Search Documents

By G. Grassmück

The question of whether the air curtain principle could be used under conditions prevailing in Canadian metal mines was investigated. A vertical, portable BERRY air curtain was tested, at first in a wind tunnel built at Ecole Polytechnique at full scale (8-by 8-ft cross section) to simulate a drift and its lateral connections, and then in the haulage ways of a metal mine under actual conditions. The results permit us to predict under what conditions this type of air curtain is capable of acting as an air stopping or flow regulator and how it could be further developed.

Jan 1, 1969

By Christian Obregón Mitma

Las inclusiones fluídas son interrupciones en la estructura cristalina de un mineral que atraparon un fluído durante o después del crecimiento del mismo. En ese sentido, el presente texto describe su aplicación a los yacimientos minerales a través de la técnica de la microtermometría que puede determinar las variables físicoquímicos de los fluídos mineralizantes de muchos tipos de yacimientos. En consecuencia, dicha técnica aporta información sobre la génesis de la mayoría de yacimientos mineralesy puede ser insustituible para guiar y orientar la exploración de un yacimiento o distrito minero.

Dec 1, 2013

By J. R. Patts, A. B. Cecala, E. J. Haas

Exposure to respirable crystalline silica (RCS) remains a serious health hazard to the US mining workforce who are potentially exposed as various ore bodies are drilled, blasted, hauled by truck, crushed, screened, and transported to their destinations. The current Mine Safety and Health Administration (MSHA) permissible exposure limit (PEL) for RCS remains at approximately 100 μg/m3 , but it is noteworthy that the Occupational Safety and Health Administration (OSHA) has lowered its PEL to 50 μg/ m3 (with enforcement dates staggered through 2022 for various sectors), and the National Institute for Occupational Safety and Health (NIOSH) has held a 50 μg/m3 recommended standard since 1976. To examine a method for reducing RCS exposure using a NIOSH-developed video exposure monitoring (VEM) technology (referred to as Helmet-CAM), video and respirable dust concentration data were collected on eighty miners across seven unique mining sites. The data was then collated and partitioned using a thresholding scheme to determine exposures that were in excess of ten times the mean exposure for that worker. Focusing on these short duration, high magnitude exposures can provide insight to implement controls and interventions that can dramatically lower the employee’s overall average exposure. In 19 of the 80 cases analyzed, it was found that exposure could be significantly lowered by 20% or more by reducing exposures that occur during just 10 min of work per 8-hour shift. This approach provides a method to quickly analyze and determine which activities are creating the greatest health concerns. In most cases, once identified, focused control technologies or behavioral modifications can be applied to those tasks.

By Alfonso Núñez

The adoption of digital technologies can lower the costs and risks for construction, commissioning, hand-over and transfer to operations eliminate many of the costs and delays associated with handovers and ensure fit for operations deliverables. In Mining, future projects could have 50/30 % less CAPEX/OPEX due to unmanned platforms, remote operations centers, and automated data collection lowering headcount. Additionally, these strategic investments can ultimately become profit centers beyond the traditional ROI paradigm, resulting in a greater return to shareholders/stakeholders for our customer organizations.

Sep 29, 2023

By Alan D. Hartman

Standard metering of electric arc furnaces usually uses root mean square (RMS) or true root mean square (TRMS) measurements for determining power. Only sinusoidal signals are accurately described by RMS meters, and dc or high-frequency components normally are lost in standard TRMS metering. This can lead to inaccuracies when electrical signals are not sinusoidal, contain dc components, or include fast risetime perturbations, as is the case with the electric signals from an electric arc furnace. Electric arc furnace electrical waveforms, observed in research carried out by the U.S. Bureau of Mines, show high-frequency components and significant deviations from sinusoids. These perturbations and distortions make metering difficult for standard power meters. The inaccuracies in metering can cause further problems if those sensors are used in control systems. For control strategies requiring rapid response, any averaging scheme loses information that can be used in control decisions. In order to obtain better signals for both monitoring and control, a study of instantaneous, RMS, and TRMS power monitoring devices was conducted. From this study it was concluded that precision integrated circuits should be used to obtain instantaneous power with a bandwidth of at least 25 kHz. The information from these devices is more representative than that of standard meters and can be used in predictive control.

Jan 1, 2010

By A Andersen

DURING an investigation of the copper-rich portion of the copper-silicon-iron system as part of an extensive research program on P.M.G. alloys, which was begun in 1937 in the research laboratory of the Phelps Dodge Corporation, it became apparent that the binary copper-silicon system below 7 per cent Si needed revision, therefore an investiga-tion was undertaken. Both X-ray methods and microscopic technique were employed. Despite the many investigations that have the clarification of this sys-tem as their object, no two successive reports on the system have agreed in placement of the alpha-phase solubility limit, and uncertainty about the secondary phase first to appear has been voiced several times.3,4,5 It was therefore not surprising, when T. Isawa's6 and M. Okamoto's7 works were reported at the time we were finishing up our experimental work, to find essential disagreement between their results and ours. But when C. S. Smith's latest work on the copper-silicon system8 was published just as we were finishing our laboratory report, it was indeed gratifying to find that the latter's diagram and ours checked in all essen-tial features, except the temperature of the peritectic line above 830° C. Many attempts were made to retain the beta phase during the present investigation, but none was successful. Isawa,6 however, reports that he has been able to obtain X-ray photograms of the beta phase. The structure, he states, is body-centered cubic with a lattice constant of 2.848 A.. at 7.2 per cent Si. Okamoto7 and Smith8 both use the designation Kappa for the hexag-onal phase, and to avoid confusion this designation will be adhered to in the present paper.

Jan 1, 1939

By J Arola, B Kettunen, W M. Bond

Separation of fine and coarse particles as separate streams prior to flotation, and their differential treatments, could substantially increase recovery and reduce collector consumption. A series of simulations was carried out to quantify the benefits from plant scale implementation of such a treatment at the Ispat Inland flotation circuit (Minorca mine). The study involved detailed plant sampling and sample analysis to generate the data needed for simulation studies. Samples were taken from all the streams from flotation feed to final concentrate, as well as cell lips and cell pulp. Sampling was repeated for the second ore blend that was processed by the plant during different periods of a year. Sample analysis involved sieve analysis and size by size chemical analysis for total iron, magnetic iron and silica. Raw data were mass balanced, and flow rates within the circuit were calculated. Mass balanced data were used to calculate model parameters representing the existing conditions. Usim Pac was used for both mass balancing and simulation studies. Available pilot and bench scale data were utilised to define the modified flow sheet and expected performance. The simulated flow sheet included classification of flotation circuit feed by hydrocyclones. While the coarse fraction followed the existing flow sheet, the fine fraction was sent to a magnetic separator. Magnetic and rougher flotation concentrates were combined to form the final concentrate. Two simulations for each blend were carried out. The first one assumed that there would be no change in size by size kinetic behaviours of both gangue and magnetite due to this modification. This was named as the worst case scenario, in which particles had a longer residence time due to reduced flow rates within the flotation cells. The second scenario anticipated that there would be an increase in recoveries of gangue and magnetite going into froth launder due to more efficient use of collector in absence of fines. Results showed that pre-classification of flotation feed could improve the flotation recovery by 0.3 - 0.5 per cent, with the major benefit being significant reduction (40 - 60 per cent) in the amount of collector used.

Jan 1, 2005

By John F. Papp

The objective of this U.S. Bureau of Mines study is to calculate an accurate, reliable estimate of chromium and nickel content of stainless and heat-resisting steel produced in the United States. The columbium, manganese, molybdenum, titanium, tungsten, and vanadium contents of this steel are also calculated. Such contents are required for estimating the quantity of alloying element recovered from recycled stainless steel and consumed by market sectors. In this investigation, the elemental fraction of stainless and heat-resisting steel was calculated as the ratio of the weight of element contained in stainless steel to the weight of stainless steel produced. The elemental fraction has been calculated as a time-averaged, grade-averaged value. The elemental fraction was averaged from 1962 through 1983, and averaged over the grades for which production was reported by the American Iron and Steel Institute during that time period. The 1962-83 average elemental fraction of U.S.-produced stainless and heat-resisting steel was calculated for chromium to be about 0.17 ± 0.01; columbium, 0.00014 ± 0.00003; manganese, 0.015 ± 0.005; molybdenum, 0.004 ± 0.001; nickel, 0.07 ± 0.01; silicon, 0.009 ± 0.001; titanium, 0.0004 ± 0.0001; tungsten, 0.0001±0.00003; and vanadium, 0.00003±0.0000l.

Jan 1, 1991

By T. SPOLAN, G. W. Jones, R. E. Kennedy

Information relative to the explosibility of acetylene at elevated pressures and means of handling acetylene safely under these conditions is of considerable interest at present. American practice limits the pressure at which acetylene may be generated and distributed to poiIits of' use. The pressure in portable acetylene generators is 15 pounds per square inch gage. Tests made by the Bureau of Mines have shown that 15 pounds per square inch gage is too high to prevent explosiofiS of gaseous acetylene in the absence of air; in fact, dry acetylene gai can be exploded at pressures greater than 5.9 pounds per square inch gage. The Bureau has been interested in the explosibility of acetylene for many years because of its continued: use for illumination in many metal mines and its general use in cutting 1illd~--eldifigoperations in the mining maus-try.

Dec 1, 1948

By Jr. Koch

As a means of investigating the distribution and variability of gold in ore from the Homestake mine, Lead, S. Dak., the Bureau of Mines performed a designed sampling experiment, and assay results were statistically interpreted. Fifty-six feet of diamond-drill core from five boreholes was sawed into l-inch-long cylinders, which were sampled randomly and were assayed. Analyses of variance of the assay results were used to compare and assess the different types of variation: within drill holes, among paired drill holes, among unpaired drill holes, and among furnace runs. The extreme variability in gold mineralization found is the natural variability on the smallest scale that can be detected by fire assay; most of the variability is associated with among-feet rather than within-feet sample intervals. Because of the extreme variability, one-half of the gold is in 3 percent of the samples.

Jan 1, 1967

By H. Dale Nichols

[The growing importance of the Sundence (Jurassic) formation an a source of oil, in the Rocky Mountain area has prompted the making of a series of porosity determinations of core samples collected. from the reservoir sands of the Lance Creek oil field, Niobrara. County, Wyo. These analyses are preliminary to a stud of fluid and energy relations in the Basal Sundance reservoir of that field, and the determinations of porosity will be used in subsequent studies requiring, calculations of the volumetric capacity of the reservoir and estimation of the reserves of oil and gas. However, the porosity characteristics an of the Sundance sands in the Lance Creek field are factory that affect the solution of many current practical problems of development and operation. Primarily for that reason but also because it is recognized that porosity values of different oil-production sands are of widespread interest throughout the industry, the results of the initial work have been presented in tabular and graphic form with no attempt to evaluate their significance as they relate to the production history of the field.]

Jan 1, 1938

By Rachel Ribeiro Possamai

No processo de fabricação de componentes mecânicos existem vários fatores que contribuem para gerar distorções de forma após o tratamento térmico, sendo um deles o desalinhamento na distribuição da zona de segregação. Este artigo tem como objetivo caracterizar as segregações em barras de aço ABNT NM 87 Grau 1045, assim como determinar sua variação dentro de um mesmo lote. Para tanto, foram retiradas amostras de diferentes posições de uma rota de trefilação combinada, nas quais foram realizadas análises químicas e microestruturais, com o intuito de caracterizar as zonas de segregação ao longo de um fio-máquina durante o processo de trefilação. Os resultados das análises químicas mostram uma maior concentração de carbono na zona de segregação, com um pico de 0,7% em massa. A análise microestrutural apresenta uma maior concentração de perlita próximo ao centro. As análises macrográficas demonstram que há uma variação na segregação dentro do mesmo lote, tanto em posição quanto em concentração.

Aug 17, 2017

By G. E. Rowan

"DURING the dark ages, the cherished dream of chemists was to find a process for converting base metal into gold. Many a wealthy-but-gullible patron lost a fortune in the search. Men who work with metals today are a bit more realistic. I haven't heard of a metallurgist who expects to develop any one alloy that will resist all corrosive media. In the field of stain-less steels, there are about forty different types of alloys that are used where corrosion is a •problem.A stainless product is ordinarily selected because it offers one or more of the following qualities:(1) Resistance to corrosion (2) Resistance to oxidation at high temperatures (3) Good mechanical properties at room temperature (4) Good mechanical properties at high or low temperature (5) Attractive appearance (6) Ease of maintenanceToday we are interested in discussing the stainless steel family of alloys because of their .ability to resist corrosion. We• will not try to explain the Theory of Corrosion. Let us assume that, when surface potential and oxide formations are properly controlled, iron will resist attack in various chemi.cal solutions. The addition of alloying elements to iron does this for stainless steels. The principal stainless alloys used by various Canadian industries are listed in the accompanying Table."

Jan 1, 1959

By Gordon O. Prickett

In two case studies we look at strategies of acceptance that the analyst can employ to gain entrance and to see his problem solution out to use. The first example comes from metal mines. The problem area was excessive usage and cost of wear parts in the concentrator and an atmosphere of crisis over frequent and unexpected breakdowns. The second case pertains to coal exploration. Better methods were being sought for representing coal quality in developing reserve tonnages. The first strategy is - Develop a detailed Human Impact Statement. The second strategy is - Write down in plain language with the keeper of the problem what he will consider as success in dealing with his problem.

Jan 1, 1978

By Gerald L. Finfinger

The Bureau of Mines conducted an experimental degasification project in Island Creek Coal Co.'s Virginia Pocahontas No. S mine. Methane from the overlying Pocahontas No. 4 coalbed was entering mine workings in the Pocahontas No. 3 coalbed through fractures in the roof rock. Small-diameter (l-S/B-inch) holes were drilled into the overlying coalbed to reduce the gas pressure and intercept methane flows, which were piped to the surface through an underground 6-inch-diam steel pipeline. The total methane flow rate from the vertical holes averaged 150,000 ft3/day for the first month. Methane flows into the mine were reduced by 47 pet, thereby demonstrating the effectiveness of this form of degasification in reducing ventilation requirements and providing a safer working environment.

Jan 1, 1979

By R. Kola

Since more than 15 years the Waelz process at "Berzelius" in Duisburg has proved suitable for reprocessing the zinc and lead containing dust and .sludge which inevitably occur in making steel in EAF-plants. The produced Waelz-oxide is agglomerated in a hot-briquetting plant and charged to an Imperial Smelting Shaft Furnace to recover the valuable elements in form of metallic zinc and lead. In view of the actual importance of the dumping problems of the EAF wastes a description of the "Berzelius" treatment route is given but also the situation in Western Europe is illustrated. Dust from stainless steel production is successfully treated in the Scan Dust Plasma Process in order to recycle Chromium and Nickel, while the resulting Zinc-Dust is treated via the Waelz-ISF-Route. For treatment of low Zinc-containing dust, sludge and fines from integrated steelworks, pilot scale tests have been carried out successfully in the Circulating Fluid Bed in order to recover metalized iron and .zinc/lead fume. A 30,000 tpy Demonstration Plant is planned?.

Jan 1, 1990

By Martin G. Casto

Mixer-settler extractors, among the oldest forms of extraction equipment, have been used since the beginning of this century. Over the past years, a very large number of mixer-settler devices have been designed and operated. Both batch and continuous flow mixer-settlers have been used. The continuous flow mixer-settler extractor offers a great number of advantages over other extraction equipment. The main advantage of the continuous flow mixer-settler is that it is a compact device. A large number of stages can be assembled in a relatively small area, and more stages can be added fairly easily. Many improvements have been made in the design of mixer-settlers. These improvements occurred in almost every phase of mixer-settler' operation; interface control, mixer design, intrastage pumping, interstage flow of the two liquid phases, and stage construction. It is believed that Barstow1 used one of the first continuous mixer-settler extractors. This mixer-settler had concurrent flow within each stage and countercurrent flow overall. The flow for both phases took place by gravity. The Barstow device and other early mixer-settlers had no separate interface control for each stage, therefore, "tilting" of the stages was necessary. In 1934 Holley and Mott2 designed a mixer-settler in which the heavy phase was recirculated within each stage by the use of a valve controlled central line instead of by a pump. Gordon and Zeigler3 in 1939 were among the first to use an adjustable valve to control the interface levels in a mixer-settler, making tilting of the extractor unnecessary. In 1952 Coplan et al. 4 used a modification of the Holley-Mott idea to build a highly improved mixer-settler with flat common walls, and with the

Jan 1, 1971

By R. L. Grayson, R. C. Althouse, L. A. Layne, M. J. Klishis

Introduction The researchers combine a detailed microanalysis of accident data and roof bolting field observations to develop new and meaningful risk indices for the roof bolter job classification. These indices incorporate information that has not been used in traditional measures of risk. The significant parameters that these new indices incorporate are the total number of accidents occurring within a particular work activity, the amount of time a miner usually spends performing the work activities in which the accidents occurred, and the average severity of the injuries incurred in the accidents. Being specific for a particular job, they aid comparisons among work tasks performed in the bolting cycle. The indices' specificity provide anew basis for reexamination of training and operational development of miners for specific jobs. Microanalysis The roof bolting microanalysis was performed by examining the empirical data and written summaries for all bolting accidents reported in the West Virginia Safety Information System (WVSIS) for the years 1983-1987. The WVSIS database contained more than 15,000 accident narratives. The microanalysis of bolting accidents covered 2083 reported personal injuries (RPIs). This large number of injuries, performed at an industry-wide level, provides a broad picture of the nature of roof bolting injuries. The analysis focuses on the activities associated with the cyclical routines of the roof bolting process. For this analysis, roof bolting tasks were categorized into work routines based on the sequence of work activities performed by roof bolters. Four work routines were identified within the overall bolting cycle. And these routines comprised 70% (1217) of all roof bolting accidents at the face. The routines include: face area preparation; tramming, positioning and setting the automated temporary roof support (ATRS); drilling holes; and installing bolts. The types of injuries most common within a routine and the average severity of those RPIs were also identified. Table 1 gives a breakdown of the percentage of accidents by the bolting routines. Another 19% of the roof bolting RPIs cannot be classified in a particular routine because of the vagueness of the narratives. However, it was clear that these accidents involved drilling holes or installing bolts. These results are consistent with previous research. It identified drilling and bolting, followed by tramming, as the most frequent sources of injuries (Helander, Krohn & Curtain, 1983). [Table 1-Accidents by bolting routines at the face Accidents Bolting routine Percent Number Face area preparation 18.2 222 Tram, position, ATRS 23.3 284 Drilling holes 34.2 416 Installing bolts 24.2 295 Total 1217] Roof bolter operators were involved in 82% (1706) of the 2083 accidents. The RPIs incurred by classified roof bolters occurred largely on working sections (95%) and at the face area on the working section (75%). Approximately 23% of the 1706 roof bolter RPIs occurred during tasks which were not part of the bolting cycle. These included belt utility work, providing supplies and section moves. Miners in other job classifications who were involved in roof bolting accidents accounted for the remaining 18% of the 2083 roof bolting RPIs. Among this group were section utility men and general laborers (41%), section machine operators (38%), and electricians and mechanics (11%). Another 9% were performing on-section supervisory functions. Face area preparation Face area preparation work led to a substantial number of injuries, although it accounted for the lowest number of injuries of the four routines. Several tasks were associated with the injuries incurred in this routine. Table 2 shows the percentage of injuries associated with face area preparation. [Table 2- Accidents occurring during face area preparation 26.6% Setting temporary and supplemental supports 24.8% Scaling roof and ribs 21.2% Installing ventilation devices 15.8% Handling supplies and materials 11.6% Miscellaneous tasks] The injuries commonly involved overexertion and 'struck by' falling coal and rock. Handling materials often led to overexertion injuries. Nearly 66% of the scaling-related injuries and about 33% of the injuries incurred during the setting of temporary supports involved 'strikes' by equipment, materials, top and rib. Tramming, positioning and setting the ATRS During tramming operations, workers were often struck by components of the machine and hit by loose roof and rib. Poor footing also led to slips, sometimes against the moving machinery. Table 3 gives a breakdown of accidents in this routine. Control levers were a significant problem in this routine.

Jan 1, 1993

By D. J. Parker

This report is based on data collected in and about the Liberty mine of the Liberty Fuel Co. by D. J. Parker and W. W. Kessler on December 13 and 14, 1933. An important phase of an examination to determine the general condition of a mine with respect to safety is the collection of dust samples from rock- dusted areas. Definite conclusions, based on intelligent interpretation of the analyses of such samples, can be reached only when the general condition of the mine is known. A similar examination and report were made on this property in January 1930 by D. J. Parker and R. I. C. Manning. Since that time much has been done by the management to improve safety conditions in this mine. The changes made will be noted in the course of this report. The mine is in Spring Canyon at Latuda, Carbon County, Utah, and is served by a branch line of the Denver & Rio Grande Western Railroad about 7 miles long and connecting to the main line near Helper, Utah. The writer desires to express his sincere appreciation for the many courtesies and helpful cooperation extended by Superintendent George Schultz and Mine Foreman F. W. Koelling.

Nov 1, 1934

By W. M. Traver

During World War II, the Bureau of Mines investigated a large number of ore deposits in the United States and Alaska in a search for domestic sources of strategic minerals. Deposits chosen for exploration included those expected to contain metals of importance in the successful prosecution of the war. This report describes exploration of a district of known antimony occurrence on Coyote or Antimony Creek near Antimony, Garfield County, Utah. A preliminary report by Paul T. Allsman, Chief of the Bureau's Salt Lake City branch made in August 1941, recommended further investigation, and proposed methods for performing the work. The project, begun in November 1941 and completed in January 1942, included trenching and sampling in four of the most promising parts of the area The Federal Geological Survey cooperated in the work by detailed mapping and assisted in the interpretation of geologic data.

Jan 1, 1949