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By Thomas O. Glover

Cameroon continued to enjoy sustained economic growth that began with its independence in 1960. Growth in the gross domestic product (GDP) averaged 2.8% per year during the 1960's and the first half of the 1970's. Starting in 1976 and for the succeeding 10 years, the GDP accelerated rapidly owing to the coming on-stream of Cameroon's small but domestically significant offshore oil industry. In 1985, the GDP grew by 7.8%, but in 1986, it was only up 5.5%. The country's sustained economic growth in dollar terms of gross national product (GNP) per capita reached $1,075 in 1986. The ranking in GNP per capita by the International Monetary Fund put Cameroon in the middle-income category for developing countries. The sustained economic growth rate up to 1986 was due to the injection of income from oil into the economy, but crude oil price reductions in 1986 brought a slowdown. In 1986, crude oil production grew to 200,000 barrels per day, an increase of 8.2% from that of 1985. Most of the oil came from the Société Nationale Elf Aquitaine (SNEA) wells in the multifield Rio del Rey complex. Additional output came from the Moudi Field operated by Compagnie Française des Pétroles S.A. Proven oil reserves in Cameroon were 540 million barrels. At 1986 production rates, and in the absence of further discoveries, Cameroon will have exhausted its recoverable oil reserves by the year 1995. Owing to worldwide crude price reductions, the country's oil income fell 60% between 1985 and 1986, from $1.82 billion2 to $0.72 billion. Cameroon's refinery operator commenced operating the Sonara refinery in 1981 at Point Limboh. Sonara's capacity of 43,000 barrels per day was small by most standards. In 1986, natural gas reserves, estimated at 100 billion cubic meters, were not produced commercially because there were no domestic users. Proposals for a multibillion-dollar liquefied natural gas plant at Kribi had been submitted; however, work on the plant had not commenced.

Jan 1, 1988

By M. L. Fenger

This report describes a study of the factors which affect medium voltage (661 - 1000 volts) and high voltage (1001 - 7500 volts) trailing cable couplers for use in underground coal mines to connect trailing rabies. Improvements in quality, dependability, and safety of medium and high voltage couplers are presented in the form of requirements for couplers. The results of an investigation of high voltage trailing cable coupler design and of whether trailing cable couplers must have a metallic shell as required by CFR 30 part 75.805 are presented. Conclusions and recommended research programs are included that describe the present situation and future development approaches.

Jan 1, 1978

By Peter Swanson, John Rettkowski

As part of a research program to reduce injuries and fatalities in the U.S. mining workforce, NIOSH is investigating the potential use of noncontact vibration measurements to identify hazardous ground fall conditions. In the present study, the effectiveness of remote vibration sources in exciting resonant responses in damaged structures is examined. Initial experiments were performed on a damaged concrete slab in a controlled environment. Vibration response was measured with a laser Doppler vibrometer using both single-point and two-dimensional array recordings. Excitation sources included direct mechanical impacts to remote portions of the slab and a remotely located industrial demolition hammer. Surficial damage was effectively delineated with both sources through visualization of vibration response in spectral bands selected to discriminate wave propagation from large-scale slab resonance effects.

By E. M. Murphy

Comparative data from ASTM method of test E-162 and large-scale trials in the Experimental Mine show that the flame-spread quality of brattice cloth and other ventilation control materials can effectively be evaluated by either method. Materials having a flame spread index of 25 or less, as determined by the simpler and more economical laboratory test ASTM E-162, do not present a serious fire hazard when used in coal mines.

Jan 1, 1972

By J. C. Engel

Recent innovations in mine safety include the use of mercury vapor lamps for mine vehicle illumination. Such lamps, however, extinguish whenever the line voltage at the machine momentarily sags or is interrupted. The lamps must then cool for several minutes before they will restart. By supplying reduced high frequency power to the lamps from an auxiliary source, it is possible to maintain ionization in the arc tubes preventing the lamps from extinguishing. Essentially an auxiliary high frequency supply, the keep alive system provides additional power to the lamps automatically whenever the lamps are in danger of dropping out. The system can also provide the operator with the ability to dim the lamps at will for periods of up to three minutes by simply interrupting the 60 Hz power to the conventional ballasts. Each unit, housed in a steel explosion proof enclosure with a volume of approximately 0.6 ft3, is capable of servicing up to six 175 watt H-39 mercury lamps and two 100 watt H-75 reflector flood lamps. A total of 16 units were produced for the USBM under this contract and its extension.

Jan 1, 1979

By Lucia Kuizon

The Cactus Springs Roadless Area Review and Evaluation (RARE II) study area (No. A5188) comprises 12,800 net acres (5,180 ha) in San Bernardino National Forest in west central Riverside County, California, about 20 air miles (32 km) southeast of Palm Springs. Mineral investigations are made by the U.S. Bureau of Mines on National Forest lands identified as Further Planning Areas in the RARE II program. The Bureau of Mines reviewed literature, mining claim records, and production files; examined the study area; and mapped and sampled mineral properties where appropriate.

Jan 1, 1983

By C. Lurie

This final report describes the work performed by Gulton Battery Corporation under USBM Contract No. HO-112033, entitled "Research and Development on Lithium-Nickel Fluoride Batteries For Mint Life Support Equipment". The lithium-nickel fluoride couple was chosen For this investigation because of its high theoretical energy density (626 Wh/lb), its ability to operate at ambient temperatures and the fact that it showed promise as a secondary system. The theoretical energy density of the lithium-nickel fluoride couple is ten times greater than that of the widely used lead-acid battery and three times greater than the silver-zinc battery which has the highest theoretical energy density of the commercially available secondary systems. The experimental program first evaluated the cell components individually. The results of these studies then formed the basis for investigations of cell performance using experimental three-plate cells. These cells consisted of one nickel-fluoride and two lithium electrodes. All work was performed in a glove box under an argon atmosphere which was sufficiently pure to maintain the shiny appearance on freshly prepared lithium surfaces. The major portion of the work effort was concerned with the nickel fluoride electrode. Binder, conductive diluent, fabrication technique, as well as the nickel fluoride active material itself, were considered. Criteria for binder materials were established and six classes of materials encompassing thirteen binders were evaluated. The candidate materials were initially screened for appropriate chemical and physical properties and finally evaluated in three.-plate cells, Two epoxy powders emerged as the most promising binders. Two types of conductive diluent were evaluated. The first is a carbon black of low bulk density and high surface area. This material is a good conductive diluent; however, electrodes fabricated with it lacked good mechanical strength. It was hypothesized that a uni¬form, small particle size, low specific surface area would improve the mechanical properties of the electrodes. Therefore, two samples of graphicic materials, milled to uniform powders in the one-to-ten micron range were evaluated. Electrodes prepared with the graphitic materials had superior mechanical properties, However, their electrical performance was significantly poorer and voltage losses of 0.2 to 0.3 volts were observed. Several electrolyte solutions were evaluated. N-Methyl-2-Pyrrolidone was tested but found to be incompatible in the presence of lithium. Lithium perchlorate, lithium hexafluoroarsenate, and lithium bromide were tested as two-component electrolytes in propylene carbonate solvent and their performance compared with that of the single electrolyte solutions, Lithium perchlorate gave the best performance. Lithium hexafluoroarsenate was also evaluated in methyl formate and appears to give equivalent performance. The lithium perchlorate-propylene carbonate system is preferred as it is easier to handle and less expensive.

Jan 1, 1973

By Susan M. Moore

Many challenges are faced by workers in lower-seam (42 inches or less) mines. The lower-seam heights confine mine workers to their knees as they perform their daily tasks such as installing roof bolts, delivering supplies, repairing belt, or cutting coal. Miners working in these lower seams often consider kneepads to be their only line of defense against knee injuries. However, healthy knees do not start and stop with kneepads. Other interventions such as changing postures, proper hygiene, and work station design may also be used to reduce mine workers? risks for developing knee injuries. Incorporating these and many other interventions into a mine worker?s ?way of life? is an important step to ensuring a long, healthy career and retirement. Keeping knees healthy is also a key aspect to reducing costs in low-seam mines as the industry battles rising health care costs, and training/recruitment of replacement workers is time-consuming and costly. Educating the workforce about the possible interventions to reduce knee injury risk is a primary objective for the National Institute for Occupational Safety and Health?s (NIOSH) Pittsburgh Research Laboratory (PRL). Therefore, NIOSH researchers, along with industry and academia, developed a training package to educate the mining community about some possible interventions beyond kneepads that may be used to help decrease knee injury rates. Increased awareness and simple changes are the first steps to reducing knee injuries.

May 1, 2008

By R. L. Zick, J. D. Byars, T. P. Mucho

Recently, a large Pittsburgh seam longwall mine was nearing depletion of a major portion of its current reserves and had begun to develop in a different direction from its original portal area to access additional reserves. This meant that a large area of the mine would be abandoned and sealed. However, continued use of the original mine portal area required that the water accumulating in the abandoned mine would eventually need to be pumped to the surface. This would be in addition to the discharge water associated with the new portion of the mine. Several pumping and sump options were investigated to handle the quantity and quality of the anticipated discharge water. This paper describes some of these options, their advantages and disadvantages, and the final engineering decisions. Some problems and unanticipated outcomes, as well as the eventual solutions are discussed, including: (1) estimates of pump requirements, (2) water pool size, (3) eventual water quality, (4) anticipated inflows, and (5) integration into the overall mine water system.

By Alexander May

The Bureau of Mines, in cooperation with the Florida phosphate mining industry, investigated the dewatering of waste phosphatic slimes. Part of this investigation was to determine the electrophoretic mobilities and cation exchange capacities of the slimes. The mobilities and exchange capacities are reported for samples of slimes taken from 15 plants operating in the Florida land-pebble phosphate district that includes Polk,Hillsborough, Manatee, Hardee, and DeSoto Counties. The electrophoretic mobilities determined were all negative, ranging from -0.24 to -1.93 (micrometers per second) per (volt per centimeter). Also reported are frequency distributions of electrophoretic mobilities, electrophoretic mobilities of slime diluted with distilled water and electrophoretic mobilities of sand-slime mixtures. The cation exchange capacities ranged from 17 to 45 milliequivalents per 100 grams of slime solids.

Jan 1, 1975

MFIRE is a computer simulation program that performs normal ventilation network planning calculations, and dynamic transient state simulation of ventilation networks under a variety of conditions. The program is useful for the analysis of ventilation networks under thermal and mechanical influence. MFIRE simulates a mine's ventilation system and its response to altered ventilation parameters, external influences such as temperatures, and internal influences such as fires. Extensive output enables detailed quantitative analysis of the effects of the proposed alteration to the ventilation system Network simulation using digital computers has become widespread throughout the mining industry in recent years. However, as the sophistication of the simulator increases (MFIRE, for example), the complexity of input data requirements and interpretations of results requires more skill and knowledge from the users. Perhaps the most difficult part of using MFIRE is to construct the data set describing the mine's physical layout and its ventilation properties. The initial attempts to get the data set running often reveal unknown or ignored aspects of the mine's ventilation. MFIRE was written in Fortran 77 and compiled with Microway1 Fortran for the Intel 80386 based computers with a 80387 math co-processor. The source code is portable and available for users who wish to modify the source code to operate on other computers. This user manual describes the development of MFIRE, the input format and requirements, the output, common errors, fire parameters, and examples MFIRE application. Valuable reference material is included in the appendices. Knowledgeable users may skip directly to the PROGRAM INSTALLATION AND OPERATION section to begin using MFIRE immediately.

Jan 1, 1995

Objective To develop safety training tools for mine safety and health trainers that can be used for both new-miner training and annual refresher training. Background For the past 3 years, NIOSH has been developing training materials for mine safety trainers in response to gaps identified during stakeholder meetings. Most materials have been directed to the hazards of underground mines, but the recent passage of Part 46 of CFR 30 required new-miner and annual refresher training in aggregate operations. One result was the identification of another audience needing basic information about safety in mining. Trainers characterized trainees in this segment of the industry primarily as young males, many of whom had little work experience. Approach Training specialists from the Arizona State Mine Inspector’s Office approached NIOSH researchers early in2002 about the possibility of a collaborative project to develop safety training materials for new trainees in aggregate operations. A preliminary search of MSHA accident statistics identified over a dozen common hazards that could be targeted in a training video. A storyline was developed for review by safety specialists in the aggregate industry, and a script was written to cover the selected hazards. Although the target audience was primarily new hires, the finished video was also to be relevant to more experienced workers.

Jan 1, 2003

By J. Frederick Stampfer

Current certification testing of self-contained breathing apparatus includes tests with human subjects wearing the apparatus while exercising. During these tests, certain apparatus variables are measured during rest periods. Because of concerns that the present tests may not accurately simulate the stresses to which an apparatus is subjected in the field, the Bureau of Mines proposed new human subject tests. It was also felt that different measurement techniques would supply more reliable data on the apparatus response to these stresses. The Los Alamos National Laboratory was asked by the Bureau to evaluate the proposed tests and monitoring techniques. The major conclusions derived during this study are these: (1) The proposed tests are not too physically demanding. (2) As long as human test subjects are used, a minimum subject weight should be required for certification tests. (3) Important apparatus variables are the breathing resistance, temperature, and carbon dioxide and oxygen concentrations of the inhaled gas. (4) Continuous monitoring should be used, rather than monitoring only during rest periods. (5) New pass/fail criteria based on realistic estimates of the user's physiological requirements, as tempered by present and future engineering limitations, are needed. (6) When available, breathing machines, rather than human subjects, should be used for most certification testing. (7) A more realistic ergonomics test than that proposed is needed. (8) A gas leak test for the system and a facepiece leakage test are also needed.

Jan 1, 1983

By J. Mitchell Linnet

Bureau of Mines personnel examined mines, prospects, and mineralized areas to determine the mineral resources and potential of deposits in the Bucks Lake and Chips Creek RARE II areas in Plumas and Butte Counties, California. These areas lie along the west slope of the Sierra Nevada on opposite sides of the North Fork Feather River and encompass an area of 62,800 acres (25,400 ha). Metasedimentary and metavolcanic rocks of the Pennsylvanian Calaveras Formation are intruded by plutons of Mesozoic age. Mineral; of economic iterest are in quartz veins in metasediments close to these plutons; they are principally gold and silver with minor amounts of copper, lead, and zinc minerals. Molybdenum, copper, silver, and tungsten minerals occur in tactite along metasedimentary-granitic rock contacts. In both areas, auriferous Tertiary channel gravels have been extensively developed. Asbestos occurs in ultramafic rocks in both areas, and a limestone deposit was explored in the Chips Creek area. Gold is the principal economic mineral in the Bucks Lake RARE II area. The Shenandoah Mine (fig. 1, no. 19) contains 7,500 tons (6,800 t) of indicated and inferred subeconomic gold resources in sulfide-bearing, silicified metamorphic rocks of the Calaveras Formation (table 1). Similar rocks have yielded gold at the Edman and Megowen Mines, adjacent to the area. A high potential exists for additional lode resources in the area around the Shenandoah Mine. Callahan Mining Corporation personnel believe a multi-million ton disseminated gold deposit underlies the property.

Jan 1, 1983

By S. J. Duda

Procedures for detecting and locating seismic sources are adapted to the case of entrapped miners. During an emergency the entrapped miner is likely to generate seismic signals, by knocking against the walls of the shaft. With a seismic array station deployed near the disaster area, the seismic signals can be recorded. Two algorithms are presented for the location of the source from the arrival times of a seismic phase: The first algorithm produces one, most probable location, under the assumption of constant velocity of propagation of seismic waves in the medium. The second algorithm is similarly applicable, however without any restriction on the seismic velocities in the medium between the source and the array. While the first algorithm uses an analytic approach, the second one is based on a trial and error procedure. The second algorithm gives locations with arbitrarily high accuracies, depending only on the accuracy of arrival time measurements and on the compatibility of the true velocity distribution and the assumed velocity model. The algorithm is shown not to require under certain conditions direct .arrival time measurements, thus eliminating a potential source of errors in the location of entrapped miner.

Jan 1, 1973

By D. Randolph Berry

Foster-Miller Associates has developed a set of guidelines to permit hoist manufacturers, mine owners, and MESA mine inspectors to design, purchase, install or inspect a safe and effective Emergency Escape Hoist, as required by the Coal Mine Health and Safety act of 1969. A series of surveys were carried out to determine: 1. The attitudes and local needs of the MESA District Managers. 2. Current escape hoist installations. 3. Equipment available for future designs. 4. Foreign methods and equipment for mine rescue. From these survey studies, preliminary guideline objectives were developed.

Jan 1, 2012

By J. H. Crary

This report summarizes the results of a one-year agreement for research on the electromagnetic environment in coal mines, which was conceived as the beginning of a long term cooperative program between ITS and the Bureau of Mines. The concepts on which it was originally based are a result of the report on mine rescue and survival by the Committee on Mine Rescue and Survival Techniques of the National Academy of Engineering, dated March 1970. This report drew particular attention to the need for improved communications during and following mine disasters. In particular, the outstanding problems identified were the location of, and communication with, trapped miners. Some tentative solutions, generally involving long-wave electromagnetic signals, were offered. Consideration of the problems of disaster location and communication soon leads to consideration of the communications techniques (or lack of them) for use under normal mining conditions. In particular, if a disaster communication and/or location system is to be readily available and operable under disaster conditions, it should also be usable during mining operations. In this way operators can become familiar enough with the system to operate it during disaster conditions, as well as provide a mechanism for regular testing.

Jan 1, 1972

By Theodore R. Jolley

The estimated recoverable reserves in the area in the vicinity of Eska 2 mine are, 699,300 tons in the Chapin and Emery bas of the Maitland group. Those recoverable reserves are in the area between the Eska fault zone and Jonesville fault and extend down dip from the outcrops. No reserves were developed by the Eska 2 entry or by drill hole 14-16 in the Eska fault zone. The small quantity of reserves in the vicinity of the Eska 2 mine is insufficient to justify development of a now, modern .nine in this area. The estimated recoverable reserves in the area east of aka Creek are 974,500 tons in the Eska, Shaw, and Martin beds of the Eska group. Most of those reserves occur in the south limb of the syncline. It will be necessary to practice subjacent mining methods to recover these reserves in the Eska group. The Eska bed developed by the diamond drilling in this area comprises coal end few thin partings. The Shaw and Martin beds comprise two bunches of coal separated by partings, and the product from full-bed mining will require thorough preparation.

Jan 1, 1952

By Michael S. Miller

During U.S. Bureau of mines mineral investigations, in 1981 and 1983, no mines, prospects, or mineral resources were identified in the Little Sand Spring Wilderness Study Area (WSA). Placer gold values in near-surface samples from alluvial fans within or near the WSA contained no more than 66 cents gold per cu yd, at $400 per troy ounce gold price. Sand and gravel and carbonate rocks occur in large quantities, but transportation costs to distant markets preclude their classification as resources. Nitrogen, lithium, clay, pumice, perlite, aragonite, and agate occurrences in the WSA are small or low-grade. The Silvia Mine, adjacent to the WSA contains gold-, silver-, copper-, and lead-bearing shear zones which strike toward the WSA. INTRODUCTION The Little Sand Spring WSA, encompassing 33,500 acres, is approximately 56 mi east of Big Pine, California, by paved and graded dirt roads (fl;. 1). Elevations range from 2,600 ft in Death Valley Wash to 5,600 ft along the California-Nevada boundary. The nearest permanent facilities are at Grapevine Ranger station and Scotty's Castle (Death Valley Ranch), about 9 and 11 mi, respectively, south in Death Valley National Monument.

Jan 1, 1983

By L. J. Prosser, Robert Anderson

Advance knowledge of roof conditions can lead to improvement in roof control strategies that will reduce roof falls and ultimately will reduce injuries to mine workers. J.H. Fletcher and Company, in cooperation with West Virginia University, has been developing a system to meet these needs by collecting torque, thrust, and rotation speed data during drilling operations. Recent improvements in analysis algorithms to detect anomalies in the roof structure as well as various display enhancements for real time mapping and evaluation of roof structures have been incorporated into current Fletcher Information Display system. The unit has also been housed in an explosion-proof container to allow use in coal mine applications. Recently, the system has undergone extensive field trials in several limestone mines and one coal mine. During these trials, the National Institute for Occupational Safety and Health assisted Fletcher in verifying the accuracy of the roof mapping capability of the system by comparing the display information to bore hole scoping observations and drill corings. It was concluded from this assessment that the intelligent drilling system can complement scoping and core analysis to provide a more complete picture of roof strata and is capable of seeing features or conditions that are not always obvious in these more traditional methods.