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Provide respiratory protection and a clean work environment for stationary or semimobile workers at minerals processing plants. Approach An Overhead Air Supply Island (OASIS) was developed which filters, conditions, and evenly disperses an envelope of clean air over a worker's head, thereby insuring reduced dust levels and a clean work environment. How It Works The concept for the OASIS derives from an earlier Bureau development of a canopy air curtain for continuous mining machines (see Technology News #21). In this application, the benefits of a reliable, self-contained, self-cleaning industrial-duty air filtration and distribution system are extended to the minerals processing field. The OASIS draws dust-laden room air into a filtration system, removing the dust and delivering clean air to a specific 16-square-foot area. It consists of: ? a self-cleaning primary filter ? a heater (cooling coil optional) ? an airflow distributor and secondary filter (combined)

Jan 1, 1985

By J. H. Perry

The Bureau of Mines is conducting research to determine the effectiveness of long holes in degasifying an area of the Upper Split of the Lower Sunnyside coalbed at Kaiser Steel Co.'s Sunnyside No.1 mine. These holes were drilled from the two outside entries of a section that was closed to mining because of excessive methane emissions. Two holes drilled to 430 and 450 feet produced initial gas flows of 160,000 and 127,000 cfd, respectively. Sixteen days after the completion of the second hole, the total gas production declined to just over 144,000 cfd. In 9 months of degasification, over 35 MMcf of commercial-quality gas has been removed from the coalbed. The combined gas flows declined to 106,000 cfd in the 9-month period. The two holes have reduced face emissions by about 40 pet.

Jan 1, 1978

By John C. Franklin

The Bureau of Mines conducted extensive laboratory and limited field tests to determine whether a polymeric material could effectively reduce the emanation rate of radon gas from uranium ore. In the laboratory 46 different single-coat materials and 14 two-coat applications were tested. The laboratory tests showed that up to 100 percent of the radon gas could be sealed into the rock. Materials tested in the laboratory were polyesters, furan resins, epoxies, latices, and totally inorganic coatings. From the laboratory work six different materials were selected for field testing. The first test was single-coat materials in five static chambers; the second test used two-coat applications in an open chamber. Both tests were conducted in the Dakota mine at Grants, N. Mex. During the second test, the amanation rate of radon gas was reduced up to 62 percent.

Jan 1, 1975

By D. W. Frommer

Processing of nonmagnetic taconites by selective flocculation-des liming and anionic flotation of calcium-activated silica has been investigated using innovative procedures as a means of improving operating costs. Areas chosen for cost-cutting evaluation were grinding, fine screening, and water conservation and reclamation. The investigation was performed on Marquette range nonmagnetic taconites in the Bureau of Mines Twin Cities Metallurgy Research Center flotation pilot plant, at feed rates ranging between 900 and 1,100 lb/hr. With fully integrated water reclamation, flotation concentrates containing 65.8 percent Fe and 3.4 percent Si02 were made in the best operating period, with accompanying weight and iron recoveries of 40 and 74 percent, respectively. During this same period, the estimated cost of both flotation and water reclamation reagents was only $0.80 per ton of concentrate (1968 pricing basis). This cost is about 15 percent lower than obtained previously at this Center for flotation reagents only. The investigation demonstrated additional potential savings in operating costs of approximately $0.96 per ton of concentrate through autogenous grinding as a substitute for ballmilling. Fine screening of intermediate concentrates was employed advantageously, but the frequency of blinding may be a factor militating against use of the screen in this flotation system.

Jan 1, 1973

By Roy Greenfield

Estimates are given for the distance from a seismometer at which a miner can probably be detected. The procedure in making these estimates was to first establish the natural noise levels at the output of a surface seismometer for the 25 to 100 Hz frequency passband. The noise levels give the range of values which may be expected in areas with no man-made noise. For each noise level, we give the detection threshold which, when exceeded, indicates that a signal has been received. Based on the signals recorded by Westinghouse, curves are given which show the peak signal amplitude as a function of source- to-receiver distance (slant range). Curves are given for the Westinghouse seismic thumper, a 50-pound timber, and a sledge. For a given type of source, the receive signal strength depends more strongly on slant range than on any other factor. However, there is approximately a five-to-one scatter in the amplitudes. Thus, further study of factors affecting the signal amplitude might allow better estimates to be made for any particular geological setting. Combining the signal amplitude with the detection thresholds for the different noise conditions gives the distances at which a miner should be detected. These are given in Table l* below. [ ] The text also gives the increase in detection ranges which should occur if steps are taken to increase S/N by 10 dB. We feel that 10 dB is a conservative estimate of the improvement possible. During an actual rescue operation, the seismic crew and system should be capable of making on-site estimates of their detection capability, based on measurements of the site noise, and upon the best available estimates of the

Jan 1, 1974

By George S. Koch

A statistical analysis of silver assay data from rotary-drill-hole cut-tings and diamond-drill-hole cores from the Round Mountain prospect, Custer County, Colo., demonstrates several useful methods for estimating grades and tonnages of ore from the drilling of wide-spaced holes in disseminated deposits of precious metals. A new method of are appraisal is introduced which estimates grade and tonnage of are by calculating convex hulls (smallest convex polygons) for sample points with assay values above specified cutoff grades. Analyses of variance compare the consistency of data from rotary-and diamond-drill holes, from rotary-drill holes sampled at 2-and 4-foot intervals, from two methods of sample preparation, and from atomic-absorption and fire assaying. Evidently, data from the two types of drill holes, from holes sampled at the two intervals, and from different methods of preparation are in agreement. Atomic-absorption silver values are consistently lower than fire-assay silver values.

Jan 1, 1971

To find solutions for common safety problems encountered in the handling of trailing cables, based on observations at many different surface mining operations. Approach Practices in handling trailing cables were Investigated through personal visits to over 40 mines, supplemented by visits to cable manufacturers and cable repair service companies. The most effective solutions to the safety problems en-countered were noted and are described In the project final report. Examples are given in this Technology News. Accident Experience Most cable-related injuries occur as a result of workers lifting, pulling, tripping, or being struck by the cable. The Table gives the frequency of occurrence for injuries reported during a recent 3 1/2 year period.

Jan 1, 1982

By George H. Schnakenberg, Aleksandar D. Bugarski

This report reviews the performance and applicability of technology for the control of emissions from diesel-powered equipment used in underground coal and metal/nonmetal mines. The methods discussed include Mine Safety and Health Administration-approved low-emission engines, engine derating, fuels, fuel additives, diesel oxidation catalysts, and diesel particulate filters. The potential of each of these technologies is examined individually and in combination. The performance estimates are derived from the published literature and presented in narrative and Tabular form. The purpose of this report is to help the mining industry select the most appropriate method to reduce underground exposures of miners to diesel exhaust in the context of the recently developed diesel regulations. It is important to note that the control technologies discussed in this report have received limited evaluation in underground mines. Additional research is ongoing, and some engineering design changes may need to be implemented before all of these diesel emission control technologies can be safely and successfully used in underground mines.

Jan 1, 2002

By Eugene Baker, Joseph Cervik, Albert Sainato

In Europe, water infusion is used widely to reduce generation of respirable dust during mining. Its use in the United States is limited to a few plow operations in the Pocahontas No. 3 Coalbed. This Bureau of Mines report describes the technology for infusing water in to a longwall panel and reports the results of a recent demonstration in the Lower Sunnyside Coalbed that achieved dust reductions averaging 58 pct. Because water infusion increases moisture content of the coalbed, face air velocities in excess of 500 ft/min (2.5 m/s) are possible, further diluting dust levels before dust entrainment occurs. An economic analysis shows a 23-pct reduction in operating costs when coal production is increased by changing from unidirectional mining to bidirectional mining with water infusion.

Jan 1, 1983

By Verne E. Hooker

Stress relief measurements were made at three underground test sites associated with the Henderson project, American Metal Climax, located in the rugged, mountainous region between Loveland Pass and Berthoud Pass on the Continental Divide in Colorado. Sufficient data were obtained to determine the three-dimensional stress ellipsoid for each site. The measurements were made at hole depths greater than one diameter of the mined opening; thus, calculated stresses are representative of premining in situ conditions. The vertical components of stress are in good agreement with overburden depth including the influence of mountain topography. Horizontal components of stress substantially increase with depth. These components are believed to be influenced by stresses presumably of tectonic origin. The largest measured principal stress was 5,900 psi at a depth of 3.708 feet. The predominant orientation of maximum principal stress for the determinations at greatest depth is in the NW-SE quadrants.

Jan 1, 1972

By M. L. Skow, Maurice Deul, M. G. Zabetakis

This Bureau of Mines report presents a brief summary of the explosion trends in United States coal mines for the past 160 years. These trends show that in spite of the overall improvements in mine safety, the number of fatalities from ignitions of methane has actually increased in recent years. Suggestions are made of procedures that can be utilized to reverse this trend.

Jan 1, 1972

By Stephen A. Swan

Bureau of Mines research has not included analyses of mining dredge safety since 1948. Because of the increasing use of dredges, 63 fatal accidents and several hundred nonfatal injury accidents involving dredges were examined. Also, 31 working dredges and 3 dredge manufacturers were visited to acquire qualitative information. Drowning accidents represented 59 pct of the fatalities and are delineated in detail. Also, countermeasures against other hazards are discussed.

Jan 1, 1985

By J. E. Chilton, Jr. Dubaniewicz

Many mines rely on toxic gas sensors to help maintain a safe and healthy work environment. This report describes a prototype monitoring system developed by the U.S. Bureau of Mines (USBM) that uses light to power and communicate with several remote toxic gas sensors. The design is based on state-of-the-art optical-to-electrical power converters, solid-state diode lasers, and fiber optics. This design overcomes several problems associated with conventional wire-based systems by providing complete electrical isolation between the remote sensors and the central monitor. The prototype performed well during a 2-week field trial in the USBM Pittsburgh Research Center Safety Research Coal Mine.

Jan 1, 1995

By H. A. Watson

Fluorine-containing polymers are comparatively new materials that exhibit very desirable characteristics not usually found in non-fluorine containing polymers. Among these characteristics are heat and flame resistance, desirable electrical properties, and chemical inertness. Polytetrafluoroethylene and polymonochlorotrifluoroethylene are examples of such polymers commercially available. In practical applications it is reasonable to expect thermal position of these materials if they are subject to high enough temperatures. The temperatures at which thermal decomposition takes place and the nature of the gaseous products of decomposition are considered pertinent data in intelligent use of these materials. The purpose of the tests discussed herein was to determine: (1) The temperatures at which gases were produced when small specimens of the two polymers were located and (2) determine the identity of the major constituents of gaseous products.

Jan 1, 1950

Control respirable dust in underground coal mines through selection of optimum water spray pressures. Approach Through underground trials at longwall and continuous mining operations, the relationship between operating water spray pressure and respirable dust levels at the machine operator's location was determined. Defining the Application Water sprays are used for two significantly different control applications. On longwall mining machines, sprays are commonly installed both on the body of the machine and on the cutting drum. Sprays on the body of the machine are used to redirect dust which has already become airborne away from the machine operator. Each spray acts as a small fan, directing the primary airflow over and around the machine and towards the face, away from the operator. The energy of this system is directly related to the spray pressure. Higher pressures move more air, but care must be taken not to cause turbulence and boilout into the walkway. Sprays mounted on the drum are, effective at suppressing the respirable dust at the bit/coal interface and preventing it from becoming airborne. Again, these sprays must not impart excessive energy to the dust particles thus stirring up more dust than they suppress. While mounting sprays on the shearer drum is standard industry practice, there is no reliable technology available to successfully mount water sprays on the cutting drum of continuous miners. Instead, sprays are mounted on the machine body, close to the drum, and directed at the cutting head. This allows the water to reach the bit/coal interface and mix with the cut material. Here again, care must be exercised to prevent these sprays from imparting excessive energy to the dust particles and stirring up more dust than they suppress. These sprays can also cause dust "rollback" from the face, toward the operator, if operated at too high pressures.

Jan 1, 1986

By J. H. Maysilles

The Bureau of Mines, U.S. Department of the Interior, is investigating several types of low-grade uranium deposits. Projections indicate that an increased percentage of future production will be derived from such sources. One material studied was from the Coso Mountains of California; this material contained 0.04 to 0.12 percent U3O8. The deposit contains at least two distinct types of mineralization. The material representing the bulk of this deposit was amenable to acid leaching; 80 to 85 percent U308 extraction resulted from leaching with 20 to 40 pounds per ton of sulfuric acid. No oxidizing agent was required. This ore fraction could be treated by either agitation or percolation leaching. Uranium recovery and purification from the acid leach solution was accomplished using anion exchange followed by precipitation with hydrogen peroxide and ammonia. The second type of mineral was very refractory to acid leaching; a maximum extraction of only 44 percent was obtained with sulfuric acid. Nitric and hydrochloric acids were ineffective also.

Jan 1, 1978

Provide exhaust face ventilation to remotely-controlled continuous mining machines making extended advances without exposing workers to unsupported roof. Approach Modify the sprayfan to move additional air to and from the coal mine face. Unmodified, sprayfans are capable of ventilating the face with 20-foot brattice setbacks. Additional sprays on the rear of the mining machine allow setbacks to be extended up to 40 feet.

Jan 1, 1988

By Kelly C. Strebig

Laboratory tests were conducted by the Bureau of Mines to determine the effect of depth of cut and bit type on respirable coal dust generation. Apparatuses were constructed to contain the coal samples, measure the linear cutting forces, and analyze the dust generated. Single-bit tests were conducted in Illinois No. 5 and Pittsburgh seam coals with five bit types at four depths of cut. The results showed that bit type did not significantly influence dust production. On the other hand, deep-cutting bits were more efficient and generated substantially less respirable dust per pound of coal broke than shallow-cutting bits.

Jan 1, 1975

By Joseph B. Huvos

Said to be one of the world's most under-developed countries, Benin had a gross national product (GNP) estimated at $1 billion in 1980.2 Contribution of the mineral industry such as cement and limestone to the GNP was negligible, but exploration of mineral potential continued Minerals.-The United Nations Development Program (UNDP) conducted an investigation of three deposits from 1977 to 1980: Phosphates (Mekrou), gold (Perma), and chromite (Buem). A phosphate rock deposit containing about 4.5 million tons recover- able by opencast techniques was discovered. It was not known if the gold and chromite deposits were recoverable economically. Iron ore deposits of some 230 million tons near Loumbo-Loumbo are at present not exploitable because of lack of infrastructure in the northern part of the country. Geologic mapping with British and French assistance was also pursued in 1980.

Jan 1, 1982

The Bahamas Oil Refining Co. (BORCO) refinery in Freeport continued to operate at less than half its full 500,000-barrel-per-day capacity. Although owned through subsidiaries by the Carey Energy Corp (65%) and Standard Oil Co. of California (35%), BORCO is ineligible for participation in the Crude Oil Entitlements Program granted to companies operating within the United States proper or its territories. Like some other Caribbean refineries, BORCO has suffered a loss of normal market outlet due to the wt advantage afforded U.S. refineries by the Entitlements Program. Saudi Arabia, Nigeria, and Libya are the major suppliers of crude for the refinery. Its principal products, motor spirits, aviation fuel, distillate fuels, and residual fuel oils, were marketed in the United States and Puerto Rim. The Government-owned Bahamas Development Corp. and Burmah Oil Co. Ltd., held discussions pertaining to a renegotiation of Burmah Oil's management contract for the Grand Bahama Oil Transshipment terminal. The desired contract modifications were not made public but financial problems have plagued the terminal and its operation since construction started in 1972.

Jan 1, 1981