Search Documents

By D. J. Parker

This report is based on data collected in and about the Liberty mine of the Liberty Fuel Co. by D. J. Parker and W. W. Kessler on December 13 and 14, 1933. An important phase of an examination to determine the general condition of a mine with respect to safety is the collection of dust samples from rock- dusted areas. Definite conclusions, based on intelligent interpretation of the analyses of such samples, can be reached only when the general condition of the mine is known. A similar examination and report were made on this property in January 1930 by D. J. Parker and R. I. C. Manning. Since that time much has been done by the management to improve safety conditions in this mine. The changes made will be noted in the course of this report. The mine is in Spring Canyon at Latuda, Carbon County, Utah, and is served by a branch line of the Denver & Rio Grande Western Railroad about 7 miles long and connecting to the main line near Helper, Utah. The writer desires to express his sincere appreciation for the many courtesies and helpful cooperation extended by Superintendent George Schultz and Mine Foreman F. W. Koelling.

Nov 1, 1934

By A. B. Hooker, P. G. Guest, E. J. Gleim

"From time to time the United States Bureau of Mines has received reports of gas explosions alleged to have been caused by correctly assembled flame safety lamps. In most of the mines where the explosions occurred the lamp was in use at a working face where the velocity of the ventilating current would be relatively low. The inference has been that the lamp was correctly assembled but that the gauze became sufficiently overheated to ignite the surrounding atmosphere.As part of its routine investigation of flame safety lamps the Bureau of Mines subjects each lamp to a test in still and moving atmospheres to determine its safety. Heretofore, as long as the lam, successfully passed this and other tests no determinations as to the margin between success and failure were made; hence, in attempting to answer inquiries concerning the reported explosions it was found desirable to be able to give actual gauze temperatures as a measure of the comparative safety of lamps under various conditions. The previous laboratory tests of flame lamps in still mixtures were made in a chamber or ""gallery"" of relatively small volume where the lamps might have been subject more or less to the smothering effect of the combustion products. It was therefore decided to make a special series of tests to obtain the gauze temperatures of both bonneted and unbonneted lamps in still and low velocity mixtures, using a larger gallery to offset any smothering effect.These tests are believed to represent the first attempt at measuring gauze temperatures by means of themocouples. The results will not only be of interest but will also be helpful to many in determining the status of flame safety lamps relative to gas ignitions in mines."

Feb 1, 1929

By W. M. Traver

As a direct result of the second World War, consumption of nickel in the United States has increased to such an extent that it has been considered timely to investigate undeveloped deposits of the nickel minerals. Funds were made available to the Bureau of lines in 1941 to investigate the extent, occurrence, and quality of nickel ores in the Mirror Harbor area. The Federal Geological Survey mapped' and studied the area during the summer of 1941 and Robert S. Sanford, an engineer of the Bureau of lines, made a preliminary examination in June 1942. A contract for drilling the deposits under the direction of the author was let in July 1942.

Jan 1, 1948

By Harry W. Campbell

In 1986 at the request of the U.S. Bureau of Land Management, the U.S. Bureau of Mines studied the 2 acre North Sisters Rocks Wilderness Study Area (OR-12-8) in order to evaluate its identified mineral resources. The Wilderness Study Area is located in Curry County, Oregon, about 15 miles north from Gold Beach. No mines, prospects, or mining claims were located inside the study area, and no mineral resources were identified. Stone from the study area could be quarried and used for construction purposes; however, two nearby quarries have sufficient stone to satisfy local construction needs. INTRODUCTION This report describes the USBM (U.S. Bureau of Mines) portion of a cooperative study with the USGS (U.S. Geological Survey) to evaluate mineral resources and mineral resource potential of the North Sisters Rocks WSA (Wilderness Study Area) 1/ at the request of the BLM (U.S. Bureau of Land Management). The USBM examines individual mines, prospects, claims, and mineralized zones, and evaluates identified mineral and energy resources. The USGS evaluates potential for undiscovered resources based on areal geological, geochemical, and geophysical surveys. Results of investigations will be used to help determine the suitability of the North Sisters Rocks WSA for inclusion into the National Wilderness Preservation System. Although the immediate goal of this and other USBM mineral surveys is to provide data for the President, Congress, government agencies, and the public for land-use decisions, the long-term objective is to ensure the Nation has an adequate and dependable supply of minerals at a reasonable cost.

Jan 1, 1987

By Robert H. Ridgway

Chromite has been produced commercially for slightly more than a century. Developed, at one time, chiefly as a chemical pigment raw material, it has subsequently found extensive application in other chemical industries - as a refractory material for furnace linings and as the sole source of the metal chromium. For some years prior to 1914, its use as a refractory predominated; but post-war development in alloy steels, principally stainless steels, enhanced the metallurgical demand in the form of ferrochrome with a consequent increase in the demand for chromite. More recently direct reduction of chromite in alloy-steel manufacture has been applied to a limited extent. Alloy steels containing varying amounts of chromium, with or without other alloying elements, now find extensive use in a ride variety of ways - in structural material, machines, industrial equipment transportation by land, sea, and air, sanitary equipment, food preservation, and a multitude of other uses. In recent years chromium plating has had wide application and has become important. industrially, but the amount of raw material consumed

Jan 1, 1936

By John J. Sammarco

Light-emitting diodes (LEDs) are emerging as viable replacements for incandescent (INC)-based cap lamps used in mining. The photometric and energy characteristics of these light sources differ in important ways. This paper describes the performance of LED and INC sources in cap lamps in terms of correlated color temperature, color rendering, light output, electric power, ambient temperature and air flow, and light source aging. Importantly, these characteristics can influence a miner?s ability to spot mining hazards thus impacting safety. Second, some of these characteristics interact with the operating life of the cap lamp?s battery power, such that differences between LED and INC sources can be magnified toward the end of a 10-h battery discharge cycle. Empirically, we have determined that after 8 h at an ambient temperature of 25 ?C, the average light output of an INC cap lamp can decrease to about 69% of its initial value when powered by a lead-acid battery, and it can decrease to about 65% of its initial value when powered by a nickel-hydride battery. An LED-based cap lamp using a constant current drive circuit can maintain about 96% of its initial value when powered by a nickel-hydride battery. Real-world tests addressing the effects of ambient temperature and air flow on the light output of an LED and INC cap lamp were conducted in the National Institute for Occupational Safety and Health Safety Research Coal Mine. The LED cap lamp yielded a vertical average illuminance improve­ment of approximately 9.5%, and the INC cap lamp yielded a vertical average illuminance degradation of approximately 4%. The differences between LED and INC cap lamps were further quantified by the calculation of ?mesopic luminance? data that indicated for the same photopic luminance (i.e., as measured using a conventional light meter) the LED cap lamp could be up to 38% more efficient than the INC cap lamp with a lead-acid battery at the end of the 10-h driving cycle. Lastly, accelerated life tests were used to empirically determine light output depreciation as the INC light source age approached its useful life. There was about a 35% decrease in light output. This is quite considerable, particularly given that the light output will decrease an additional 30% to 45% over the period of a 10-h shift. The implications of the differences between LED and INC sources are discussed. This information is crucial in determining how visual performance could be affected for real-world conditions where batteries discharge during the work shift and as the light source ages. To date, only idealized conditions have been used for LED and INC cap lamp visual performance research.

Jan 1, 2009

By T. N. McVay

The various applications of beryllium and its compounds in atomic - energy technology and a growing recognition of possible increased utilization of the metal in the aircraft and space - missile fields have resulted in increased interest in domestic and world reserves of beryllium . Unfortunately, little dependable data on beryllium resources and reserves are available , as past consumption of the element has been small and only limited prospecting and exploration work has been done . The scarcity of resource information is attributed partly to the difficulty of recognizing beryllium minerals in the field . These minerals frequently do not have distinctive characteristics of specific gravity, color , or other physical properties , that enable ready identification by the average prospector . This is particularly true of fine - grained minerals . As a result , a simple field test for identifying beryllium- bearing rock is needed . Recognizing this , technologists of the Federal Bureau of Mines investigated several of the proposed qualitative chemical tests for beryllium . This report describes various modifications of one of these methods to make it more suitable for use in the field . In the modified method , duplicate samples are fluxed -- one with potassium bifluoride and one with potassium bisulfate -- followed by dissolution of salts in water , conversion of the solution to an alkaline condition, addition of morin , and examination of the solution for fluorescence under short -wave ultraviolet light . This method provides a fast , dependable field test for beryllium minerals containing as little as 0.2 percent beryl or its equivalent . The test involves no radiation hazards , and it can be performed by persons having no technical training ; therefore , it should be useful to prospectors in discovering beryllium mineralization .

Jul 1, 1960

By A. Wahab Khair, Richard D. Begley

"This paper presents results of destructive tests performed on rectangular coal specimen under the influence of two vertical and simultaneous wedge indentation forces. Several wedge designs and spacings were utilized in compression tests. The objective of these experiments was to qualitatively monitor the effect of different wedge designs and spacings on the stress distribution within the coal specimen.Coal samples from the Waynesburg coal seam were cut and trimmed to cubical dimensions of approximately 5 X 10 X 20 cm. These specimen were subjected to parallel compressive forces through two vertically applied wedge indentors. Loading was achieved with a hydraulic hand pump in order to facilitate interferogram construction. The load increments were limited due to the sensitivity of the holographic interferometric technique (holometry) in measuring small displacements; therefore, interferograms were taken only during similar increments in order to allow for a qualitative comparison between different wedge design and spacings. In some cases, interferograms were taken immediately before and after failure of the specimen.Introduction Failure Modes Three distinct modes of failure occur when geologic materials are subjected to wedge indentation forces. As shown in Figure 1, a crushed zone is located immediately adjacent to the indentor while chipping can occur if the fractures initiated in the crushed zone extend upwards to the free surface.. The third failure mode is a zone of intricate frac¬tures located between the crushed zone and the chipping zone. Several experiments have been conducted over the years to better understand crater formation and stress distribution within geologic materials under the influence of an indentor. Generally speaking, crack initiation and propogation observed in these experi¬ments correlate fairly well with wedge indentation theory; however, the nature of the .fractures is greatly influenced by different material properties such as grain size and cleavage planes. In other words, a wide range of behavior has been found in different rocks subjected to wedge penetration. For example, it has been observed that some rocks are merely crushed and indented while others are more prone to cracking and chip formation. Therefore, the development or nondevelopment of chips depends mostly on wedge geometry, rock type and depth of penetration. This work is part of the study associated with opti¬mization of cutting parameters, which is best modeled by using brittle materials and subjecting them to rigid wedge penetration tests."

Jun 1, 1988

Researchers with the National Institute for Occupational Safety and Health (NIOSH) have developed a training module to educate both new, inexperienced miners as well as veterans on important issues related to self-rescue and escape procedures. These include: (1) physical and environmental conditions that can be encountered in a mine after a major explosion, (2) knowledge of emergency meeting locations and escape routes, (3) the importance of using self-rescuers, even in seemingly clear air, to keep the lungs isolated from contaminants, and (4) why miners should not go off to look for others who are missing. In addition, the module may stimulate miners to think about and discuss mine explosions and the devastating effects of such an event.

May 1, 2009

By H. C. Hamontre

The liquid-level gage described in this report is an instrument designed to locate liquid levels in wells rapidly and accurately and, with auxiliary equipment described, to follow moving liquid levels automatically. The depth at which the instrument makes contact with the liquid in a well is indicated at the surface by a depth meter on the cable to which the instrument is attached. When the gage is used to follow a surging moving level, the liquid depth is indicated continuously at the surface. This report contains a description and illustrations of the gage and outlines the operating procedures. The instrument is 1-3/4 inches in diameter and approximately 6 feet in length and may be operated through 2-inch tubing. The gage consists essentially of a float that moves upward with respect to the rest of the assembly, causing a change in the flow of electric current from the surface when the liquid level is reached. The instrument has been tested under a variety of conditions and has been found to be sensitive to changes in liquid level of 1/2 inch. Its accuracy is limited principally by the accuracy of the wire-line depth indicator used. It is not affected by pressure or temperature, and it can be run in open hole or under pressure through a lubricator. It employs only one electric circuit and can be run on an Amergraph single-conductor cable (type 1-H-0) ,

Jan 1, 1954

By Foster Fraas

Electrostatic separation depends on a number of electrical and mechanical properties such as conductance, contact potential, dielectric constant, and particle shape. In routine testing it is desirable that the application of each of those properties be investigated. The conductance property is best utilized in a separator having an ionic field, whereas the contact potential requires a separator with a pure static field. Dielectric constant and particle shape also influence the response in these two fields. There is no separator on the market that can be adjusted for all these requirements. The separator described in this paper is satisfactory for this purpose and is provided with a dielectric electrode, which permits formation of high-intensity static fields.

Jan 1, 1951

By R. V. Ramani, S. Shankar

"Available literature on the effect of re-entrainment on overall airborne dust concentration in mine airways or the fundamental mechanisms of coal dust re-entrainment in mine atmosphere is scant (Shankar and Ramani, 1991 ). Therefore, as part of the Respirable Dust Center's ongoing research, the following three-part study was undertaken:• a study of the re-entrainment phenomena of anthracite and bituminous coal dust particles in a wind tunnel under the influence of varying air velocities;• a study of the same in the Lake Lynn Laboratory Mine of the USBM with both air flow and walking by personnel causing re-entrainment; and• the mathematical modeling and computer simulation of the re-entrainment phenomenon.In this paper, results from the re-entrainment studies in the wind tunnel and the Lake Lynn Laboratory mine are presented. Comparing the results from the two studies,it was observed that increasing the air velocity increased the rate of re-entrainment ( Shankar and Ramani, I 994a) and the rate of re-entrainment decreased with the time of exposure of the source dust to the flowing air. In addition, when the source dust was composed of particles of different sizes, the airborne dust concentrations due to re-entrainment were higher than when the source dust was composed of particles of the same size. The contribution of airborne dust concentration due to air flow was negligible compared to the contribution due to walking. IntroductionIn underground coal mines, dust is produced primarily during the process of mining and during such activities as pillar spall, loading, belt transfer and roof fall. The generated dust is entrained and then collects on surfaces through dispersion, diffusion and eventual deposition. Removal forces, such as flowing ventilation air or turbulence caused by walking and moving vehicles, can re-entrain the deposited dust (Hall, 1955). A portion of the re-entrained dust remains airborne and increases the concentration of airborne dust in mine airways.The presence of airborne coal dust in mine airways in large concentrations can be hazardous. Health effects include coal workers' pneumoconiosis (CWP) and silicosis, and it can be a nuisance affecting visibility. In addition, as is common during methane explosions, if the concentration of airborne coal dust becomes significant, there could be a coal-dust explosion (Singer, Cook and Grumer, 1972; Singer, Harris and Grumer, 1974; Edwards and Ford, 1988). Through concerned research efforts over the last decade, significantprogress has been made in reducing the airborne dust concentration in mine atmospheres. However, secondary sources, such as re-entrainment, have not been studied in-depth. It is important to understand the phenomenon of re-entrainment and its potential contribution to the airborne dust concentration in mine airways for further decreasing airborne dust hazards in mines."

Dec 1, 1996

By Fred C. Turin, Lisa J. Steiner, Kim M. Cornelius

Like many experienced workers, remote control continuous miner operators perform their everyday jobs making choices and decisions that they may not consciously think about. While performing tasks, they are continuously processing feedback and cues which guide them for the next move. Initial training teaches the operators the tasks necessary to operate the equipment and perform the job. However, with experience they are better able to deal with hazardous conditions and non routine situations. To better understand what potential cues and feedback help to guide the operators, a questionnaire was developed to learn what factors affect decisions. Operator responses address issues related to specific tasks, equipment operation, visibility, lighting, and communication issues. The information collected is useful to understand what cues experienced operators use to make task performance decisions. Results will be used to develop interventions and training for safe and effective operator performance.

By Knox Van Dyke, Vincent Castranova, Lixin Wu, Mark J. Reasor, James M. Antonini

"One of the proposed mechanisms involved in the pathogenesis of silicosis is that inhaled silica dust activates a ""respiratory burst"" in pulmonary phagocytes, such as macrophages and neutrophils. This increase in oxidative metabolism results in enhanced generation of reactive oxygen species which if produced in excess, would overwhelm natural defense mechanisms and cause damage to the lung parenchyma. This damage would then result in scarring, fibrosis, and decreased gas exchange.Weiss and LoBuglio' have listed several oxygen species produced by phagocytes which may be involved in cellular injury. These oxidants include superoxide anion, hydrogen, peroxide, hydroxyl radical, and hypochlorous acid. Superoxide anion (0;) is generated from molecular oxygen by the plasma membrane bound enzyme NADPH oxidase according to the following reaction:Once generated, superoxide anion can form hydrogen peroxide:In the presence of myeloperoxidase and halide, hydrogen peroxide can form hypochlorous acid:Superoxide and hydrogen peroxide can also form highly reactive hydroxyl radicals. Hydroxyl radicals can be generated slowly by the Haber-Weiss reaction:In addition. hydroxyl radical production can be catalyzed via the Fenton reaction:Hydroxyl radicals can also be generated from the reaction of superoxide and hypochlorous acid as follows:Recent investigations suggest that, in addition to the reactive oxygen species discussed above, nitric oxide may be a potential mediator of silica-induced toxicity.2-4 Nitric oxide (NO') can be generated by the cytosolic enzyme nitric oxide synthase according to the following reaction:NO synthase exists in two forms. i.e.. a constitutive. Ca2+-calmodulin-dependent form and an inducible. Ca2+-calmodulin-independent form. In pulmonary phagocytes. the activity of the constitutive form of NO synthase is low. However. NO synthase can be induced in macrophages and neutrophils by a variety of stimulants such as lipopolysaccharide. interferon y. chemotactic peptide, platelet activating factor, or leukotriene B4.3.5Once generated. nitric oxide can combine with superoxide anion to form peroxynitrite as follows:Peroxynitrite is a potent oxidizing agent. In addition, peroxynitrite can form peroxynitrous acid. which in turn can produce hydroxyl radical and nitrogen dioxide (all of which exhibit strong oxidizing potential) by the following reactions:Oxygen metabolites have been shown to cause lung damage in vivo.6 Such damage includes edema. leakiness of the alveolar endothelial/epithelial barriers, and airway constriction.7 Superoxide and hydrogen peroxide have been associated with membrane damage and cell lysis.8 These oxidants have also been associated with alteration of cytoskeletal structures at cell-cell junctions and elevation of transepithelial conductance in cultured monolayers.9 Macrophages or neutrophils can be stimulated by bacteria or phorbol myristate acetate to produce sufficient oxidant levels to lyse lymphoma cells.10 This cell killing is inhibited by catalase but is unaffected by superoxide dismutase. hydroxyl radical scavengers. or azide. i.e., an inhibitor of peroxidase. This implicates hydrogen peroxide as the active oxidant. Similarly. Weiss et al.11 have reported that hydrogen peroxide is critical in the death of cultured endothelial cells due to neutrophil activation. In addition. hydroxyl radicals generated by monocytes have been associated with cell injury.12 Lastly. peroxynitrite has been shown to oxidize sulfhydryl groups and to inactivate proteinase inhibitor making the lung more susceptible to damage caused by phagocytotic enzymes.' Therefore. a strong case can be made that activated pulmonary macrophages and neutrophils are capable of causing oxidant injury. This chapter presents in vitro and in vivo data indicating that silica is associated with the production of reactive oxygen species from these pulmonary phagocytes."

Jan 1, 1998

By Steven W. Schmauch

In 1985, at the request of the U.S. Bureau of Land Management, the U.S. Bureau of Mines studied 27,930 acres of the 52,000 acre East Fork High Rock Canyon Wilderness Study Area, CA-020-914/NV-020-006A, in order to evaluate the mineral resources. The study area is located in Humboldt and Washoe Counties, NV, about 45 miles east of Cedarville, CA. Bureau of Mines personnel reviewed pertinent literature and county mining records and examined prospects or mineralized areas. There are no organized mining districts and no historical or active claims in the study area; one small pit lies in the southwest corner of the study area. Based on published literature, sample results and field observations, there are no recognized mineral, geothermal, or fossil fuel resources. Epithermal mineralization indicators are not present or exposed. Sand and gravel deposits in the study area are not likely to be developed as other deposits are closer to market areas.

Jan 1, 1986

By Lloyd A. Morley, Alan M. Christman

1. Anonymous. "Getting Down to Earth," booklet 25T, James G. Biddle Co, Plymouth Meeting, Pa. (1970) pp. 1-48. 2. Anonymous. "Megger Ground Tester, Special Instructions," booklet 25-J-1, James G. Biddle Co, Plymouth Meeting, Pa. (1961) pp. 1-16. 3. AIEE Committee. "Application Guide on Methods of Substation Ground¬ing," AIEE Transactions on Power Apparatus and Systems (April 1954) pp. 271-277. 4. AIEE Committee. "Voltage Gradients Through the Ground Under Fault Conditions," AIEE Transactions on Power Apparatus and Systems (October 1958) pp. 669-692. 5. American Standards Association. "American Standard Safety Rules for Installing and Using Electrical Equipment in and about Coal Mines," U. S. Bureau of Mines Information Circular 8227 (1964). 6. Armstrong, H. R. "Grounding Electrode Characteristics from Model Tests," AIEE Transactions on Power Apparatus and Systems (December 1953) pp. 1301-1306. 7. Beck, Edward. Lightning Protection for Electric Systems, McGraw¬Hill, New York (1954) pp. 281-295. 8. Bellaschi, P. L. "Impulse and 60 Cycle Characteristics of Driven Grounds," AIEE Transactions (March 1941) pp. 123-128. 9. Bellaschi, P. L. "Lightning Strokes in Field and Laboratory," Elec¬trical Engineering, Vol. 58 (November 1939) pp. 466-468. 10. Bellaschi, P. L., Armington, R. E., and Snowden, A. E. "Impulse and 60 Cycle Characteristics of Driven Grounds-II," AIEE Tran¬sactions (1942) pp. 349-363. 11. Bewley, L. V. "Theory and Tests of the Counterpoise," AIEE Transac¬tions (August 1934) pp. 1163-1172. 12. Brereton, D. S. and Hickok, H. N. "System Neutral Grounding for Chemical Plant Power Systems," AIEE Transactions on Applica¬tions and Industry (November 1955) p. 315. 13. Bruce, C. E. R. and Golde, R. H. "The Lightning Discharge," Journal of the Institute of Electrical Engineers, London, Vol. 88 (December 1941) pp. 487-505.

Jan 1, 1976

By R. V. Ramani

"In a 1985 seminar, we were told that over-optimism abounds in Artificial Intelligence (AI), that AI is neither a science nor a technology yet, and that we will be both exhilarated and disappointed with AI. In fact, even today, there is no single accepted definition of AI; however, certain features have been identified by AI researchers as essential to consider an entity (e.g. machine or program) to be intelligent. According .to Shank (1987), these features include communication (to be able to communicate with), internal knowledge (knowledge about itself), world knowledge (awareness and knowledge about the world outside), intentionality (knowing what one wants and a plan to seek it, ie. goal seeking behavior), and creativity (being adaptable to changing conditions). None of these figures would individually define intelligence; however, each would be a part of intelligence in its own way.The prospects for the development of entities with AI have never been as good as they are now. The combination of advancements in computer hardware and .software along with new insights into the ways in· which we store knowledge and use it for problem solving has enhanced the potential for the creation ~f intelligent entities. After some unbounded optimism of a major breakthrough in the fifties and frustrating disappointments in the two following decades, it appears now that AI has emerged from research labs to industrial practice. This is confirmed by the growing number of repeat applications of AI in business and industry to the extent that AI can now be considered a technology.AI applications are categorized into several distinct areas such as Natural Language Processing, Speech Recognition and Synthesis, Expert Systems, Robotics, Machine Vision, etc. Of these practical realizations, Expert Systems (ES) has the greatest potential for meeting the decision-making needs of the manager in the ever-growing complex scoio-technical systems. Prof. Feigenbaum, an expert and leader on expert systems, has defined Expert System as"" ... an intelligent computer program that uses knowledge and inference procedures to solve problems that are difficult enough to require significant human expertise for their solution. Knowledge necessary to perform at such a level, plus the inference procedures used, can be thought of as a model of the expertise of the best practitioners of the field."""

Jan 1, 1989

By H. H. Schrenk, Carlton E. Brown

"INTRODUCTION The angle at which a hole is drilled has long been thought to affect the amount of dust disseminated into the air during wet drilling. The amount disseminated has been reported as increasing rapidly with the approach of the angle of the hole to the vertical (up) position. 4/ This has been explained commonly as being caused by a decrease in contact of water with the face of the drill hole; increase in amount of sludge dropping through the air; and increase in amount of sludge running down the drill steel and being thrown into the air by the rotation of the drill steel and by leakage of air from the front head of the drill.The steep up angles of the holes drilled are responsible, at least partly, for the higher dust concentrations found in such places as raises, compared with those at level faces, where most of the holes are drilled at angles farther from the vertical (up) position. The mining industry is coming to realize more and more the importance of the angle of the drill hole as a contributing cause of the high dust concentrations found in some raises. Much work is being done to counteract the effect of the angle of the drill hole on dust dissemination. The rate of rater flow through drill steels is being increased by the use of water tubes of larger diameter or by higher water pressures to obtain better contact between water and the face of the drill hole. Traps are being developed to catch the sludge from the drill hole and allow it to drain down through a special pipe before it drops through the air or runs down the drill steel. Drills that permit little or no air to leak from the front head along the drill steel are being designed and used. Care is being taken to prevent the exhaust from the drill dispersing the sludge into the air."

Feb 1, 1938

By A. B. Hooker, L. C. IlsLey

"Field inspections and data relative to the use of rubber-sheathed trailing cables in mines show that much cable is ruined or its probable life shortened by being overheated in service.The length of cable required to make connection from a source of supply to a machine at the face workings may be 100 to 500 feet. As a rule, the cable is carried on a reel and unreeled as required; and thus in most cases soma of the cable is not removed from the reel. The overheating generally occurs in that part of the cable which is left on the reel.Factors that determine the heating of trailing cables are:1. The size of the conductors in the cable.2. The maximum energy to be supplied through the cable, based upon the horsepower of the motor and the degree to which the motor is loaded.3. The voltage of the supply and the variation of the voltage at the receiving end.4. The time length of current flow and whether continuous or intermittent.5. The kind of current (direct or alternating).6. The amount of ca· le left or the reel.7. The type of cable used.8. The kind of reel used.In connecti0n with an investigation of the general performance of rubber-sheathed trailing callas, the Bureau of Mines has made a limited study of some of these factors, including the following points:"

Jul 1, 1931

The Mine Safety and Health Administration (MSHA) defines an independent contractor as "any person, partnership, corporation, subsidiary of a corporation, firm, association or other organization that contracts to perform services or construction at a mine." Contractors that perform specific types of work are required to report the number of employees who perform work at coal mines and at noncoal mines.

Jan 1, 2004