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The STATE MINERAL SUMMARIES publication provides estimated data and summaries of mineral activities at the State level for 1989. Most of the estimates are based on nine months data. These summaries have been prepared in cooperation with State geological surveys or related agencies. Individual State summaries are published separately as State Mineral Industry Surveys and copies can be obtained from the appropriate State Activities field office.

Jan 1, 1990

By Ed L. Schrader

Kaolin of the Georgia-south Carolina "Clay Belt" are used in a wide variety of filler and extender applications. Sane applications specifically require the performance enhancement delivered by incorporating kaolin into the product formulations. Other applications are less specific in requirements for an inert mineral filler. In order to be a feasible candidate for filling and extending, a mineral or mineral product must be generally inert (except where specific interaction with the filled medium is desired), inexpensive, easily handled and transported in a variety of forms, accessible to a broad segment of the desired market, and must exist in sufficiently large ore reserves as to assure production for many years. Of course, more precise requirements are necessary in specific applications of a prospective filler material.

Jan 1, 1985

By R. S. Kinasevich, D. D. Crabtree, D. W. Fuerstenau, T. P. Meloy, A. L. Mular

The effect of such variables as feed size, particle shape, cleavage, and hardness on the relative proportion of impact, abrasion, and chipping events in a tumbling mill is demonstrated. The concept of an average event, which is a combination of the three comminution mechanisms, is introduced. It is postulated that the average event in a particular mill determines not only the size distribution but also the energy-size reduction relationship for the comminution process. Fragmentation of particles in tumbling mills appears to result from a combination of impact, abrasion, and chipping grinding.' The relative rates of size reduction attributable to any of the basic grinding mechanisms must depend upon a number of variables, such as feed size, particle shape, hardness, and the number and kind of particles in the mill. The purpose of this paper is to show experimentally how these variables in the properties of materials affect the size distributions obtained by grinding the material's in a laboratory tumbling mill. The resulting size distributions will be intetpreted in terms of a combination of three comminution mechanisms. METHODS AND MATERIALS In this study, minerals of widely differing properties were ground either separately or as mixtures in laboratory mills using rods or balls for grinding media. The materials used include quartz, Tuolomne, limestone (99.8% CaCO3), barite, corundum, galena, pyrite, glass beads, and crushed glass. The mill used was 8 in. in diam. and 9-1/4 in. long. For the ball milling tests, 17.6 kg of steel balls (36: 7/8 in. balls, 178: 1 in. balls, and 44: 1-1/8 to 1-1/4 in. balls) were used. For the rod milling experiments, 17.6 kg of steel rods 9-1/16 in. long (25: 5/8 in., 10: 3/4 in., and 5: 7/8 in. in diam.) were used. In each test, 1 kg of solids were ground wet at 60% solids at 77 rpm. In all cases except where otherwise specified, the feed to the mill was 4 x 8 mesh material. Size distributions of the ground products were determined by a wet-dry sieving procedure with Tyler series sieves. Size distributions of mixed products containing limestone were determined by dissolving the limestone with acid and sizing the residue. EXPERIMENTAL RESULTS AND DISCUSSION If the size distribution of the product from a tumbling mill depends upon the relative proportion of impact and attrition (abrasion and chipping) events, altering the grinding conditions may change these proportions and consequently alter the size distribution of the product. Data to illustrate this point can be taken from Gaudin's classic 1926 paper.2 In one series of experiments, Gaudin ground quartz of different initial sizes for four hours in a laboratory ball mill with 7/8-in. balls. In Fig. 1, his data are reproduced as the cumulative fraction finer than the stated size for the following initial feed sizes: 13.3 x 9.4 mm, 6.7 x 4.7 mm, 2.6 x 1.6 mm, and 0.83 x 0.59 mm. As the feed size was decreased, a dramatic change in the shape of the size distribution curves took place, even though the amount of minus 100-mesh

Jan 1, 1964

By G. Dale Cor, Will H. Coghill, M. F. Williams, I. L. Feld

"INTRODUCTION During the past several years the Southern Experiment Station of the Bureau of Mines, with the cooperation of the University of Alabama, has given attention to hydraulic classification. One of the things this work has revealed is a variability not generally recognized in the conditions of teeter at different depths. This report depicts the passage of material through a teeter column and its emergence as a classified product.The work was made possible through the development of a classifier for several hundred pounds per hour permitting a small quantity of coarse spigot material to be discharged without the usual interruptions caused by stop-pages. Previous designs of small classifiers have been unsatisfactory because the,orifice used to control the quantity of spigot product as subjectto stoppages, particularly when attempting to discharge a small quantity of although the classifier used in this work has been described in detail in a previous publication 6/ its principal features will be discussed briefly herein. The main subject matter of the paper is based upon the three figures that illustrate in panorama the conditions that exist in a classifier during the continuous classification of bituminous coal, anthracite coal, and an iron ore trailing."

Jan 1, 1946

By E. P. Youngman

This paper is one of a series of digests of foreign mining legislation and court decisions that is being prepared in advance of a general report relative to the right of American citizens to explore for minerals and to can and ore rate mines in various foreign countries. This interpretation of the mining laws of the Irish Free State has been prepared from the best available material in Washington and is released subject to amplification and correction, if necessary, by American foreign-service officials. INTRODUCTION This paper is based upon the mines and minerals act, 1931, enacted by the Legislature (Oireachtas) of the Irish Free State (Saorstát Eireann), December 22, 1931, the lull title of which is "An act to establish a board to perform functions in relation to mines and minerals, to authorize the making of lenses of mines and minerals belonging to or vested in Saorstát Eireann, to name provider for facilitating the working of other mines and minerals and, for imposing restrictions on the working of minerals required for the support of buildings and works, to amend the law with respect to mines, and for other purposes incidental to the matters aforesaid.'

Jan 1, 1933

By Richard O. Y. Breese

Geologically and commercially, the term diatomite is applied to the nearly pure sedimentarv accumulation of diatom frustules- the microscopic skeletons of unicellular aquatic algae belonging to the class of golden brown algae, bacillariophyceae. The sediments are fine-grained, siliceous, and consist primarily of amorphous opaline silica with only minor amounts of organic residue, secondary minerals, and co-deposited non-diatomaceous or crystalline clastic debris. In the geological sense, the name diatomite implies sedimentary accumulations that have reached appreciable thickness and when thick enough, such accumulations consequently may have possible commercial potential. Although the term diatomite is popularly and inappropriately applied to any sediment in which there is an abundance of diatom frustules, alternative terminology is more correctly employed to describe the less pure diatomaceous sediments, for example: clay-bearing diatomite or diatom-bearing clay. Synonyms in current usage include diatomaceous earth and kieselghur. More antiquated and obsolete terminology includes tripoli-powder, tripolite, and infusorial earth. Worldwide, diatomites occur within Tertiary to Recent lacus- trine and marine sedimentary facies. Although diatomite is wide- spread throughout the world, deposits that contain high purity, commercially versatile ore are uncommon. Physical properties of the diatom and of processed diatomite that provide unique commercial value in a broad spectrum of market end-uses include ornate fine structure, low bulk density, and high porosity and surface area. Properties of equal importance are mild abrasiveness, high absorptive capacity, insulating ability, relative inertness, and high brightness. End-use markets are diverse and range from insulating brick and absorbents through quality sensitive filter aids and premium quality functional fillers. Notwithstanding both the economic attractiveness of the specialty markets and the commercial versatility of the high purity deposits, deposits of lesser purity are mined in nearly all parts of the world for less demanding uses. Mining costs are minimized through open pit quarrying, but in Europe, Asia, Africa, and South America underground mining methods are also employed. Blasting is not required because diatomite is soft and easily broken loose with mechanized equipment. Following gentle crushing, the ore is dried, milled, and processed into one of three broad categories of products: naturally milled, straight calcined, and flux calcined grades. Each of these principal categories is further subdivided into additional grades through particle size adjustment of the powders. Agglomeration of particles, alteration of fine structure, and color change are achieved through calcination. Flux calcination further accentuates these changes. Production throughout the world is dominated by the United States, followed by Romania, the former Soviet republics, and France. Other major producers include Spain, Mexico, Iceland, Korea, Japan, and Germany. Denmark is a major producer of Moler earth products, which consist of a diatomite-clay mixture. HISTORICAL BACKGROUND The first industrial use of diatomite can be traced back some 2000 years to the Greeks and to the use of diatomaceous earth as a component in lightweight building brick and in ceramic pottery. It was not until the mid-1800s, however, that the unique properties of diatomite were first recognized and the market end-uses explored and developed. One of the most important of the early uses followed the development of dynamite by Alfred Nobel in the mid-1860s, whereupon diatomite was used as a component of the explosive to improve stability and safety. Other early uses included low temperature insulating and refractory bricks and as a component in insulating and fireproofing construction panels. During the 1920s, processing technology underwent a very rapid evolution with the development of calcination, flux calcination, and air classification technologies. Through these technologies, innumerable different size and grade classifications could be made for market applications and for rapidly diversified end- uses. Today, the application of processed diatomite for filter aid is the largest of the quality sensitive end-uses. Specific filtration uses include the clarification of beer, wine and liquor, vegetable oil, syrup and sugar, pharmaceuticals, and swimming pool water, to name a few. As a functional filler and extender, processed diatomite is ideally suited for application in paint, rubber, and plastic formulations. Other filler applications include use as an anti-blocking agent in plastic film, anti-caking agent for fertilizer, thermal insulating material, catalyst carrier, polish, abrasive, pesticide and fertilizer carrier, and chromatographic supports. Throughout much of the world diatomite is still used as a component of insulating brick and as an absorbent.

Jan 1, 1994

By J. J. Rutledge

I. Description of the Clinton Ores and Associated Rocks. The Clinton rocks in Stone valley comprise (1) thick layers of deep-red shale, (2) layers of reddish-gray shale interspersed with beds of sandstone and thin beds of extremely fossiliferous limestone, and (3) yellowish-gray shales alternating with thin layers of olive-colored shales. These layers of shale are all very thin and are at no point massive.' A bed of gray-white sandstone varying in thickness from 12 to 30 ft. occurs in the upper portions of the Clinton shales. This is called the ore sandstone, a name given to it by Rogers and adopted also by the Second Pennsylvania Geological Survey. It is the surest guide to the presence of the iron-ore bed, which lies below its lower edges at distances varying from 10 to 20 ft. This ore sandstone, in the valley, lies generally at very low inclinations, but often is locally subjected to considerable changes in dip. At its outcrop this ore sandstone weathers very easily and yields a rather sparse crop of stone, composed of dirty, iron-stained boulders. Upon the roads these boulders are quite well rounded, and bear fragments of crinoid stems and other fossil forms. The ore sandstone exhibits at many points evidences of former movements in this very great thickness of the shales, and as it is the only stratum in this series competent to transmit and record stresses due to structural movements, its evidence is of considerable importance in determining the occurrence of movements in times past.

Jan 1, 1910

By E. Peek, L. Becze, K. Reading

"Gallium oxide is an important semiconductor material used in optoelectronic devices (flat panel and solar cell) catalysts and sensors. One of the methods to produce ?-Ga2O3 is the so-called hydrothermal route. It is practiced by Neo Gallium Compounds and comprises of two steps: (1) the production of mainly gallium-oxy-hydroxide in a pressure vessel by reacting metallic gallium with water at 200-220 ºC and (2) the calcination of gallium-oxy-hydroxide at 700-750 ºC to convert it into ?-Ga2O3. This paper describes this pressure hydrometallurgy process supported with relevant thermodynamic data and presents the characteristics of the ?-Ga2O3 powder produced for commercial purposes. INTRODUCTIONGallium is a relatively new metal, having been predicted by D. Mendeleev in 1871, discovered by P.E. Lecoq de Boisbaudran in 1875, and first commercially produced in the USA in 1943. Gallium is not rare, being more abundant in the earth crust than antimony, bismuth, molybdenum, silver and tungsten. However, few gallium minerals exist in nature, and the dispersion of gallium within other minerals add to the complexity of its recovery. In practice, gallium is found in dispersed state primarily in bauxites and in some sphalerites, and, to a much smaller extent, in some coals. At present, a very large proportion of the primary gallium in the world is recovered as a by-product of aluminum plants, mostly Bayer plants, where gallium is extracted from a bleed of the Bayer liquor (Roskill, 2011). In 2011, world production of primary gallium was estimated at 200 metric tonnes. In addition, there is a significant contribution of recycling to the overall yearly availability of the metal.Gallium exhibits fairly remarkable properties: it is liquid above 29.76 ºC, can be supercooled, and with its high boiling point (2204 ºC), is the metal with the widest liquid range. Gallium is magnetic, and is an excellent conductor of both heat and electricity. Gallium also displays a marked anisotropic electrical conductivity (Roskill, 2011). All these properties render gallium almost irreplaceable in the semiconductors (GaAs, GaN, GaSb, GaP wafers) and the optoelectronics industry (flat panel, solar cell)."

Jan 1, 2012

By Wm. Reuben Webster

BRASS is an alloy of copper and zinc. The brasses (using this term to denote all useful proportions of the two constituents) are the most valuable and widely employed of all [ ] nonferrous alloys, because of their high resistance to ordinary corrosive agencies and the very wide range of properties that may be imparted to them by variations in the proportions of the constituents and by variations in mechanical treatment and heat-treatment. Fig. I shows the normal physical properties, as determined by standard tensile tests, of the series when in the annealed condition. Fig. 2 shows the effect of varying amounts of cold-working on an almost pure brass containing 70 per cent copper and 30 per cent zinc. Fig. 3 shows the effect of annealing at various temperatures on the same alloy. This effect is somewhat modi [ ] fled by the degree of cold-working to which a brass has been subjected, as shown by Fig. 4. A fourth test, which is empirical, has been found useful because of its simplicity -the hot hammer test. Samples Y2 in. in diameter and ¾ in. long are placed in a suitable furnace. These are withdrawn one at a time at successively higher tempera¬tures and are subjected to the blow of a drop hammer weighing 50 lb. with a drop of 4 ft. The percentages of' reduction in length of the cylinders are plotted against temperatures and give a comparative measure of plasticity at different temperatures. The results of this test on several

Jan 1, 1942

By N. J. Themelis, A. W. Last

Autogenous grinding, broadly defined as the self-comminution of ore in a cylindrical tumbling mill without using auxiliary grinding media, was first applied in the early 1930s in the so-called Hadsel mills (Hardinge, 1955) as seen in [Fig. 1], mainly used in gold mines on the US West Coast. A number of these mills were built in sizes of 6.1 to 7.3 m (20 to 24 ft) in diameter and 1.5 to 1.8 m (5 to 6 ft) in length but were later abandoned because of operating and maintenance problems. Further development of autogenous grinding led to the Hardinge wet grinding mill, the Aerofall dry grinding mill, and others. A tabulation of all known autogenous and semiautogenous installations around the world was sent recently to the authors by G. J. Kushner of Koppers Metal Processing Division. In the size range of 7.3 to 9.8 m (24 to 32 ft) in diameter, it lists a total of thirty mills used in the processing of copper ores. An additional 120 units are listed in the same size range for the processing of iron ores and other minerals. The largest mills in existence are 11.1-m-diam X 4.6-m-long (36-ft-diam X 15-ft-long) mills in Minnesota, powered by 8950 kW (12,000 hp) motors and used in taconite beneficiation. It is indicative of the phenomenal growth of this technology that none of the above 150 mills was in operation prior to 1964. Grinding rates in autogenous mills are very sensitive to variations in ore breakage characteristics and even with fairly constant ore type can exhibit large fluctuations in throughput. Autogenous grinding also depends on availability of a fraction of the ore to be ground in the form of "competent" rock which can withstand to a certain degree the tumbling and impact action within the mill. If the ore is uniformly "soft", it will soon be crushed into small size particles and further grinding, which depends on the existence of large size rocks in the mill, becomes impossible. This apparently is the case with most copper ores, as discussed by Bachman, Last and Nabbs (1970) who described pilot testing of a large number of ore samples from Kennecott 's Chino Mines. Under circumstances where autogenous grinding is impractical, it is possible to realize most of its benefits by utilizing large grinding balls in place of the "competent" rock and practice what has become known in the mining industry as semiautogenous grinding. In semiautogenous grinding (SAG), a grate discharge tumbling mill is fed the product of a primary crusher or run-of-mine rock. Forged steel or alloy grinding balls, in proportions ranging from 3.10% of the total volume in the mill, are used to complement the self-grinding ability of the ore. Semiautogenous circuits can be either designed for single-stage closed-circuit grinding which produces a final product for recovery processes, or for two-stage operation in which the SAG mill product is fed to a second stage of grinding in a conventional ball mill.

Jan 1, 1981

By C. Richard Tinsley, Norman Miskelly, S. James Hodge

Construction of the Ranger uranium project, located 230 kms east of Darwin in the Northern Territory, Australia, commenced in January 1979. Energy Resources of Australia Ltd (ERA) was incorporated in February 1980 to acquire all the rights in the project. The total cost to ERA of these rights was A$407 million, made up of A$125 million in cash to the Federal Government and the issue of 125 million A$1.00 shares at par, plus a payment of A$16 million in cash to each of Peko-Wallsend Ltd. (Peko) and EZ Industries Ltd. (EZ). ERA's cash requirements to complete the project were estimated in October 1980 to be A$553 million. Project loans, secured by first ranking debenture stock, were arranged for a total of US$390 million, while second-ranking debenture loans totalling A$60 million were [ ] obtained from the vendors, Peko and EZ. Overseas participants (power utilities who had agreed to purchase uranium yellowcake under contract) arranged to take up 25% of the equity capital for A$102.5 million; Peko and EZ were allotted 30.5% each as satisfaction of vendors' consideration; and 14% representing A$57.5 million was issued to Australian residents in an underwritten public flotation in November, 1980. The loan and equity financing arrangements required the successful resolution of many complex and interlocking factors, including technical and economic feasibility, agreement with Aboriginal interests, compliance with Government policies, and securing of sales contracts.

Jan 1, 1985

By Keith L. Harris

Economic activity in the United States picked up in the third quarter, according to the latest estimate released by the Department of Commerce. Real gross national product (GNP)--the Nation's output of goods and services--grew at a seasonally adjusted annual rate of 4.3%, or $17.6 billion, compared with a rate of 1.9% for the second quarter of 1985 and 1.6% for the third quarter of 1984 (table 1). The 4.3% rate is one percentage point above the preliminary estimate reported in the August/September issue of Minerals and Materials. Most of the upward revision was due to the change in business inventories and Government purchases, while the figure for net exports was revised downward substantially. The 4.3% growth bettered by 1.5% the average rate of growth in GNP from 1974 through 1984 and was 1.1 % above that of the period from 1975 through 1984 and 0.7% above that of 1980 through 1984. Of importance to the minerals industry was the $14.4-billion growth in personal consumption expenditures, $10.2 billion of which was for durable goods (especially domestically produced automobiles) and the growing residential investment. The net export deficit continued to grow, however, and investment in nonresidential structures, producers' durable equipment, and business inventories declined. Prices, as measured by the GNP fixed-weighted price index, increased at an annual rate of 3.1% in the third quarter, compared with 3.9% in the second quarter. The slower rate of inflation resulted mainly from a decline in energy prices, following second-quarter increases. Fourth-Quarter Prognosis Many of the economic data available for October and November indicate that the economy is growing modestly and will continue to grow over the next 3 to 6 months. The composite index of leading indicators, designed to predict economic activity within 3 to 6 months, rose 0.3% in October, the sixth consecutive monthly advance, according to the Department of Commerce. Six of the 11 available leading indicators were positive: Stock market prices rose, as did sensitive material prices, credit outstanding, and manufacturers' new orders for consumer goods and materials; initial claims for unemployment insurance decreased, and firms were getting slower delivery of goods. Four of the indicators were negative: Business formations, homebuilding permits, contracts and orders for plant and equipment, and money supply all declined. The average hours worked per week, already at a high level, remained unchanged.

Jan 1, 1985

By R. Q. Honaker

It has been shown that naturally hydrophobic carbonaceous materials such as coal and graphite can be selectively coagulated and separated from hydrophilic impurities without using oily agglomerants, flocculants or electrolytes. The coagulation occurs at C-potentials significantly higher than those predicted by the classical DLVO theory, suggesting that it is driven by the hydrophobic interaction. In the present work, the energy barriers for the coagulation of a hydrophobic coal sample have been calculated using the extended DLVO theory which incorporates the hydrophobic interaction energy in addition to the dispersion and the electrostatic energies. For the coagulation of minerals present in the coal, the classical DLVO theory has been used for the energy barrier calculation. The results of these calculations provide an excellent correlation with the results of a series of Selective Hydrophobic Coagulation (SHC) tests conducted with run-of-mine coal and graphite samples.

Jan 1, 2004

Computer programs commonly used to simulate mining operations generally require a fair amount of data. The common data input methods have been by either creating an ASCII data file or answering numerous questions during the data input phase. Both methods of data entry are tedious, time consuming, and inflexible. A screen handling system has been developed to drive FORTRAN-77 application software for the MS-DOS environment. The system utilizes keyboard functions with an aid of extended ANSI codes. It also allows a multi-view input data entries.

Jan 1, 1990

By Edwin R. Phelps, Charles W. Porterfield

BACKGROUND OF SURFACE MINING Surface mining refers to the process of removing the material (over- burden) overlying a coal seam and exposing the coal so that it can be loaded out and conveyed by trucks or other methods to the preparation plant or other facility. Surface mining has not always been important in the coal industry. In the early 1900s, almost all of the coal mined in the United States was mined by underground methods. In 1900, about 192 Mt (212 million st) of bituminous coal mere mined and less than 1% was mined by surface methods. The development and use of larger equipment has allowed surface mining to gain prominence throughout the years. Table 1 shows the total production of coal by mining method in the United States for ten-pear periods since 1920 and indicates the growth of surface-mined coal production. Surface mining will undoubtedly continue to account for a large percentage of the coal production in the US for many years because: 1) The capacity of surface mining excavators has continued to increase. Today, mining companies are using shovels (see Fig. 1) which are able to move up to 137.6 m3 (180 cu pd) in each bite and draglines (see Fig. 2) which move up to 168.2 m3 (220 cu pd) in each bucketful. 2) Increasing tonnage from the thick western coal seams is being produced by surface mining methods. 3) Surface mining has normally had lower costs and a better safety record than underground mining. 4) Surface mining normally recovers a much higher percentage of the coal reserve than can recovered by underground mining. 5) Some coal measures call best be extracted by surface mining

Jan 1, 1981

By K. H. Zhang, Y. P. Gao, J. Q. Zhao, Q. Li, J. C. Ma

Compared with sinusoidal oscillation, non-sinusoidal oscillation enhances the ability to control waveform and meets different oscillation requirements by adding an independent parameter, which is the key technology for high-efficiency continuous casting. A new waveform of mould non-sinusoidal oscillation is proposed in this paper, that is, a velocity waveform that is composed only of straight lines and parabolas, which not only has good dynamic characteristics, but also further enhances the feature of non-sinusoidal oscillation. Compared with sinusoidal oscillation, the negative strip time is reduced by 15.9%, the maximum negative strip velocity difference is increased by 38.3%, and the maximum positive strip velocity difference is decreased by 27.8%. The formulas of oscillation process parameters can be clearly deduced, and the isoplethic curves of oscillation process parameters when multi-parameter simultaneously changes are drawn. The negative strip time decreases as the modification ratio, frequency, and casting speed increase, but increases as stroke increases. In order to maintain the stability of negative strip time, an oscillation synchronous control model for optimising oscillation basic parameters was developed. Through practical application, the mean oscillation mark depths decreased by 10.1 μm and the flux consumption is increased from 0.37 kg/t to 0.45 kg/t in the non-sinusoidal oscillation model, which meets the requirements of normal production.

Oct 24, 2025

By A.M. Wala

A new radioactive tracer method to measure airflow in inaccessible airways has been developed for situations when studies of the mine ventilation system are not possible using conventional flowmeters (anemometers). The new method has been tested in the ventilation laboratory at the University of Kentucky and in the Experimental Underground Coal Mine at the U.S. Bureau of Mines. This new tracer method has been utilized in leakage, dilution and flow velocity measurements in laboratory and field (mine) experiments.

Jan 1, 1996

By H. C. Spaulding

The rapid increase, during the last few years, in the number and magnitude of applications of electric power-transmission to commer cial uses in this country, has been due principally to three causes: first, the ability and enterprise of those who have been identified with the progress of electrical industries, since electric illumination became an economic fact instead of a laboratory-experiment: sec ondly, the readiness of the American people to adopt new and ad vanced methods as soon as their superiority has been fairly demon strated; and thirdly, tile economy and flexibility of the apparatus employed, when properly designed and constructed, and installed under suitable conditions. Basing our judgment on the world's advance in scientific devel opments during the past century, we may reasonably conclude that in no other country would the pioneeis of electrical invention, whose names have now become household words, have received the prompt and plentiful financial support which has enabled them to inaugurate undertakings of exceptional magnitude, even in this era of tremendous monetary organizations. And, on the other hand, we have seen, in the numerous financial and engineering failures inseparable from such rapid development, the natural results of a too implicit faith in electrical omnipotence. It is not to be wondered at that conservative engineers have been slow to adopt this new and mighty agent in the solution of exten sive problems, and under circumstances where a single failure means not only a greater or less financial sacrifice, but the loss, in a greater or less degree, of professional reputation. Be mechanical engineer, while recognizing the fact that thousands of horse-power are to-day transmitted by electrical means, from sunning the lathe in a dentist's office to the operation of a fifty-ton travelling crane; from passing a cooling draught of air through a

Jan 1, 1891

By A. Lubinski, J. L. Logan, W. S. Althouse

A4ost gas twells and flowing oil wells are completed and treated through a string of tubing and a packer. Changes in temperature and in pressure inside or outside the tubing will: (I) if free motion of the tubing inside the packer is permitted, increase or decrease the length of the rubing; or (2) if free motion is prevented, induce forces in the tubing and on the packer. If pressure inside the tubing is greater than outside, the tubing may buckle helically even in the presence of a packer-to-tubing tension. The tubing will always buckle, and much more severely, if free motion is permitted. The buckling may be prevented by pulling the tubing in sufficient tension. The prediction of these forces and tubing movement has here to fore been based upon calculations that did not inciude helical buckling. This paper preseitts means with which these length or force changes can be calculated while taking into account the effect of helical buckling. To avoid damaging formations, failure of remedial operations, or damage to the tubing or packer, application is made to practical problems involving calculations of the required length of seals, amount of sluckoff or tension, and prevention of permanent corkscrewing. INTRODUCTION Leakage of a packer may result in costly failures of such operations as squeeze cementing, hydraulic fracturing, etc. To avoid such failures, the authors are often asked questions pertaining to the length of necessary seals, the amount of necessary slackoff, etc. Published work' does not take into account helical buckling of tubing. Investigation of helical buckling was prompted by the fact that allowance must be made for this phenomenon in order to provide relevant answers. In the past, theoretical work on helical buckling was confined to conditions for which such buckling does not The mathematical treatment of behavior in a buckled condition, given in the Appendix, is novel. Assumptions upon which this investigation is based are listed and discussed in a special section. The following are a few of the many kinds of problems which may be solved with this paper. 1. Consider a packer in which tubing may move. Such movement will occur after pressures and temperature are changed. The paper provides means for: (a) calculating the amount of such movement and, therefore. the required length of seals; and (b) calculating the necessary amount of initial slackoff, for which there is no danger of unsealing the packer, if the length of seals is given. Such calculations, as well as those which follow, tully take into account the fact that part of the movement ib due to elastic helical buckling of the lower part of the string. This buckling may occur even in tubing under tension. Insufficient initial slackoff for a given length of seals, or insufficient length of seals for a given slackoff, may result in costly failures. A field case of such a failure will be given further in this paper. 2. In the case in which tubing cannot move in the packer, changes of pressure and temperature result in tubing-to-packer forces and forces in the tubing above the packer, both of which may be calculated. This knowledge is important because, if these forces are too large, the) could damage the packer or the tubing. 3. For wells in which wireline tools are to be run through the tubing, the paper provides means to keep the tubing from buckling, thereby permitting free passage of tools. 4. In deep wells, mainly in the presence of large casing, tubing may become "corkscrewed", i.e., take a permanent helical set. A field case is described further in the text. Using this paper, one may calculate in advance conditions under which permanent corkscrewing would occur, and then take preventive steps. HELICAL BUCKLING Consider a string of tubing, freely suspended in the absence of any fluid inside casing, as shown in Fig. I(a). Now consider an upward force F applied at the lower end of this tubing. This force compresses the string; and if the compression is large enough (which is always the case in actual problems), the lower portion of the string will buckle into a helix, as shown in Fig. 1 (b). The lower end of the tubing is subjected to a compression F. This compression decreases with the distance from the bottom and becomes nil (neither compression nor ten-

By J. R. Patts, J. P. Rider, J. A. Organiscak, A. B. Cecala

"NIOSH recently completed a 15-month study at an underground limestone mine crusher booth which evaluated three research parameters: (1) the effectiveness of a single-filter filtration and pressurization system for improving the air quality inside the operator booth, (2) comparing the effectiveness of ? > 99 and ? > 95 experimental prototype filters in the system, and (3) evaluating the use of three different pressure monitoring devices to determine the performance of the filtration and pressurization system over time. The protection factor was quantified monthly using particle counters in the respirable dust range (0.3–10 µm), and gravimetric dust samples were gathered at the beginning and end of the overall study. Under static conditions and after outlier removal, the single-filter filtration unit installed offered a protection factor between 8 and 216, depending on the filter type and loading condition. The particle counting analysis shows that the ? > 95 filter offers a protection factor greater than 4-times that of the ? > 99 filter when evaluated over 60 minutes. The booth pressure monitors provided data that proved to be a valid indicator of system performance over time. INTRODUCTION Designed and installed correctly, enclosed cabs, operator booths and control rooms offer mine workers protection from physical hazards, such as flying rock, debris, and noise, as well as a more comfortable environment in regards to temperature and humidity [1]. But while it may be easier to quantify whether the A/C unit is working (measuring the temperature) or observe whether the cab offers protection from flying debris, it can be somewhat more difficult to quantify its performance in reducing respirable dust hazards. For over 15 years, NIOSH has been conducting applied research to improve the air quality inside of enclosed cabs of mobile equipment [2-5]. This work has led to the identification and mathematical modeling of enclosed cab filtration systems [6]. The same principles that govern the performance of filtration systems on mobile equipment are applicable to stationary enclosures such as operator booths and control rooms [1, 7]. Stationary enclosures are similar to enclosed cabs; however, the volume of the work area can be significantly larger. In addition, workers who perform their duties in stationary enclosures tend to stay within the room for a greater percentage of the day, as opposed to workers on mobile equipment who may enter and exit frequently. Structural integrity can be easier to maintain as well, as there is typically less vibration and stress placed on these compartments as compared to mobile equipment. In addition to offering protection from dust and flying debris, enclosures must ensure that workers have a healthy supply of fresh air to avoid elevated levels of CO2, which are known to cause headache and dizziness, impairing cognitive function. The American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) states that enclosures should have no more than 1,100 ppm of CO2 when outside levels are 400 ppm [8]. In addition, the American Society of Agricultural and Biological Engineering (ASABE) recommends a minimum airflow for enclosed cabs of at least 42.5 m3/hr (25.0 cfm) per person [9] to ensure an acceptable level of CO2."

Jan 1, 2017