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By Richard J. Mainiero

The Bureau of Mines investigated coal-mine-type short-delay electric detonators marketed by three domestic manufacturers to determine the accuracy of delays and the probability of overlap between adjacent de- lay periods. The Winzer index was computed and compared with the probability of overlap. A close agreement between the Winzer criterion and overlap probability was demonstrated. A permissible blasting unit capable of delivering a maximum firing energy of 4.0 J and a digital oscilloscope were used to measure the delay time with an accuracy of 20.25 ms. Another oscilloscope and a pulse transformer were used to record firing current. Experimental data indicated negligible overlap probability in detonators of shorter delay periods: periods 1 to 4, which correspond to 25 to 250 ms. However, a significant probability of overlap was detected in some detonators of longer delay periods: periods 5 to 9, which cor- respond to 300 to 500 ms.

Jan 1, 1985

This is an audience, I know, that shares my interest in a subject that is currently getting a lot of attention -the tendency of our Nation to draw increasingly on overseas supplies of certain mineral commodities, and proportionately less on domestic sources for these minerals. That we do obtain substantial quantities of some essential minerals from abroad is easy to demonstrate. That we will continue to do so in the foreseeable future is not in doubt. Uncertainty begins, however, when we try to interpret the significance of these facts. As with many phenomena, their meaning is open to a variety of interpretations.

Jan 1, 1980

By Austin B. Clayton

The magnetite deposits of the Big Ore Bank, in Lincoln County, N.C., were mined during the reconstruction period following the Civil War. The country rock at the Big Ore Bank property consists of micaceous schists and schistose quartzite with a few beds of dolomitic marble. Magnetite occurs with micaceous chlorite schist and is often so schistose that it is hard to distinguish from associated minerals. A magnetic survey by the North Carolina Geological Survey indicated several magnetic anomalies that appeared to justify exploration. The Bureau of Mines drilled 10 diamond-drill holes, totaling 4,493 linear feet, to delineate the deposits. More than 500 sludge samples and 119 core samples were collected for analysis. The project was begun in November 1943 and completed in April 1944.

Jan 1, 1948

By Stephen Krickovic, J. E. Carpetta, T. D. Moore

Air quantity-pressure and methane concentration surveys were conducted by the Bureau of Mines in accessible portions of an area being pillared in a Pittsburgh coalbed mine in West Virginia. These included two mined-out and three active butt headings and a bleeder system. The particular mine workings were started in virgin coal directly from a set of main headings; the main reason for the study was the difficulty usually encountered in adequately bleeding the gobs under such conditions. Although the two separate return airways in each active butt heading and the North and 1 Left bleeders contained acceptable methane concentrations (0.01 to 0.78 percent in the butts and 0.73 to 1.0 percent in the bleeders) with significant total methane removal (109 cfm in butts and 631 cfm in bleeders), there were relatively large areas in the gobs with possible minimal airflows. This condition appears to have developed from lack of systematic regulation of the airflow across the gobs and appears to indicate the existence of considerably more methane in the probably low flow areas in the gob.

Jan 1, 1973

By E. D. Gordner

U. S. Bureau of Mines

Jan 1, 1923

By F. S. Crawford

This report deals with the effectiveness and economy of installing mine timbers treated with preservatives in long-life service locations. Early in the present century, when mine timbers and labor were plentiful, it was not general practice to install treated timbers in such places. Because national sources of good mine timber are declining steadily, the mining industry must now conserve timber. Moreover, the cost of installing and replacing mine timbers has been rising. Therefore, even the simplest of treatments can be expected to give some return on the investment when applied to timbers that are to be installed in relatively permanent locations. Better methods of treatment will produce better returns. In a service test of maple timbers treated by the hot-and cold-bath method and installed in main haulageways of the Athens mine of the Cleveland Cliffs Iron Co., Negaunee, Mich., zinc chloride-treated timbers had an average useful life of 13.3 years; borax-treated timbers, 11.2 years; and sodium fluoride-treated timbers, 7.7 years. Untreated timbers used as controls had an average useful life of 3.8 years.

Jan 1, 1950

By R. M. Gammell

"INTRODUCTION The Farmer prospect was examined by W. R. Green, an engineer of the Bureau of Mines, in June 1944. As a result, studies of this property were included in a general preliminary investigation of the Etevens County lead-zinc deposits by the Bureau in 1945. The exploratory work was designed chiefly to supplement the surface examination by determining the nature of the mineralization below the zone of oxidization. The results of the small-scale diamond-drilling program undertaken at the property are presented in the following report.ACKNOWLEDGMENTSIn its program of exploration of mineral deposits, the Bureau of Mines has as its primary objective the more effective utilization our resources to the end that they make the greatest possible contribution to security and economy. It is the policy of the Bureau to publish the facts developed by each exploratory project as soon as practicable after its conclusion. The Mining Branch, Lowell B. Moon, chief, conducts preliminary examinations, performs the actual exploratory work and prepares the filial report. The Metallurgical Branch, R. G. Knickerbocker, chief, analyzes samples and performs beneficiation tests."

Mar 1, 1947

By D. S. Colby, E. M. SEELEY

The total production capacity of the natural-gasoline industry increased to 27,212,000 gallons (647,905 barrels) daily on January 1, 1950, from 21,322,000 gallons (507,670 barrels) daily on January 1, 1948. The rate of growth during these 2 years averaged 13 percent per year, compared with 9 percent per year from 1946 to 1948 and 6 percent from 1944 to 1946. The total number of operable plants on January 1, 1950, was 554, 5 more than at the beginning of 1948. The number of absorption plants increased by 12, the number of cycling plants by 7, and the number of combination plants by 4. The number of compression plants and charcoal plants continued to decrease. Absorption plants accounted for 67 percent of the total capacity on January 1, 1950, compared with 62 percent 2 years previous. Eighty-two per- cent of the expansion in these 2 years was in absorption-plant capacity. Cycle plants accounted for 24 percent of the total industry capacity at the beginning of 1950, compared with 27 percent on January 1, 1948. The average daily capacity of absorption plants increased from 38,400 gallons at the beginning of 1948 to 50,600 gallons at the beginning of 1950. During the same period, the average daily capacity of cycle plants decreased from 150,200 gallons to 144,100 gallons. Texas showed the largest gain in number of plants 13 absorption, 4 compression, and 4 cycling plants. The State accounted for 67 percent of the gain in capacity and on January 1, 1950 had 50 percent total national capacity. Louisiana followed with 7 additional plants. Pennsylvania reported 14 and West Virginia reported 13 fewer plants than in 1948. Most of these reductions were in the number of compression plants.

Jul 1, 1950

By T. A. Hendrickson

The Bohemia district, situated about 30 miles southeast of Cottage Grove, Oreg., in the Calapooia Range, has been the major producer of lead and zinc in Oregon. Sporadic production has been Maintained from the district since its early discovery about 1858. In 1942, a selective-flotation mill was built at the Champien mine, which operated for only a short time and was forced to close because of the war and lack of labor. The Champion mill reportedly has been operated as a custom mill for the treatment of ore from the Musick and Helena mines, located in the district sometime in the past. This report summarizes the results of laboratory ore-dressing studies made on ore samples from the Musick and Helena Mines.

Jan 1, 1951

By Arne Landsberg

Experiments were made with a batch reactor to determine the effect of gas pressures, temperature, and gamma radiation intensity on the reaction CO + Ch ? COC12. The equation, [dp = 0.0110 (1 - 0.01t) (PCOI)1/2 PC12] where [dP] is the change of pressure of phosgene with time (atm/hr), t is the temperature (°C), PCO and PC12 are the reactant pressures (atm), and I is the radiation intensity (r/hr), was found to best fit the data. Oxygen and a large ratio of reactor surface to volume retarded the reaction, but inert gases had no effect. A low-temperature reactor system is proposed to take advantage of the conditions which give a high reaction rate with gamma radiation and a simple scheme of product purification.

Jan 1, 1970

By D. Harrington

In recent years over 100,000 persons have been killed annually in the United. States by accidents; about one-fifth of these have been workers in some of our industries; about one-third have been killed by motor vehicles; about another third have mot death in home accidents, chiefly falls, burns, scalds, explosions, poisons, asphyxiations, suffocations, cuts, scratches, and so forth; and the rest have been killed in public accidents, excluding those caused by vehicles but including accidents on railroads or electric cars, drowning, and deaths by firearms and. other means. Definite statistics on nonfatal accidents are not readily available, but at least 10,000,000 fairly serious accidents probably occur in the United States annually. The latest industrial-accident statistics are obtainable from 1935 National Safety Council publications, in which annual industrial fatalities are divided about as follows (in round numbers): Agriculture, 4,500; trade and service, 4,500; construction, 3,100; transportation and public utilities, 2,900; manufacturing, 2,600; mining, quarrying, petroleum, etc., 1,900.

Jan 1, 1938

By Forrest T. Moyer

Injury experience in the mineral mining and processing industries during 1968 was slightly improved in the nonfatal-injury record but worse in the fatality record. The resulting frequency rate of all injuries was slightly better, whereas the injury-severity rate retrogressed appreciably from the figure for 1967. Overall operating activity, as measured by man-hours of worktime, was slightly higher in 1968. However, there were several major segments of the mineral industries in which activity was lower owing to reduced demand for mineral products and to several major work stoppages. These statistics comprise the injury and work experience of all personnel engaged in production, exploration, development, maintenance, repair, and force-account construction work, including supervisory and technical personnel, and working partners and owners at mineral-producing and mineral-processing establishments in the United States. Data concerning officeworkers are excluded except for the oil and gas industry for which such information is not separable. All injury rates and totals are calculated from data before rounding. The data for 1968 are preliminary except for the anthracite, coke, petroleum and natural gas, native asphalt, peat, and slag industries, which are final. The figures represent full coverage for all industries except oil and gas for which coverage is not complete, particularly with respect to small companies.

Jan 1, 1970

By Steven J. Page

The increasing concern for dust control in metal and nonmetal mining prompted the Bureau of Mines to investigate the comparative effectiveness of three wet dust control techniques for face drilling. Previous attempts to achieve effective dust control on face drills with dry collectors have not met with success, the largest problem being sustained effective dust capture at the face. Results show that (1) foam-through-the-drill can provide 95-pct average total dust reduction in gypsum; (2) water mist-through-the-drill can provide approximately 91-pct average total dust reduction and 93-pet average respirable dust reduction in salt; (3) external boom-mounted water sprays can provide approximately 50-pet average dust reduction for both total and respirable dust in salt. The investigation showed that (1) foam and water in small quantities are very effective dust control techniques for face drills when applied through the drill steel at the point of dust generation, and (2) boom-mounted water sprays are only minimally effective for dust control on face drills.

Jan 1, 1981

By Robert D. Schmidt

This Bureau of Mines report describes the development and application of a computer model for simulating the hydrological activity associated with in situ leaching. The model is intended to provide uranium resource developers with a description of the flow behavior of leachants and ground water during the development, production, and restoration phases of a leaching operation involving an arbitrary pattern of injection and recovery wells. Different aquifer environments are modeled, using a closed-form solution to the partial differential equation that describes three-dimensional changes in piezometric head as a result of pumping from leachant injection and recovery wells. The computer program can model a maximum of, 50 arbitarily located wells. Numerical techniques involving difference quotients and Taylor expansions about time points are used to derive time, velocity, areal sweep, and fluid volume parameters associated with leaching hydraulics. These parameters are output by the program in graphic and tabular formats. Other numeric methods insure that the program running time is minimized without significantly affect-ing the accuracy of results.

Jan 1, 1980

By Charles P. Lazzara, Charles D. Litton, Frank J. Perzak

This U.S. Bureau of Mines report details the results of a series of large-scale experiments where small coal fires were used to ignite the conveyor belt at air velocities ranging from 0.76 to 6.1 m/s. In the tests, electrical strip heaters imbedded within a pile of coal were used to heat the coal to a point of flaming ignition. The flaming coal subsequently ignited the conveyor belt located approximately 5 to 10 cm above the coal pile. During the tests, temperature, CO, and smoke levels were continuously measured in order to determine both alarm time and level as the fire intensity progressed through the stages of smoldering coal, flaming coal, and flaming coal plus flaming belt. Analysis of the data leads to certain conditions of air velocity and sensor alarm levels that are required for early detection of conveyor belt entry fires. Two nomographs are presented, which define sensor alarm levels and sensor spacings as a function of belt entry cross-sectional area and belt entry air velocity.

Jan 1, 1991

By C. A. Allen

"The problem of signaling to the hoisting engineer from a moving cage in the shaft has been considered by many mine operators for a number of years. There are several methods in use in different mining districts, and so far as the writer is aware they have been further developed in Utah than in any other state. The latest installations are of interest because they use a very low-voltage circuit for the shaft wires and also because the wiring can be so arranged that the hoist can be stopped from the cage, if so desired.The first installation in Utah was in the shaft of the Centennial-Eureka mine under the management of C. E. Allen. It was placed in operation in the summer of 1899, end has been in continuous and satisfactory operation for 21 years. The arrangement consists or two bare wires down the shaft carrying a current at 60 volts potential, with a device on the cage for making connection between the two wires. This device is simply a short piece of wire which is thoroughly insulated from the cage and is operated by a short lever. Whenever the cage rider wishes to signal the engineer he pulls down the lever, forcing the short wire out against the two bare wires, thus making a circuit which rings the bell in the hoist-room. A similar device was planned in the Grand Central shaft at Mammoth, Utah, but was later abandoned. The cause of failure was reported to be that the shaft was very wet."

Jun 1, 1920

By Launa Mallett, Charles Vaught, Michael J. Brinich

The lack of good communication is a very real problem in mine emergencies. Sometimes critical information is not communicated to those who need it to make decisions. At other times, those on the receiving end of a warning do not think to ask the right questions. What happens in underground coal mine fires is a case in point. The authors interviewed 48 workers who escaped three serious fires in western Pennsylvania. In each case the location of the fire was known but did not get communicated to many of those who had to evacuate. Sometimes, even the nature of the problem was not clearly communicated. Some workers began their evacuation knowing nothing about what was happening. In an effort to improve emergency communication National Institute for Occupational Safety and Health (NIOSH) researchers worked with safety professionals to determine what sorts of information are critical in a mine emergency. An extensive list was generated, which proved too long to be remembered by individuals. The list was therefore collapsed into six categories. A communication protocol was derived from these categories.

By R. S. Conti, C. D. Litton

This U.S. Bureau of Mines (USBM) report discusses the results of research conducted in the USBM experimental mine at its Lake Lynn Laboratory to determine the alarm times of smoke and carbon monoxide(CO) sensors, and a point type heat sensor (PTHS) to slowly developing coal-conveyor belt fires. The tests were conducted at air velocities of 0.44 and 0.97 m/s. The data clearly indicate that smoke sensors provide earlier warning of fire than 10 ppm CO sensors, and that 10 ppm CO sensors provide earlier warning than PTHS. A success rate of 1.0 (indicating detection of every test fire) was obtained for both smoke and CO sensors. For the PTHS, the success rate was 0.57 at the lower air velocity, decreasing to 0 at the higher air velocity. Data are also presented showing the sequence of fire events and detection events at the two air velocities as a function of time. Results show that early detection and warning of underground mine fires will improve the probability of miners’ escape.

Jan 1, 1995

By Kevin Michael, David C. Byrne

In previous issue of Spectrum (October 1999, 16/4), a system of measuring the attenuation provided by insert-type hearing protectors was described, That report described experiences using the FitCheck (Michael & Associates, Inc.) system in a pilot project involving the steel industry during 1998.[ ]

By Seymour Wasserman

To develop noise control designs for secondary crushers in Taconite plants. Taken into consideration: 1. Acoustical criteria 2. Day-to-day operational considerations and maintenance accessibility 3. Materials of construction 4. Adaptability of design to other Taconite plants having crushers 5. Cost of noise control treatment.

Jan 1, 1977