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By Theodore James Kurela

Analysis of adverse technical issues has traditionally relied on a snapshot of the state of the operation complemented with both the melt shop’s archived data and eyewitness accounts of adverse events. The GrafTech ArchiTech System is helping EAF shops solve problems faster by combining continuous analysis of information with statistically based alerts of process deviations. After one year of system implementation, a number of cases have been detected and communicated to melt shops worldwide. The objective of this paper is to examine a few of these cases; the early detection, statistical analysis, deviation reporting and the resulting countermeasures implemented.

Aug 17, 2017

By Arthur F. Taggart, T. C. Fitt, A. W. Thomas

IT was noticed early by operators that high recoveries and flocculation of the sulphide minerals were closely correlated in agitation-froth flotation. Later, this readily visible flocculation was found almost invariably to be due to the binding together of the oiled sulphides by minute air bubbles, and is now known to be characteristic of pulps in which at least one of the mineral species is coated with an insoluble collecting oil. In 1930 it was reported1 that in differential flotation a correlation exists between Brownian movement of particles in the pulp and their nonfloatability, and that Brownian movement and dispersion are likewise correlated, whence it would appear to follow that dispersion of a mineral particle in a flotation pulp denotes a particle condition unfavorable to flotation. In 1934 it was postulated2 that Brownian movement, dispersion and nonfloatability all flow from the condition of the surface of the dispersed particles. It was also postulated at that time that the surfaces of dispersed particles are ionized, the ionized compound being a product of reaction between a component of the particle and a. component of the pulp, of a mass solubility of the general order of a fraction of a milligram to 15 to 20 mg. per liter. It was then further asserted, and has since been confirmed by Bankoff,3 that sulphides so conditioned with soluble collectors as to be floatable flocculate without the intervention of air bubbles as binding media. The present paper comprises an inquiry into the nature of the bound and counter ions in zinc sulphide dispersed by sodium arsenate. A part of its findings was mentioned in the 1934 paper above cited.2 The tests show that: I. When powdered granular zinc sulphide is immersed in aqueous solutions of sodium arsenate, arsenate ion is abstracted from solution and anchored to the solid surface, while sulphate and lower sulphoxy ions are concurrently displaced therefrom in substantially stoichiometric quantities. 2. The ion counterbalancing the anchored arsenate ion is zinc. 3. Dispersion and Brownian movement of zinc sulphide are concurrently maxima at an arsenate-ion concentration lying between 0.01 and 0.001-molar sodium arsenate. 4. Any condition or reaction that tends to remove the zinc arsenate coating from the zinc sulphide particles decreases dispersion and Brownian movement concurrently. EXPERIMENTAL Three samples of zinc sulphide were used. Lot I was C.P. zinc sulphide, washed well beyond absence of chloride, as shown by test with silver ion. Lot 2 was prepared by precipita-

Jan 1, 1943

By Vaughn Moyer

A method for incorporating well drawdown effect into reservoir calculations is presented in detail, together with examples of its use for widely divergent conditions that could be normally encountered in oil reservoir sands. Tentative conclusions as to the effect such factors as permeability, producing interval, well spacing, or well damage caused by completion or repair practice could have upon economic ultimate recovery are reached. It is carefully pointed out that the conclusions reached are subject to limitations indicated in the text, and placed upon all calculations made in the paper. Introduction Papers have been presentedl-3 in which theoretical depletion histories for reservoirs under equilibrium conditions and no appreciable well-bore drawdown pressure are determined. However, except for a limited number of cases, appreciable drawdown Pressures in a well bore exist, and Pressure and saturation gradients consequently vary throughout a reservoir. This Paper is an attempt to incorporate well-pressure drawdown into reservoir history, and to analyze certain factors, such as those involving recovery, well spacing, and productivity index, from the standpoint of permeability and drainage radius. BY incorporation of drawdown into reservoir history, it is believed that theoretical considerations will more closely approxi- mate actual reservoir behavior experienced in an oil field. For purposes of simplification, a solution gas-drive type field1 without primary gas cap, has been selected. Basic Data and Assumptions Details of equilibrium saturation conditions for no drawdown production for various pressures in a reservoir are deter-minable by methods described by several are permitting the construction of a curve of oil saturation vs Pressure for any selected combination of initial interstitial water and hydrocarbon saturation (Fig I). This curve is then a description of equilibrium saturation conditions at any given pressure in a reservoir. Developing the above, details of saturation and flow permeability may thus be determined for any increment or portion of a well drainage area or reservoir. In this manner the effect of pressure differential (drawdown) may be incorporated into reservoir and well drainage considerations. It is pointed out that this method thus makes use of no-drawdown equilibrium production data, superimposing a draw-hwn effect upon them. It also assumes that net flow conditions in any considered increment of reservoir are not materially altered by the entrance of fluids from other increments into them, but approach equilibrium for the existing pressure and saturation (i.e., each increment behaves in more or less independent fashion, dependent largely upon the equilibrium considerations mentioned above)

Jan 1, 1948

By Vaughn Moyer

A method for incorporating well drawdown effect into reservoir calculations is presented in detail, together with examples of its use for widely divergent conditions that could be normally encountered in oil reservoir sands. Tentative conclusions as to the effect such factors as permeability, producing interval, well spacing, or well damage caused by completion or repair practice could have upon economic ultimate recovery are reached. It is carefully pointed out that the conclusions reached are subject to limitations indicated in the text, and placed upon all calculations made in the paper. Introduction Papers have been presentedl-3 in which theoretical depletion histories for reservoirs under equilibrium conditions and no appreciable well-bore drawdown pressure are determined. However, except for a limited number of cases, appreciable drawdown Pressures in a well bore exist, and Pressure and saturation gradients consequently vary throughout a reservoir. This Paper is an attempt to incorporate well-pressure drawdown into reservoir history, and to analyze certain factors, such as those involving recovery, well spacing, and productivity index, from the standpoint of permeability and drainage radius. BY incorporation of drawdown into reservoir history, it is believed that theoretical considerations will more closely approxi- mate actual reservoir behavior experienced in an oil field. For purposes of simplification, a solution gas-drive type field1 without primary gas cap, has been selected. Basic Data and Assumptions Details of equilibrium saturation conditions for no drawdown production for various pressures in a reservoir are deter-minable by methods described by several are permitting the construction of a curve of oil saturation vs Pressure for any selected combination of initial interstitial water and hydrocarbon saturation (Fig I). This curve is then a description of equilibrium saturation conditions at any given pressure in a reservoir. Developing the above, details of saturation and flow permeability may thus be determined for any increment or portion of a well drainage area or reservoir. In this manner the effect of pressure differential (drawdown) may be incorporated into reservoir and well drainage considerations. It is pointed out that this method thus makes use of no-drawdown equilibrium production data, superimposing a draw-hwn effect upon them. It also assumes that net flow conditions in any considered increment of reservoir are not materially altered by the entrance of fluids from other increments into them, but approach equilibrium for the existing pressure and saturation (i.e., each increment behaves in more or less independent fashion, dependent largely upon the equilibrium considerations mentioned above)

Jan 1, 1948

By Hajime Miki, Gde Pandhe Wisnu Suyantara, Shigeto Kuroiwa, Eri Takida, Tsuyoshi Hirajima, Masashi Yamane, Yuji Imaizumi, Mitsuru Sawada, Keiko Sasaki

Selective flotation of molybdenite and chalcopyrite using various oxidation treatments (i.e., ozone treatment, hydrogen peroxide, and Fenton-like reagent) was studied in this work. It was found that ozone treatment produced a depressing effect on both minerals, resulting in a lower separation of both minerals. On the other hand, oxidation treatment using hydrogen peroxide (H2O2) and Fenton-like reagent could deliver selective oxidation on chalcopyrite surface and depress its floatability. However, bench-scale copper- molybdenum (Cu-Mo) flotation tests show that oxidation treatment using H2O2 required a higher dosage of H2O2 and a longer treatment time in order to deliver comparable flotation results to that of conventional Cu- Mo flotation using NaHS treatment. On the contrary, Fenton-like reagent could deliver selective Cu-Mo flotation results comparable to that of NaHS treatment at a lower dosage of H2O2 and a shorter conditioning time. Contact angle measurements and X-ray photoelectron spectroscopy (XPS) analysis were employed to understand the depressing mechanism of these oxidation treatments. It was found that the chalcopyrite surface covered by various oxidation products that render the surface hydrophilic. Meanwhile, the surface of molybdenite was slightly oxidized, making the surface remained hydrophobic. INTRODUCTION Molybdenite (MoS2), the main source of molybdenum, is associated with copper sulfide minerals, mainly chalcopyrite (CuFeS2), as a trace mineral. Molybdenite is a valuable mineral and plays an important role in making the copper-molybdenum (Cu-Mo) processing plant economically viable (Laskowski, Castro, & Ramos, 2013). Therefore, it is important to recover molybdenite efficiently and effectively and separate it from copper minerals. Conventional separation of copper and molybdenum minerals is usually carried out in selective Cu- Mo flotation process using a copper depressant (i.e., sodium hydrosulfide (NaHS), Noke’s reagent, or cyanides) (Ansari & Pawlik, 2007; Bulatovic, 2007). However, this process still suffers due to imperfect molybdenum recovery. Moreover, the copper depressants use in this process are toxic and harmful to the environment. As alternative, various methods have been developed to replace these toxic and hazardous depressants, for example, by synthesizing new non-toxic or low-toxic depressants or by using various oxidation methods such as sodium hypochlorite in an alkaline medium, manganese dioxide, oxygen, and plasma pre-treatment (United States Patent Office Patent No. US 2559104 A, 1951; Patent No. US2238250 A, 1941; Barzyk, Malysa, & Pomianowski, 1981; Hirajima et al., 2014). However, the oxidation phenomenon and mechanisms are still not clear since detailed surface analyses have not done and the plasma pre-treatment method is facing technical issues for industrial scale application.

Jan 1, 2019

By B. M. Larsen, T. E. Brower

INTRODUCTION THIS discussion is based on statistical manipulation and evaluation of operating data from several commercial blast furnaces which include rather wide variations in practice. We are concerned here mainly with the effect of manganese on sulphur elimination under operating conditions in commercial blast furnaces, but this effect can be outlined more clearly by including certain other variables such as silicon in iron and slag basicity, which are all in part interrelated. Real progress in understanding all of the smelting-zone reactions in this process requires more laboratory studies of slagmetal melts similar to those in the blast furnace, with careful control of oxygen pressure. Such experimental work is very difficult, however, and in the meantime, with the present scarcity of more fundamental data, such statistical trends and correlations as can be obtained from commercial furnace operating records may help in choosing laboratory test conditions as well as adding to our knowledge of operating procedures. We do not know just why the furnace data are apparently so irregular that statistical treatment of large numbers is needed to obtain accurate trends. It is .partly caused, no doubt, by the many simultaneous variables present, but there are perhaps also such factors as: (I) the continual swings up and down so characteristic of the process; (2) difficulty of accurate sampling of co-existing phases, as well as (3) the presence of both equilibrium and rate factors as a result of the fast driving of the process, In desulphurization, for example, the flow of thin layers of slag and metal over solid coke surfaces, plus the contact between droplets of iron falling through the slag layer in the hearth, would lead one to expect a close approach to equilibrium, On the other hand, most of the critical part of sulphur removal may occur in a short time and distance below the tuyeres with perhaps an accompanying decrease in oxygen pressure and the concurrent reduction of much of the silicon and manganese, so its degree of approach to equilibrium may be quite variable. PROBABLE CHEMISTRY OF DESULPHURIZATION Since there is little evidence that sulphur atoms in the iron solution are associated to any appreciable extent in molecules such as MnS, the transfer from slag to metal and back again can be written:* [(FeS) -, [FeS],[I] hence the following reactions seem most probable in the slag phase, (FeS) + (CaO) = (CaS) + (FeO), [2] and, (FeS) + (MnO) ;:2 (MnS) + (FeO). [31]

Jan 1, 1948

By E. DeGolyer

(San Franciso Meeting, September, 1915) I. INTRODUCTION THE Furbero oil field lies in the Gulf coastal plain of Mexico between the important ports of Tampico and Vera Cruz and about one-third of the distance between the two points from the latter (Lat. 20° 22' N., 97° 30' W. Gren.). It is in the State of Vera Cruz, about 14 miles west by south of the village of Papantla in the canton of the same name, and is the most southern of the developed oil fields of the Tampico-Tuxpam region being a distance of 50 miles south by east from the Potrero del Llano field and 42 miles in the sane direction from the Alamo field. The field has been developed by the Oil Fields of Mexico Co. and is in the midst of a large block of lands owned or leased by then. Communication is through the port of Tuxpam with which it is connected by a narrow-gauge railway and 6-in. pipe line some 52 miles in length. This field is of more than ordinary interest since it represents a type of oil deposit hitherto unknown. So far as I am aware, no other commercially valuable deposit of oil is known to occur under conditions of accumulation similar to those found here. The igneous nature of the so-called `sand' encountered in drilling was not recognized until a number of wells had been drilled; and it was not until recently. that the geological relations of the sill or laccolith, which gives rise to the accumulation of oil, were known and the so-called `anticline' was known to be, in part at least, the result of igneous intrusion. Geological surveys in this general region were made in 1900-1901 by W. H. Dalton and in 1907-1909 by P. C. A. Stewart, F. W. Moon, Leonard V. Dalton, and Dr. Max Muhlberg. More recent surveys have been made, however; under the direction of the author, by E. L. Ickes, B. C. Belt, B. Hartley, and Harve Loon-us. Notes of the earlier examinations were not available with the exception of the report by Dr. Muhlberg who apparently first recognized the true nature of the Furbero intrusion. This paper is indebted to his work and that. of the more recent surveys for much of the detail regarding stratigraphy and to Messrs. Percy Furber and Arthur C. Payne, President and General manager of the Oil Fields of Mexico Co. for permission to publish, and for much of the in-

Jan 9, 1915

By Alexander Bowie

In many places throughout the Western mountain plateau regions of the United States coal beds in place have been burned over very extensive areas, the fire evidently originating on the nakedly exposed outcrop of the coal bed and gradually burning its way into the bed for considerable distances under very heavy cover. The surface evidences of the burned-out coal beds are seen in the calcined and discolored rocks overlying the places of the outcrops. The greater the mass of the burned coal the higher the results of its combustion can be seen in the overlying strata. I have noted many instances of this condition in the States of South Dakota, Wyoming, Colorado, New Mexipo, and Arizona. In the lignite fields of Dakota and Wyoming I noted stretches of level country many square miles in extent where the surface rooks were roasted and vitrified by the burning of a great bed of lignite lying nearly level and with a light cover; this is probably the most favorable natural condition for the burning out of a coal bed. The less the depth of the rock covering overlying the coal bed, the better the chance for a continuous supply of air to the fire; but when the coal bed dips heavily into the ground, or even if level, if it passes under a hill or mountain which gives the bed a heavy covering of strata, the fire has more chances of being extinguished from natural causes than in the first condition described. The distance which a crop fire may extend into a coal field is very much influenced by the dip, the thickness of the coal bed, and the nature of the rock covering immediately overlying it. In reasoning on this subject, it would seem logical to assume in the case of a coal-bed cropping at the base of a hill and dipping into it, with an extensive drainage surface above the crop line, that a crop fire would be promptly extinguished by the caving in of the overlying strata and the precipitation of the rainfall from the drainage surface above the outcrop through the breaks formed in the caving strata. This consideration would be more or less effective according to the climate of the location and the nature of the overlying strata. In a humid climate where the rainfall was heavy the water from the natural precipitation alone would probably extinguish a crop fire before it could work its way very far under cover, but in an arid climate this preventive does not seem to be effective.

Jan 1, 1915

By D. L. Martin, E. R. Parker

IN a previous paper, one of the authors observed that the rate of cooling from the anneal prior to testing greatly influenced the life of copper under sustained load at 200°C. Furnace-cooled bars of oxygen-free copper (with, and without silver) had a life four to twenty-five times that of the water-quenched specimens. The addition of 0.054 per cent silver to the oxygen-free copper increased the life at a stress of 20,000 lb. per sq. in. from about 2 hr. to 50 hr. Fractures in these bars were intercrystalline. An explanation was advanced to account for the profound influence of cooling rate on the rupture properties at 200°C. The suggestion offered was that at the high annealing temperature the minor constituents are distributed at random. By water quenching, this condition is maintained at room temperature, whereas furnace cooling permits some segregation at the grain boundaries. The higher concentration of the minor constituents in the grain boundaries results in a strengthening, so that a longer life at a given stress and temperature results. Small amounts of cadmium or manganese have also been found to increase the life of copper at 200°C., and to a much greater extent than silver .2 The increase in the long-time strength of copper resulting from small additions of cadmium or silver appears to be related, indirectly at least, to the higher softening temperatures of such alloys. The elements, such as silver or cadmium, which greatly increase the rupture life of copper also cause large increases in the softening temperature. As little as 0.05 per cent of cadmium or silver is sufficient to raise the softening temperature more than 100°.3,4 The effects of cooling rate and of minor constituents on the rupture properties are of considerable fundamental as well as practical interest; therefore a more detailed study of their nature was conducted and is reported in this paper. EXPERIMENTAL PROCEDURE Materials The materials studied in this investigation may conveniently be classified in two groups: one consisting of a wide variety of commercial coppers, and the other composed of special high-purity, laboratory-prepared coppers. The commercial materials were tested to determine whether or not the effect of cooling rate occurred with all coppers, whereas the high-purity coppers were investigated in order to establish a basis for evaluating the effect of minor constituents on the rupture properties. In Table I are given the analyses of the coppers tested. The samples I to 6 are commercial materials and were obtained for the most part from stock supplies.*

Jan 1, 1943

Engineering Experiment Station, University of Arkansas, Fayetteville, Ark. W N Gladson, Dean and Director The Engineering Experiment Station has published a number of bulletins, only a few of which are of particular interest in this directory: Bulletin 3, Arkansas coal or oil for domestic heating; 4, Road materials of Arkansas, 5, A study of Arkansas coals, 6, Portland cement materials in Arkansas; 11, Natural gas versus Arkansas coal for house heating. Circular 3, Short cuts to combustion efficiency with natural gas Address the Engineering Experiment Station for any of these publications.

Jan 1, 1933

By H. C. Verakis

This paper summarizes blasting accident data for over a quarter of a century (1978-2004) for all types of surface and underground mining operations in the United States. Although many billions of pounds of explosives and blasting agent have been used by the mining industry, the accident safety record has improved significantly in the past 25 years. Over the past decade, approximately 5 billion pounds of explosives and blasting agents were used annually in the United States. Coal mining has been and continues to be the dominant user of blasting agents.

Jan 1, 2006

By Freeman Bishop

Mercury is the latest ecological disaster. It was believed to be no pollution problem because it is heavier than water and expected to fall to the bottom of streams. But the Food and Drug Administration (FDA) found that mercury in a dozen states and several Canadian provinces was being ingested by fish. A Deadly Dose First to sound the alarm was Canada when a graduate student's research revealed that mercury contamination in Lake St. Clair had reached 1.4 pmm. which is almost three times the 0.5 ppm the FDA's allowable maximum.

Jan 1, 1970

By Brown D. N, Troth D. A

Large blast furnaces demand high standards of preparation of feed materials which must meet tight specifications of chemical and physical quality. Measurement of these factors must be expeditious but the nature of the coke, sinter, ores and fluxes and the large tonnages involved requires substantial mechanical sampling plant. The equipment, its operations, and its problems, associated with the 5000 t.p.d. No.5 blast furnace at Australian Iron and Steel Pty. Ltd., Port Kembla, are described and the efficacy of chemical blending achieved in the ore blending yards and sintering operation, is reported.

Jan 1, 1976

By J. P. Witherow

The blast-filmace plant of the Crozer Steel and Iron Company was built under contract by Witherow & Gordon, of Pittsburgh, Pa. The furnace is 70 feet high by 16 feet bosh, tunnel-head 12 feet 8 inches, and hearth 9 feet in diameter. The columns are 20 feet high above furnace level, below which they extend 2 feet. The shell is 23 feet diameter at bottom and 19 feet at top. The plate iron is 3/8 inch at bottom, and tapers to 1/4 inch, the top ring being 5/16 inch.

Jan 1, 1884

By T. D. Rourke, Fred H. Kulhawy, O&apos

From mid-1976 to early 1978, a 5.64 m diameter tunnel, 2491 m long, was excavated by a modified Robbins full-face TBM under shallow cover in highly stressed sedimentary rock in Rochester, NY. In-situ stress measurements were made, and tunnel behavior was monitored with MPBXs, inclinometers, tape extensometers, and instrumented steel ribs. Detailed geologic mapping was also done. In this paper, the as-monitored tunnel behavior is described, and the TBM performance is evaluated from field records. Recommendations are also made for future tunneling in similar geologic environments.

Jan 1, 1981

By Geno Saccomanno

INTRODUCTION Cancer of the lung in uranium miners has been reported by many authors. In fact, it has become a most popular subject for comment by environmentalists, health physicists, and newspaper writers. I believe it appropriate for me to discuss cancer of the lung in uranium miners in a general way commenting briefly on etiology, incidence, tumor cell types, and particularly, tumor development and treatment. Cytological development of cancer in its incipient stages, particularly the in situ stage, relates to potential cure with photoradiation, early diagnosis, and treatment. Our observations of the cytological response to this modality of diagnosis and treatment will be discussed briefly since this area will also be covered by Doctor Balchum. The cause of lung cancer in uranium miners is primarily due to two carcinogens; cigarette smoking and radon daughter radiation. Cigarette smoking has continued at the same intensity over time among uranium miners; about 60% of the miners are cigarette smokers and 40% are non-smokers. Radon daughter exposure to the uranium miner has varied from mine to mine, but over the last 20 years has been reduced to a minor fraction (.3 WL) of the level that prevailed in many of the mines during the 1950-1960 era when many of the miners were exposed to more than 10 WLM. Sputum samples have been examined on as many uranium miners as responded on the Colorado Plateau since 1956. Autopsy studies were done whenever this was permissible. In some instances, only tissue from a biopsy of a node or lung was available for study. Smoking histories were also taken. Approximately 200,000 sputum samples were examined and histological examinations of lung lesions were made from 312 cases. METHODS The method of sputum cytological collection and preparation was reported previously. I The lungs were fixed with formalin and prepared for sectioning by Dr. Oscar Auerbach with his block-section method. RESULTS Three-hundred-twelve lung cancers from uranium miners were examined. The tumor types and the age at death for each type, smokers and non-smokers, are given in Table #1. The incidence of the tumors in the smokers and non-smokers is given in Table #2. The incidence of small cell carcinoma of the lung has decreased from an incidence of 76% of all the lung cancers found in uranium miners to 22% of these lesions (Figure #1). The decrease in incidence of this tumor is probably due to decreased exposure to radiation in the mines.

Jan 1, 1981

By J. A. Finch

In this paper, the author offers a personal view of what the next 30 years holds for mineral processing. Restating that mineral processing will remain a vibrant industry in raw material production, growth opportunities in waste management are identified. The processing sequence familiar now (mining ?mineral processing ?extraction) will become more interwoven. In situ processing (i.e., milling underground) will evolve from concept to demonstration. Opportunities to exploit physical properties altered in chemical (pyro- and hydro-) processing will present themselves. In primary grinding, the path to AG/SAG milling will progress with little deviation but opportunities in regrinding are wide open. Flotation will see the trend to designing bubble/particle reactors accelerate simultaneously with a vigorous response from mechanical cell suppliers. Gravity separation remains a bastion of the lone inventor but this author anticipates that the new lines will come from the waste management business. The paper concludes with the examination of the “research cycle” and identification of growth in small “high tech” companies and university research centres

Jan 1, 1998

By John Randall

It is a fair assumption that the main purpose of any diagram is to present facts to the eye in more convenient form than they could be tabulated in figures, and this implies that a screen diagram should set forth in a convenient and familiar form certain facts as to the character of the material screened regardless of the screen standards used, and it seems particularly desirable on account of the well-known differences in the size of openings of different laboratory screens having the same nominal mesh. In making screen-sizing tests it has been customary first to consider the largest size, going progressively to the smallest, and this seems to have led to the practice of placing the smallest size .at the right-hand side of the diagram and measuring toward the left. This is not altogether convenient and might be changed to advantage, but for illustration I have preserved that feature and present the method just as I have used it for over 2 years. Direct plotting in which the intervals on the diagram are proportional to the sizes of the openings, or to the arithmetical difference between them, seems at first sight more natural and is extremely useful for certain purposes, but it makes the diagram very crowded in the smaller screen sizes while the larger ones occupy unnecessary space, making it less convenient for most purposes, and for that reason the method here discussed is the well-known one based on the ratio between openings, and is plotted in logarithms instead of the direct values of the screen opening. Metric coordinate paper is convenient, although not necessary; it is recommended, as the use of the metric scale gives a diagram of convenient size, but any scale of equal parts may be used. In order to make any screen diagram translatable in terms of any standard screen size, it is necessary to have noted on the size scale of the diagram all points corresponding to the openings of the various screens in question, instead of a single series of points as with a single screen. In drawing the diagram assume 0.001 in. (corresponding approximately to 0.025 mm.) to be the smallest size to be considered and fix this as the zero point at the lower right-hand corner of the diagram. This value is selected because the values are to be plotted in logarithms, and the logarithm of 1 is zero. Then lay off to the left for the position of each screen

Jan 1, 1918

By Karl L. Konnerth

THE rapidly increasing use of machinery for the mining of coal and operations incidental thereto has materially changed conditions from a safety standpoint. A few of the coal-producing states have recognized the need for specialized electrical equipment for use in mines and have introduced certain requirements in their State safety regulations, notably Pennsylvania. This paper discusses the principal problems involved in maintenance of such equipment. PERMISSIBLE: EQUIPMENT "Permissible" electrical equipment is equipment that has met certain prescribed standards for use in mines where hazardous conditions may occur and has been recommended by the U. S. Bureau of Mines. Such machinery is available on the market for most coal-mining operations--for instance, coal cutting, transportation, drilling, loading, working-place illumination, shot-firing and pumping. A notable exception is the trolley-reel gathering locomotive which, although its parts may be explosion-tested by the Bureau, has not been approved as permissible for the following reasons: I. The trailing cable is subjected to more severe service than on other equipment. 2. State regulations do not require that a working place be examined for methane before a locomotive enters it. 3. Even with two-conductor cable, imperfect or inadequate bonding may cause the emission of sparks at the wheels of the locomotive and at rail joints. 4. As the locomotive is equipped with a trolley pole, and as the trolley wire may be installed and used in unsafe territory in spite of rigid State regulations, a trolley-reel gathering locomotive is always a potential hazard. MAINTENANCE The proper procedure for maintenance of permissible equipment may be divided into three parts: (I) inspection, (2) actual maintenance and (3) changes or improvements to existing machines. To secure the fullest benefits through the use of permissible equipment it is necessary that all men involved understand the principles underlying the safety features of this equipment and realize the significance of defects, so that neglect and indifference in the maintenance thereof may be eliminated. Inspection From the standpoint of safety it is desirable no doubt to make a suitable inspection of permissible electrical equipment once a week, but the opening of every enclosed compartment at each inspection may do more harm than good. The openings to such compartments are closed with various types of covers very accurately machined, often made of the softer alloys to reduce weight, and fastened with a multitude of bolts, screws, washers, and other small parts. Frequent handling of these covers may cause sufficient damage to defeat their original purpose and intent.

Jan 1, 1941

By John Randall

IT is a fair assumption that the main purpose of any diagram is to present facts to the eye in more convenient form than they could be tabulated in figures, and this implies that a screen diagram should set forth in a convenient and familiar form certain facts as to the character of the material screened regardless. of the screen standards used, and it seems particularly desirable on account of the well-known differences in the size of openings of different laboratory screens having the same nominal mesh. In making screen-sizing tests it has been customary to first consider the largest size, going progressively to the smallest, and this seems to have led to the practice of placing the smallest size at the right-hand side of the diagram and .measuring toward the left. This is not altogether convenient and might he changed to advantage, but for illustration I have preserved that feature and present the method just as I have used it for over 2 years. Direct plotting in which the intervals on the diagram are proportional to the sizes of the openings, or to the arithmetical difference between them, seems at first sight more natural and is extremely useful for certain purposes, but it makes the diagram very crowded in the smaller screen sizes while the larger ones occupy unnecessary space, snaking it less convenient for most purposes, and for that reason the method here discussed is the well-known one based oil the ratio between openings, and is plotted in logarithms instead of the direct values of the screen opening. Metric coordinate paper is convenient, although .not necessary; it is recommended, as the use of the metric scale gives a diagram of convenient size, but any scale of equal. parts may be used. In order to make any screen diagram translatable in terms of any standard screen size, it is necessary to have rioted on the size scale of the diagram all points corresponding to the openings of the various screens in question, instead of a single series 'of points as with a single screen. In drawing the diagram assume 0.001 in. (corresponding approximately to 0.025 mm.) to be the smallest size to be considered and fix this as the zero point at the lower right-hand corner of the diagram. This value is selected because the values are to be plotted in logarithms, and the logarithm of 1 is zero. Then lay off to the left for the position of each screen

Jan 9, 1917