Search Documents

By R. E. Zimmerman, T. W. Guy

IN approaching the problems of sampling coal, a brief statement of certain facts that are more or less taken for granted may be helpful: 1. The coal-mine operator needs reliable data as to the physical and chemical characteristics of his coal in order to plan and control intelligently its mining, preparation, and marketing. The consumer needs such data in order to select the equipment and the coal best suited to meet his requirements, to check the quality of fuel delivered, and the efficiency of its use. Various government control agencies require such data as a basis for classifications and establishment of limits, for use in carrying out the requirements of federal, state or municipal laws. 2. All such data must be obtained by analyses, measurements, or tests made on samples, which are taken to represent the coal tested. It is now becoming generally recognized that, in accordance with statistical laws, test results from samples are not expected to represent the exact qualities of the lot or lots from which they are taken, except within statistical, or "expected" limits. Such limits are definitely specified by some present standards of the American Society for Testing Materials and the British Standards Institution. 3. Samples that give ash within satisfactory limits are usually assumed to be sufficiently accurate for other analyses, except under special conditions such as meeting close specifications for coals showing wide variability in sulphur, fusibility of ash, or other quality. 4. In modern coal sampling the increment is recognized as the basis for taking samples. For a given accuracy the number and weight of increments specified are increased with: (a) the expected ash, and (b) the top size designation of the lot to be sampled. 5. It is extremely important that every sampler recognize that: the specified number and weight of increments are minimums, and that the precautions to be used in order to take them properly are also minimums; that in the reduction of the gross sample the sizes specified for the coal after each stage of the crushing are maximum; that the quantities specified to be taken after each crushing stage are minimum; that any short cuts or failures to meet the requirements specified will reduce the statistical accuracy of the results, although it is possible that one or two checks on a few results may seem to show otherwise.

Jan 1, 1950

By K. R. Van Horn

RESIDUAL stresses in metals operate under a cloak of mystery, as they have neither been seen in the laboratory nor detected by means of the microscope. In spite of their phantom-like nature, they frequently exert metallurgical effects that cannot be ignored. In some cases the results have been detrimental, causing rejections or premature failures, but frequently the effects have been highly beneficial to the producer or consumer of metal products. First, however, what is a residual stress? When a metal is plastically deformed by bending, rolling, pressing, or by a phase transformation or precipitation from solid solution, or by a sharp temperature gradient resulting from nonuniform cooling, quenching, or welding, it remains in a state of strain. The strains or strain gradients produced by such operations and retained after all external forces are released are known as residual strains, and the accompanying stresses as internal or residual stresses. Many defects or failures in metal products have been ascribed to residual stresses, sometimes erroneously, because there was no other apparent explanation after the usual metallurgical tools of diagnosis had been applied. For example, during World War 11, the forged aluminum alloy aircraft cylinder head in the reciprocating engine began to replace the cast head with the familiar cooling fins. The fins were machined in the solid forged head by an ingenious milling operation. One plant reported an epidemic of excessive distortion during the delicate high-speed milling. A thorough examination revealed that the composition, heat treatment, mechanical properties, and metallurgical quality of these heads were comparable to those of forgings that machined satisfactorily. It was then claimed that the cause of the machining difficulties was connected with residual stresses resulting from the quenching during the solution heat treatment. An elaborate stress analysis actually demonstrated, however, that the magnitude of residual cooling stresses was lower in the cylinder heads which machined poorly than in those which were satisfactory in this respect. Subsequent tests proved that the machining problems in this case originated from variations in the tools and tool design. Sources of Residual Stresses in Metals Residual stresses are of two origins—mechanical and thermal. Thus, stresses may be produced in a metal by any cold-working process. The distribution and magnitude of these mechanically produced stresses can be calculated in a satisfactory, although approximate, manner for such simple cases as bending, torsion, and expanding of tubes. However, most manufacturing processes are too complex, and the original stress-strain relations in the products are not sufficiently known to permit calculation of the resulting residual stresses. Also, a specific process, such as wire drawing, may vary in complexity or uniformity of working, and large or small residual stresses may result, depending on the conformation of the dies and other features of the working process. Neither substantially unidirectional deformation, such as can be imparted by stretching a metal product having essentially the same mechanical properties throughout the cross section, nor deformation

Jan 1, 1954

By D. M. McFarland

A FEW years ago a novel electric detonator known as the split-second or millisecond delay electric blasting cap was introduced for use in quarry blasting. Regular electric blasting caps fired in series may be depended upon to fire within a millisecond or so from the first to the last in a series. Regular delay electric blasting caps are provided that fire one period after the other period in intervals of 1/2 to possibly 11/2 sec. Most split-second or millisecond delays are designed to fire one period after the other period in possibly 25 to 50 millisecond intervals. The ear is not capable of detecting time intervals of this magnitude. The primary thought at the time millisecond delays were introduced was to investigate the results on rock breakage by firing a line of holes in a quarry face so that charges in adjacent holes would not be detonated simultaneously. This could not be accomplished satisfactorily with regular delays. The time interval between successive periods of 1/2 to 1 sec was sufficient to permit considerable movement of the burden. If the burden of one hole was reduced to a great extent by the firing of an adjacent hole, the firing of the hole with the reduced burden would likely reveal this lack of confinement by a terrific report and wild throw of rock. In the early blasts with millisecond delays it was observed that instead of the usual sharp report, the blast had a muffled sound and vibration was not as perceptible as when simultaneous firing was used. Because many quarry operators were being threatened with injunctions or suits for damages by neighbors who claimed structural damage to their buildings, millisecond delays were tried extensively in quarries. In the majority of these trials, the results were very satisfactory. The seismologists recorded the ground movement created by many blasts and verified the initial observations that millisecond delays could be used to reduce vibrations appreciably. In the past few years the advantages of this principle of nonsimultaneous firing of the charges in blasts has become generally accepted. Today the quarry operator who has vibration troubles, inadequate breakage, and excessive backbreak and has not investigated the possibilities of millisecond delay blasting is ignoring a remedy that has proved satisfactory for many. His complacency may be costing him money. Because of the results attained in quarry blasting, it was logical that millisecond delays should be tried in construction work such as in road cuts. As formations in this type of work are likely to change rapidly with advance of the cut, it is more difficult to evaluate results than in quarry blasting. However, this improved control over timing has been beneficial in limiting throw, promoting fragmentation, and reducing overbreak. In blasting near buildings the reduction in vibration and in throw has been especially helpful. As blasters employed in construction work learn what may be accomplished by closer control over the time of firing of explosives charges, more and more millisecond delays are being used to supplant instantaneous electric blasting caps. Improved Fragmentation Underground With this background of promising results, it was not surprising that millisecond delays should go underground. In limestone mining use of millisecond delays as compared with use of cap and fuse or electric blasting caps showed improved fragmentation in stopes and in slabbing operations. Then an opportunity developed to use millisecond delays in some tunnels being driven in a limestone mine (fig. 1). Using the normal charge employed and merely substituting three millisecond delay periods for three regular delay periods, there was a noticeable difference in the appearance and the position of the pile of rock after a blast. A greater portion of the face was exposed, the crest of the pile was farther from the face, and the pile was heaped high along the center line of the tunnel leaving room to walk along the ribs to the face. Fragmentation was appreciably increased. It gave the impression that the slabs had been thrown against each other with tremendous force, promoting the movement of the broken rock along the center line of the tunnel away from the face. Because the drilling and the charge weights were unchanged, the evidence was convincing that the difference in timing was responsible for the difference in results. Probably a greater portion of the energy from the explosives had been expended in doing useful work on the rock. Zeros followed by two periods of millisecond delays were used in the V cut and in two slabs to either side of the cut in this simple round. When millisecond delays, substituted period for period for regular delays, are first tried in a drift round in a mine, and the usual charge of explosives

Jan 1, 1951

By D. M. McFarland

A FEW years ago a novel electric detonator known as the split-second or millisecond delay electric blasting cap was introduced for use in quarry blasting. Regular electric blasting caps fired in series may be depended upon to fire within a millisecond or so from the first to the last in a series. Regular delay electric blasting caps are provided that fire one period after the other period in intervals of 1/2 to possibly 11/2 sec. Most split-second or millisecond delays are designed to fire one period after the other period in possibly 25 to 50 millisecond intervals. The ear is not capable of detecting time intervals of this magnitude. The primary thought at the time millisecond delays were introduced was to investigate the results on rock breakage by firing a line of holes in a quarry face so that charges in adjacent holes would not be detonated simultaneously. This could not be accomplished satisfactorily with regular delays. The time interval between successive periods of 1/2 to 1 sec was sufficient to permit considerable movement of the burden. If the burden of one hole was reduced to a great extent by the firing of an adjacent hole, the firing of the hole with the reduced burden would likely reveal this lack of confinement by a terrific report and wild throw of rock. In the early blasts with millisecond delays it was observed that instead of the usual sharp report, the blast had a muffled sound and vibration was not as perceptible as when simultaneous firing was used. Because many quarry operators were being threatened with injunctions or suits for damages by neighbors who claimed structural damage to their buildings, millisecond delays were tried extensively in quarries. In the majority of these trials, the results were very satisfactory. The seismologists recorded the ground movement created by many blasts and verified the initial observations that millisecond delays could be used to reduce vibrations appreciably. In the past few years the advantages of this principle of nonsimultaneous firing of the charges in blasts has become generally accepted. Today the quarry operator who has vibration troubles, inadequate breakage, and excessive backbreak and has not investigated the possibilities of millisecond delay blasting is ignoring a remedy that has proved satisfactory for many. His complacency may be costing him money. Because of the results attained in quarry blasting, it was logical that millisecond delays should be tried in construction work such as in road cuts. As formations in this type of work are likely to change rapidly with advance of the cut, it is more difficult to evaluate results than in quarry blasting. However, this improved control over timing has been beneficial in limiting throw, promoting fragmentation, and reducing overbreak. In blasting near buildings the reduction in vibration and in throw has been especially helpful. As blasters employed in construction work learn what may be accomplished by closer control over the time of firing of explosives charges, more and more millisecond delays are being used to supplant instantaneous electric blasting caps. Improved Fragmentation Underground With this background of promising results, it was not surprising that millisecond delays should go underground. In limestone mining use of millisecond delays as compared with use of cap and fuse or electric blasting caps showed improved fragmentation in stopes and in slabbing operations. Then an opportunity developed to use millisecond delays in some tunnels being driven in a limestone mine (fig. 1). Using the normal charge employed and merely substituting three millisecond delay periods for three regular delay periods, there was a noticeable difference in the appearance and the position of the pile of rock after a blast. A greater portion of the face was exposed, the crest of the pile was farther from the face, and the pile was heaped high along the center line of the tunnel leaving room to walk along the ribs to the face. Fragmentation was appreciably increased. It gave the impression that the slabs had been thrown against each other with tremendous force, promoting the movement of the broken rock along the center line of the tunnel away from the face. Because the drilling and the charge weights were unchanged, the evidence was convincing that the difference in timing was responsible for the difference in results. Probably a greater portion of the energy from the explosives had been expended in doing useful work on the rock. Zeros followed by two periods of millisecond delays were used in the V cut and in two slabs to either side of the cut in this simple round. When millisecond delays, substituted period for period for regular delays, are first tried in a drift round in a mine, and the usual charge of explosives

Jan 1, 1951

By C. W. Greenhalgh

THE accuracy with which grade and tonnage of a mineral deposit may be calculated from diamond-drill assays is dependent upon: (I) the reliability of core and sludge samples and (2) the validity of methods used in grade and tonnage calculations. Limitations imposed by drilling and sampling preclude elaborate methods of computation. In adjusting core and sludge assays the importance assigned the core and sludge samples may be based on either the respective weights recovered or the respective volumes represented by each. Only when core and sludge recoveries are poor do discrepancies between adjusted assays calculated by these two methods develop, in which case the "weight" method gives emphasis to the core sample and the "volume" method gives emphasis to the sludge sample. When the sludge suffers classification within the drill hole, the weight method gives more accurate results; when the sludge sample suffers no classification, the volume method gives more accurate results. Any drilling campaign offers a compromise between desired accuracy on the one hand and expediency, limited time, money, or facilities on the other. Since the determination of grade and tonnage is an approximation at best, a proper basis for their computation requires a knowledge of the limitations imposed by all phases of work upon which the calculations depend. A rational basis for coordination of these phases of work requires determination of: (I) the degree of accuracy desired, as a function of the object of examination; (2) the degree of accuracy attainable, as a function of the limitations imposed in the drilling and sampling program; and (3) the validity of method to be used in calculating grade and tonnage from core and sludge assays. This paper presents results of a comparison made between two commonly used methods of adjusting core and sludge assays, the assumptions upon which these methods are based, and the interrelationship of the phases of work upon which these calculations are dependent. OBJECT OF EXAMINATION The purpose of prospecting any mineral deposit is to secure sufficient samples from which ore grade and tonnage may be calculated. Any mine examination, preliminary or formal, has a definite purpose, although its scope may be limited or broad. The type of examination to be conducted is dependent, therefore, upon the reason for instituting the investigation; its scope and thoroughness are directly related to economic considerations. It is highly desirable, therefore, that before starting a drilling campaign a complete understanding of the extent of examination and desired degree of accuracy be determined as a means of simplifying the drilling program and unifying the relative degree of

Jan 1, 1946

By R. L. Fleischer, R. S. Davis

BICRYSTAL specimens grown from the melt have been used extensively for investigations of the influence of grain boundaries on plastic deformation. The bicrystals are usually of predetermined orientation prepared by seeded growth from the melt in milled graphite boats. This technique has been described in detail by Chalmers.' Since the direction that the grain boundary follows during growth is affected by both thermal conditions and crystallography, a difficulty arises in maintaining the grain boundary position constant along the length of the specimen. This problem is particularly

Jan 1, 1960

By Amitava Gangulee, Michael B. Bever

The order-disorder transition in Ag-Mg alloys in the range 17 to 26 at. pct Mg was investigated and some thermodynamic, electrical and mechanical properties of ordered Ag-Mg alloys were measured. A modification of the phase diagram is proposed on the basis of measured transition temperatures. The stability of the ordered structure is analyzed in terms of the quasichemical theory. Kinetic aspects of the order-disorder transition were also investigated. The energies of ordering at 273°K of Ag-Mg alloys were measured by liquid metal solution calorimetry. The electrical resistivities and the tensile Properties of the ordered alloys were measured. The exothermic energy of ordering increased with magnesium concentration up to the composition Ag3Mg; it is discussed in terms of the quasichemical theory. Pronounced order hardening was observed and can be explained by several strengthening mechanisms, which are particularly effective because of a change in crystal structure associated with the ordering transition. IN silver-rich solid solutions containing approximately 17 to 26 at. pct Mg, long- range ordering may occur during appropriate therma1 treatments. Clare-brough and Nicholas1 first detected such long-range order in the solid solution of composition Ag3Mg and suggested that the unit cell of the superlattice contained 256 atoms. x-ray2 and electron diffraction3 investigations confirmed the occurrence of long-range order, but indicated a shifted Ll2-type structure. On the basis of recent X-ray measurements the crystal structure of ordered Ag3Mg has been confirmed as type D023.4 The present paper is concerned with the order-disorder transition in silver-rich Ag-Mg solid solutions and some thermodynamic, electrical, and mechanical properties of the ordered alloys. The effects of short-range order on the properties of silver-rich solid solutions containing up to 26 at. pct Mg are discussed in a concurrent paper.5 1) EXPERIMENTAL PROCEDURES 1.1) Preparation of Specimens. Specimens of Ag-Mg alloys containing from 18 to 26 at. pct Mg were prepared in the form of 1.0-mm-diam wires as described in Section 1.1 of Ref. 5. Disordered specimens were prepared by annealing at 773°K for 1 hr and quenching into iced brine. Ordered specimens were prepared by annealing at 773°K for 1 hr and slowly cooling to room temperature over a period of 15 days. The specimens were stored at 78°K. 1.2) Resistivity Measurements. Electrical resistivi- ties were measured by a potentiometric method.' Equilibrium values were obtained at several temperatures. The kinetics of ordering were investigated by following the time-dependent changes of the resistivity of initially disordered specimens during annealing. The specimens were enclosed in copper capsules and immersed in salt pots; the heating up was accelerated by injecting preheated helium into the capsules. 1.3) Calorimetry. The energies of ordering of the alloys were measured in a tin solution calorimeter as the difference between the heat effects of additions of completely ordered and disordered specimens of the same composition. The procedure and the method of calculation have been described.6 Magnesium was used for thermal compensation in most calorimetric runs in order to improve the accuracy.677 1.4) Mechanical Tests. Tensile tests were carried out with wire specimens at room temperature as described in Section 1.5 of Ref. 5. Microhardness measurements were also made.? 2) RESULTS AND DISCUSSION The characteristics of the order-disorder transition of silver-rich Ag-Mg solid solutions will be discussed first. Some thermodynamic, electrical, and mechanical properties of the ordered alloys will then be considered and compared with the corresponding properties of dis-disordered alloys. 2.1) The Order-Disorder Transition. 2.1.1) Thermodynamic and Structural Aspects. The transition temperatures Tt were determined from discontinuities in the slope of the equilibrium resistivity vs temperature curves. Normalized curves for three compositions are shown in Fig. 1. The transition temperature increases with the magnesium concentration and reaches a maximum at the stoichiometric composition Ag3Mg. The transition temperature of the alloy Ag3Mg was measured as 665° ± 2°K and compares with published values of 660°,1 663°,8 and 66°k.3 In the slopes of the resistivity vs temperature curves of alloys containing 22.2 and 22.5 at. pct Mg, discontinuities were observed at two temperatures. Such upper and lower discontinuities indicate a two-phase field. A modified form of the published phase diagram9 is shown in Fig. 2. A two-phase field was found only on the low-magnesium side of the composition Ag3Mg. On the high-magnesium side, the existence of a two-phase field could not be established because of insufficient resolution, but such a field must be present. This part of the phase diagram can be made complete by a eutec-toid-type reaction a = (a' + ß). The existence of a boundary between the two-phase fields (a + ß) and (a' + ß) is also in accord with published lattice parameters.3 The crystal structure of ordered Ag3Mg (type Do23)

Jan 1, 1969

By R. Clare Coffin

The production of oil in the Rocky Mountain district, including southeastern New Mexico, increased from 33,048,630 bbl. in 1930 to 34,325,163 bbl. in 1931. This increase was due to production in New Mexico, which exceeded the 1930 figure by approximately 5,000,000 barrels. Total production by fields is given in Table 1. Exploration during 1931 resulted in the discovery of a new oil-producing horizon in the Big Muddy field in Natrona County, Wyoming, and ' the discovery of a new gas pool in the Powder Wash structure, Moffat County, northwestern Colorado. Gas was discovered also in the Frontier sands of the Bunker Hill dome, Carbon County, Wyoming, but no test has yet been made by which to determine the significance of this discovery. All other exploration which resulted in increasing the known reserves of oil and gas in the district was confined to drilling in partly outlined fields where known limits of production were extended. During the year two major gas pipe lines were completed in western Montana, and one in southwestern New Mexico was extended into Arizona. One new project involving the marketing of natural gas from Wyoming fields included the conversion of an existing oil line to a gas line to serve towns in southeastern Wyoming and western Nebraska. Colorado The decline of 132,501 bbl. in the production of oil in the Colorado fields during 1931 from the figure of 1930 is due to the natural decline of existing wells, partly offset by the increased production in the Greasewood area. New exploration was limited largely to northeastern Colorado, where attempts were made to find oil in areas adjacent to the Grease-wood field. Powder Wash, Moffat County.—The Ohio Oil Co. is to be credited with the discovery of a gas field in the Power Wash structure in Moffat County, Colorado. The initial well drilled in sec. 5-11-97 encountered a sand at a depth of 2152 ft. which produced 34,188,000 cu. ft. of gas on an open-flow test. The rock pressure was reported as 630 Ib.

Jan 1, 1932

By J. Gurland, A. Gangulee

The cracking of silicon particles embedded in an aluminum matrix occurs progressively over the range of plastic deformation of the composite specimen. The fracture probability of the particles increases with increasing particle size and decreasing silicon contents. The crack orientation tends to be perpendiculay to the direction of the maximum tellsile strain. An example of a direct association between matrix slip and particle cracking is shorn. ALUMINUM-SILICON alloys of commercial compositions fail by ductile fracture in three stages:' I) initiation of cracks in the silicon particles, 2) growth of cracks into cavities, and 3) rupture of the aluminum matrix separating the cavities. The present work is concerned with the first stage: the initiation of cracks in the silicon particles. EXPERIMENTAL PROCEDURE Aluminum samples with 2.8, 6.1, 9.6, and 13.2 vol pet Si, respectively, were cast from commercial al- loys. Machined tensile specimens (2 in. gage length) were annealed in air at 1000°F for 100 hr, and then pulled at a strain rate of 0.025 per min. The grain size (average linear intercept) of the aluminum matrix was 0.24 and 1.6 mm in the 6.1 and 13.2 pet Si alloys, respectively. The particle size of silicon in alloys of one composition (6.1 pet Si) was varied by either modifying the castings with 0.15 pet Na or prolonging the annealing time. The average particle size was measured by linear and planar analysis, assuming spherical particles of uniform size. The particle sizes and compositions of all samples are tabulated in Fig. 8, together with the identifying symbols used in the graphs. The respective numbers of broken and unbroken silicon particles were determined from metallographically prepared longitudinal sections by counting a total of approximately 2000 particles per sample. EXPERIMENTAL RESULTS 1) Crack Initiation During Deformation as Function of Composition. Nominal stress-strain curves of four specimens of different compositions, but approximately equal particle sizes, are presented in Fig. 1. The fraction of broken particles, P (no. of broken particles/ total no. of particles), is shown in Fig. 2 as function of true stress and in Fig. 3 as function of nominal strain. The last point of each composition line in Fig. 2 rep-

Jan 1, 1968

By Edward H. Robie

OF the current Adirondack iron mine development, the Benson Mines operation of the Tones and Laughlin Ore Co. (Jones & Laughlin Steel Corp. wholly owned subsidiary) is the last to go into operation. Following an active construction program in 1943, the mine. concentrator and sintering plant were scheduled to enter production in the fall. This description therefore cannot include any operating data, and details of equipment and flowsheet have not as yet been released.

Jan 1, 1943

By W. J. Sharwood

In the cyanide process, gold and silver are dissolved from crushed ore as double alkali-metal cyanides, from which they may be precipitated by such positive metals as sodium (amalgam), aluminum, or zinc, or by electrolysis. Two extreme conditions may be noted. Some works, especially slime plants practising decantation, use a relatively large volume of solution—possibly 4 or 5 tons per ton of ore—nearly all of which may require precipitation, so that the solutions handled are of much lower value per ton than the ore. On the other hand, in some leaching plants it is possible to extract with very little solution, and to percolate some of this more than once through the charge before precipitation, so that the solution to be precipitated may be much less than half the weight of ore, and proportionally richer. Solution intended for further use need not have all its precious metal removed, but any that has to be thrown away should be impoverished as far as is economically possible. In spite of certain advantages possessed by other precipitants, zinc in some form has been almost universally used.. In some of the first attempts to utilize cyanides as gold solvents, a "piece or plate of zinc" was suggested as a precipitant, but extension of surface was early recognized as a desideratum. . Macarthur and the Forrests adopted a "metallurgical filter" of zinc shaving, turned from disks or rolled sheets. They had previously experimented on other forms of zinc, ax! Mscarthur records having tried zinc dust, which had of course been long known as a general reducing agent. It had also been known and used as a precipitant of precious metal from plating and photographic solutions, and comminuted zinc had been patented for recovering copper, etc., from ore leaches. Other inventors proposed the virtual making of zinc powder by the attrition of balls of zinc, and by similar means, during the passage of a stream of gold-bearing solution. Sulman claimed the use of zinc dust, or fume, in a special apparatus, effecting a more or less regular feed of dust and solution by means of intermittent siphons; the mixture or "emulsion" (as it is still called) rising with diminishing velocity through an inverted cone in which it

Jan 1, 1918

By C. W. Green-Halgh

The accuracy with which grade and tonnage of a mineral deposit may be calculated from diamond-drill assays is dependent upon: (1) the reliability of core and sludge samples and (2) the validity of methods used in grade and tonnage calculations. Limitations imposed by drilling and sampling preclude elaborate methods of computation. In adjusting core and sludge assays the importance assigned the core and sludge samples may be based on either the respective weights recovered or the respective volumes represented by each. Only when core and sludge recoveries arc poor do discrepancies between adjusted assays calculated by these two methods develop, in which case the "weight" method gives emphasis to the core sample and the "volume" method gives emphasis to the sludge sample. When the sludge suffers classification within the drill hole, the weight method gives more accurate results; when the sludge sample suffers no classification, the volume method gives more accurate results. Any drilling campaign offers a compromise between desired accuracy on the one hand and expediency, limited time, money. or facilities on the other. Since the determination of grade and tonnage is an approximation at best, a proper basis for their computation requires a knowledge of the limitations imposed by all phases of work upon which the calculations depend A rational basis for coordination of these phases of work requires determination of: (I) the degree of accuracy desired, as a function of the object of examination; (2) the degree of accuracy attainable, as a function of the limitations imposed in the drilling and sampling program; and (3) the validity of method to be used in calculating grade and tonnage from core and sludge assays. This paper presents results of a comparison made between two commonly used methods of adjusting core and sludge assays, the assumptions upon which these methods are based, and the interrelationship of the phases of work upon which these calculations are dependent. Object of Examination The Purpose of prospecting any mineral deposit is to secure sufficient samples from which Ore grade and tonnage may be calculated. Any mine examination, preliminary or formal, has a definite purpose, although its scope may be limited or broad. The type of examination to be conducted is dependent, therefore, 'pan the reason for instituting the investigation; its scope and thoroughness are directly related to economic considerations. It is highly desirable, therefore, that before starting a drilling campaign a complete understanding of the extent of examination and desired degree of accuracy be determined as a means of simplifying the drilling program and unifying the relative degree of

Jan 1, 1946

By T. B. Counselman

An iron blast furnace of 1000 tons daily capacity will produce a 100,000 cu. ft. per minute of blast-furnace gas. This contains a 25 per cent of carbon monoxide, and has a B.t.u. value of about 95. gas is used primarily for heating the stoves of the blast furnace, secondarily, under boilers, for steam production. Occasionally it is used in gas engines. The raw gas coming out of the furnace carries about 10 grains of dust per cubic foot of gas, under best operating conditions. With furnace "rolling" or slipping, this quantity may temporarily be gre increased. This dust would, of course, deposit on the checkers o: stoves, or plug the burners under the boilers; therefore the gas : be cleaned. Flow Sheet The first step in the cleaning operation, as shown by the flow s Fig. 1, is a dry dust catcher, of which there are several forms, partially cleaned gas next goes to a primary wet washer, where v sprays knock down most of the solid particles. If further cleani desired, the gas may then go to electrical precipitation. Again, the removed is collected in water. Dry dust catchers reduce the dust col from 10 grains to between 4 and 6 grains per cubic foot, and rec roughly half of the total flue dust in the gas. The wet washers rea most of the remaining dust, reducing the dust content to about 1/4 per cubic foot. Electrical precipitators, if used, further reduce the content to about 0.01 grain per cubic foot of gas. The flow sheet s the dust content of the gas at various steps in the treatment and als content of solids in the water. It should be noted that some plant less water on the primary wet washer than indicated, and that ofte solids content of the scrubber water will be 300 grains per gallon, or much higher. Reasons for Recovering Flue Dust.—There are two main incentive recovering flue dust from the scrubber water: (1) the value of the (2) stream or lake pollution, where such a reason applies.

Jan 1, 1937

By T. W. Guy

IN approaching the problems of sampling coal, a brief statement of certain facts that are more or less taken for granted may be helpful: 1. The coal-mine operator needs reliable data as to the physical and chemical characteristics of his coal in order to plan and control intelligently its mining, preparation, and marketing. The consumer needs such data in order to select the equipment and the coal best suited to meet his requirements, to check the quality of fuel delivered, and the efficiency of its use. Various government control agencies require such data as a basis for classifications and establishment of limits, for use in carrying out the requirements of federal, state or municipal laws. 91. All such data must be obtained by analyses, measurements, or tests made on samples, which are taken to represent the coal tested. It is now becoming generally recognized that, in accordance with statistical laws, test results from samples are not expected to represent the exact qualities of the lot or lots from which they are taken, except within statistical, or "expected limits. Such limits are definitely specified by some present standards of the American Society for Testing Materials and the British Standards Institution. 3. Samples that give ash within satisfactory limits are usually assumed to be sufficiently accurate for other analyses, except under special condi¬tions such as meeting close specifications for coals showing wide variability in sulphur, fusibility of ash, or other quality. 4. In modern coal sampling the increment is recognized as the basis for taking samples. For a given accuracy the number and weight of increments specified are increased with: (a) the expected ash, and (b) the top size designation of the lot to be sampled. 5. It is extremely important that every sampler recognize that: the specified number and weight of increments are minimums, and that the precautions to be used in order to take them properly are also minimums; that in the reduction of the gross sample the sizes specified for the coal after each stage of the crushing are maximum; that the quantities specified to be taken after each crushing stage are minimum; that any short cuts or failures to meet the requirements specified will reduce the statistical accuracy of the results, although it is possible that one or two checks on a few results may seem to show otherwise.

Jan 1, 1943

By C. C. Singleterry, D. L. Katz

The critical phenomena have been studied during the past century but our knowledge of the critical temperatures and pressures of complex hydrocarbon mixtures still is very limited. The critical temperatures and pressures of pure substances have been examined in large numbers120 and in great detail.11.17 No experimental determinations of the critical phenomena have been reported on such complex hydrocarbon systems as a reservoir fluid. The critical temperature is defined by Taylor18 as follows: "there is some temperature for each gas above which the gas cannot be liquefied. This temperature is called the critical temperature." The critical pressure of a pure substance is the vapor pressure at the critical temperature. It should be noted that these definitions refer to a given substance in the pure state and do not mean that the pure substance cannot be liquefied in the presence of a second constituent. The normal procedure for obtaining the critical temperature of a substance is to heat it in a glass tube 1,20 under pressure until the meniscus between the liquid and vapor phase disappears, although other methods, especially for mixtures, have been used.13,14 However, when considering oil and gas reservoirs, it is more enlightening to consider a critical phenomenon that occurs when a mixture of oil and gas are compressed at a reservoir temperature until the meniscus disappears because the two phases become equal in composition. This conception, along with erroneous applications of the definition of the critical phenomena of a pure substance to that pure substance when it is part of a complex mixture, has caused confusion even among persons familiar with the classical theories. The purpose of this paper is to discuss the critical phenomena of pure substances and mixtures and to report experimental data on a mixture of

Jan 1, 1939

By C. C. Singleterry, D. L. Katz

The critical phenomena have been studied during the past century but our knowledge of the critical temperatures and pressures of complex hydrocarbon mixtures still is very limited. The critical temperatures and pressures of pure substances have been examined in large numbers120 and in great detail.11.17 No experimental determinations of the critical phenomena have been reported on such complex hydrocarbon systems as a reservoir fluid. The critical temperature is defined by Taylor18 as follows: "there is some temperature for each gas above which the gas cannot be liquefied. This temperature is called the critical temperature." The critical pressure of a pure substance is the vapor pressure at the critical temperature. It should be noted that these definitions refer to a given substance in the pure state and do not mean that the pure substance cannot be liquefied in the presence of a second constituent. The normal procedure for obtaining the critical temperature of a substance is to heat it in a glass tube 1,20 under pressure until the meniscus between the liquid and vapor phase disappears, although other methods, especially for mixtures, have been used.13,14 However, when considering oil and gas reservoirs, it is more enlightening to consider a critical phenomenon that occurs when a mixture of oil and gas are compressed at a reservoir temperature until the meniscus disappears because the two phases become equal in composition. This conception, along with erroneous applications of the definition of the critical phenomena of a pure substance to that pure substance when it is part of a complex mixture, has caused confusion even among persons familiar with the classical theories. The purpose of this paper is to discuss the critical phenomena of pure substances and mixtures and to report experimental data on a mixture of

Jan 1, 1939

THE decision of the lower court (United States District Court for the Southern District of New York) in the suit of the Dwight & Lloyd Sintering Co., vs. John E. Greenawalt has been affirmed by the United States Circuit Court of Appeals for the Second Circuit. In the original suit, infringement of seven patents was alleged, these covering the process of producing a sinter .out of finely pulverized metalliferous ores as practised in shallow pans operating intermittently in distinction to the Dwight 6: Lloyd continuous machine. The court found that the long delay in bringing suit precluded any recovery of profits from the defendant under the basic down-draft sintering patent, although Dwight & Lloyd are recognized as the inventors of this' contribution to the art and its .importance is acknowledged.

Jan 1, 1928

"The Butte, Anaconda & Pacific railway extends from Butte to Anaconda. The electrification comprises 30 miles of main line single track, and includes sidings, yard and smelter tracks. When complete the electrified trackage will total about 90 miles on a single track basis.The traffic conditions are unusually severe as they consist principally of hauling copper ore from the Butte mines to the smelters at Anaconda, as well as hauling all the mine supplies, lumber, etc., in both directions; this traffic amounts to approximately 5,000,000 tons of freight per year. The maximum grade against the load is .3 per cent and the maximum train consists of 50 loaded steel ore cars, weighing 3,400 tons. .The locomotive units, two of which will be used for freight trains, weigh approximately 80 tons each. In addition to the freight business, there will be a certain amount of passenger traffic.The power for operating the Butte, Anaconda & Pacific railway is generated by, the Great Falls Power company, and is transmitted to the sub-stations at 100,000 volts. The synchronous motors are supplied with power at a potential of 2,300 volts, 60 cycles, 3-phase. Voltage regulators are installed in each sub¬station to secure the benefit of synchronous condenser effect of the motors.The passenger and freight locomotives are exactly similar, with the exception of the gearing.The roller pantograph mounted on the top of the cab is operated by air from the engineers position.The adoption of the 2,400-volt apparatus for so important a system, where the conditions of operation are so severe, is interesting of itself, as indicating the trend that future electrifications of importance may follow. A trolley potential of 2,400 volts was only adopted after a thorough investigation of other systems already in operation."

Jan 1, 1913

By J. M. Lommel, B. Chalmers

The transfer of material from the solid to the liquid states can be accomplished in several ways. It occurs by the application of heat in the more familiar metallurgical operations of melting but it can also be accomplished by solution in a liquid, as can occur in systems using liquid metals for heat-transfer media. The kinetics of this reaction were studied to learn more of the separate steps in the process. In the case of a pure material at its melting temperature, Te,A,, thermal energy must be supplied to the solid in an amount equal to the latent heat of fusion in order for the solid-to-liquid transfer to occur. The rate at which heat is supplied, and hence the rate of melting, is a function of the temperature gradients in the system. This phase transfer can also occur in the absence of temperature gradients in the system illustrated in Fig. 1, which is a partial phase diagram between the components A and B. A solid of composition CI will

Jan 1, 1960

By W. E. Gaby

THE form of dip chart here presented for the use of the profession was devised by the author when he was confronted with a particularly heavy job of geological section making and. did not have any of the usual tables or charts at hand. This was at the property of the Teziutlan Copper Co. in Puebla, Mexico, where the orebodies are much faulted and lie conformably with a slightly inclined and. much folded schist. Because of the low dip and the folding of the orebodies, the engineering, and geological data respecting them were best represented on vertical cross-sections quite closely spaced. A less finished form of the chart was published in the Mining & Scientific Press of Aug. 6, 1921, with an explanation of its use. I have checked the new drawing for accuracy against the calculated table given, and constructed an explanatory diagram beneath. As some geologists are accustomed to using the table, I have included it, since no advantage is obtained by mere interpolations from the chart to get the required angle, except as it gives a mental picture of this angle. The chart gives a more rapid and much easier solution when cases multiply so that it becomes desirable to eliminate the tedious manipulations of a separate protractor. In fact, using the parallel ruler as des-cribed, it is not even necessary to make note of the angle sought. It is brought out graphically, leaving the mind free to note the correlations. The chart itself may be made more convenient by reproduction on celluloid with a slot running on the zero line of the protractor.

Jan 9, 1922