show inter-granular brittleness. Furthermore, the material made brittle in this way could be restored by treating at the same temperature in hydrogen containing a hydrocarbon vapor. I discussed this matter some years ago in a paper on inter-granular cement. It therefore appears likely to me that Mr.

Jan 5, 1916

By Dale E. Walker

The Captain mine came into being under the following circumstances: 1) Commonwealth Edison had need for fuel for the generation of electricity in their Chicago service area. 2) Southwestern Illinois Coal Corp. had an ample supply of coal in the Illinois No. 6 and No. 5 seams. 3) The Gulf, Mobile & Ohio R.R. had a one-line transportation system with the capability of transporting coal from the Captain mine to Commonwealth Edison. These fortuitous conditions permitted an effective three-way partner- ship to develop. Commonwealth Edison had built a new generating station at Joliet, Ill., across the Illinois River from the existing station, to supplement their power-generating capacity for the Chicago area (Fig. 1). The annual requirement of the Joliet station is approximately 4.5 million tons of coal. From large reserves of coal in the No. 6 and No. 5 seams, Southwestern Illinois Coal Corp. contracted to supply Commonwealth Edison with approximately 6 million tons annually from its Captain mine. The logical carrier was Gulf, Mobile & Ohio, whose mainline travels through this coal field and also passes by the Joliet station on its way to Chicago. This railroad has been moving Southwestern's coal from the Streamline mine for more than 30 years. The basic ingredients of timing, scheduling, moving, and handling were adopted by the three parties, the precise details being worked out jointly. To do this, each group had to know its requirements exactly. The initial schedule was drawn up and tentatively approved, with each party taking a hard look at its own requirements and commitments to make certain that the schedule could be met on a normal daily basis. With only minor changes, the final schedule was adopted, each participant feeling that it had a sufficient factor of safety to maintain steady operation. Each party agreed to help the other in time of emergency. When a delay occurs in any part of the operation, the other

Jan 1, 1969

By W. A. Boyer

MINE hoisting ropes can be loaded to capacity only when the strength of each component is exactly known. Characteristic curves provide this information. When load and rate of acceleration are specified for an individual rope, the characteristic curve assumes a predetermined shape. The factor of safety, is the value drived by dividing the breaking strength of the rope by the total stress on the rope where it goes over the sheave wheel. Total stress is made up of the weight of skip and cage, weight of ore, weight of rope between sheave and rope clevise or attachment, friction load, and acceleration force. Bending stresses are neglected in this discussion, as sheaves and drum di- ameters are assumed to be large enough to reduce these stresses to a negligible value. Fig. 1 gives a family of characteristic curves for 13/8-in. improved plow steel hoisting ropes of 6 x 19 or 6x21 construction with hemp core. The curves will hold for all rope sizes of this specified quality when they are subjected to an acceleration rate of 1.608 ft per sec2. As acceleration rates of most deep shaft hoists are close to this value, this family of curves is presented as a standard. Deviation is slight for other rope sizes. Note that for 0, which is the most important, the deviation is within the width of the line on the graph. In a comparison of values for ropes of 5/8-in. and 21/4-in. diam the deviation ranges from a maximum 1.2 pct at 0 ft to 0.6 of 1 pct at 5000 ft. The value of 5.55 is the same for all ropes at 2500 ft. The tabulated columns to the left of the curves are values of total connected load for each size of rope from 5/8-in. to 21/4-in. diam inclusive. With each of these connected loads the safety factor characteristic curve for the rope will be as indicated.

Jan 1, 1957