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By Donald N. H. Chi

The unsteady, one-dimensional, compressible-flow equations have been solved numerically for a deflagration propagating through a gallery of finite length closed at the ignition end and open at the opposite end. These equations were solved for two situations wherein (1) the propagating flame was extinguished after 0.1 sec or before the return of aerodynamic disturbances reflected from the open end, and (2) the flame was allowed to propagate a full 0.8 sec until it was extinguished. It was found that the process of sudden flame extinguishment creates rarefaction waves that, upon entering the burned zone, produce resonance within the burned cavity. For the relatively small value of the product of the expansion ratio (8.5) and the effective burning velocities of 7.4 m sec-1 for the first experiment and 4.9 m sec-1 for the second experiment, it was found that the acoustic approximation provides an adequate estimate of the pressures developed ahead of the flame during the system's early history.

Jan 1, 1974

Lower costs associated with hands-on training in donning and using a CSE ,self-contained self-rescuer (SCSR). Background In June 1987, the Mine Safety and Heath Administration (MSHA) issued an Emergency Temporary Standard (ETS) requiring that all persons entering underground coal mines must be given bands-on SCSR training. The ETS will shortly be replaced by a new standard requiring this hands-on training. Bureau of Mines research has shown that the most effective means of delivering this training is to have the trainee go through a six-step training procedure while in a kneeling position. Once the miner has looped the neckstrap over his or her head, he or she completes the donning sequence in this order: 1) activate oxygen; 2) insert mouthpiece; 3) put on nose clips; 4) put on goggles; 5) adjust neck and waist straps; and 6) replace miner's cap and prepare to move out. This procedure is repeated until the miner demonstrates that he or she is proficient at the task.

Jan 1, 1988

Develop a training program to help mine workers effectively fight small fires in underground Goal mines. Training would enable miners to make rapid judgments on whether to attempt extinguishment, and how best to use the firefighting equipment on hand. Approach Fire reports were analyzed to define and delineate physical and behavioral variables which affect firefighting activities, and to determine effective procedures for extinguishing small fires. A course was then designed to train miners in such procedures. Finally, the course was reviewed by industry experts and administered to a group of miners to determine needed revisions and to validate the course. How It Works Analysis of fire data showed that six items should be emphasized in teaching proper fire response: 1. Alertness to fire potential. 2. Immediate power cutoff. 3. Internal, external communication. 4. Teamwork in fighting fires. 5. Role of ventilation and position of men inby the fresh air side. 6. Effective use of fire suppressant materials.

Jan 1, 1983

Improve ground control in longwall gate entries by developing a practical method for evaluating longwall pillar designs. Background Longwalls have emerged as the most important technology to be applied to underground mining since the continuous mining machine. Longwall mines currently produce more than 30 pct of all the underground coal mined in the United States, up from less than 5 pct just 15 years ago. Safe longwall mining depends on maintaining ground control in the gate entries, the lifelines that provide access to the longwall face. In multientry retreat mining as practiced in the United States, rows of chain pillars are left to protect the gate entries (see figure 1). Chain pillars are subject to severe and complex abutment loads during the process of longwall panel extraction. The design of these pillars is often the single most important element in gate entry ground control and has been the subject of intensive Bureau of Mines research.

Jan 1, 1991

By Ann G. Kim

The Bureau of Mines investigated factors that influence the formation of methane and other hydrocarbon gases in coal, which is an integral part of the coalification process. Coalification begins with a biogenetic stage in which plant debris decomposes and peat is formed; methane and CO2 are the predominant gases produced during this stage. During the diagenetic stage of coalification hydrogen and the hydrocarbon gases methane, ethane, ethylene, propane, propylene, butene, iso-and normal butane, and pentane are formed by dissociation of the organic material. Methane may also be produced by a secondary reaction of hydrogen with unsaturates or by the reduction of CO2. The gas contained in coalbeds is a mixture of methane, C2 through C5 alkanes, CO2, O2, N2, H2, and He; its heating value is equivalent to that of natural gas. The gas content of coal depends on many variables, but an empirical relationship between adsorptive capacity, rank, and depth has been observed.

Jan 1, 1978

By Harold W. Lipper

Helium production and shipment reached new peaks in 1.361. The Bureau of Mines produced 727 million cubic feet, 13 percent more than the 1960 record, and shipped 552 million cubic feet, 16 percent more than the 1960 record. Production exceeded demand for the third successive year, enabling the Bureau of Mines to add 174 million cubic feet to the volume stored underground for future use. At the end of 1961, the total volume of helium in underground storage in the Clifside gasfield was 44-7 million cubic feet. Contracts to implement a long-range helium conservation program were completed with four companies, obligating all the contracting authority of $47.5 million a year made available by the Congress. The four companies will finance, build, and operate helium extraction plants to recover from natural gas an annual average of 3.1 billion cubic feet of helium that would ordinarily be wasted when the helium-bearing natural gas is used for fuel.

Jan 1, 1962

By H. E. Powell

The mineral dressing research here reported is part of a continuing program by the Bureau of Mines to develop new or improved concentration processes for oxidized or partly oxidized lead and zinc ores. A sample of low-grade sulfide-oxide, lead-zinc ore from Jasper County, Mo., containing galena, cerussite, pyromorphite, hemimorphite, smithsonite, and sphalerite was concentrated by froth flotation and tabling to a grade of 66 percent lead. Because of the presence of a high content of slime-size values, the overall recovery of lead was limited to 64 percent at this grade. Tests to recover the zinc by froth flotation and by gravity concentration did not give satisfactory results. INTRODUCTION Since its establishment, the Rolla Metallurgy Research Center has con-ducted studies of base metals as a part of its overall program (1, 2, 3, 4, 5,6,7).3/ This research has been, and is, directed to beneficiating complex and submarginal ores, to retreating rejects from commercial installations, and to developing fundamental data.

Jan 1, 1960

By Oliver C. Ralston

OUTSTANDING TRENDS of the year included the following: 1. Concentration and beneficiation of iron ores to provide improved blast-furnace feed and extend ore reserves. 2. Successful development of pelletizing and sintering procedures for fine iron ores. 3. The realization that cyclone separation could replace existing classifiers in many grinding circuits. 4. The rapidly blossoming metallurgy of ultrapure silicon and improvements in zone melting. 5. The rapid increase in the use of liquid-liquid extraction and ion exchange in hydrometallurgy. 6. The industrial application of vacuum melting on the 100-ton scale. 7. The hope for developing a columbium (noibium) base alloy for high-temperature use. The technologic advancement in metallurgy that had the greatest effect on the American economy was the beneficiation of iron ores to give improved feed for blast furnaces and indirectly extend our ore reserves. This was not a sudden development but rather culmination of a decade of intensive effort.

Jan 1, 1958

By James R. Means, George Bowser

A new phone system was developed that provides eight full duplex communications channels over a single twisted shielded phone line, with no central switching station or line amplifiers. This system greatly simplifies installation and maintenance over that required with conventional switching systems. The system is based on microprocessor technology and digital frequency synthesis. Frequency division multiplexing is used over a bandwidth of approximately 300 kHz, and a baseband voice channel (compatible with conventional pager phones) is provided as a backup to assure communication if the multiplex features fail. Multiplex operations are controlled over a 30-kHz digital channel. The system is designed to operate with up to 16 km (10 miles) of cable plant and a maximum phone separation of 8 km (5 miles). The digital techniques permit a limited amount of monitoring and control capability to each phone. This consists of two pair of contact inputs or outputs, to be used as desired. These "flags" may be read or controlled by a dispatcher's phone.

By J. A. Eisele

As part of its goal of maintaining an adequate supply of minerals to meet national economic and strategic needs, the Bureau of Mines has studied the removal of iron from simulated aluminum nitrate leach liquors by solvent extraction. Iron must be removed from aluminum nitrate liquor produced by leaching calcined kaolinitic clay with HN03 to reduce the iron level in alumina to less than 0.02 wt-pct Fe203 for use in reduction cells. The parameters reported are for (1) extracting iron from a feed containing 1.5 g/l Fe with di(2-ethylhexyl) phosphoric acid (EHPA), (2) stripping loaded organic phase with 20-pct HCI, and (3) water washing of loaded and stripped organic phase. Recommended operating conditions are two extraction stages using 15 vol-pct EHPA in kerosene and three stripping stages using 20-pct HCI. Results are also given for tests using other extractants and stripping agents.

Jan 1, 1982

Provide sound battery safety guidelines for mine workers who maintain mobile surface mining equipment. Approach Battery-related accidents account for about 5 percent of all nonfatal disabling injuries in coal and metal nonmetal surface mines. These accidents occur despite the fact that appropriate battery safety technology (maintenance-free batteries, cable removers, fault detectors, hot-jumping systems, etc.) exists. Mine operators are not always aware of the safety measures that could be taken because this safety information is widely scattered in numerous unrelated technical reports, vendor brochures, and journal articles. A literature search of these reports and a review of relevant industry standards, handbooks, and references on battery safety, followed by discussions with mining company and MSHA personnel, provided the Bureau of Mines with the background necessary to develop procedures for proper and safe battery usage. These procedures were condensed and written in nontechnical language to serve as guidelines in assuring battery safety during maintenance of mining equipment.

Jan 1, 1986

The National Institute of Occupational Safety and Health has classified diesel exhaust as a potential human carcinogen. Though standards for diesel particulate matter (DPM) in the work place have not been established, concern for the health of miners is prompting mine operators to consider methods for reducing worker exposure to diesel exhaust. Approach One of many methods for reducing DPM being investigated by the Bureau of Mines is the use of additives in diesel fuel to improve combustion. Research Results Three fuel additives have been tested in Caterpillar and Deutz diesel engines which are similar to types used in underground mines. One iron-based additive containing ferrous picrate had no effect on emissions. A second iron-based additive containing ferrocene reduced DPM between 5 and 45 pet depending on engine operating conditions. The 37-pct reduction for an 8-minute duty cycle, which includes a wide range of transient loads and speeds, is considered to represent in-mine performance.

Jan 1, 1990

By Samuel R. M. Burton

This Bureau of Mines report describes a method for determining parts per million (ppm) of helium-4 (He-4) in helium-3 (He-3) to an accuracy of ±5% by mass spectrometry. Gravimetrically prepared primary standards were used for the calibration of a Dempster 1800 magnetic sector mass spectrometer. A comparison between a 2.49% He-4 in hydrogen mixture and a 2.49% He-4 in He-3 mixture shows that He-3 can be replaced with hydrogen as a diluent for standards with comparable mass spectrometry sensitivities for He-4. Using hydrogen as a diluent allows analysis of He-3 samples for He-4 when He-3 for preparation of standards is not available and also conserves the rare He-3 isotope. Standards of He-4 in Hz were prepared for calibration of the mass spectrometer for quantitative determinations of He-4 in the 2-to 100-ppm range. A minimum detectable limit of 2 ppm He-4 is obtained by this method.

Jan 1, 1989

By Forrest T. Moyer

The safety record of the mineral and mineral-fuel mining and processing industries in 1965 was improved slightly, as indicated by the reduced injury-frequency and severity rates. The overall operating activity was higher in 1965 as measured by the gains in the number of men working and in the total man-hours of worktime. Injury Experience.-The rate of occurrence of all disabling work injuries in the mineral industries was 17.65 per million man-hours in 1965. This overall rate comprised frequencies of 0.28 for fatal and 17.37 for nonfatal work injuries, of which both were slightly better than the corresponding rates of 0.29 and 17.53 in 1964. Fatalities totaled 537; 5 less than in 1964. However, the total of 32,982 nonfatal injuries was 575 higher than in 1964. This larger number of nonfatal disabilities was offset by the increased worktime so that the nonfatal frequency rate decreased in 1965.

Jan 1, 1967

By M. M. Tilman

The Bureau of Mines investigated the precipitation strengthening of lead¬-base alloys containing 0.5 through 4 weight-percent combined Cd plus Sb. The Cd and Sb were alloyed in a 1-to-1 atomic ratio which maintained compositions along the quasi-binary section Pb-CdSb. Tensile properties, creep rates, and stress-rupture values were obtained on alloys in the aged condition. The highest tensile strength was observed in an alloy of Pb-3 CdSb, After aging for 6 months at 90°±3° F, this alloy had a mean tensile strength of 8,950 psi with 15-percent elongation. An aged alloy of Pb-1 CdSb exhibited a steady state creep rate of 1.2 X 10-3 percent per day at a stress of 500 psi and a temperature of 90°±3° F. Times to rupture at stresses up to 4,000 psi and at a temperature of 90°±3° F were obtained for some compositions.

Jan 1, 1970

Four catalytic converters for diesel exhaust systems were tested to determine their effectiveness in reducing the amount of harmful substances discharged into the air. Tests were conducted with four different catalytic converter designs, using two diesel engines as exhaust gas generators. (Of the four noble metal catalytic converters, three are commercially available.) Testing showed that the catalysts varied widely in oxidation efficiency at light to intermediate engine loads, but that all were very effective in reducing emissions of CO, HC, aldehydes, and odor intensity at heavy loads (engine operating modes resulting in high exhaust temperatures). Particulate loading, particulate size, and NOx emissions were generally unaffected by any of the catalysts. The catalysts had one ad-verse effect on exhaust quality--increased sulfate emissions. Because of the potential problem of sulfate emissions, the exclusive use of catalytic reactors for emissions reduction does not appear to be satisfactory. However, when used with a means for subsequent removal of sulfates, a catalyst can function as a key component in an emissions control system for diesel engines operated in underground mines.

Jan 1, 1978

By Thomas O. Glover

Cameroon's mineral industry continued to be dominated by crude petroleum, The economic development of the country depended on the production and export of crude on. Output was estimated to be 49 million barrels in 1985 compared with 56 million barrels in 1984 and 47 million barrels in 1988. The country's only refinery consumed approximately 12% of the daily production of crude oil while operating at slightly over 50% capacity. The refinery output, however, supplied the domestic need for motor fuel and heating oils. Cameroon's economic prospects were heavily dependent on the oil sector, which bad been responsible for the recent strong growth in the economy. The country consistently sought to avoid the problems associated with an overdependence on oil and followed a relatively broad-based development strategy, using oil revenues to sustain and encourage growth in other sectors. Approximately 75% of the gross domestic product (GDP) was attributed to the mineral industry in some form. GDP growth was approximately 6.5% during 1985.

Jan 1, 1987

By John C. Machisak

THIS CHAPTER of the Minerals Yearbook relates to employment data and injury experience in the metal, nonmetal, and quarrying industries. Combined statistical data on the mineral industries as a whole can be found in volume Ill. Each industry in the chapter is shown separately, and no attempt has been made to combine and show an overall picture. The voluntary reporting of data on injuries and employment by operators of metal and nonmetal mines and quarries has contributed substantially to the promotion of safety in these industries. Data on injury and employment in the clay mining and milling industry are included for the first time. Table 6 contains data for clay mines only for 1955 and for clay mines and mills for 1956. The clay-mill figures are included with other nonmetallic mills in table 5. The information for norunetallic mills was compiled and published for the first time in the 1955 issue of this report.

Jan 1, 1958

By Wing G. Agnew, John A. Johnson, McHenry Mosier

"INTRODUCTION AND CONCLUSIONSThe first three reports of investigations 5/ in this series, pertaining to the investigation of stemming at the Mount Weather Testing Adit dealt with the dust produced by blasting, the effect of stemming on gases generated by blasting, and the relative advantages and disadvantages of different types of stemming and no stemming when used with 60-percent ammonia gelatin dynamite.This report covers an investigation of the length of stemming material through which a primer will fire and detonate a charge of dynamite, such as a missed hole.The practice of drilling a new hole a foot from a missed hole to blast out the missed hole should be prohibited. It is dangerous, as is evidenced by the number of miners killed through drilling into missed holes. It is even more hazardous in a mine on a multiple-shift basis, in which the same miners do not drill succeeding rounds."

May 1, 1942

By Nancy S. Raymon

The Bureau of Mines investigated the effect of controlled additions of selected metal oxides, as well as the adjustment of the calcia-to-silica ratio on the high-temperature strength of refractory-grade periclase. Increases in the hot flexural strength of some periclase materials in the range of threefold to fourfold were obtained with additions of Zr02 and by adjustment of the CaO:Si02 ratio to the 2.5 to 3.0 level. Results show that for each periclase refractory raw material, there exists a combination of level of Zr02 addition and an adjustment to the CaO:Si02 ratio that optimizes the hot flexural strength of each of these materials. Data also indicate that the improved hot strengths can be attributed to the high-temperature secondary phases formed between the different levels of periclase impurities and the additives, resulting in improved intergranular high-temperature bond strength.

Jan 1, 1982