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By Harold M. Mooney

RESISTIVITY measurements for determining depth to bedrock, water table, and other geo- logic discontinuities have had only limited success. Many of the difficulties can be attributed to complex geology and to basic limitations of the method; current flow through a continuous medium is a diffusion phenomenon, emphasizing irregularities near the source and smoothing out those at a distance. Some of the failures, however, are due to careless field work and incompetent interpretation. A forthcoming publication1 may help to reduce difficulties of this sort. The writer here attempts to bring order into the multiplicity of interpretation methods and, to a limited extent, to evaluate them. For all methods, the field data to be interpreted consist of apparent resistivity values plotted against electrode separation, Fig. 1. The interpretation should give depths to one or more geologic horizons. Direct currents and the Werner four-electrode configuration will be assumed, since these are widely used, although the interpretation problems remain essentially the same for other electrode configurations. Alternating currents higher than, say, 20 cycles per second introduce complications beyond the scope of this paper.

Jan 9, 1954

By H. Herman, C. Chiou, M. E. Fine

From variation in Young's modulus and Vicker's hardness during GPl zone formation in A1-2 at. pct Cu the following was observed: 1) the presence of grain boundaries does not have any perceptible? effect on the aging reaction; 2) the modulus charge is orientation dependent; 3) the activation energy for zone growth is confirmed to be 11 * 1 kcal per mole; 4) reaging after reversion is preceded by an incubation time that varies with temperature. An analysis is applied to the present data and to data of other workers and kinetic laws dependent on the quenching rate are determined. In Al-base Cu alloys the decomposition product of a supersaturated solid solution at low temperatures (for example 25°C) and the first product at moderate temperatures (for example 150oC) are Guinier-Preston zones of the first kind (GPI).' These zones are nonideal and are thought Jo 'Onsist roughly of sheets of Cu atoms up to 150A in diam and one or two atoms thick.' The kinetics of the reaction, ass — a2

Jan 1, 1961

By T. Nakao

Fujiwara quarry had been operated by the glory-hole benchcut mining system, but as it became difficult to meet expanding demand with this system, a central-shaft mobile crushing plant (MCP) system was introduced in 1979. This MCP is equipped with a hydraulic walking system manufactured for the first time in Japan. Central-shaft mining is now the common mining method of Japanese limestone quarries. With this method, crushing facilities are usually installed at the bottom of the shaft. But at the Fujiwara quarry, MCP was adopted and installed on the quarry surface. Many MCPs are operated in foreign countries, but few examples exist in Japan. Normally, Japanese limestone deposits lie in high mountain, obviously making it inconvenient for MCPs to walk in and around the quarry. This difficulty, however, was overcome, and the MCP has operated satisfactorily and efficiently for two years since its installation. To overcome difficulties in the central-shaft MCP mining system, two mining methods are employed: the slice-down method and the block-cut method.

Jan 1, 1985

By Harry C. Swanson

TRANSPORTING concrete from mixer to forms has always been a problem. Twenty-five years ago this task was generally accomplished by means of wheelbarrow or concrete buggy. On large dam jobs, as the number of these projects increased, the gantry crane or highline came into use. Today several methods of handling concrete are employed on smaller surface construction jobs, for example, transit-mix trucks or dumpcrete trucks, which have crawler cranes with buckets for placing concrete into forms. In 1944, during early stages of developing Mather mine A shaft, several large underground concrete jobs were necessary. At this time the Cleveland-Cliffs Iron Co. purchased the first pumpcrete machine, introduced by the Chain Belt Co. of Milwaukee. The machine was used to pour approximately 200 cu yd of concrete for a dam, or bulkhead, located 400 ft from the shaft. Concrete was mixed on surface, lowered down the shaft 1000 ft in a 2-cu yd bucket hung under one skip, spouted into the bowl of the pumpcrete machine from the bucket, and pumped directly into the forms.

Jan 4, 1954

By John J. Croston

IN the closing months of 1936 the copper industry gave every evidence that it was at last on the threshold of an improved era. At the beginning of the year prices stood at 9 ¼ ¢, which in itself was a great improvement over prices prevailing for the three previous years. Industry generally was showing signs of moving forward in this country, and business was definitely good in certain foreign quarters. The threat of war and preparations for rearmament in Europe and Asia acted as a further stimulus to purchasing. By midsummer the situation had so improved and stocks had been so reduced that the cartel of foreign producers (including American producers with foreign mines) decided to increase the production quota to 75 per cent on Aug. 1. Large-scale buying gave continued strength to the price and by Oct. 1 the quota was increased to 80 per cent, and again on Oct. 15, to 85 per cent. Notwithstanding this the price of copper continued its advance and on Nov. 1, with stocks declining continuously, the cartel increased operations to 95 per cent, then to 105 per cent on Nov. 5. In the meantime the domestic producers, because of the great increase in home consumption, had increased their production by nearly one-half. At the close of the year copper sold at 12¢ per pound, and since the turn of the present year has reached 17¢. This rapid increase has not been wholly justified. Much of the increase was due to the legitimate demands of recovering industry, but rearmament orders plus accumulation of reserve stocks in case of war, purchases in anticipation of labor strikes and purely speculative activities on the London Metal Exchange accounted for the balance. Certainly in view of the state of industry and the general world price level, it appears unnecessarily high. Talk of a copper shortage is sheer nonsense, the recent condition in the market being created by overbuying, leaving but a small volume for speculative supplies. It takes some months for an increase in mine output to reach the market, but production is again overtaking apparent consumption, stocks have begun to increase, and this, together with the reopening of many small

Jan 1, 1937

By H. Rush Spedden, A. M. Gaudin

Although the number of minerals that are ferromagnetic‡ or highly paramagnetic is strictly limited, it has been known for some time that many minerals have slight but supposedly characteristic magnetic susceptibilities. With the exception of pyrrhotite, however, sulphides have been thought nonmagnetic. A new magnetic separator has been made available recently in limited quantity to research laboratories. This device, the Frantz Isodynamic Separator, has been used for the separation of various non-sulphides from each other. Its application to the separation of sulphides, however, does not seem to have been reported. In the Richards Mineral Dressing Laboratories, the success achieved through the use of this device in separating associated sulphides has been so startling as to lead us to believe that it constitutes a magnificent adjunct to heavy-liquid separation and to quantitative mineragraphy as a tool for the mineral investigator. The separator (Fig. I) consists of: 1. A powerful magnet, the strength of which can be adjusted by, means of a rheostat; 2. A vibrating chute of nonmagnetic metal on which the mineral to be separated is made to flow (Fig. 2); 3. A feed bin and adjustable feeder; 4. Receptacles for the collection of products; 5. Means for changing, setting, and accurately reading the two slopes of the chute; viz., the cross slope and longitudinal slope. The separator is made operative by the special shape of its pole pieces, which ensures a strongly converging field. It is said by the makers of the machine that the pole pieces apply a constant mechanical force to a particle of given susceptibility, regardless of its position in the operating space of the separators." Susceptible particles, therefore, behave as though of lower specific gravity than under ordinary circumstances. This effect, combined with the slopes of the chute and the action of the vibrator, causes a stratification not unlike thai obtainable on a shaking table. The chute is of rectangular cross section, and shallow; it is broadened toward the discharge end and divided longitudinally by a partition into two compartments that lead to the collecting receptacles. Although the separator probably can be used to make separations at fairly coarse

Jan 1, 1943

By John J. Croston

In the closing months of 1936 the copper industry gave every evidence that it was at last on the threshold of an improved era. At the beginning of the year prices stood at 91/4c, which in itself was a great improvement over prices prevailing for the three previous years. Industry generally was showing signs of moving forward in this country, and business was definitely good in certain foreign quarters. The threat of war and preparations for rearmament in Europe and Asia acted as a further stimulus to purchasing. By midsummer the situation had so improved and stocks had been so reduced that the cartel of foreign producers (including American producers with foreign mines) decided to increase the production quota to 75 per cent on Aug. 1. Large-scale buying gave continued strength to the price and by Oct. 1 the quota was increased to 80 per cent, and again on Oct. 15, to 85 per cent. Notwithstanding this the price of copper continued its advance and on Nov. 1, with stocks declining continuously, the cartel increased operations to 95 per cent, then to 105 per cent on Nov. 5. In the meantime the domestic producers, because of the great increase in home consumption, had increased their production by nearly one-half. At the close of the year copper sold at 126 per pound, and since the turn of the present year has reached 17c. This rapid increase has not been wholly justified. Much of the increase was due to the legitimate demands of recovering industry, but rearmament orders plus accumulation of reserve stocks in case of war, purchases in anticipation of labor strikes and purely speculative activities on the London Metal Exchange accounted for the balance. Certainly in view of the state of industry and the general world price level, it appears unnecessarily high. Talk of a copper shortage is sheer nonsense, the recent condition in the market being created by overbuying, leaving but a small volume for speculative supplies. It takes some months for an increase in mine output to reach the market, but production is again overtaking apparent consumption, stocks have begun to increase, and this, together with the reopening of many small

Jan 1, 1937

By John Croston

IN the closing months of 1936 the copper industry gave every evidence that it was at last on the threshold of an improved era. At the beginning of the year prices stood at 9 1/4¢, which in itself was a great improvement over prices prevailing for the three previous years. Industry generally was showing signs of moving forward in this country, and business was definitely good in certain foreign quarters. The threat of war and prep-arations for rearmament in Europe and Asia acted as a further stimulus purchasing. By midsummer the situation had so improved and stocks to been so reduced that the cartel of foreign producers (including American producers with foreign mines) decided to increase the produc-tion quota to 75 per cent on Aug. 1. Large-scale buying gave continued strength to the price and by Oct. 1 the quota was increased to 80 per cent, and again on Oct. 15, to 85 per cent. Notwithstanding this the price of copper continued its advance and on Nov. 1, with stocks declining con-tinuously, the cartel increased operations to 95 per cent, then to 105 per cent on Nov. 5. In the meantime the domestic producers, because of the great increase in home consumption, had increased their production by nearly one-half. At the close of the year copper sold at 120 per pound, and since the turn of the present year has reached 170. This rapid increase has not been wholly justified. Much of the increase was due to the legitimate demands of recovering industry, but rearmament orders plus accumulation of reserve stocks in case of war, purchases in anticipation of labor strikes and purely speculative activities on the London Metal Exchange accounted for the balance. Certainly in view of the state of industry and the general world price level, it appears unnecessarily high. Talk of a copper shortage is sheer nonsense, the recent condition in the market being created by overbuying, leaving but a small volume for speculative supplies. It takes some months for an increase in mine output to reach the market, but production is again overtaking apparent consumption, stocks have begun to increase, and this, together with the reopening of many small

Jan 1, 1937

By H. Rush Spedden, A. M. Gaudin

Although the number of minerals that are ferromagnetic‡ or highly paramagnetic is strictly limited, it has been known for some time that many minerals have slight but supposedly characteristic magnetic susceptibilities. With the exception of pyrrhotite, however, sulphides have been thought nonmagnetic. A new magnetic separator has been made available recently in limited quantity to research laboratories. This device, the Frantz Isodynamic Separator, has been used for the separation of various non-sulphides from each other. Its application to the separation of sulphides, however, does not seem to have been reported. In the Richards Mineral Dressing Laboratories, the success achieved through the use of this device in separating associated sulphides has been so startling as to lead us to believe that it constitutes a magnificent adjunct to heavy-liquid separation and to quantitative mineragraphy as a tool for the mineral investigator. The separator (Fig. I) consists of: 1. A powerful magnet, the strength of which can be adjusted by, means of a rheostat; 2. A vibrating chute of nonmagnetic metal on which the mineral to be separated is made to flow (Fig. 2); 3. A feed bin and adjustable feeder; 4. Receptacles for the collection of products; 5. Means for changing, setting, and accurately reading the two slopes of the chute; viz., the cross slope and longitudinal slope. The separator is made operative by the special shape of its pole pieces, which ensures a strongly converging field. It is said by the makers of the machine that the pole pieces apply a constant mechanical force to a particle of given susceptibility, regardless of its position in the operating space of the separators." Susceptible particles, therefore, behave as though of lower specific gravity than under ordinary circumstances. This effect, combined with the slopes of the chute and the action of the vibrator, causes a stratification not unlike thai obtainable on a shaking table. The chute is of rectangular cross section, and shallow; it is broadened toward the discharge end and divided longitudinally by a partition into two compartments that lead to the collecting receptacles. Although the separator probably can be used to make separations at fairly coarse

Jan 1, 1943

By L. F. Mondolfo

An investigation of the relationship between properties of the elements and type of binary diagram formed was conducted. It was found that, for each type of equilibrium diagram, the factors for the size, valence, electronegativity, period, melting point, entropies of fusion, and sublimation calculated for each pair of elements cover a range of values. However, these factors show sufficient relationship to the equilibrium diagram so that the correlation of several of them can be used to predict the type of diagram formed, or at least limit the choice to only a few types. ThE goal of the metallurgist concerned with alloy development has always been to find a method that predicts the properties that can be obtained when a certain metal is added to another one. In most cases a qualitative predictiton of properties can be made if the equilibrium diagram is known. However, this means that for new metals the alloy development has to start with the experimental determination of the equilibrium diagrams. Because this determination is at least as complicated and time-consuming as the determination of the properties themselves, most alloy development has taken place by trial and error, and the study of the equilibrium diagrams has followed rather than preceded the creation of new alloys. Alloy structures and properties depend on the interaction between electrons and a complete knowledge of these interactions would permit prediction of structure and properties of alloys. Unfortunately direct measurement of these interactions is extremely difficult and somewhat doubtful and only properties that depend on them can be measured easily and with certainty. Study of the relationship between properties of the elements and equilibrium diagrams is not new. Besides the well known Hume-Rothery rule of the necessity of an atomic diameter fit within 15 pct for extensive miscibility in the solid, and the wide knowledge of the effect of such factors as size, electronegativity, electron-atom ratio on solid state features,"' work relating to liquid state and liquid-solid reactions can be found in the literature. Of particular interest is the work by Axon,3 who investigated the effect of size and melting point on a selected number of eutectic and monotectic dia-

Jan 1, 1962

By Frederick Laist

This paper is a review of Montana reverberatory smelting practice covering a period of approximately fifty years, during which time the small furnaces that had been in use elsewhere for a century or more, without much change in size or method of operation, were revolutionized and were developed into the huge, continuously operating furnaces of today. A study of Montana practice is particularly instructive, since reverberatory furnace smelting for the production of copper matte received more attention there than in other smelting centers and many of the improvements that finally resulted in establishing the preeminence of this type of furnace over the blast furnace originated in Butte and Anaconda. The material in this paper was gathered from original sources, wherever possible, and all of the illustrations were made from original drawings, some of which have been simplified and worked over so as to be better adapted for reproduction. The aim has been to trace the modifications in design and operation which took place during the period in question—the reasons for the changes and the results achieved through them. For developments during the first twenty years, the technical literature of the period was freely drawn upon, but I am particularly indebted to W. M. Kelly, general foreman at the Anaconda Works, whose recollections and personal experience extend back to the early days. I wish to acknowledge the use made of publications of E. P. Mathewson, William Wraith and L. V. Bender, as well as information obtained here and there from friends and associates. The resume of Great Falls practice was compiled from correspondence, notes and drawings found in the files of the old Boston & Montana Co. and the tabulations showing the performance of furnaces at Butte and Anaconda are adapted from plant records and correspondence in the files of the Anaconda Copper Mining Company. The paper deals with some interesting comparisons that were made between furnaces operated under various conditions in connection with the Carson Case, and results obtained when using natural gas as fuel. This part of the paper may be considered original to the extent that these results have not previously been published.

Jan 1, 1934

By M. E. True, B. L. Stone

To cope with the problems encountered when drilling at greater depths and to reduce the amount of physical effort required on the part of drilling crews in making round trips, a new type of semiautomatic power-operated drilling machinery has been developed which permits round trips to be made without the drill pipe being touched by hand. This equipment consists of hy-draulically operated tongs which perform the stabbing, spinning, and tong-ing operations, and two power-operated racking units mounted in the derrick for carrying the pipe to and from the center of the hole and positioning it on the mat and in the rack. With this equipment all of the operations of the various units are controlled remotely by manipulation of hydraulic valve levers and electric switches. INTRODUCTION As horsepower rises to meet the demand for deeper drilling, it is necessary to increase the weight of surface drilling equipment. Also, the duration of repetitive operations in making round trips to change bits is greatly increased with depth. Harder formations encountered at greater depths reduce bit life rapidly, resulting in more frequent round trips and in some instances more time is consumed in changing bits than in drilling. Since the introduction of the first rotary employed to drill for oil in 18951, there has been relatively little change in the general procedure for making up, breaking out, stabbing, and racking drill pipe in making round trips to change bits. The conventional method of making round trips with the drill pipe requires that drilling crews lend strenuous physical assistance to manually operated tools. Although many new devices have been developed to improve efficiency, increase speed of making round trips, improve safety, and reduce the amount of physical effort required in handling drill pipe, it is considered a vital necessity to substitute automatic or semiautomatic power-operated machinery for many of our more or less manual operations if extremely deep drilling is to be carried out successfully on a production basis in the same manner as our shallower drilling of today. Field tests have been made of remotely controlled power-operated tongs, spinner, stabber, and racking equipment. The tongs, which include a built-in pipe spinner, are mounted on a column, are capable of gripping and supporting the weight of a 90-foot stand of drill pipe, and are provided with means for moving the pipe vertically as well as to and from the center of the hole. The racking equipment consists of two units, one at the level of the conventional monkey board and the other at the first girth on the ladder side of the derrick. Most of the physical effort of making round trips with drill pipe has been eliminated in that all of the operations of tonging, spinning, stabbing, and racking of pipe on the floor are controlled by an operator in a seated position by manipulation of hydraulic and electric valve levers and buttons. The driller is relieved of operating the cathead, leaving only the hoisting and slips to be controlled. Complete round trips are made without the drill pipe being touched by the drilling crews. Although the speed of pulling or running a single stand with the power-operated equipment is approximately the same as that with conventional equipment, it is possible to maintain this rate for long periods, whereas fatigue slows crews working conventionally during round trips, especially under adverse weather. After completing round trips with this equipment, drilling crews are not exhausted, consequently, are able to perform effectively their duties while drilling, which is essential for maximum over-all efficiency. Safety is substantially improved as the derrickman performs his duties from a platform enclosed by rails and the tong lines and spinning chain are eliminated from the derrick floor. The hazards encountered in racking drill pipe on the floor and in stabbing are also eliminated. Figure 1 shows a drawing of a derrick equipped with the power-operated drill'pipe handling equipment.

Jan 1, 1949

By M. E. True, B. L. Stone

To cope with the problems encountered when drilling at greater depths and to reduce the amount of physical effort required on the part of drilling crews in making round trips, a new type of semiautomatic power-operated drilling machinery has been developed which permits round trips to be made without the drill pipe being touched by hand. This equipment consists of hy-draulically operated tongs which perform the stabbing, spinning, and tong-ing operations, and two power-operated racking units mounted in the derrick for carrying the pipe to and from the center of the hole and positioning it on the mat and in the rack. With this equipment all of the operations of the various units are controlled remotely by manipulation of hydraulic valve levers and electric switches. INTRODUCTION As horsepower rises to meet the demand for deeper drilling, it is necessary to increase the weight of surface drilling equipment. Also, the duration of repetitive operations in making round trips to change bits is greatly increased with depth. Harder formations encountered at greater depths reduce bit life rapidly, resulting in more frequent round trips and in some instances more time is consumed in changing bits than in drilling. Since the introduction of the first rotary employed to drill for oil in 18951, there has been relatively little change in the general procedure for making up, breaking out, stabbing, and racking drill pipe in making round trips to change bits. The conventional method of making round trips with the drill pipe requires that drilling crews lend strenuous physical assistance to manually operated tools. Although many new devices have been developed to improve efficiency, increase speed of making round trips, improve safety, and reduce the amount of physical effort required in handling drill pipe, it is considered a vital necessity to substitute automatic or semiautomatic power-operated machinery for many of our more or less manual operations if extremely deep drilling is to be carried out successfully on a production basis in the same manner as our shallower drilling of today. Field tests have been made of remotely controlled power-operated tongs, spinner, stabber, and racking equipment. The tongs, which include a built-in pipe spinner, are mounted on a column, are capable of gripping and supporting the weight of a 90-foot stand of drill pipe, and are provided with means for moving the pipe vertically as well as to and from the center of the hole. The racking equipment consists of two units, one at the level of the conventional monkey board and the other at the first girth on the ladder side of the derrick. Most of the physical effort of making round trips with drill pipe has been eliminated in that all of the operations of tonging, spinning, stabbing, and racking of pipe on the floor are controlled by an operator in a seated position by manipulation of hydraulic and electric valve levers and buttons. The driller is relieved of operating the cathead, leaving only the hoisting and slips to be controlled. Complete round trips are made without the drill pipe being touched by the drilling crews. Although the speed of pulling or running a single stand with the power-operated equipment is approximately the same as that with conventional equipment, it is possible to maintain this rate for long periods, whereas fatigue slows crews working conventionally during round trips, especially under adverse weather. After completing round trips with this equipment, drilling crews are not exhausted, consequently, are able to perform effectively their duties while drilling, which is essential for maximum over-all efficiency. Safety is substantially improved as the derrickman performs his duties from a platform enclosed by rails and the tong lines and spinning chain are eliminated from the derrick floor. The hazards encountered in racking drill pipe on the floor and in stabbing are also eliminated. Figure 1 shows a drawing of a derrick equipped with the power-operated drill'pipe handling equipment.

Jan 1, 1949

By D. G. Russell

Two techniques have been developed with which the applicability of pressure build-up analyses can be extended to include pressure data which previously have been considered virtually unusable. One of the interpretation methods makes possible the analysis of pressure build-up performance during the wellbore fill-up or after production period which occurs soon after a well is closed in. The other technique is an extension of a method for analyzing pressure build-up performance during the late-time portion of the pressure build-up which occurs after boundary eflects first begin to alter the shape of a conventional pressure build-up curve. With both of these methods it is possible to obtain estitnates of the kh product, the skin factor and the reservoir pressure. In addition, with the late-time analysis technique it is possible to obtain an estimate of the contributory drainage volume of the well being tested. This means that in some cases a check on reservoir limit test and (or) material-balance calculations can now be obtained from pressure build-ups. Both methods are slightly more time-consuming than conventional pressure build-up analysis methods because trial-and-error plots of pressure data must be made. The late-time method for analysis of pressure build-ups is in principle applicable to the late-time portion of a two-rate flow test or a pressure drawdown test. The interpretation formulas and procedures for these types of tests are also outlined. In these cases, as with pressure build-ups, it is significant that an estimate of the contributory pore volume is also obtained. On the basis of limited experience with the new techniques, it appears that satisfactory estimates of the kh product, skin factor, reservoir pressure and, for late-time analysis, contributory drainage volume can be obtained. INTRODUCTION The analysis of bottom-hole pressure build-up behavior in closed-in wells has been a a subject of interest in petroleum engineering circles for many years. In fact, few other subjects have received as much attention as pressure buildup analysis methods have. The cause for this interest is essentially twofold in nature. First, the pressure behavior of a well can normally be measured with a reasonably high degree of accuracy so that good data for analysis can be obtained. Secondly, over a fairly wide range of operating conditions, valuable information as to the quality of the reservoir rock and completion efficiency of the well can be obtained at a nominal cost. In recent years, numerous papers have been prepared on the effects of various operating conditions and reservoir heterogeneities on pressure buildup behavior. Very little work has been done, however, on extension of pressure build-up analysis methods to those pressure data which are not amenable to analysis by the present methods. The theory upon which the analysis of shut-in bottom-hole pressure build-up data is based is derived from the solution of the radial flow equation for a slightly compressible fluid for constant-rate conditions. It requires that the well be closed in for a sufficient period of time to obtain a clearly defined linear portion on the plot of observed bottom-hole pressure vs log (t + ?t)/ ?t (where At is shut-in time, and t is producing time to the instant of shut-in). From the slope of the plot and other normally obtainable data, the formation permeability, the well damage or skin factor, and the reservoir pressure at infinite shut-in time (if the reservoir were infinite) can be estimated. The successful application of this procedure depends on being able to recognize the straight-line section on the basic pressure build-up plot. The presently used pressure build-up interpretation theory also assumes that a well is closed in at the sand face and that no production into the well occurs after shut-in. In practice, of course, the well is closed in at the surface, and inflow into the well continues until the well fills sufficiently to transmit the effect of closing-in to the formation. This adjustment period is commonly referred to as the "afterproduction" or "fill-up" portion of the pressure build-up. During the period that the well fill-up effect is most pronounced, the basic pressure build-up plot is nonlinear. At later shut-in times after the effects of a drainage boundary have been felt at the well, deviation from the straight-line behavior of the pressure build-up plot also results. In many cases either of these effects or a combination of both can make the straight-line portion on the pressure build-up plot difficult to recognize. Obviously, an extension of pressure build-up analysis methods to include the afterproduction period and the period in which boundary effects are being felt would be desirable and might render valuable pressure data which for years have been considered virtually unusable. The principal reference of note concerning pressure buildup analysis during the afterproduction period is a paper by Gladfelter, Tracy and Wilsey.1 In the approach of these authors it is necessary to measure the rate of influx into the well during the afterproduction period. This is done through sonic measurements or through measurement of tubing-head and casing-head pressures simultaneously with

Jan 1, 1967

By H. R. Green, D. M. Lamb, A. D. Taylor

The design of slurry launders has usually been based on strictly empirical concepts. An examination of the most common procedures reveals that they do not account for many of the variables that are recognized as significant for slurry transport. These may include flow rate, volume concentration of solids, solids specific gravity, solids size distribution, particle shape, launder geometry, and roughness of the wetted surface. It was decided to develop a design procedure, which would accomplish two things:

Jan 8, 1978

By Henry P. Ehrlinger

The Alta and St. Louis mines of the Alta Mines, Inc., produce a somewhat oxidized ore with a talc gangue that presents quite a problem in milling. For several years the mill recoveries were relatively low and there seemed to be no cure for this condition even with increasing the various collecting agents and frothers to two or three times of what they should be. The usual alibi of "oxidized ore" was given as the reason for these results and the matter stood there for some time until these investigations were started. Flowsheet As a brief outline of the flowsheet the ore is crushed to minus I in. in a Telsmith jaw crusher and then fed to a 64½ Marcy grate mill. The resulting product from the grate mill is passed over a trommel where the coarse particles (plus 7 mesh) are returned to the grinding circuit through the classifier. The under 7-mesh pulp is passed over two Denver mineral jigs where a high grade concentrate is produced, thence over two Wilfley tables where a table concentrate is produced and about 80 pct of the oxide lead recovered. The tailings from these tables are pumped back to the classifier and after classification the 30 pct pulp density product, which overflows the lip, is passed into a series of 10 Denver economy flotation cells where a lead-copper concentrate is produced. Three products are made and shipped to the smelter termed jig, table and float concentrates. Results with various Reagents In March of this year work was started on the metallurgical problems of the mill and, as is shown in Table I, the results obtained were not too efficient. Tests were run with various reagent combinations that were recommended for ores of this nature but there was no appreciable effect on the recoveries. The grades of the flotation concentrates were reduced by the insoluble picked up and retained by these more powerful collectors and frothers. Results with "Metso" In past work on ores of this type the use of "Metso" had improved gold and lead recoveries, but no effect on the silver and copper recoveries had been noted. To

Jan 1, 1949

By Henry P. Ehrlinger

THE Alta and St. Louis mines of the Alta Mines, Inc., produce a somewhat oxidized ore with a talc gangue that presents quite a problem in milling. For several years the mill recoveries were relatively low and there seemed to be no cure for this condition even with increasing the various collecting agents and frothers to two or three times of what they should be. The usual alibi of "oxidized ore" was given as the reason for these results and the matter stood there for some time until these investigations were started. FLOWSHEET As a brief outline of the flowsheet the ore is crushed to minus I in. in a Telsmith jaw crusher and then fed to a 64 1/2 Marcy grate mill. The resulting product from the grate mill is passed over a trommel where the coarse particles (plus 7 mesh) are returned to the grinding circuit through the classifier. The under 7-mesh pulp is passed over two Denver mineral jigs where a high grade concentrate is produced, thence over two Wilfley tables where a table concentrate is produced and about 80 pct of the oxide lead recovered. The tailings from these tables are pumped back to the classifier and after classification the 30 pct pulp density product, which overflows the lip, is passed into a series of 10 Denver economy flotation cells where a lead-copper concentrate is produced. Three products are made and shipped to the smelter termed jig, table and float concentrates. RESULTS WITH VARIOUS REAGENTS In March of this year work was started on the metallurgical problems of the mill and, as is shown in Table I, the results obtained were not too efficient. [ ] Tests were run with various reagent combinations that were recommended for ores of this nature but there was no appreciable effect on the recoveries. The grades of the flotation concentrates were reduced by the insoluble picked up and retained by these more powerful collectors and frothers. RESULTS WITH "METSO" In past work on ores of this type the use of "Metso" had improved gold and lead recoveries, but no effect on the silver and copper recoveries had been noted. To

Jan 1, 1947

By T. N. Rhodin

There can be two types of films on solids, those which are stable in mono-layers and those which tend to aggregate into three dimensional structures. A great number of metal films formed by condensation onto a solid base are unstable in the sense that they will aggregate into crystals providing the atoms possess sufficient surface mobility. The crystalline structure of the film is strongly influenced by the base in many systems and, in some cases, a single orientation prevails when the force fields around the atoms in the supporting crystal are sufficiently strong.' Relatively little is available in the literature about the nature of these forces and the role they play in promoting a preferred orientation of the atoms arriving at the substrate surface. An understanding of their periodicity and magnitude relative to the surface forces characteristic of the film itself should provide insight into the critical dependence of film orientation on the nature and temperature of the substrate. In addition, this effect may be very useful in preparing samples for surface studies. The study of the physical and chemical characteristics of pure metal surfaces has been severely handicapped by the presence of strongly adherent foreign films. Furthermore, the randomness of the surface orientation has obscured interpretation of experimental results. Evaporation of metals in high vacuum onto carefully selected substrates under ideal conditions for preferred orientation appears suited to the preparation of flat, oxide-free, oriented films for surface reaction studies. Many factors influence their structure and some understanding of the mechanism of their formation is a necessary prerequisite for obtaining satisfactory surfaces for study. The dominant factors in defining film structure are film thickness and growth rate and the nature, condition, and temperature of the substrate. GENERAL ASSEMBLY The system was enclosed in an 18 in. bell jar which rested on an L-shaped neoprene gasket on a ground steel plate as indicated in Fig 1. Rapid evacuation of the system to 10-6 mm mercury was facilitated by a 4 in. manifold, 2 in. packless valve, and an extra large diffusion pump. Suitable arrangement of valves on a secondary manifold readily permitted introduction of purified gases

Jan 1, 1950

By George S. Rice

Those who for the first time see, at a mine, a great hole caused by subsidence; or, going underground, see an extensive fall of roof or hanging wall are apt to regard such an occurrence as an accident and not a normal condition of exhaustive mining. Moreover, the public is inclined to believe that a cave or subsidence of the surface is the result of carelcssness in mining or the rapacity of the mine operators in "robbing pillars," a tern too loosely used in descriptions of coal mining. This belief is fostered by the common-law requirement that an owner of the surface or of surface improvements is entitled to full support of the surface. Court decisions have upheld this law even when that owner has sold or leased the underlying mineral, unless a clause in the sale or lease contract exempts the mining company from paying the owner of the surface for damages that may result from mining. Another reason for this belief is the earlier practice (which is still extensively followed in this country) of leaving all coal pillars unmined, except as they have been thinned by so-called robbing; by not extracting the pillars, the surface may be supported by them for years, perhaps for generations. Inasmuch as the practice of leaving permanently in the mines from one-third to one-half of the mineral is wrong, with respect to conservation of a national resource, it behooves the mining engineers to assemble data and disseminate information on the subject, pointing out that subsidence must follow complete extraction, unless expensive methods of back-filling are employed, such as are used in Germany and France. These methods inevitably increase the cost of mining and the price of the mineral produced. It is popular to speak of "waste in mining" without a realization that much so-called wasting is unavoidable unless subsidence is accepted and provision made therefor where the surface is valuable, or else the only present known alternative of hydraulically placing sand or crushed stone filling in the excavations, at an increased cost of the mineral product to the consumer.

Jan 1, 1923

By George S. Rice

Those who for the first time see, at a mine, a great hole caused by subsidence; or, going underground, see an extensive fall of roof or hanging wall are apt to regard such an occurrence as an accident and not a normal condition of exhaustive mining. Moreover, the public is inclined to believe that a cave or subsidence of the surface is the result of carelcssness in mining or the rapacity of the mine operators in "robbing pillars," a tern too loosely used in descriptions of coal mining. This belief is fostered by the common-law requirement that an owner of the surface or of surface improvements is entitled to full support of the surface. Court decisions have upheld this law even when that owner has sold or leased the underlying mineral, unless a clause in the sale or lease contract exempts the mining company from paying the owner of the surface for damages that may result from mining. Another reason for this belief is the earlier practice (which is still extensively followed in this country) of leaving all coal pillars unmined, except as they have been thinned by so-called robbing; by not extracting the pillars, the surface may be supported by them for years, perhaps for generations. Inasmuch as the practice of leaving permanently in the mines from one-third to one-half of the mineral is wrong, with respect to conservation of a national resource, it behooves the mining engineers to assemble data and disseminate information on the subject, pointing out that subsidence must follow complete extraction, unless expensive methods of back-filling are employed, such as are used in Germany and France. These methods inevitably increase the cost of mining and the price of the mineral produced. It is popular to speak of "waste in mining" without a realization that much so-called wasting is unavoidable unless subsidence is accepted and provision made therefor where the surface is valuable, or else the only present known alternative of hydraulically placing sand or crushed stone filling in the excavations, at an increased cost of the mineral product to the consumer.

Jan 1, 1923