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By D. J. Christie, W. C. Hellyer

Three autogenous grinding flowsheets were considered as follows: 1) Primary autogenous grinding of a -8-in, primary crusher discharge to produce a product suitable for second stage pebble milling, or a flotation feed product in a single stage of grinding. 2) Intermediate autogenous grinding in which +4-in. rock media is screened from the primary crusher discharge and employed as grinding media to grind a tertiary crusher product to flotation feed size in a single stage.

Jan 8, 1972

By Janshi Sen

Vertical-intensity magnetometers, for instance the Hotchkiss Superdip and the Askania vertical field balance, are now widely used, because vertical-intensity charts give definite information for the location of upper pole, dip and strike, and approximate shape of the deposit. Again, a slow and steady increase of dip over a large area indicates a large deep-lying deposit, while a large dip limited to a small area and falling away rapidly suggests a small and shallow one. The complication comes more from the richness of the ore. A large body of lean ore near the surface might produce the same vertical-intensity chart as a rich ore at depth. This paper presents a method for calculating the maximum depth of a single-pole deposit and another for a two-pole mineral body, by utilizing data of both vertical and horizontal intensities as obtained by a Thalen-Tiberg magnetometer. As shown on the left side of Fig. I, lean ore, rich ore and a single pole produce the same magnetic field. The depth of the pole, where G is the vertical intensity at point A due to the pole; F, the horizontal intensity of the same; and a, the distance from the point of maximum vertical intensity or the vertical projection of the pole on the surface to the point of observation A. If an entirely covered deposit is indicated by magnetic measurements and boring cost estimated from the calculated depth is so reasonable as to encourage drilling, the ore should be struck somewhere within the limit of the calculated depth by the borehole. A number of such points as A should be taken for calculation, erratic results should be rejected and the average figure used for cost estimation.

Jan 1, 1946

By Janshi Sen

Vertical-intensity magnetometers, for instance the Hotchkiss Superdip and the Askania vertical field balance, are now widely used, because vertical-intensity charts give definite information for the location of upper pole, dip and strike, and approximate shape of the deposit. Again, a slow and steady increase of dip over a large area indicates a large deep-lying deposit, while a large dip limited to a small area and falling away rapidly suggests a small and shallow one. The complication comes more from the richness of the ore. A large body of lean ore near the surface might produce the same vertical-intensity chart as a rich ore at depth. This paper presents a method for calculating the maximum depth of a single-pole deposit and another for a two-pole mineral body, by utilizing data of both vertical and horizontal intensities as obtained by a Thalen-Tiberg magnetometer. As shown on the left side of Fig. I, lean ore, rich ore and a single pole produce the same magnetic field. The depth of the pole, where G is the vertical intensity at point A due to the pole; F, the horizontal intensity of the same; and a, the distance from the point of maximum vertical intensity or the vertical projection of the pole on the surface to the point of observation A. If an entirely covered deposit is indicated by magnetic measurements and boring cost estimated from the calculated depth is so reasonable as to encourage drilling, the ore should be struck somewhere within the limit of the calculated depth by the borehole. A number of such points as A should be taken for calculation, erratic results should be rejected and the average figure used for cost estimation.

Jan 1, 1946

1. A passenger rickshaw in China. 2. A Pekin cart carrying coal, on dirt roads; the cost works out to 15 or 20 c. per ton-mile. 3. Coolie with wheelbarrow. This one has a small load, but barrow men carry ordinarily 250 lb., occasionally 400 if with a helper. He goes about 18 miles a day and the cost is about 25c. gold per ton-mile, though it varies widely. 4. Coolie delivering coal balls in Pekin. He carries about 65 lb. On some roads with a different arrangement a coolie carries 133 lb., making about one ton-kilometer per day. 5. Truck used by the Government Fuel Yard at Washington. Carries 71/2 tons in an hour as far as a barrow man carries 1/4 ton in a day.

Jan 8, 1928

The first practical and successful use of a laser-beam guidance system for a tunnel machine drilling to a remote target has been achieved at the Bureau of Reclamation's Navajo Indian Irrigation Project near Farmington, N. Mex. Using such a guidance system, the Hughes Tool Co.'s "Betti I" drilled a 10,000-ft long tunnel in eight months and 18 days to within 5/8-in, of established line and grade. The electronic system which guided the "Betti I" features a gas laser whose beam is aimed at two light-sensitive targets on the boring machine. From these targets, the operator of the machine receives electric signals on a read-out panel which tell him the machine's precise location within the tunnel. The operator can then make any adjustments necessary to maintain line and grade while drilling ahead.

Jan 6, 1966

By William Kelly

An extensive swamp covers a large part of the town-site of Norway and adjacent laud. Through this swamp run two parallel oreformations. In the north one is the Aragon mine. The south one passes into the swamp on the Harrison property. On the edge of the swamp, about 1000 feet from the Aragon mine, a diamond drill, in the fall of 1889, located the ore-bearing formation and a probable ore-body. To explore further and develop this ore, the Penn Iron Mining Company proposed, in the spring of 1890, to sink a shaft. The drill had shown the depth of the glacial drift to be more than 60 feet. A test-pit near the location of the proposed shaft had struck, at a depth of 20 feet, an amount of water which a 200gallon pump was unable to lower. At the Aragon, a few years before, a shaft had been sunk to hard pan with great difficulty and many delays by the usual method of driving laths. Under the conditions it was decided to sink a caisson- or dropshaft. Two 40-horse-power boilers, a Lidgerwood engine with 4foot drum, and a good derrick were set up; and two No. 10 Kuowles

Jan 1, 1892

By Douglas Baker

Zinc concentrates assaying approximately 54% zinc and 30% sulfur are roasted in a suspension type roaster to yield a zinc oxide calcine assaying about 65% zinc and 0.40% sulfur. This calcine is the feed material to the sulfuric acid leaching section of an Electrolytic Zinc Plant. The SO2 gases resulting from the elimination of sulfur from the concentrates are passed through a waste heat boiler for the generation of high pressure steam, cleaned by a baghouse, and delivered to the humidifying tower of a sulfuric acid plant system. The gases are then treated in a mist precipitator for final fume removal and then converted to sulfur trioxide in a three pass contact system using vanadium pentoxide catalyst for the manufacture of sulfuric acid. Waste heat steam is used to power the steam turbine which drives the acid plant blower.

Jan 1, 1970

ALTHOUGH I have told you before (in the chapter on making the main mould for guns) how to support the core, I wish to repeat it here briefly and in a more orderly fashion, so that you may understand it better. For it is a thing of great importance to the profit of the owner as well as to the honor of the master, because he who does not locate the core in the middle makes the gun weak and incapable of shooting straight, and shows great lack of skill as a master. In short, it is very necessary to do this well. The first of these methods that I described to you is an iron, one dito wide, made into a ring which has four arms in a cross, or sometimes three. This is put in the mould where [88v] the last cornice begins, one palmo or half a braccio from the foot. Secure it in the middle of the diameter,

Jan 1, 1942

Abbott, Franklin E. Adgate, Frank Aertsen, G. Aid, Kenneth Albert, H. I. Alexander, D. B. W. Allan, Wm. G. Allen, R. 0. Allen, Roy H. Aller, Mr. and Mrs. F. D. Altmayer, Maurice Ambler, Harry A. Ambrose, A. WV. Ammon, Mark A. Ammon, Mr. and Mrs. Robt. Anderson, George H. Anderson, Mr. and Mrs. L. D. Andros, S. 0. Appleby, W. R. Archer, R. S. Armitage, Paul Arobb, Alden D. Arthur, Walter Ashman, A. 0. Atkinson, R. H. Aupperle, J. A. Austin, D. F. Avery, G. E.

Jan 11, 1919

(Under this heading will be published notes sent to the Secretary of the Institute by members or other persons. ) Position in sales department is open for a mining engineer with experience in mine ventilation and possessing some knowledge of fan design; one competent to lay out ventilating systems to meet various conditions. No. 2. A large company manufacturing mining machinery has an opening in one of its Western agencies for a young mechanical engineer who has had some experience in designing along general machine shop lines, and who is familiar with cost systems. No. 3. A large university desires to secure a prominent metallurgist for a vacant professorship in metallurgy. No. 4. Opening at a mine in New Jersey for a technical graduate to begin work as chairman on the surveying squad. Salary $50 per month to start. No. 5.

Jan 11, 1913

By Earl L. H. Sackett

This laboratory centrifuge is unique in its low cost and ease of construction, its particular adaptability to problems encountered in an ore dressing laboratory and its simplicity of operation. It will treat a sample of the size ordinarily used in a laboratory flotation test. The centrifuge was designed at the Baroid Sales Division of the National Lead Co., Malvern, Ark., and built in a local machine shop to serve as a laboratory machine which would produce results comparable with those obtained in the large scale centrifugal deslimers in use in our Magnet Cove mill. The apparatus has served quite well in this capacity and has also proved effective as a deslimer on a variety of ore dressing problems. The cost of making this machine was relatively low and it is simple to operate. It is strictly a batch machine, but when operated under proper conditions, gives results which agree quite closely with large continuous-flow machines of the same type. Effective separation of minus 5 and 10 micron material is made in an undispersed pulp in a short time.

Jan 4, 1950

Why should I pay $8.50 an hour for dealer repairs when my own mechanics work for $3.50?" The numbers vary, but that's the argument most contractors use to justify doing their own repairs. They don't realize it, but they're probably losing big money. For instance, it takes nearly a quarter of a million dollars in tools alone to equip a shop comparable to an average equipment dealer's facilities. A contractor must buy a lot of expensive, specialized tools he seldom uses, or else settle for the inefficiency of having repairs done by his mechanics with relatively unsophisticated tools. His building soaks up money in rent, maintenance insurance, taxes. His mechanics demand good wages. It even costs money when mechanics aren't repairing equipment. Mechanics get full wages for slack periods and cleanup time, too. This doesn't count as service manhours, but it's still part of the total repair cost. To help contractors uncover these hidden expenses and find out the true cost of owning a shop, some equipment dealers have devised a do-it-yourself "shop cost analysis form."

Jan 1, 1970

By W. L. Korbee, P. Hazebroek, M. Prats, E. E. Allen, C. A. 225-000-000-017 Verbraak, H. C. van Elst

In a recent paper,' one of us has presented some experimental evidence on the relationship between twinning and brittle fracture in steel. From metallographic examinations of brittle fracture it could be derived that mechanical twins and microcracks are formed already in front of a running brittle fracture. A tentative explanation based on the evaluation of the statistical distribution of mechanical twins vs various angles to the fracture was given in the above mentioned paper. It was suggested that these twins are caused by stress waves emitted by a running brittle fracture. With the aid of high-speed photography and the use of photo-stress sheet we are now able to study in more detail the propagation of a brittle fracture and the emittance of stress waves connected with fracture. A typical example is given in Fig. 1. In this figure a running brittle fracture in an ordinary Thomas steel is shown. The experiment was performed on a Robertson apparatus and the stress waves caused by the fracture were made visible with photo-stress

Jan 1, 1962

IT is not necessary to enter into a long discussion of ordinary bells, because every master carpenter or blacksmith knows how to make those levers with a crossbar that are called storks. This is nothing other than a board that has a thick and heavy head and looks more like a dolphin than a bird. This has a long tail in the form of a handle so that it makes a more powerful lever. As can be seen in every bell tower and other place where there are bells, it has, crosswise above the point where the cannon of the bell is fitted and fastened in, an iron bar which is arched and which has its two ends turned horizontally. These are made round so that they may turn easily when they are held by two steel rings or in two metal grooves or on glass pillows. In this, the more the transverse rod is arched,

Jan 1, 1942

Percolation infers the passage of a liquid through, the interstices of any material or materials permitting it. Leaching is the process of extracting soluble matter by percolation. Lixiviation is analogous to leaching. Percolation and leaching may occur simultaneously. A filter may be used either to strain suspended or finely divided matter from a liquid, when it is known as a clarifier, or to separate a liquid from a solid. Clarification usually infers the addition d: some settling or flocculating agent which permits the decantation of the clear supernatant liquor. The simple separation of solid from liquid, such as occurs when a thickened flotation concentrate is filtered, is usually termed dewatering. The word filtration is used more to cover the complex process of separating, as far as possible, solid from liquid by vacuum or pressure, removing the residual solution by wash, and at the same time leaching any recrystallized, absorbed, or undissolved matter, by percolation with the solvent. The final product of metallurgical treatment should be reported as a recovery when the yield is refined metal. When the metallurgical operations are incomplete and a concentrated but not refined-product is obtained, the metal content should be reported as an extraction.

Jan 1, 1919

T. M. Morris (Measurement and Evaluation of the Rate of Flotation as a Function of Particle Size, P. 794), was the commanding officer of a patrol craft charged with guarding Aleutian waters against infiltration by the Japanese during World War II. Before going into service, he was an assistant research engineer with Anaconda Copper at Anaconda, Mont., and later a metallurgist with Tennessee Copper Co. Presently he is a professor in the Department of Metallurgy, Missouri School of Mines, Rolla, Mo. A member of the AIME, he is a graduate of Columbia University and the University of Missouri, with a Bachelor of Science, Master of Science and a Ph.D. Professor Morris is the author of a previous paper for the AIME, Measurement of the Equilibrium Forces Between an Air Bubble and an Attached Solid in Water. An outdoor man by predilection, he enjoys bird watching and hiking in his free time.

Jan 1, 1952

By K. R. Grube, D. N. Williams

It is often desirable to perform fatigue studies at relatively high strains and at low strain rates. A low-cost fatigue machine has been constructed for this purpose which has proven quite versatile. This machine is based on the principle of repeated bending of a strip sample over a shaped mandrel. A photograph of a group of fatigue tests in progress is shown in Fig. 1. The test sample is held in place between two shaped mandrels having a flat at their base to grip the sample firmly. A cam-driven loading frame is used to bend the sample alternately over each mandrel. The sample slides freely in this frame and is held in place by a light spring to accommodate increases in sample length. The pivot point for the loading frame is selected so as to minimize movement at the loading point during operation. The number of cycles to failure is recorded by a rachet counter which is kept in operation by a series electrical connection through the sample and is operated by the drive cam. The maximum strain imposed at the sample surface on bending from one mandrel to the other is readily calculated from the relationship, where t is the sample thickness and r is the radius of curvature of the mandrels. The rate of straining can be controlled by control of the cam speed. The device as shown in Fig. 1 is set up to run six samples at ambient temperature. A much larger number of samples can be run at one time without difficulty. ALSO-, by slight realignment of the components the mandrel unit can be enclosed in a separate chamber permitting control of test temperature and environment. This permits a variety of fatigue and corrosion fatigue problems to be studied.

Jan 1, 1963

A development which could prove significant was the announcement on September 18 by Lone Star Industries, Inc., Greenwich, Conn., that the Snyder process which utilizes shock phenomena to break down ore in seconds, is operational. J. R. Kringel, chairman and president of Lone Star, says this about the process: "This new approach to the comminution of ores not only provides better mineral liberation at lower capital and operating costs, but it also makes a significant contribution toward the more efficient utilization of the country's rapidly depleting mineral reserves." The Snyder process consists of loading the material into a chamber, introducing a compressible working fluid such as steam under 300-500 psi, or as low as 80 psi, and then opening a millisecond-action discharge valve, causing the material to become entrained in the expanding fluid. The mixed fluid moves through a duct toward a discharge zone at near-sonic velocity, and is subject to a variety of extreme shock phenomena which accomplish the desired size reduction and mineral liberation.

Jan 11, 1972

By AIME AIME

MEDELLIN, the famous old capital of the Province of Antioquia in Colombia, is in the heart of the Cauca Valley, famous for its beauty and wealth. Through the kindness of R. S. Botsford, we present a panorama of the city, showing the 5000-ft. mountains in the background, a picture of the cathedral, locally said to be the largest building in South America, and a sketch of the diversion work on the Nari river, near Alejandria, where C. J. London is opening 42 kilometers of placer ground. One of the hydraulic elevators at the mine is also shown. Medellin was formerly much isolated but 19 now connected with navigation on the Magdalena River by a railway from Puerto Berrio, passing through a recently completed tunnel under the central Andes.

Jan 1, 1930

By R. W. Heins, N. Street

Recently Hiller1 reported results on the impairment of the strength of quartz glass rods through wetting, indicating that there was general agreement with the prediction of the Griffith formula in that for the liquids used the rods were weakest in water i.e. the liquid which probably had the greatest free energy of immersion. The Griffith equation predicts that the tensile stress necessary to propagate a crack of length c is where ? is the interfacial free energy, E Young's modulus. Since for a solid immersed in a liquid of surface tension ?L and contact angle 8 at the solid-liquid-gas contact, ?s - ?SL = ?L cos ? where ?s is the surface free energy of the solid. Hence comparison between ?L cos 0 and strength impairment should be possible. In a study of the usefulness of the Kuznetsov pendulum2 as a means of studying rock drillability we have determined the effects of various liquids on the pendulum hardness of Bavarian limestone. The pendulum used had diamond points (Burgess Vibro-graver), a period of 1.14 sec and a total on sample weight of 1191 g. The decline of the pendulum oscillations was recorded by a light beam on light sensitive paper carried on a kymograph. Rehbinder's expression relating hardness to amplitude attenuation as a function of time can be written In A = - (1/H) t + In Ao where A, A, = amplitude at time t and initial amplitude respectively, H = hardness parameter, and t = time. The line of best fit to the experimental points was determined using the IBM 7090 electronic computer, the computer also gave A, by extrapolation to zero time. The results for the various liquids tested are given in Table I and Fig. 1. The limestone surfaces were highly polished before testing and each reported hardness value represents the average of at least ten separate determinations of the pendulum decline curve. On each newly prepared surface the water value was again determined (also

Jan 1, 1964