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"The town of Monson in Piscutaquis County, Maine is the, center of an important site industry. Monson slate has a nation-wide reputation, particularly for electrical switch boards, and the deposits have been worked for the manufacture of such products for many years. Open-pit quarrying is the method most commonly employed in obtaining slate. Underground methods have been used in the Peaon Bottom district near Delta, Pennsylvania, but the quarries that were thus operated are now abandoned. Underground methods have been used more extensively in foreign countries, the most famous example being the slate mines at Angers in France, where an over-head stoping method has been employed successfully for many. It is only under special conditions that underground methods can be successfully used. If the deposit is wide and relatively thin, or if the material is too unsound to constitute a safe roof, open-pit methods must be used, for slate is too low-priced a commodity to justify the heavy expense of any timbering methods. It is only where the deposit is relatively narrow, of great depth, and sufficiently sound to afford a strong roof that ordinary mining may be employed.The best slate beds in two of the three quarries operated at Monson are no worked by underground methods. The chief bed worked by the PortlandMonson Slate Co. is 10 feet thick, stands vertical and strikes N. 63º F. The slaty cleavage is vertical and crosses the strike of the beds at an angle of 5 to 10°. The grain or second direction of splitting is vertical and perpendicular to the cleavage. In addition to the 10-foot bed, to 2-foot beds and one 5-foot bed are available but are not now utilized. In theMonson Maine Slate Co. quarry (the old Pond quarry) a greater number of beds available, but at present quarrying is confined to a single bed about 9 feet thick which dips 30º S.E. and strikes N. 47ºF. The slaty cleavage is vertical and strides N. 45º F., while the grain strikes N. 45-50º W. and is also vertical."

Nov 1, 1920

Develop a simple and economical technique for determining the absolute stresses and the change of stress on the surface of roofs, floors, or walls in miners. Approach Use a commercially-available, permissible, Whittemore-type gage to determine the stress at the surface of a mine opening and to monitor any stress changes that might take place. How It Works The following equipment is used: ? One steel templet (for laying out a 60° rosette on the: rock surface). See first photograph. ? One 3/8-inch rock drill bit for drilling holes for the rosette pins. ? Six stainless-steel rosette pins. ? One Whittemore-type mechanical strain gage. ? One drill (not shown). ? Epoxy for cementing the rosette pins. ? Tape to hold the pins while the epoxy sets. The following procedure is used to determine the absolute stress on the rock surface. 1) Spot the location of the rosette pins with the templet. 2) Drill the pin holes and set the pins with epoxy cement. 3) Measure and record the distance between the pins across three diameters of the rosette with a 10-inch Whittemore-type gage. See diagram. 4) Drill a 1 1/2-inch diameter hole in the center of the

Jan 1, 1981

This Bureau of Mines report on underground mine communications addresses methods and equipment to meet the communication requirements of working sections and places of coal and metal-nonmetal mines. A review of the status of trapped miner detection is also presented.

Jan 1, 1977

By I. S. Solet

This study, of the liquidus temperatures and densities of molten alloys of zinc and aluminum was made as part of a broader investigation on refining of scrap aluminum. One of the methods of refining involves the separation of liquid and solid phases by gravity segregation and by filtration. More accurate data were required on the liquidus temperatures and the densities of molten' mixtures of the metals than were available in the technical literature. New data on the liquidus curve were obtained by thermal analysis. The new temperatures are, for the most part) somewhat higher than those reported previously by other investigators. The density of molten mixtures of zinc and aluminum were found to be less than would be calculated by assuming that the two metals occupy the same respective molal volumes in solution as they do as pure metals.

Jan 1, 1949

By J. F. Barkley

As part of the work of serving as Chairman of Subcommittee 3, Health and Industrial Requirements, of the American Society of Mechanical Engineers' Committee on Air-Pollution Controls, the author assembled the following information on accepted maximum permissible concentrations of air pollutants from the standpoints of health, damage to vegetation, damage to property, and requirements of industrial processes. A search in technical literature was made followed by direct inquiry to all State governments as to their regulations. The subcommittee membership - G. D. Clayton, senior sanitary engineer, Public Health Service, United States Department of Health, Education, and Welfare, Detroit, Mich., Dr. L. Greenburg, commissioner; Department of Air Pollution Control, New York, N.Y., Dr. M. Katz, Defence Research Chemical Laboratories, Ottawa, Ontario, Canada, and Dr. H. H. Schrenk, research director, Industrial Hygiene Foundation of America, Inc., Mellon Institute, Pittsburgh, Pa. - reviewed the information and made very helpful comments and corrections.

Jan 1, 1954

By H. E. Peterson

This report revises an earlier publication by the Bureau of Mines on tungsten analytical procedures and expands the coverage by including appropriate procedures for the critical impurity elements that commonly occur in tungsten ores and concentrates (13).3 The basic methods described are not original, but many of the modifications to improve reliability and sensitivity were developed by the Bureau. Gravimetric and colorimetric methods currently used for the determination of tungsten in ores, mill tailings, and concentrates are described. Colorimetric procedures are preferred for low concentrations of tungsten, whereas either procedure is satisfactory for moderate concentrations. Conversely, a gravimetric method is preferred for the determination of tungsten in concentrates.

Jan 1, 1963

By Jon C. Volkwein

Dust concentrations inside and outside enclosed cabs on several types of mining machinery were measured by the Bureau of Mines. Results indicated that properly enclosed cabs can offer significant dust protection for machine operators. Recommendations for improvements in cab technologies were discussed.

Jan 1, 1979

By W. M. Weigel

"The use of sand for the filtration of municipal water supplies is comparatively recent use in this country, although at the present time, most cities of any size that draw their water supply from surface sources use sand filters in their purification system. Not only are sand filters employed to remove sediment and suspended matter, but they also take out most of the bacteria in the water.The first comprehensive research and study of sand for this purpose was probably that of Hazen for the Massachusetts Board of Health in 1891 and 1892, although sand filters had been employed for a considerable time before, specifications for filter sand drawn since then have been largely based on the results of Hazen's work,The general requirements for filter sand are more exacting than for any of the different kinds of sands, except the chemical specifications for glass sand. Filter sand must be uniform in size and within certain limiting sizes. In addition, it must be clean and free from clay and organic matter and of fairly high purity. Early investigations established the fact that an excess of fine materiel increased the friction and decreased the rate of flow through the filter, and that the size of the finer particles rather than the courser, determined the effective size. Also, that large grains tended to cause irregularities in flow in different parts of the bed. There is no requirement as to grain shapes, except that they be not flat or elongated, since, so far as known, either rounded or angular grains are equally efficient.Based on Hazen's investigations, two factors are quite generally used to control the average size and uniformity of size of the sand. These are defined as follows: The ""effective size"" of a sand is such that 10 per cent by weight of the seed is finer than this size, end 90 per cent is coarser. It is expressed in millimeters, The ""uniformity coefficient"" is defined as the ratio of the size of grain which has 60 per cent finer than this size to the size which has 10 per cent finer (the ""effective size""). It is evident that the smaller this coefficient, the more uniform is the seed. If all the grains were exactly the same size, the coefficient would be 1."

Jul 1, 1924

By M. J. Friedel, D. F. Scott, T. J. Williams

In an effort aimed at monitoring mining-induced stress changes that may influence ground failure, the US Bureau of Mines conducted a series of active 3-D seismic tomographic surveys at the Homestake (Lead, South Dakota) and Lucky Friday (Mullan, Idaho) mines. Existing rock bolts were used to mount geophones and as strike points for introducing seismic energy using a 3.6 kg sledge hammer. Travel time measurements were recorded spanning up to 160 m between drifts at several levels. The tomographic uncertainty was minimized by computing iso-velocity surfaces of constant probability based on statistics from multiple reconstructions and a threshold criteria. Periodic imaging using tomographic velocity surfaces demonstrated that temporal and spatial changes in the local stress field occurred in response to ground failure and stope advancement at a gold and silver mine, respectively. Keywords: Temporal imaging; Mine-induced stress; Seismic tomography; Geophysics

Sep 9, 1996

By William H. Schiffbauer, William D. Mayercheck, August J. Kwitowski

This report summarizes work sponsored by the Bureau of Mines in the development of a remote operating system (ROS) for controllng a thin-seam continuous miner (TSCM) 500 feet or more distant from the extraction face. Detail s are provided on ROS subsystems including the continuous miner, video equipment, controls and displays, the electronic control system, and the operator station.

By James P. Rider, Jay F. Colinet

The National Institute for Occupational Safety and Health (NIOSH) has conducted benchmarking surveys at longwall operations across the country to identify current operating practices and the types of controls being used. Gravimetric and instantaneous dust sampling was completed to quantify dust generation from major sources and determine the relative effectiveness of the different control technologies. Results from the underground dust surveys will be presented as an update on longwall dust control technology and operating practices.

Provide reasonably priced, reliable fire protection for front-end loaders. Approach Automatic fire sensing and suppression systems were developed and ruggedized for use on front-end loaders operating in harsh mine environments. How It Works Temperature sensors mounted in the loader's engine, transmission, and articulation areas detect the heat from a fire while it is still small and controllable. This triggers the release of the ABC class dry chemical extinguishing agent through a fixed piping system onto the fire. The system can also be manually activated from either the cab or ground level. Locations of the principal components of the system are shown in the drawing. Two control subsystems were designed to respond to varying fire protection needs and mine conditions. One subsystem only initiates discharge of the extinguishing agent. The other subsystem initiates visual and audible operator alarms if there is a fire sensed or if there is a fault in the control circuit.

Jan 1, 1979

By D. Dolinar, T. P. Mucho

Horizontal stresses are caused by global plate-tectonic forces. During 1995 alone they were largely responsible for the closing of two longwall mines in the United States. This paper presents six case histories from Pennsylvania, West Virginia, Kentucky and Alabama. In each case, a mine encountered roof falls or difficult ground conditions at the headgate caused by horizontal-stress concentrations. The problems are detailed, and the control measures adopted are described. In most cases, nearby longwall panels without stress concentrations were trouble free. The paper also discusses detailed measurements that were made at two adjacent Pennsylvania longwalls. One headgate was oriented to avoid a horizontal-stress concentration, and the other was not. Eliminating the stress concentration dramatically reduced roof support loads and roof deformation. The paper concludes that proper panel orientation and sequence is the key to maintaining headgate ground control. The optimum orientation is not parallel to the maximum horizontal stress, as previously thought, but rather it is 20° in the stress shadow of the gob. Other stress-control techniques, including artificial support, are briefly discussed.

By Irving Hartmann

The fire end explosion hazard of excessive coal-dust deposits in mines has been recognized for many years, and important measures have been developed for reducing dust formation and to alley loose dust near its source. Nevertheless, in the course of normal mining it has been estimated that 1 to 3 percent (in some thin, friable seams up to 10 percent) of the total coal mined is reduced to dust of through-20-mesh fineness. In highly mechanized, continuous mining operations the production of fines is even greater. Most dust is trapped near its point of origin and removed from the mine, but large quantities are transported by the air current and by haulage into entries, where the greatest proportion settles on the floor and the balance on the rib and roof surfaces. The latter is generally finer in particle size than the floor dust; this, coupled with its more advantageous position for dispersion, makes the rib-roof dust (also to be referred to as overhead dust) a greater potential explosion hazard.

Jan 1, 1954

By L. J. Froisland

The U.S. Bureau of Mines conducted laboratory studies on sulfuric acid (H2S04) digestion of alunite [KA13(S04)2(OH)6] as a means for treating domestic deposits of this mineral. Digesting alunite ore in boiling H2S04 at concentrations of 88-wt-pct acid or higher breaks down the alunite and permits a convenient separation of potassium and aluminum. The digestion reaction is a complex sulfation reaction occurring in two stages. In this reaction, the potassium component extracts into the H2S04 for eventual recovery as potassium sulfate k2s04 in a separate unit operation. Aluminum is left as acid-insoluble aluminum sulfate [A12(S04)a], which can be extracted by a 95° C water leach. Additional purification of AI2(S04)a produced in this study is needed to meet cell-grade alumina (Al202) purity specifications. Extraction and separation of potassium and aluminum from the alunite ore were consistently above 90 pct.

Jan 1, 1989

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 Rudolf Kudlich

"The realization that fuel costs, high as compared with those enjoyed prior to the war, are apparently permanent, has caused steam power plant operators to apply their best efforts towards improving the fuel economy of their plants.Though they have given much attention to the reduction in combustion losses by improving methods of firing and improved equipment, and to diminishing the heat losses by more care in maintaining clean heating surfaces and tight and adequate baffling, they have almost universally neglected the waste that occurs from discarding unconsumed combustible with the boiler refuse.This loss varies between extremely wide limits, depending on the quality of the coal, the type of plant and the firing practice in general, the higher the ash content of the coal the greater will be the amount of combustible appearing in the refuse, and the losses will be greater as the boilers are driven at higher ratings. The refuse from stoker fired boilers is apt to have a lower aver-eve percentage of combustible than that from hand fired boilers if operated at the same rating, but stoker fired boilers are usually pushed to higher ratings and the combustible in the refuse will run higher.In actual operating practice the amount of unconsumed combustible in the boiler refuse may range from a few percent to as high as forty or fifty percent. In an informal statement one well known combustion engineer estimates that the average amount of combustible in the refuse from a large stoker fired central station boiler plant is about 15 or 20%. Assuming that the coal burned contains 12% of ash, and allowing for flue dust losses, approximately two percent of the coal will be lost through this channel. The operating engineer of one large modern central power plant reports that when burning coal of about the same ash content, the average amount of combustible in the refuse was in the neighborhood of 33%, en tailing a loss of approximately 4% of the heating value of the fuel fired. Where the coal used daily runs up into hundreds of tons, an appreciable economy could be effected by recovering this percentage."

Sep 1, 1924

By E. J. Kloos

The Bureau of Mines developed a test for evaluating gas masks designed to protect against phosphine gas; phosphonium iodide is used as a source of phosphine. Gas masks approved by the Bureau for respiratory protection against phosphine include the GMC-SS-1, Mine Safety Appliances Co.; the LG-10 and LG-10G, Willson Products Division, The Electric Storage Battery Co.; and the 084-PHOV-R, Acme Protection Equipment Co.

Jan 1, 1966

By Richard F. Hewlett

This report describes a comparison of methods for computing grade and tonnage of ore, leach, and waste material for a mined-out portion of the Silver Bell Oxide porphyry copper deposit, and these computed values are compared with the actual tonnage of these classes of material produced during mining operations. Comparisons with production records have been made by using both exploration drill-hole assays and development blast-hole assays. The polygonal method is the most accurate for this deposit, because it more closely represents the lateral mineral distribution in the deposit. This is demonstrated by plots of the total-copper assay distributions of the development blast-hole assays for a specific bench. The investigation also shows that the smaller vertical assay interval (based on a 5-foot vertical churn-drill-hole sample) yields a more accurate estimate of both grade and tonnage than the 40-foot composite assay interval (based on the average of eight 5-foot assay values). This can be attributed to the fact that selective mining within a bench can separate out much of the waste and leach material that is included as ore in the 40-foot composite assay computations.

Jan 1, 1970

By M. L. Whisman

Radiotracer techniques were developed for stoichiometric studies of photochemical reactions associated with atmospheric smog formation. Stock blends of separate hydrocarbon and oxygenated compounds were prepared and calibrated. 14C-labeled reactants and products in reaction systems involving hydrocarbons and nitrogen oxides at the ppm level were analyzed for qualitative and quantitative data. Precision and accuracy of these methods developed by the Bureau were determined by replication and statistical treatment of data, and these methods are described.

Jan 1, 1969