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By James C. Cawley

The Bureau of Mines has empirically determined ignition probability versus current for resistive circuits in an 8.3% methane-air atmosphere. Simple ignition probability, defined as the number of ignitions divided by the total number of sparks, was determined, and the corresponding currents were recorded. The experiment was designed to minimize the probability of not observing an ignition that should occur during a series of tests. For resistive circuits in 8.3% methane-air mixtures, the experimental results indicate that ignition was not achieved below 2,000 rnA at 20 V dc, 350 rnA at 30 V dc, 150 rnA at 40 V dc, and 175 rnA at 50 V dc. The simple probability of ignition corresponding to these currents is esti-mated to be, respectively, 1.0 x 10-6, 1.7 x 10-7, 3.0 x 10-7, and 1.0 x 10-5 The ignition mechanism seems to break down below this point, implying that a threshold current value exists below which spark ignition does not occur.

Jan 1, 1987

By C. L. Karr

U.S. Bureau of Mines (USBM) research has shown that fuzzy logic and genetic algorithms (GA's) have great potential for industrial process control. A technique has been developed by the USBM in which GA's are used to substantially reduce the time needed to design fuzzy logic controllers (FLC's).This technique shows promise as an efficient, robust approach to developing control systems. The research described in this report is twofold. First, the basic approach to developing an FLC using GA's is presented. The GA-designed FLC is developed for a specific physical system, a pH titration system. Second, empirical results are presented in which variations in the FLC implementation are compared. Specifically, the effects of altering five aspects of the pH FLC are considered: (1) membership function form, (2) number of fuzzy classes, (3) the center-of-area method, (4) implication operator, and (5) fuzzy rule form. Results indicate that (1) the technique in which GA's are used to design FLC's is effective, and (2) when this technique is used, variations in FLC implementation have little effect on FLC performance in a chosen control problem.

Jan 1, 2010

By N. Kumar Kittusamy

The purpose of this study was to assess the adequacy of the cab design and to determine the percentage of musculoskeletal symptoms among workers. A questionnaire was designed to assess demographics, work information, job history, and musculoskeletal symptoms in operators of heavy construction equipment. Information concerning equipment included design of the seat/chair, levers, pedals, bothersome vibration, quality of egress from the equipment, proper preventative maintenance and repairs, and age of the equipment. The body regions that were evaluated included the neck, middle/upper back, low-back, shoulder/upper-arm, elbow/forearm, wrist/hand, hip, knee, and ankle/foot. One hundred and eighty nine operators completed the questionnaire. The results indicate that these workers are at risk for developing musculoskeletal disorders, the need to perform a larger survey to further substantiate the outcome, and the need to quantify risk factors (i.e., whole-body vibration and static sitting postures).

Jan 1, 2003

By Jack Wasserman, Don Wasserman, Logan Mullinix, Shekhar Khanal, Kelly Neal

This paper presents current finding on truck driver average exposure to acceleration for several different manufacturer’s cab-over trucks on a variety of roads in different countries. The predominant time, for this aspect of the study has been spent in the area around London, England and Warsaw, Poland. The ECE directive 2002/44/EC has provided specific guidelines for vehicle operators 8 hour average acceleration exposure. The primary considerations have been on truck design including the air-ride driver’s seat. The truck manufacturers have produced truck cabs that have some separate suspension from the truck frame. The truck seat manufacturers have been producing air-ride suspension seats for the cab. Both of these designs have had the objective of meeting the ECE directive and providing the vehicle drivers with some degrees of comfort. This paper will provide some information on the ability of the vehicles to operate on a variety of roads and meet the objectives. Method The primary method for evaluation of the driver’s exposure has been the use of a seat pad attached to the driver’s seat. Although this sensor system provides the critical information for the driver, an understanding of the reasons for the values requires additional measurements. The initial study in England used both driver and passenger seat pads, as shown in Figure 1, as well as triaxial accelerometers mounted on the base of the seat. The latest studies used significantly more transducers to better understand the relative rotations and translations on the truck frame, the cab, and the driver. [ ]

Jan 6, 2006

The overall objective of this study is to gather operational data from selected surface coal mining systems in the United States, and to assess the potential production and economic capacity of the systems. The study includes: four mines, each using a different mining technique and different equipment. One mine was selected from each of the major coal fields: Midwestern, eastern,, northwestern, and southwestern. The Midwestern Mine is located in the Central Plains and produced 1.45 million tons of raw coal during the study year The Midwestern Mine uses the area mining or box-cut technique. A large in-pit shovel and a bucket wheel excavator are used to remove the overburden. Coal is removed by a loading shovel and transported to the dumping point by large off--highway trucks.

Jan 1, 1975

Objective: To identify and evaluate a permanent stopping to direct ventilation airflows in large-opening metal/nonmetal mines.

May 1, 2006

Isometric strength is defined as the capacity to produce force or torque with a voluntary isometric (muscle[s] maintain[s] a constant length) contraction. The key thing to understand about this type of contraction and strength measurement is that no body movement occurs during the measurement period. The tested person's body angles and posture remain the same throughout the test. Isometric strength has historically been the type most studied and measured. It is probably the easiest to measure and to understand. Some strength researchers feel that isometric strength data may be difficult to apply to some "real life" situations because in most real circumstances people are moving - they are not static. Other researchers counter that it is equally difficult to determine the speed of movement of a person or group of persons doing a job (each moves in his or her unique manner and speed across the links and joints of the body). Thus, dynamic strength test data collected on persons moving at a different speed and/or in a different posture from the "real world" condition will be just as hard to apply. In truth, neither is better - they are different measurements. Both researchers and users should collect and use data that they understand and that fits their application. Workplace Assessment When a worker is called on to perform a physically demanding lifting task, the external load produces moments - tendencies to produce motion, also called torques - about various joints of the body.(1) Often these moments are augmented by the force of gravity acting on the mass of various body segments. For example, in a biceps curl exercise, the moment produced by the forearm flexors must counteract the moment of the weight held in the hands as well as the moment caused by gravity acting on the forearm's center of mass. To perform the task successfully, the muscles responsible for moving the joint must develop a greater moment than the combined moments of the external load and body segment. It should be clear that, at each joint of the body, there is a limit to the strength that the muscle can produce to move ever-increasing external loads. This concept forms the basis of isometric muscle strength prediction modeling.(1) The following procedures are generally used with this biomechanical analysis technique. First, workers are observed (and usually photographed or video-taped) as they perform physically demanding tasks. For each task the posture of the torso and the extremities are documented at the time of peak exertion. The postures are then re-created using a computerized software package, which calculates the load moments produced at various joints of the body as the task is performed. The values obtained during this analysis are then compared to population norms for isometric strength obtained from a population of industrial workers. In this manner, the model estimates the proportion of the population

Jan 1, 1998

By R. S. Lang, C. C. Merrill

The recovery of zinc from oxidized zinc minerals by the caustic soda leach and electrolytic or chemical precipitation was investigated . With the exception of willemite ( 2 ZnO • Si0₂ ) oxidized zinc minerals were readily soluble in 180 to 240 g / 1 NaOH solutions . A high- grade zinc flake was recovered electrolytically from solutions which had been treated with zinc powder to precipitate copper and lead . Solutions were recycled to the leach stage with a recovery of about 85 percent of the zinc from an ore containing 21.2 percent zinc . Electrolysis was conducted at a current density of 120 amp / ft2 with a power consumption of about 1.5 kwhr /lb zinc . Zinc was also recovered from leach solutions by dilution of the solutions , carbonation of the solution , or the addition of sulfur to boiling solutions . A dilution ratio of 5 : 1 precipitated 59 percent of the zinc in 9 days . Carbonation of the solutions precipitated the zinc as zinc oxide ( ZnO ) and solutions could be recausticized for recycling . Zinc precipitated as the sulfide with sulfur was easily filtered and washed . Approximately half of the sulfur added to solutions was lost in the form of sodium thiosulfate ( Na S₂03 ) .

Jan 1, 1965

By F. R. Lee

[THE Bureau of Mines was established in July 1910 to conduct research and to Establish standards for mining equipment and practices which would conserve human life, natural resources, and property in the mineral industries. Several lists of equipment approved by the Bureau as permissible for use in gassy coal mines have a been issued since then. The lists covering all approved equipment except breathing apparatus and explosive have been consolidated info two publications: Bulletin 543, Permissible Equipment Approved to January 1, 1953, and Information Circular 5220, Permissible Mine Equipment Approved By The Bureau of Mines During 1953-62. The purpose of this publication is to supplement Bulletin 543 kind Information Circular 8220 with a listing of permissible equipment approved during 1963 and 1964. The schedules (standards) under which equipment listed herein have born approved are as follows (titles and dates of approval and revision are given in footnotes): Schedule 2F,3 schedule 6D,4 schedule 7C,5 schedule 8C,6 schedule 9B,7 schedule 10C,8 schedule 12D,9 schedule 22,10 schedule 24,11 schedule 25B,12 schedule 28,13 schedule 29A,14 schedule 30,15 and schedule 31.16]

Jan 1, 1966

Occupational illnesses are more difficult to identify than on-the-job injuries. Many illnesses related to occupational exposures may not be diagnosed until years after exposure; by that time, exposed workers may have changed jobs or left the workforce. Other approaches to identifying occupationally related illness are analysis of death certificate data (see chapter 2) and medical examination studies of workers known to have high exposures to hazardous agents. Figures 5-1, 5-3, 5-4, 5-6, 5-8, and 5-10 show, for each commodity, the percent of illness conditions reported to MSHA by nature of condition. Heart attacks that occurred on the job are reported without regard to work-relatedness. Figures 5-2, 5-5, 5-7, 5-9, and 5-11 show rates by year during 1986-1995 for selected conditions. Since there are many limitations on the accuracy of illness reporting, the frequencies and rates shown here should not be considered directly comparable across commodities. Figure 5-12 shows estimates for hearing loss by age among coal miners compared to a nonoccupationally noise-exposed population. These data come from a study by Franks [1996] of a group of audiograms obtained on coal miners by a commercial company. Using the NIOSH definition of hearing impairment, i.e., an average hearing threshold level for both ears that exceeds 25 dB at frequencies of 1,000, 2,000, 3,000 and 4,000 Hz, the figure shows that by age 30, more than 10% of miners suffer hearing impairment; by age 50, 90% of miners have hearing impairment. In contrast, only 10% of the nonoccupationally noise-exposed population suffer hearing impairment at age 51, and 50% of the nonoccupationally exposed population have hearing impairment at age 69. Figure 5-13 shows a similar analysis of commercial audiograms on male metal/nonmetal miners [Franks 1997]. At age 20, approximately 2% have hearing impairment using the NIOSH definition of hearing impairment described above. This increases to 7% at age 30, 25% at age 40, and 49% at age 50. In contrast, only 9% of the nonoccupationally noise-exposed comparison population have hearing impairment at age 50. Franks' analysis showed a different pattern for female metal/nonmetal miners; they developed hearing loss at the same rate as would be expected for a non-noise-exposed female population.

Jan 5, 2000

By J. Fletcher Smoak

Consumption of abrasive materials in the United States increased 22% in value over that of 1982 to $320 million; of which, 59% was manufactured abrasive, 35% was industrial diamond (natural and synthetic), and 6% was natural abrasive. Production value of natural abrasives, excluding industrial diamond, remained virtually unchanged. Production of crude tripol, a porous siliceous rock, decreased slightly; however, shipments of processed tripoli increased 13% in quantity and 32% in value. Production of garnet, an abundant iron-aluminum silicate, continued to increase primarily because of further increases in production from one plant that had completed an expansion program in late 1981. Production of special silica stone, both crude and finished, decreased in 1983 because of reduced demand for oilstones

Jan 1, 1984

By Chris Nelson

Two pieces of European Union (EU) legislation together establish requirements for protection against risks from vibration at work. The vibration directive1 specifies duties of employers to protect workers from risks from exposure to vibration; the machinery directive2, specifies duties of manufacturers and suppliers regarding the safety of machinery marketed in the EU. This paper discusses both directives and the standardisation programmes that support them. It also addresses the implementation of these requirements in Great Britain. Employers’ duties: the vibration directive This directive requires employers to assess and control risks to health and safety arising from hand-arm vibration (HAV) and whole-body vibration (WBV). Member States were required to implement the directive in national legislation by 6 July 2005. Employers are required to eliminate vibration risk at source, or reduced to a minimum. The duties include: assessing risk and exposure; planning and implementing the necessary risk control measures; providing and maintaining suitable work equipment; providing workers with information and training on risks and their control; and monitoring and reviewing the effectiveness of the risk control programme. Daily exposure exceeding a specified action value triggers a requirement for a programme of technical and organisational measures to minimise vibration exposures and the resulting risk, and the provision of health surveillance. Exposures above a specified limit value are prohibited. When conducting their risk assessments, employers are required to “assess and, if necessary, measure” the vibration exposure of workers, for comparison with the action and limit values. Vibration measurement in the workplace is not expected in all cases and the use of vibration information from equipment manufacturers is specifically mentioned. This provides a link with the machinery directive (see below). Manufacturers’ and suppliers’ duties: The machinery directive The machinery directive, first introduced in 1989, is intended to remove barriers to trade. It puts duties on manufacturers and suppliers who place machinery on the European market to design their products to eliminate or reduce risks to health and safety and to warn the user of any residual risks, providing information required for safe use (for example, operator training, maintenance and selection of consumables). There are specific requirements for minimising risk from vibration in the design and construction of the machine and, in the case of hand-held, hand-

Jan 6, 2006

By David C. Grant

A laboratory technique for simulating in-situ uranium mining was developed and used to determine the effects of leaching variables on permeability, uranium recovery, leach solution interaction with the ore-aquifer environment, and post-leach chemical leakage. In particular, ammonium bicarbonate, the commonly-used leach solution, was examined in great detail. Agitation leach tests were conducted to examine the effect on ammonium sorption and desorption of clay content, solution and clay ammonium levels, pH, and the type and concentration of other anions and cations in solution. Initial column tests were performed to determine the degree of ore-aquifer interaction that could be expected for various leach solutions; sulfuric acid, and ammonium, sodium, and potassium bi-carbonates. Subsequent tests examined various methods to restore the ores by lowering the post-leach chemical leakage. The restoration tests examined the use of reducing agents (e.g., ammonium bisulfite, sodium bisulfite; and sodium sulfite), ore blocking and stabilizing agents (e.g., sodium silicate, aluminum chloride, and magnesium-calcium salt).and ammonium displacement agents (e.g., aluminum chloride and lanthanum chloride-sulfate)

Jan 1, 1980

By V. F. Parry

[Approximatel~r 7-1/2 illion tOlls of subb1tnminous coals are mined an-nuall in Colorado, Wyo~ing, and Montana, of which 50 percent probably reaches dome ,-tic conswno:os. r:L'he moi s t'_re of the se subbi t1.Uninous coal sis high, averae;:t.:ug about 25 :!,)ercent \-Then they are :nined. T'ne coals are non-caking d ~~ack to a vari ble degree when exposed to nornal atmospheric conditions. ~hey a~e gpod domestic fuels, are considered to be smokeless in most furn~ces, and have been used. f, r f!1an: y ars in hand-fired domestic furnaces in hich tnc practice i~ to e~ploy large lureps for efficient com-]

Jan 1, 1941

By H. N. Smith

IN 1944 the Congress passed the Synthetic Liquid Fuels Act that authorized the Secretary of the Interior, acting through the Federal Bureau of Mines, to conduct basic research and construct and operate demonstration plants to produce synthetic liquid fuels from coal, oil shale, and other substances. As a basis for the oil shale investigations to be undertaken in this country, the progress of foreign countries in developing and using oil shale as a source of liquid fuels was studied by the technical missions of the Federal Bureau of Mines. Oil shale mines, retorting plants, and refineries were visited; geological information on the nature and occurrence of the foreign oil shales was obtained; and samples of the oil shales were collected where possible. Samples collected by these missions or acquired by other means came from Australia, Brazil, Canada, France, Manchuria (China) , New Zealand, Scot-land, Spain, Sweden, Thailand, and Union of South Africa. These countries represent a large part of the locations where oil shale developments have taken place. The major omissions are the Estonian, German, and Russian developments.

Jan 1, 1959

By R. P. Vinson

Assessment of workplace exposures is an important tool for helping to minimize dust-related occupational illness and diseases. Real-time particulate monitoring can effectively locate areas where dust controls are needed and determine how well they are working. An affordable, person-wearable, real-time dust monitor is needed. The SKC Inc. Dust Detective (SKCDD) fulfills those requirements (Disclaimer: Mention of any company or product does not imply endorsement by NIOSH). The SKCDD consists of a disposable sampling tube (DST) connected to a small hand-held sampling pump. The SKCDD was developed through a Cooperative Research and Development Agreement (CRADA) between the National Institute of Occupational Safety and Health (NIOSH) and SKC Inc. The relationship of dust concentrations measured by personal gravimetric samplers to those measured by the SKCDD was determined in a laboratory aerosol chamber. A comparison of the means and the relative standard deviation of triplicate measurements of each type of sampling device demonstrated the SKCDD to be a viable alternative means for measuring dust. While it provides accurate measurements for specific coal types, it requires correction factors (those correction factors still need to be calculated) for other coal types.

By N. Greninger

The Bureau of Mines examined the possibility of a seasonal variation of respirable dust concentration in U.S. coal mines. The first step was to review company and MSHA-inspector dust samples that had been collected during the past several years in 14 selected mines for compliance purposes. Results indicated severe scatter in data; most standard deviations of the dust concentrations measured in winter and summer months were comparable in magnitude with the mean values of dust concentrations for the seasons. Therefore, a detailed statistical analysis was conducted. At the 90% confidence level, the company samples of three mines had winter means 0.15 to 0.54 mg/m3 higher than the summer means; six mines had negligible seasonal variations; and five mines had winter means that ranged from higher to lower than the summer means. Inspector data, however, were too sparse for analysis. In view of both the low frequency of occurrence of a seasonal effect and its wide scatter in several of the mines, the study was ended with the conclusion that seasonal varia-tion in respirable dust levels, in general, is an insignificant factor.

Jan 1, 1986

By W. A. Calhoun

"INTRODUCTION A letter from S. D. Strauss, vice president of Metals Reserve Company, Washington, D.C., dated May 22, 1945, to the chief of the Metallurgical Branch, Bureau of Mines, in Washington; includes the following: Because of the present critical shortage that exists in the supply of corundum required by certain industries in war production, the Reconstruction Finance Corporation, Mr. W. C. Keeley, Vice Chairman for Metals and Minerals, War Production Board, has recommended that the Reconstruction Finance Corporation though Metals Reserve Company, proceed with preliminary mill testing of the corundum ore in Gallatin County, Montana, and that the results of that testing be transmitted to the War Production Board. If the results of the testing work are considered satisfactory, Metals Reserve Company will then provide for the actual mining and milling of the ore for the production of corundum concentrates.Pursuant to the above stated recommendation by the War Production Board, Metals Reserve Company desires to make -use of the facilities of the Bureau of Mines testing plant at Rolla, Missouri, for conducting sink and float and other concentration tests on representative samples of the Montana corundum ore. Two, and possibly three samples of ore are to be tested which will have an aggregate weight of approximately 50 tons."

Dec 1, 1947

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 Eugene T. Sheridan

The 22d annual survey of the packaged-fuel industry by the Bureau of Mines, United States Department of the Interior, revealed that 26 plants in 8 States were in operation and reported production in 1956. The demand for packaged fuel in the United States has declined gradually since the end of World War II, and the number of operating plants has decreased from 70 in 1946 to 26 in 1956. Annual productive capacity of the industry has decreased also during this period, and the decrease in capacity was about proportional to the decrease in operating plants. Packaged-fuel plants are relatively small, and 85 percent of the active plants in 1956 had an annual capacity of less than 10,000 tons. The same situation prevailed in 1946, when 84 percent of the plants had a capacity of less than 10,000 tons. Total capacity for the 26 active plants in 1956 was 174,600 tons, an average of 6,715 tons per plant. Operating rates in 1956 were the highest since 1951, and the rate of production for the industry averaged 37 percent of capacity.

Jan 1, 1958