Search Documents

By A. D. Bryant

APPROXIMATELY 2 1/2 million tons of silica sand and ground silica with a value of $7.25 million is produced annually from the Ottawa, Illinois, district. These silica products come from the well known St. Peter sandstone formation which covers part of the Mississippi Basin extending from St. Paul on the north to the central part of Arkansas on the south and from Muncie, Ind., on the east to Kansas City on the west. Practically the whole state of Illinois is underlain by this formation except where removed by erosion. Sand produced from the St. Peter sandstone in the Ottawa district is noted for its purity, uniformity, and quality. In addition to various screened grades for industry about 10 pct of the total production of the Ottawa district is ground into silica flour for use in glass, abrasives, enamel, porcelain, tile, for foundry and filter sand, and other uses.

Jan 3, 1953

By Rosewell H. Johnson

Discussion of the paper of ROSWELL H. JOHNSON, presented it the San Francisco meeting, September, 1915, And printed in Bulletin No. 102, June, 1915, pp. 1291 to 1294. WILLIAM A. WILLIAMS, San. Francisco, CaI.-A sliding. scale of royalties was proposed to the Department of the Interior in connection with the fixing of royalties to be charged upon oil leases made on the Osage Reservation in Oklahoma. The possibility of evasion and difficulty of enforcement required close inspection to satisfy all interests, particularly in connection with the exemption from royalty on oil to equal maintenance and interest on the junk. Mr. Johnson discusses the block method, the period method, and the cumulative method, and favors the adoption of the cumulative method with a proviso that the wells should be permitted to be pumped until the gross income is as low as the maintenance cost, which would mean exemption from royalty on the smallest wells. He recommends that depth be the variable factor upon which the sliding royalty is based and suggests that on partially developed territory in the Osage, the royalty be one-sixth for oil wells averaging less than 2,000 ft. in depth, one-eighth for wells from 2,000 to 3,000 ft., and one-twelfth above 3,000 ft.; for the rest of the Osage he suggests one-eighth above 2,800 ft. and one-twelfth below that depth. The net result, if Mr. Johnson's suggestions had been accepted in the Osage, would have been to reduce the then existing rate of royalty and considerably increase the cost of administration. The difficulties in determining the size of wells to be exempt and the possibility of obtaining oil at different depths in the same well might lead to complications which are avoided by charging a flat royalty as now universally charged throughout the United States. It is not uncommon to reduce the royalty when the production of the wells becomes unprofitable at an existing rate of royalty, accomplishing very much the same results as Mr. Johnson has attempted to accomplish by the cumulative royalties, and probably in a manner far more satisfactory to the operator and the lessor. A. C. MCLAUGHLIN, San Francisco, Cal.-The net revenue of the well depends, first, on the cost of production; second, on the amount of oil produced; therefore it would be impossible under Mr. Johnson's system to set a royalty which would be fair to all concerned. If it is impossible to set it at the beginning, it is certainly further impossible to do it from day to clay. I think it is entirely impracticable of application.

Jan 12, 1915

By Hugh H. Waesche

Of all the military services, the Signal Corps is the most concerned with piezoelectric minerals because of its function as a supply service to the strategic and tactical military forces. Consequently this paper is written from the point of view of one associated with that organization. The Signal Corps is responsible for the research, development, and supply of communications, radar, and components to the using services of the Department of the Army and to some extent the Other branches of the National Defense Department. Their work therefore includes the study of the sources* characteristics, and application of quartz and other piezoelectric materials. These materials have become a vital consideration in strategic planning and are essential for efficient tactical operation by all the Armed Forces. The Signal Corps at the beginning of world War 11 Was respon-sible for both Army Ground and Air Force electronic equipment. Since that time this Army service organization has probably done more in the development of frequency control devices using piezoelectric materials than any other group. The U.S. Department of the Interior, Bureau of Mines, Minerals yearbook of 1945, shows that during the four war years, 1942 through 1945, 9,598,-410 Ib of quartz crystal were imported for all uses and of this total, 5,168,000 lb were consumed to produce 78,320,-000 crystal units for electronic application. Other government records confirm these data which conclusively show that approximately 53 pct of the crystalline quartz imported was consumed in the production of electronically applied quartz crystal units. It may be assumed that some effort was made to maintain a stockpile over demands for all purposes. and this would mean that the actual percentage of quartz used electronically was considerably over the 53 pct figure. These data only emphasize that electronic application of crystalline quartz was the greatest requirement, and per- haps the actual value in this application to national defense is many times greater in importance than is apparent on first inspection. Current electronic research and development programs of the Armed Forces are planned around the fundamental use of piezoelectric minerals for frequency control and this at present, at least, means quartz. Definition and Early Development The word piezoelectricity is formed from combination of the Greek word "piezein". meaning "to press," and "electricity." It is that property shown by numerous crystalline substances whereby electrical charges of equal and opposite value are produced on certain surfaces when the crystal is subjected to mechanical stress. It appears to be intimately associated with the better known property, pyro-electricity and in fact, the two may be manifestations of the same phenomeuon. This property was discovered by Pierre and Jacques Curie in quartz, tourmaline, and other minerals in 1880 while studying the symmetry of crystals. The converse effect, that is, mechanical strain in the crystal when placed in an electrical field, was predicted by the French physicist, G. Lippman, in 1881, and verified by the Curies almost immediately. As has been the case with many discoveries of similar character in the basic sciences, not much attention was paid to this property for man)- years except as an entertaining curiosity. Between 1890 and 1892 a series of papers was published by W. voigt in which the theoretical physical properties were put into mathematical form. The first practical application of piezoelectricity occurred during World War I when professor P. Langevin of France used quartz mosaics to produce underwater sound waves. The same mosaics were used to pick up the sound reflections from submerged objects which were in turn, amplified by electronic means and used to determine the distances to such objects. This device was intended for use as a submarine detector but development was not completed in time for war service although it was used later for determining ocean depths. About the same time, A. M. Nicholson, of Bell Telephone Laboratories, developed microphones and phonograph pickups using Rochelle salt crystals. A major step in the application of piezoelectric quartz came in 1921, when professor W. G. Cady, of wesleyan university, showed that a radio oscillator could be controlled by a quartz crystal; from that date, this use of quartz has increased steadily, reaching its peak in world war 11 as is shown by the figures previously given. Essentially all American electronic equipment for communication, navigation, and radar, utilized quartz crystals for the exacting frequency control required. Crystalline Minerals with piezoelectric Properties QUARTZ Hundreds of piezoelectric crystalline materials are known, most of which are water soluble. Of these, quartz appears to be without a peer for electronic frequency control. Unfortunately, the quartz must be of superior quality. It must be free of mechanical flaws, essen-tially optically clear, free of both Brazil and Dauphiné twinning and must be, for average uses, over 100 g in weight. Because of these stringent requirements, raw quartz of the quality desired is of rare occurrence. In addition to quartz, several other naturally occurring crystalline materials are known to have the piezoelectric property and could perhaps be substituted for quartz in some applications. These

Jan 1, 1950

By AIME AIME

THOUGH born in England-on Nov. 23, 1372 William Wraith was brought to this country at the age of ten. Eight years later he entered the University of Illinois, transferring to the Michigan College of Mines where he got his E.M. in 1894. For the next three years he was a mine surveyor for the fuel department of the Santa Fe Railroad. Then he got into the copper-mining industry, which has occupied his attention for the last forty years. First he was engineer, at Butte, for the Boston & Montana company, and then helped to build the Washoe smelter at Anaconda, of which he was assistant superintendent from 1906 to 1913. The Anaconda company then sent him to Salt Lake City as manager of its subsidiary.

Jan 1, 1938

By Blake M. Caldwell, Harrold D. Owen

The continued use of permanent-type, we11 completion Iras pointed LIP the need for more powerful through-tubing perforating equipment. A new expendable shaped charge perforator has been developed in which the charges are run through the tubing in a vertical position and then opened out to a horizontal position when at the desired shooting zone. The performance of this new tool is comparable to that of conventional casing type perforators. This paper describes the new tool and its applications. Performance data in targets rind under various actual well conditions are presented. INTRODUCTION The general acceptance and increasing use of pernianent-type well completion by the oil industry has indicated the need for through-tubing perforating equipment with performance comparable to that of conventional casing type perforators.'.' To achieve the performance desired, a new, expendable, shaped charge perforator has been developed with adequate power for effectively perforating both 51/2-in. and 7-in. casing below tubing. This has been accomplished without resulting severe damage to the casing and can he obtained under extremes of pressure and temperature. The design of this new tool is a radical departure from previous concepts of tubing guns since it was felt that the two major limitations imposed by previous designs severely handicapped performance. The first of these limitations was the restriction imposed upon the length of the charges by the necessary small inside diameter of the carrier. This resulted from the necessity for compromises in designing a hermetically sealed gun small enough to allow free passage through 2-in. tubing, yet with sufficient wall thickness to withstand some minimum pressure. In an effort to overcome this limitation, the charges were in some cases placed at an angle with the axis of the well with resulting loss in effective depth of penetration. The second limitation concerned the extreme distance of the charges from the casing when the gun was fired. An example of the latter situation is demonstrated by the fact that a conventional 13/4-in. tubing gun centralized in 51/2-in., 17-lb casing has a clearance of more than 1-9/16-in. on all sides. This means that a considerable portion of the force from each charge must be expended in penetrating this 1-9/16-in. of well fluid before it even reaches the casing. With the gun centered in 7-in., 23-lb casing, the amount of fluid penetration required of each jet is in excess of 21/4-in. In a situation where the 13/4-in. gun is touching one side of the 51/2-in., 17-lb casing, the jets from the charges on the opposite side have more than 3%-in. of fluid to penetrate. A similar situation in 7-in., 23-lb casing necessitates the penetration of more than 4-9/16-in. of fluid. The penetrating effect of the charges is severely impaired in passing through so much fluid. Under such conditions, there is usually insufficient force left to penetrate the casing. Previous studies have shown the decided disadvantage of having to shoot through such an excessive quantity of well fluid.'.' The problem. then, was how to position large powerful charges close to the casing prior to firing and still manage free passage through 2-in, tubing. The solution appeared to be in some method of folding sealed charge units in an open type, expendable. 13/4-in. carrier for travel through the tubing, and unfolding them upon their arrival at the shooting zone in the casing. It was desired to control the mechanism electrically from the surface through the regular shooting cable, making the release of the charges independent of the physical characteristics of the well, yet with a provision to prevent the gun from firing until the

Jan 1, 1955

By Woolf, W. G.

Filtration of hot (60°C) supersaturated zinc sulphate solution (sp gr 1.540) from slimy leach residues at the electrolytic zinc plant of Sullivan Mining Co., Kellogg, Idaho, is de- scribed. Separation of liquids and solids in the finished leach is by Burt filters modified to meet conditions of high-acid, high-density process for electrolytic zinc. Operating characteristics of the Burt filter on this pulp are presented.

Jan 1, 1950

By E. M. Furness, A. S. Henderson

ORIGINALLY the Babbitt experimental plant grinding circuit consisted of one rod mill 101/2 ft diam by 12 ft long in open circuit followed by two ball mills 101/2 ft diam* 12 ft long in parallel cir- the slow-speed ball mills. The next step was to improve rod mill operation by changing the speed of this mill. Such an attack would affect only one mill and would allow slower speed on the ball mills. The rod mill, as originally purchased, operated at 15.45 rpm. Additional pinions were purchased to test this mill at 16.45, 17.45, and 18.45 rpm. When the mill speed was increased by the use of these pinions, rod breakage with this short mill increased out of all proportion to the improved grinding, until at 18.45 rpm breakage became as high as 7 lb per

Jan 1, 1958

By H. H. Stoek

Among the mining and metallurgical achievements of the latter part of the nineteenth century, not the least is the incep tion and successful prosecution by mining men of a technical educational movement which in magnitude surpasses any similar movement ever before set on foot. The following account of this undertaking has been prepared at the request of the Secretary of the Institute :*

Jan 1, 1899

By Donald C. Myntti

INTRODUCTION A major segment in a successful heavy equipment maintenance and repair program is the provision of well-laid out and well-equipped shop and service facilities The facilities described here will be those required for a large, high tonnage hard rock open pit mine utilizing rotary drills, shovels, haulage trucks, support equipment, and service trucks. The term support equipment covers the equipment required to support the drill, shovel, and truck operations, these are crawler tractors, road graders, front-end loaders, water trucks, rollers, rubber-tired tractors, etc. Service trucks are the automotive type consisting of rubber-tired over-the- road equipment. The primary structures generally involved in the total maintenance effort are as follows. (1) the main shop with an attached warehouse (the structure could also house the tire and lube shops plus the equipment cleaning stalls), (2) a service station with bulk petroleum product storage tanks, (3) a heating plant, (4) a security station (lf this is a corporate requirement), (5) operating department and employee assembly buildings, and (6) an electrical substation. Under certain conditions, many of these facilities with the exception of the substation could be combined In one or several structures. This arrangement could have a great advantage especially in areas where the heating of the structures is extremely critical.

Jan 1, 1979

By William Y. Mo

The OPEC oil embargo and the subsequent higher prices for oil have drawn public attention to the critical problems associated with security of supply of oil and other key industrial materials, especially nonfuel minerals. This concern has stimulated the interest of decisionmakers in analyzing policy options to cope with the emergency situations resulting from a sudden foreign- induced supply interruption or a cartel price increase. Several policy options are available to counteract foreign-initiated embargoes or cartel price actions. The type of response will differ depending on the commodity action intiated. A mathematical model that measures the impact of foreign-induced commodity actions on the domestic economy is formulated. The paper also presents a computer method that can be used to determine the optimum policy response to counteract such actions.

Jan 1, 1977

By Earle C. Smith

The Chairman.—Mr. Earle Smith has kindly offered to make some remarks in connection with segregation in the product, Mr. Smith: E. C. Smith,* Cleveland, Ohio—I will start this Off by a story oF the code days of the American Iron and Steel Institute. In those days, Republic did not have a big strip mill, and the question came up of the check analysis of rimmed steel. I suggested that they let me be the chairman of the Committee on Accumulating the Information on the Variation of the Composition of the Ingots of Rimmed Steel. Somebody wanted to know why I wanted to be the chairman. I said, "we don't make any of the big ingots of rimmed steel, and no matter who makes them they are so bad that you don't dare publish the information. So if 1 collect it and hide it you can't charge me with having done anything that really disrupted the commercial situation." So, everybody furnished me with a rather complete story as to the horrible variations in big rimmed ingots. I took it out to my house and put it away, and it is still there. Now, segregation in the big ingot is no longer an "academic " matter as far as I am concerned. I am in a situation like that of the German who was told in 1956 about the coming war. He said: "until it is your throat that is going to be cut, you don't pay any attention to what is happening to the otherman." 'That is the way with the problem that we have in front of us. Recently I have been told that the 'Omptroller was questioning the payment for certain articles of stamped steel that had been made from rimmed steel, because upon check analysis of the rimmed steel it had been determined that these stamped articles were nut within the compositions that were included in the specification, and therefore he as the camptroller had no alternative. It was not meeting the specification; therefore, no payment. So I I say to all of you: You can very seriously consider this matter of segregation now and on into the future on the basis of the fact that it is actually going to cost your companies, which are making these products, money unless there is some new idea about the infallibility of quantitative , chemists who analyze some of these products or lawyers who read specifications, I don't know which man is going to be the major factor in the future. if the National Bureau of Standards could in some way show the specification writers the variation between good chemists analyzing for That they expect to be umpire eel. the writers would certainly realize that some of the to to which we have calmly signed our names as being O.K. are— well, as one man said to me, they might be filled by the devil, and they certainly could be filled by the Lord, but they could not he me by mankind. I would like to inject two or three things into a segregation study which I Want you to think about, because 1 would be a little surprised if there is very much discussion of them, In the first place, we generslly make steel in the United States in the basic open hearth, and I do not think there has bee,, nearly enough consideration given to segregation German the bath before it moves into the ladle. I am sure that any of the people who handled the 9400 series of the NE series when it contained the 0,60 per cent silicon have more respect than they had previously for the segregation that is within, the ladle; that is, before the metal reaches the ingot mold, the frozen ingots and the segregation in them. Another pint to which I think We ought to sis serious consideration is the segregation of iron oxide in the ingot-iron type of material, where the distinction between that and the steel segregation is that it is actually segregat. ing iron oxide, Normally we are segregating some form of carbon or sulphur, or something like that, with the stamping steel industry now coming down into the ranges of chemistry, where the segregation of iron oxide will be just

Jan 1, 1945

By J. C. Van de Water

In June the supply of M3 army demolition powder being used for mudcapping was depleted and we switched to 4 by 8, 60% Special Quarry Gelatin dynamite. This size cartridge has proved convenient, as a half stick will handle the average boulder. By keeping the gelatin in the paper while cutting it in two, there is little contact with the gelatin and therefore fewer headaches among the powdermen. To further help prevent the headache nuisance the men are furnished with plastic coated gloves. Boulder breaking costs as reported last year were $0.426 using M3. This year, 8180 boulders have been broken with M3 at a cost of $0.472 each and 7479 with 60% Quarry Gelatin at a cost of $0.660 each. This rise in cost is due entirely to the greater cost of the Gelatin as the method has not changed.

Jan 4, 1950

The Reconstruction and Research Division of the United States Council of National Defense has, up to date, prepared two reviews on the above subjects: one covers foreign countries and the other covers the activities in the States. These reviews contain information appearing in various Governmental and public periodicals. While the information on foreign countries is necessarily incomplete and fragmentary, its summation is perhaps the most complete work of this kind so far accomplished. The information from the states consists mainly of bills and ordinances introduced in the state legislature, municipal councils, legislature committee reports, programs suggested by governors, and other state and local officials and local organizations It is realized that a good deal of this information will be useful to engineers studying conditions in the various states, and especially to those who want an insight into the general condition in all the states. For instance, the reconstruction problem in each state involving highway, reclamation, buildings, etc., are covered in detail.

Jan 8, 1919

By L. D. Mullins, E. B. Elfrink, W. L. Wahl

In the past few years several articles and papers presenting results of solution gas-drive depletion calculations have appeared in the lit-erature. Such calculations are of interest to the oil industry, for investment decisions must often be made before much is known about a reservoir. At other times, an estimate of the possible benefits to be realized from alternate production methods is desirable, and theoretical depletion calculations can serve as a floor or reference level from which to work. In any case, an estimate of ultimate oil recovery based upon engineering data is commonly required. An engineer confronted with the problem of obtaining, for a specific reservoir system, an estimate of ultimate oil recovery by solution gas-drive depletion usually will be forced to perform the calculations himself. This is despite the quantity of data in the literature. Rarely will either experience or the literature provide results from a reservoir system similar in all important respects to the one under consideration, and calculated results are not so plentiful that satisfactory interpolation procedures can be devised. Performing the calculations, however, is a tedious, time-consuming task unless an electronic computer is available, and, in practice, time and manpower are not always available for this purpose. A quick, simple, consistent method was needed for reducing the uncer- tainty in estimated oil recovery from solution gas-drive reservoirs when only minimum information about the reservoir system is available. PROCEDURE Method of Calculation The usual requisite assumptions were made so that the material balance equation could be used to calculate data for the charts. The following assumptions were made: (1) the reservoir is homogeneous and isotropic; (2) oil recovery is due entirely to solution gas drive and neither a gas cap nor a water drive nor gravity drainage is present; (3) the initial reservoir pressure is the bubble-point pressure of the reservoir fluid; (4) initial total liquid saturation is 100 per cent of pore space; (5) interstitial water saturation remains at the initial value as the reservoir pressure declines from the bubble-point pressure to atmospheric pressure; (6) equilibrium gas saturation is 5 per cent of pore space; and (7) oil and gas saturations are uniformly distributed throughout the reservoir at all times. There are no saturation gradients due to a wellbore, nor is the geometry of the reservoir system considered. The material balance equation was written in the form of a differential equation' which was integrated to determine the change in oil saturation for an assigned pressure drop. Formal integration was not possible, so recourse was made to the Runge-Kutta method' of numerical integration. All computations were performed on IBM equipment. Numerical integration yielded the change in oil saturation within the reservoir as the pressure. declined from the bubble-point pressure to atmospheric pressure. The initial oil saturation minus the change in oil saturation yielded the oil saturation at atmospheric pressure. The oil originally in place was obtained by dividing the initial oil saturation by the initial formation volume factor (differential liberation) while the oil in place at atmospheric pressure was obtained by dividing the final oil saturation by the formation volume factor at atmospheric pressure. U1timate oil recovery, expressed as a percentage of the initial oil in place, was obtained by dividing the difference between the oil initially in place and the oil in place at atmospheric pressure by the oil initially in place and multiplying by 100. PVT Data Charts were based upon 135 solutions to the material balance equation. PVT properties of the reservoir fluids were variables in this equation and had to be known as functions of pressure. The required PVT data might have been obtained from either actual reservoir fluid systems or correlated data. However, correlated PVT data were developed and employed in the calculations for the following reasons: (1) it is doubtful that 135 sets of PVT data could have been obtained for the values of variables investigated in this study, and (2) results of recovery calculations from randomly obtained PVT data could not be correlated as well as rssults from selected PVT data. The PVT data used to develop the

Discussion of the paper of BOYD DUDLEY, JR., presented at the New York meeting, February, 1915, and printed in Bulletin No. 96, December, 1914, pp. 2767 to 2782. H. 0. HOFMAN, Boston, Mass.-At the close of the paper Mr. Dudley said that his experiments in the laboratory had shown that it was possible to separate nickel from copper by means of a chloridizing roasting, but that in order to demonstrate a process of this kind, work upon a large scale would have to be carried out. I think it was in 1913, that experiments of this kind were carried out at the works of the Pennsylvania Salt Manufacturing Co., Philadelphia, in a Wedge furnace, and at Sault Ste. Marie in a Sjöstedt furnace. They showed a satisfactory separation of nickel and copper. The ore was first subjected to an oxidizing roast, then mixed with pyrite and salt, and given a chloridizing roast. A. H. Carpenter published in the Engineering and Mining Journal, vol. xcvii, p. 1085 (1914) the details of this work. The conclusion arrived at is, that if you subject sulphide ore to an oxidizing roast, finishing at the temperature at which all nickel sulphate is dissociated, i.e., 764° C., then mix it with pyrite and salt, and subject the mixture to a chloridizing roast between 600° and 700° C., you can chloridize a high percentage of the copper without chloridizing any of the nickel, and obtain thereby a satisfactory means of separating the two.

Jan 5, 1915

By I. A. Violic, L. D. Cruz, M. A. Solari

In Exxon's Los Bronces Expansion Project in Chile, a stochastic simulation is performed to resolve the complex decision problem of matching the mine to mill system capacities from both technical and economic standpoints. The unique combination of weather conditions at the mine and the 30-km (18.6 mile) belt conveyor network for ore transport to the mill necessitates this analysis in the planning phase to optimize the design capacity of the system. Appropriate statistical distributions of major equipment performance, snow storm duration, power outage, etc., are developed from actual mine local records and manufacturers' specifications. The interactions of operational constraints including ore storage capacities, number and sizes of individual equipment, ore variations, and mine and mill production rates are studied more realistically than in a traditional planning approach. Details of the computer modeling and typical results of simulation studies are discussed.

Jan 1, 1984

By R. E. Cech

Metallographic observations on hydrogen-reduced nickel oxide crystals suggest that nucleation of nickel occurs at structural singularities in the oxide. The fully reduced structure contains micron-diameter, worm-like voids occupying 40 to 50 pct of the volume. The crystallographic orientation relationships between nickel oxide and nickel resulting from oxide reduction are recorded and discussed. THE process of reduction of oxide to metal is one of considerable complexity involving a chemical reduction reaction, mass transport of reducing agent to the point of reaction and of reaction product away from it, and finally a transformation whereby metal atoms released from the oxide rearrange to form a stable reduced phase. In addition, nucleation of the reduced phase affects the overall reaction kinetics. Thus far only the thermodynamic aspect of reduction has received the attention warranted by the importance of

Jan 1, 1960

By D. D. Donald

C. J. Barber (U. S. Smelting Refining & Mining Co., Salt Lake City)—In his paper Donald describes how New Jersey Zinc Co. made surveys for a connection between the Ivanhoe and Van Mater shafts at Austin-ville, Va. Except to say that the two faces had to meet "accurately" on line and grade, Donald does not indicate the required precision. Assuming that there were 24 angles in the 11/2-mile traverse and 15 in the one-mile traverse, it can be shown that if the average error in plumbing each shaft was 230" and the average error in measuring each traverse angle was 210". then the average error at the point of -connection would have been about ±1.9 ft normal to the line between the shafts. This calculation assumes that any errors in the triangulation would be negligible compared with the errors in the plumbings and traverses, and it also neglects taping errors. With no constant errors or blunders, the latter would be important only in lines normal to the line between the shafts. To make the average error at the connection less than 1.9 ft would, therefore, require either reducing the error in the plumbings to less than ±30", or that in the traverse angles to less than ±l0", or fewer stations, or a combination of these. Referring briefly to the triangulation, because of the problem of fitting a new triangulation into older surveys of the district the orientation deserved some mention, even though the connection could have been made with an assumed bearing. It would be interesting to know how many triangles were required and what the average summation error was before making any adjustments and without considering the algebraic signs. Perhaps this is referred to indirectly in the statement that the maximum angular error distributed was 2". Turning to the shaft plumbings, it would be helpful to know how many men were employed and how long each shaft was in use. Donald says that the surface positions of W-2 and W-3 were carefully surveyed from the collar position of W-1, without indicating how this was done. The length of the backsight would be particularly important. There must have been some error in setting W-1 vertically below the stations in the headframes. How immovable were the headframes, especially the Van Mater, which appears higher than the Ivanhoe and subject to more vibration because of skip hoisting? Donald does not say whether the plumbing wires had been previously restraightened to minimize spinning (otherwise they behave like weak helical springs). The use of light steel weights is most surprising because there seem to be excellent reasons for using heavier, nonmagnetic weights. Did the shafts contain no steel sets, pipes, power cables, etc., which might attract steel? The plumbing method described by Donald was designed for deep shafts in South Africa but differed from the South African practice in two important respects. As described by Browne,6 in South Africa the line between the wires was made parallel to the long axis of the shaft, whereas in the Ivanhoe shaft the lines between the wires were diagonally across the shaft. The main reason given for the South African practice is to insure that the gravitational attraction between the wires and the rock walls is the same on both wires, and therefore does not affect the bearing of the line between them. It seems probable, however, that the effect of air currents might be minimized in the South African procedure, and might be serious with the wires in the diagonal position at the Ivanhoe shaft. In the South African case cited by Donald the wires were swinging freely (although the plumb bobs were sheltered from air currents) but in the Ivanhoe case they were dampened with the plumb bobs set in water. In the discussion of Browne's paper R. St. J. Rowland said:' It has been the practice for a long time to damp the oscillations by immersing the bobs in oil or water. The time per oscillation is thus increased, thereby extending the time taken to complete the work. The longer the suspended wire the less there is to recommend the practice . . . The theoretical time for one swing of a simple pendulum 1050 ft long is approximately 36 sec, which would be increased by dampening the plumb bob in water. Hence very few complete swings would be observed in the 5 min intervals used at the Ivanhoe shaft. In the two South African cases described by Browne, the length of plumb line in one shaft was 5425 ft, the calculated period of swing was 81.6 sec, the average actual period was 76.6 sec, and 94 complete swings were observed in 2 hr. In the other case the length of plumb line was 3116 ft, the calculated period of swing was 61.8 sec, the average period was 63.5 sec, and 86 complete swings were observed in 1 hr 31 min. Browne concluded that observations of more than 30 swings are not likely to result in sufficient gain in accuracy to be justified. Returning to the Ivanhoe and Van Mater plumbings, an objection to the method used is that all four azimuths were taken from fixed points instead of swinging wires, and that each pair of observations would— barring blunders— check closely, and so perhaps give a false feeling of security. In fact, it seems that only two azimuths were obtained from one plumbing, and not four as stated by Donald. Nevertheless, the tying in of each pair of wires from both sides of the shaft has much to commend it. Donald's description leaves the impression that if each shaft was plumbed only once, the engineers were fortunate indeed if the average error in the underground orientation was as little as 30". Because the survey was done over a period of three years, it seems likely that the plumbings were repeated, perhaps more than once. The underground traverse angles were measured by conventional methods, but because the number of angles in the overlapping traverses was not given, the angular closure given by Donald does not indicate the accuracy with which this was done. Donald's description of a method of taping lines of irregular length is welcome. The literature on taping is usually confined to lines of about one tape length, generally 100 ft. Such lines are rare in metal mining because the time, trouble, and cost of setting points at 100-ft distances underground are not warranted. (Nevertheless civil engineers may go to this expense

Jan 1, 1960

By Robert H. Merrill

During the period from 1960 through 1966, the U.S. Bureau of Mines and Kennecott Copper Corp. performed an experiment to determine the changes in stress, strain, and displacement created by changes in slope angles. The experiment was performed at Kennecott's Kimbley pit near Ely, Nev. The supporting laboratory studies were made in the Bureau's Denver Mining Research Center, where final reduction of the data and summary reports are now in progress. The experiment was divided into two phases. The first consisted of the laboratory and field investigations required to select a new slope angle and configuration; the second phase consisted of a full-scale instrumented study in the west wall of the pit. The west slope was changed from an average of 45º to a slope angle that started at 45º on the south wall and gradually in- creased to 57 ½ º at the center of the west wall, and to 61 º on the north wall. The pit was deepened from 500 to about 550 ft, and approximately 2.55 million tons of waste and ore were removed from the wall.

Jan 9, 1969

By C. E. Taylor, L. V. Fegan

With on-stream electrical-resistance measurement as a basis, Bethlehem Steel developed a system for the completely automatic control of moisture in the feed to pelletizing. This system was later successfully adapted to the sintering process, with automatic control of moisture serving to maintain the air permeability required for effective burnthrough. Control of moisture content is an important factor in the agglomeration processes by which iron ores are converted into either pellets or sinter for use in blast furnace burdens. In both pelletizing and sintering the iron ore feed must be mixed with the proper amount of water so that capillary attraction and surface tension forces can be utilized to cause the ore particles to coalesce and form larger agglomerates. The success or failure of the entire pelletizing or sintering process depends on maintaining the proper moisture. Therefore, continuous automatic control of moisture is one of the conditions for the automation and optimum use of both pelletizing and sintering processes. In pelletizing, variation in moisture can cause ball size to change and is a common cause of cycling which results in a fluctuating feed to induration. Excessive moisture can cause lumps to form at the cutter bar and contributes to the formation of buildup on the green pellet screens. Green pellets with excess moisture deform and reduce bed permeability. In sintering, accurate control of moisture is also important because moisture must be within the limits that give the bed the required permeability for good burnthrough. In response to these problems, a moisture meter, based on the principle of electrical resistance measurement, was developed. This moisture meter has been a key factor in the development of systems for providing uniform feed of concentrates in most of Bethlehem's pelletizing and sintering plants. The automatic moisture control system for pelletizing was successfully plant-tested and resulted in the following: (1) Control of moisture in the green pellets to +0.2%. (2) Up to 50% reduction of bentonite consumption. (3) Control of unscreened green pellets so that 85% of the furnace product at Cornwall was within the size range of -5/8 +3/8 in. (4) Improved quality of product with a tumble test of 94 and a "Q" index of 90 as the result of feeding a consistently uniform feed to a shaft furnace. In sintering, where sinter-mix temperature change and variable feed could cause errors in moisture measurement, the system was designed to maintain the correct moisture under virtually all plant operating conditions. It was successfully plant-tested and is now in use in most of Bethlehem's sintering plants. The system achieves: (1) Control of moisture within the desired limits for optimum production. (2) Continuous measurement and control of moisture even with intermittent feeding of mix, so that attention by the operator is seldom required. The two automatic control systems provide smoother startup, minimize upsets and contribute to the consistent control of process variables in pelletizing and sintering. MOISTURE-CONTROL SYSTEM FOR PELLETIZING Fig. 1 shows the general arrangement of the system for automatic control of moisture in pelletizing.1 In this system a bin level controller, using a single probe which regulates filter speed, maintains a uniform low concentrate level in the bin.' The moisture meter, comprised of an analyzer and control components, continuously measures the moisture in the bed and adds water to adjust to the desired level. The meter is placed in an open-loop (feed-forward) control, i.e., water addition occurs downstream from the probes. Filter vacuum must be set so as to produce a filtercake moisture which is below the optimum for pelletizing. Bentonite is added after the

Jan 1, 1969