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By Miklos D. G. Salamon, Jim M. Galvin, Bruce K. Hebblewhite

A series of mine design accidents in the late 1980s resulted in a major research program at the University of New South Wales, Australia, aimed at developing pillar and mine design guidelines. A database of both failed and unfailed Australian underground coal mine pillar case studies was compiled. A procedure was developed to enable the effective width of rectangular pillars to be taken into account. The database was analyzed statistically using the maximum likelihood method, both independently and as a combined data set with the more extensive South African database. Probabilities of failure were correlated to factors of safety. It was found that there was less than a 4% variance in pillar design extraction ratios resulting from each of these approaches. There is a remarkable consistency between the design formulas developed from back-analysis of the two separate national pillar databases containing many different coal seams and geological environments.

Jan 5, 1999

By Dara Stock, Fred Turin, Kim Cornelius, Lisa Steiner

Growing concern from labor unions, regulatory agencies, and industry about the safety of a prevalent underground coal mining method which utilizes remote control has prompted human factors field evaluation of mining activities. Remote control operations were implemented with little consideration given to human-system interactions. Ideally, collecting and analyzing information prior to implementing new technology would have helped to address potential problems. One such problem that operators and other mine personnel are faced with is the question of where they should safely position themselves to avoid injury while remotely operating machinery. To determine work methods employed by machine operators before and after implementation of the new method, work sampling techniques have been used to provide data about positioning of face crew members at different points in the mining cycle. This data provides information for optimal positioning, leading to safer operating procedures and identifying training shortfalls.

By J. A. Holmes

As part of its investigation of methods of increasing the efficiency of fuel resources, the Bureau of Mines is continuing the study of the general problems involved in the economic use of fuels in gas pro- ducers that were carried on by the technologic branch of the United States Geological Survey. In the course of this study many inci- dental problems of prime importance have demanded consideration. Among them is the determination, under practically constant con- ditions, of the duration of gas-producer tests necessary to reduce the possible error to a minimum. A discussion of this proper length of test period forms the first part of this bulletin. An attempt to dispel some of the uncertainties that arise in an investigation or to account for some of the minor phenomena often necessitates a systematic and careful study of certain chemical, ther- modynamic, or physical laws, or a combination of these, which in turn may result in information or conclusions of great value. Fur- thermore, seemingly unimportant observations often prove to bear directly upon the design, construction, or manipulation of the machine under test. In attempts to improve the gas producer considerable attention has been given by manufacturers to such questions as fixing or isolating the combustible components of the tar, utilizing the waste heat of the producer for the generation of the steam required by the plant, apply- ing the suction principle to bituminous coal and other tarry fuels, and many allied subjects. Little study, apparently, has been given to the physical-chemical conditions most suitable to the formation of hydro- gen and of carbon monoxide, with a view to regulating the percentages of these gases in generators using fuels other than anthracite coal or charcoal. An attempt was made to introduce such investigations when the operations of the government coal-testing plant began at the Louisi- ana Purchase Exposition in St. Louis in 1904, but owing to adverse conditions these problems were abandoned until the plant was trans- ferred to Norfolk in 1907. The delay in beginning this line of inves- tigations, together with the short testing season at Norfolk, limit the second part of this report to preliminary physical-chemical studies, which, however, were sufficiently significant to warrant careful ex- amination pending more complete researches, which are being carried on at the station located in Pittsburg.

Jan 1, 1911

By M. J. Ferrante

High-temperature enthalpy and X-ray powder diffraction studies were con-ducted on aluminum sulfide (Al2S3) as part of the Bureau of Mines effort to provide new data for the advancement of mineral technology consistent with environmental preservation and energy conservation. Relative enthalpies were measured with a copper-block calorimeter from 298.15 to 879 K. Tabulated values are listed for heat capacity, entropy, Gibbs energy functions, and relative enthalpies between 298.15 and 900 K. Enthalpies were also given in the form of an equation and combined with published data to calculate standard enthalpies of formation and Gibbs energies of formation for reactions of crystalline aluminum with crystalline, liquid, and gaseous diatomic sulfur. The hexagonal, rhombohedral, and cubic phases of Al2S3 were identified by X-ray powder diffraction studies, and the indexed powder diffraction patterns of these phases are given. The hexagonal phase was stable to about 852 K and was partially converted to the rhombohedral form at 879 K.

Jan 1, 1981

To find solutions for common safety problems encountered in the handling of trailing cables, based on observations at many different surface mining operations. Approach Practices in handling trailing cables were Investigated through personal visits to over 40 mines, supplemented by visits to cable manufacturers and cable repair service companies. The most effective solutions to the safety problems en-countered were noted and are described In the project final report. Examples are given in this Technology News. Accident Experience Most cable-related injuries occur as a result of workers lifting, pulling, tripping, or being struck by the cable. The Table gives the frequency of occurrence for injuries reported during a recent 3 1/2 year period.

Jan 1, 1982

By L. J. Froisland

An integrated process for recovering metal from nonmagnetic auto-shredder reject scrap was investigated by the Federal Bureau of Mines. The methods used were air classification, water elutriation, screening, magnetic separation, handpicking, and heavy-media separation. Metal recoveries in this process were projected at 39 percent copper and copper alloys, 53 percent aluminum, 96 percent iron, and 98 percent zinc die cast. An economic evaluation of the conceptual process indicated that a facility designed to reclaim the reject scrap from 200 shredded automobiles daily could be profitable. Total investment in this plant was estimated at $321,000; the discounted rate of return before taxes was 53 percent.

Jan 1, 1975

By R. L. Montgomery

The heats of solution of erbium chloride in water and in hydrochloric acid and of erbium oxide in hydrochloric acid were determined. The results reveal a discrepancy of 10.5 kcal. per gram-atom between the heats of combustion and solution of erbium reported in the literature, the heat of combustion being more negative. The heat of combustion of erbium t4)4 and its heat of solution in hydrochloric acid (1, 18) have been reported in the literature. The heat of solution of erbium chloride was determined in two studies (2, 19). The present work was undertaken to check the reported heats of solution of erbium chloride and to determine the heat of solution of erbium oxide in hydrochloric acid. The latter quantity permits the heats of combustion and solution of erbium to be compared for mutual consistency. It was also desired to determine the degree of similarity between the thermochemistry of yttrium and erbium.

Jan 1, 1961

By J. F. Barkley

"In the course of the Government's Fuel Economy Survey of its own power plants, studies and tests have been made of various oil-burning equipments under power-plant boilers. There are now many types of burners being offered in the relatively limited field of power-plant use. The majority of the types used may be grouped into two general classes- those using steam to effect the atomizing of the oil, and those using mechanical means.Burners using steam have had the most prominence in this field for a long period. The mechanical atomizing type of burner successfully applied on shipboard, however, pointed to a possible betterment in land work. The vision presented itself of a burner that would need no steam for atomizing that would permit of air inlets or registers compactly arranged as a part of the entire burner, and that would only require the natural stack draft usually available in land boiler furnaces. Hence, rather recently there has been much development along this line, resulting in various types of burners.In Table 1 are grouped test items chosen from many tests showing representative analyses of the products of combustion obtained with various burners installed in various types of furnaces. In all these tests the burners were handled by experts and represent practically the best attainable for that particular arrangement. The boiler efficiencies ranged from 70% to 80%. It will be noted that the burners using steam for atomizing were able to secure slightly better 002 and less 02 without the presence of CO."

Feb 1, 1926

By Gerald T. Homce, Michael R. Yenchek, H. Kenneth Sacks, James C. Cawley

Accidents occur when least expected, from sources that we rarely anticipate and with outcomes that can vary greatly. Anyone who has ever been involved in an automobile accident knows, the transition from driving comfortably and safely down a highway to being involved in a potentially life-threatening situation can occur in a heartbeat. Accidents on the job are no different. The mining industry has a relatively small number of electrical injuries, compared to industries such as construction or agriculture, due to the small total employment in mining. Mining does, however, have one of the highest occupational electrocution rates of any U.S. industry, at 2.8 for every 100,000 workers per year. This is approximately four times the average for all industries. Data from the Mine Safety and Health Administration (MSHA) shows that 75 electrical fatalities occurred in the mining industry between 1990 and 1999. Of these, at least 17% involved high-reaching mobile equipment that contacted overhead power lines.

By R. C. Buehl, J. P. Riott, M. B. Royer

Sponge iron is the metallic product resulting from the reduction (removal of combined oxygen) of iron ore or other iron oxides at a temperature below the fusion point of iron. It has been used for many years in the production of certain grades of high-quality steel, such as tool and cutlery steels. The sponge iron available commercially in limited quantities for such use was produced from high-grade ores that were almost free from the contaminating elements that are generally considered detrimental to the production of certain grades of carbon tool steel. Interest in sponge iron as a scrap substitute was revived when World War II began, when the serious shortage of scrap metals for use in the production of armament caused great concern as to whether steel production could be maintained at the rate necessary for vigorous prosecution of the war effort. Also, because of the severe shortage, steel manufacturers…

Jun 1, 1947

By J. Nielen van der Merwe

For the last 3 decades, coal pillars in the Republic of South Africa have been designed using the well-known strength formula of Salamon and Munro that was empirically derived after the Coalbrook disaster. The database was recently updated with the addition of failures that occurred after the initial analysis and the omission of failures that occurred in a known anomalous area. An alternative method of analysis was used to refine the constants in the formula. The outcome was a new formula that shows that the larger width-to-height ratio coal pillars are significantly stronger than previously believed, even though the material itself is represented by a reduced constant in the new formula. The formula predicts lower strength for the smaller pillars, explaining the failure of small pillars that were previously believed to have had high safety factors. Application of the new formula will result in improved coal reserve utilization for deeper workings and enhanced stability of shallow workings.

Jan 5, 1999

By Kenneth L. Cashdollar

This paper reports US Bureau of Mines (USBM) research on the explosibility of coal dusts. The purpose of this work is to improve safety in mining and other industries that process or use coal. Most of the tests were conducted in the USBM 20 litre laboratory explosibility chamber. The laboratory data show relatively good agreement with those from full-scale experimental mine tests. The parameters measured included minimum explosible concentrations, maximum explosion pressures, maximum rates of pressure rise, minimum oxygen concentrations, and amounts of limestone rock dust required to inert the coals. The effects of coal volatility and particle size were evaluated, and particle size was determined to be at least as important as volatility in determining the explosion hazard. For all coals tested, the finest sizes were the most hazardous. The coal dust explosibility data are compared to those of other hydrocarbons, such as polyethylene dust and methane gas, in an attempt to understand better the basics of coal combustion.

By H. H. Clark

The term "explosion-proof," as applied by the Bureau of Mines to an electric motor, refers to a motor inclosed by a casing so constructed that an explosion of a mixture of mine gas (methane) and air within the casing will not ignite a mixture of the same gas surrounding the motor. There are two classes of motors so constructed: First, a totally inclosed class built strong enough to withstand high internal pressures and so designed that the efficiency of all inclosing covers can be satisfactorily maintained; second, a class provided with relief openings or valves designed to relieve the pressure of an explosion within the motor casing and to cool any products of combustion dis- charged through the valves. A satisfactory motor of the first class is much more expensive to build than an equally safe motor of the second class. For this rea- son, attempts to make motors explosion-proof have been confined chiefly to motors of the second class.

Jan 1, 1912

By Richard F. Link, George W. Gladfelter, George S. Koch

Contour maps, useful in mineral industries, for example, in analysis of trends in mineralization, may be constructed through statistical methods of regression analysis programed for an electronic computer, For many applica­tions, the resulting maps are more useful and objective than conventional contour maps that are necessarily subjective because they are drawn by hand methods. In principle, an equation is found that fits a quadratic surface to observed elevations of points referred to a datum plane, The quadratic sur­face, represented by a contour map may take the form of a ridge, valley, dome, or basin, Once an equation has been derived, its coefficients may be used to construct a contour map--showing lines of equal value that are derived from the original observed data points by the averaging process of fitting the quadratic surface. Methods employed are illustrated by an example analysis, based on data from a large vein of the Fresnillo mine, Zacatecas, Mexico. Computer programs to implement the methods are described in an appendix,

Jan 1, 1964

By Jeffrey Kohler, John J. Samrnarco, Thomas Novak, Lloyd Morley

Equipment control functions that were once hardwired are being implemented with software and very large scale integrated (VLSI) devices. Often this transition has resulted in increased flexibility, improved quality, and decreased costs. At the same time, it has created new concerns and challenges concerning worker safety. The visible and well-defined ladder diagram for relay-logic has been replaced by program in which the exact outcome for varied inputs can be more obscure. In the coal mining industry,-efforts to automate longwall mining systems hove resulted in semiautonomous machines operating within the same space as workers This paper describes an effort initiated by the National Institute for Occupational Safety and Health (NIOSH to identify the safety rules related to the use of processor-controlled equipment in mining. Specific findings in the areas of human factors, hardware, and some safety are presented in this paper, and a brief description of a plan to address identified weaknesses is given.

By G. Molinda, D. Dolinar

Each year, about 2,000 falls of supported roof occur in the more than 800 underground U.S. coal mines. Therefore to help improve the design of primary support systems, the National Institute for Occupational Safety and Health (NIOSH) conducted a nationwide study of roof falls in over 2,500 km of roadways at 37 coal mines. Information on the roof falls as well as other geotechnical, mining, geologic and roof bolting factors were collected and quantified Then a multi variate statistical analysis was conducted on the data with the roof fall rate being the outcome variable The results were used to derive preliminary design guidelines for predicting the roof bolt length, capacity, and pattern required to effectively reduce the roof fall rate. The equations are fairly limited by a relatively high statistical variance in the data. Also reported is a recent survey of U.S roof bolt manufacturers that shows a significant change in bolt types used over the last ten years.

By R. V. Ramani, A. S. C. Owili-eger

The Methane Generator program is a part of the Internal Environ¬mental Sub-system of the Master Design Simulator (MDS). All the sub¬systems of the MDS are controlled and activated by the main program as required. The data requirements for the Methane Generator are supplied by the Geology and Reserves sub-system through common storage. Figure 6 shows the information flow between the Methane Generator and other systems of the MDS. It should be noted that the Methane Generator can also function independently as was described under model application. AREAS OF MISSING INFORMATION In any numerical analysis, the accuracy of the solution depends entirely upon the data available. In gas flow problems, parameters that constitute basic model input data are rock porosity, medium permeability, reservoir pressure and initial reservoir pressure dis¬tribution. Unfortunately, however, most of these characteristics are not available for a lot of coal seams. The need for actual field data cannot, therefore, be adequately emphasized here.

Jan 1, 1974

By M. Beus, R. Iverson, A. Dreschler, V. Scott

This paper describes research to improve safety during transport of ore and waste in underground mines. Field tests are underway in mines in Idaho and Montana. Strains measured on structural support members in an ore pass provided information about total forces acting on the structure as material was dumped into it. Results show that measured static loads were considerably less than actual total weight of the material dumped and that dynamic loads were subject to many factors, such as effects of blasting to remove hang-ups. Comparisons of measurements and computer results using a particle flow code indicated that several difficulties remain before achieving realistic determinations and models of the dynamic effects of particle flow in ort: passes and impact loads on the gates. Impact loads were overestimated in computer analyses as compared to loads measured in field tests. An alternative design approach based on softening the chute and control gate assembly is being proposed.

By David Gearhart, Thomas Barczak

Hydraulic cylinders a re used in several roof support systems, such as longwall shields and mobile roof supports, to provide critical ground control Many state-of-the-art hydraulic support systems operate at pressures as high as 7,000 psi to provide the necessary support capacities. Pressure in the upper stages of multi-stage cylinders can be intensified by a factor of 2 or 3 providing pressures of 20,000 psi or greater. A proper understanding of the operation of these high pressure systems is necessary to safely maintain and repair these support systems. Likewise, the performance characteristics need to be fully understood to evaluate the impact of design parameters on the capability of the support to maintain effective ground control. This paper examines the basic operating principles of state-of-the-art hydraulic cylinders and discusses relative issues pertaining to. (1) setting loads, (2) support stiffness, (3) yielding behavior, (4) errors in assessing support loading, and (S) hydraulic failure mechanisms and how to detect them

By Gerald T. Homce, Michael R. Yenchek, H. Kenneth Sacks, James C. Cawley

Abstract—Overhead electric power lines present a serious electrocution hazard to personnel in a variety of industries. Overhead lines, typically uninsulated conductors supported on towers or poles, are the most common means of electric power transmission and distribution, and are exposed to contact by mobile equipment such as cranes and trucks. Equipment contacting energized overhead lines becomes elevated to a high voltage, and simultaneous contact by personnel of the “hot” frame and ground can cause serious electrical shock and burns. Industries where risk of these accidents is greatest include construction, mining, agriculture, and communications/public utilities. An estimated 2300 accidental overhead line contacts occur each year in the U.S. This paper describes a practical low-cost concept to detect actual contact of mobile equipment with a high-voltage line and provide a warning. Accident statistics indicate that more than half of the fatalities could be prevented by such a device. Index Terms—Crane, electrical shock prevention, engineering control, mining, mobile equipment, power line.