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By John C. Edwards

The Bureau of Mines has developed a time-dependent droplet vaporization model (in the absence of forced convection) that can be applied to the vaporization of liquid Halon 1301 droplets (vapor pressure at 300 K = 14 atm) sprayed from an extinguisher. It was found that rapid surface vaporization quickly lowers the droplets' surface temperature very near to the boiling temperature, and the vaporization becomes diffusion controlled. Although the lifetime of the droplet is proportional to the square of the initial radius of the droplet, the elapsed time prior to complete droplet vaporization is not proportional to the square of the droplet radius, as an equilibrium model would indicate.

Jan 1, 1982

By S. Gallagher

If we consider ergonomics to be an exercise in matching job demands to worker capabilities, one of the principal capabilities we must be concerned with is that of human strength. Our ability to evaluate different characteristics of muscular strength has increased dramatically over the past couple of decades with the development of new and increasingly sophisticated instrumentation. One would think that armed with such advanced techniques, we might be able to develop methods to conclusively identify workers at risk of injury in physically demanding jobs. Unfortunately, this has not yet proven to be the case. Instead, what these instruments have continued to point out is how intricate a function muscular strength really is, and how complicated and ambiguous its relationship is to musculoskeletal injury. While we cannot just use isolated tests of strength to specify precisely who may be at risk of injury, studies have indicated that strength testing can be a useful tool for job design and, under certain circumstances, selection of workers for demanding jobs. However, because strength is such a complex phenomenon, there has often been some confusion regarding the proper application and interpretation of strength tests in ergonomics, especially among persons not thoroughly familiar with the limitations and caveats associated with the available procedures. The purpose of this chapter is to discuss some of the fundamental principles of strength assessment in ergonomics, so that these procedures can be better applied to control the risk of musculoskeletal disorders in the workplace 1.1. What is Strength? (And what are we Measuring?) Many of the complications associated with strength assessment arise from the simple fact that even our most sophisticated machinery does not directly measure the force or tension developed by a muscle in a living person. Instead, we can only observe the consequences of force development by a contracting muscle, or more likely, by a combination of muscles There are many ways in which we can measure the effects of muscular contraction, and the techniques we use can have a dramatic impact on the strength readings we will obtain. Consider the situation illustrated in Figure 1. In this example, the muscle exerts a constant force of 1000 Newtons (N). However, the forces we measure can vary quite dramatically depending on where we place the force cuff - from 167 N if we place it near the wrist to 500 N if we place it near the elbow. Which value should we select as properly representing the muscular strength for this elbow flexion exertion? The preceding example illustrates some important points with regard to strength assessment. Perhaps the most important is that "muscular strength is what is measured by an instrument" (Kroemer et al. 1999). It should also be clear from this example [ ] that two researchers could perform an elbow flexion strength experiqent on the same group of subjects, but if each selected different force cuff positions, they might end up with wildly differing estimates of strength. Differences in the strengths of various muscle groups in the published literature may be the results of differences in the procedures and measurement methods used by the experimenters Thus, it is critical that any strength data presented be accompanied by a detailed account of the manner in which the data were obtained. A few additional points need to be made with regard to the testing of human strength. We must be clear that what we are obtaining in such tests are not a person's maximal strength capability, but their maximal voluntary strength. The voluntary nature of the exertion introduces an unknown, but surely substantial, amount of variability in our measurements of strength. One can imagine two subjects with identical muscular strength capabilities, but with varying levels of motivation or discomfort tolerance, for example. We are likely to observe considerable differences in the voluntary force exerted by the two, but it should be understood that such results may be largely the result of psychological factors, and not differences m muscular strength per se. The important point to be made here is that not only are we unable to directly measure muscular force, what we are able to measure is modified by an invisible filter - a filter subject to a wide variety of influences and which will differ considerably for every person we test To make matters worse, this filter would be expected to change even within a given individual on a given day. From the foregoing discussion, one can perhaps better appreciate some of the difficulties with establishing a definitive relationship between an individual's measured strength and that individual's risk of injury.

By Thomas C. Miller, Rudolph Sporcic

A relatively simple and inexpensive encapsulated hydraulic device has been developed by the Bureau of Mines to facilitate study of coal bumps , and to measure pressure changes in a coalbed as it is subjected to roof loading during mining . Construction of the device and application techniques are described . Preliminary feasibility tests in the laboratory and field indicate that the device responds satisfactorily to pressure changes in coal created by roof loading .

Jan 1, 1964

Acid pollution from abandoned mines causes serious contamination of major streams in coal mining areas. In Pennsylvania alone it is estimated that 3000 miles of streams are devoid of fish and plant life because of coal mine effluent.1 The pollution arises because water and oxygen react with iron sulfide in the mine cavity to produce sulfuric acid and iron sulfate, which later find their way back into surface streams. Two general approaches to the problem are possible: (1) prevent the acid-forming reaction from taking place, (2) treat the acid mine water after it is formed so that it will not be harmful to the ecology when discharged into streams and other surface waters. The work described in this report belongs in the first category - it was based on the assumption that acid formation in the mine cavity can be prevented by keeping water (one of the reactants) out of the mine. This was to be accomplished by-forming a waterproof seal over the mine cavity which would prevent the seepage of surface water into the mine. It was planned to form such a seal at or near the surface of the ground by applying latex to the soil. Ideally a dilute latex would be applied to the soil and would penetrate to a depth of two to three feet below the surface where it would be coagulated by reacting with a constituent of the soil or by other means., A seal below the surface of the soil would have several advantages over a surface seal - it would not be subject to destruction by traffic, frost or vegetation and, more important, it would allow the use of the top soil for many agricultural purposes. A preliminary feasibility experiment was performed prior to application for the present grant. It showed that it was indeed possible to form a sub-surface seal by means of latex. A core of soil was obtained locally (Wayne, N. J.) by driving a 6.5 cm inside diameter steel pipe about 100 cm long into subsoil for a distance of 71 cm. The soil was retained within the pipe for this experiment. A part of the free space above the soil in the pipe was charged with water, and the seepage rate of the soil after it had become saturated was 15 ml/min under a total head (wet soil plus supernatant column of water) of 92 cm. After the supernatant water had drained completely, 100 ml of 5% rubber latex was added and allowed to seep into the soil. This was followed by additional water and the seepage rate was found to be 2 ml/min under the same head. This seepage rate remained unchanged when remeasured on the following day. Since there was no visible evidence of the latex in the collected drain water it is presumed to have been retained by the soil.

Jan 1, 1972

By John J. Gordon, Neil K. Cooperrider

The International Organization for Standardization (ISO) standard ISO 2631 [1,2] provides three methods for evaluation of human exposure to vibrations that contain occasional shocks or impacts. Part 1 of the standard specifies the running r.m.s. or maximum transient vibration method (MTVV) and the fourth power vibration dose value (VDV). Part 5 of the standard provides a method of computing the stress in the lumbar spine for humans exposed to multiple shocks. Alem et al [3] have reported application of these methods to data for tactical ground vehicles. This paper reports and compares VDV and spinal stress evaluations of more than 90 hours of vibration and shock measurements on North American locomotives engaged in through freight operations. The measurements evaluated in this paper were obtained for full crew shifts on 19 freight locomotive runs on mainline track in locations from New York to California. The shifts ranged in duration from 187 minutes to 497 minutes. The average speeds for the shifts were from 21.0 mph to 54.6 mph. All measurements were made on locomotives hauling freight trains in regular revenue service. Data Acquisition and Processing The results reported here were computed using test data acquired from a tri-axial seat pad, accelerometer at a sample rate of 400Hz with an anti-aliasing filter corner frequency of 100Hz. The VDVs and the lateral and longitudinal spinal stress values were computed directly from the acquired test data according to the procedures specified and described in [1] and [2]. The vertical spinal stress values were computed by converting the as-acquired test data to a sample rate of 160Hz for input to the vertical spine model, as required in [2]. The conversion of the test data from the as-acquired sample rate of 400Hz to the required sample rate of 160Hz involved up sampling or interpolating the test data to an equivalent sample rate of 800Hz, band limiting the resultant data with a low-pass filter corner frequency of 60Hz and finally down sampling or decimating the 800Hz data to a sample frequency of 160Hz. Discussion The vertical VDVs computed according to [2] for the 19 shifts ranged from 2.68 to 9.33 m/s1.75. In all but one case, the vertical values were greater than the values for the lateral or longitudinal directions. Note that the health guidance in [1] puts the lower boundary of the health guidance caution zone at a VDV value of 8.5 and the upper boundary at 17 m/s1.75. The daily equivalent static compression dose computed following [2] ranged from 0.123 to 0.434 MPa. Health guidance provided in [2] states that there is a low probability of an adverse health effect if the daily dose is less than 0.5 MPa.

Jan 6, 2006

Modify conventional mining practices to reduce significantly the amount of material brought to the surface from underground mines, or to ?re-mine? existing surface mine dumps by backfilling empty underground stopes.

Jan 1, 1994

By L. C. IlsLey

"According to accident statistics, issued from time to time by the Department of the Interior, Bureau of Mines covering fatalities in coal mines, between the years 1870 and 1921 there were 4,897 deaths caused by explosives. The legislatures and safety commissions of the various mining States have Elected and formulated many excellent regulations in regard to the handling and use of explosives in an endeavor to keep this class of accidents as low as possible. An analysis or comparison of the explosive, regulations issued by over thirty States would make a very long paper, however, by subdividing according to phases and issuing several papers it is believed that the material will be more readily available. The first phase was treated in Serial No. 2405 of the Bureau of Mines (""State and Federal Electrical Shot-Firing Regulations,"" issued in October 1922) which gave a compilation of such regulations as apply strictly to electric shot-firing. The second phase under consideration is ""Who may set off blasts in coal mines.""In some States, the person who does the firing must be an ""authorized shotfirer,"" while in other States he must have proved his ability to do this work, and again in other States he is ""any person."" The present paper covers rules and regulations relating to this phase of shotfiring, and those States having similar regulations have been grouped as follows."

Jun 1, 1923

By Mark S. Stagg, Virgil J. Stachura, John W. Kopp, David E. Siskind

The Bureau of Mines studied airblast from surface mining to assess its damage and annoyance potential, and to determine safe levels and appropriate measurement techniques. Research results obtained from direct measurements of airblast-produced structure responses, damage, and analysis of instrument characteristics were combined with studies of sonic booms and human response to transient overpressures. Safe levels of airblast were found to be 134 dBL (0.1 Hz), 133 dBL (2 Hz), 129 dBL (6 Hz), and 105 dB C-slow. These four air- blast levels and measurement methods are equivalent in terms of structure response, and any one could be used as a safe-level criterion. Of the four methods, only the 0.1-Hz high-pass linear method accurately measures the total airblast energy present; however, the other three were found to adequately quantify the structure response and also represent techniques that are readily available to industry. Where a single airblast measuring system must be used, the 2-Hz linear peak response is the best overall compromise. The human response and annoyance problem from airblast is probably caused primarily by wall rattling and the resulting secondary noises. Although these will not entirely be precluded by the recommended levels, they are low enough to pre- clude damage to residential structures and any possible human injury over the long term.

Jan 1, 1965

By C. B. Manula, R. L. Sanford, R. A. Rivell

Development of the Rail-Haulage Sub-assembly for the Production Sub-system (UGMHS)* required the use of ,a newly formulated model in order to best satisfy the requirements. Many of the ideas of the former single-stage rail simulator included in the original version of UGMHS have been used, together with the results of experience gained in applying the earlier model to a variety of operating situations (Sanford, 1969). The sub-assembly is developed as an independent system and, as such, can be used to analyze track systems using production distri¬butions as data input. In addition, since this model is designed to replace the original sub-assembly in UGMHS, the linking procedure is identical with respect to bi-directional information flow. The flow of coal from production sections, for example, fills the mine cars, but a condition of "out of empties" or "full of loaded" at a loading station will shut down inby production sections. A requirements analysis was conducted to determine specifically how the model could best serve the user. Operating management had the largest input in developing the following requirements for the Rail Sub-assembly: a) data input in mixed narrative - numeric form to permit user identification of the input variables; b) a user option to extract several ranges of detail in model output, i.e., an average shift summary of minimum retrieval

Jan 1, 1974

By Travis Q. Lyday

Gold continued to dominate mineral production in the group of volcanic islands and atolls of Melanesia in the southern Pacific Ocean, which comprise the British Commonwealth nation of Fiji. The Fijian mineral sector, however, remained of minor importance in terms of export earnings, Government revenues, and employment to the economy of the country, which was primarily agrarian with sugar as its mainstay. The Vatukoula gold-silver mine on the north side of the main island of Viti Levu remained the largest and most important mining operation, as well as Fiji's only operating metalliferous mine. In October, Western Mining Corp. (Fiji) Ltd. (WMCF), a wholly owned subsidiary of Australian-registered Western Mining Corp. Holdings Ltd., increased its interest in the Vatukoula joint venture from 10% to 20% by exercising its option with Emperor Gold Mining Co. Ltd., also of Australia. The assumption of mine management operations at Vatukoula in 1983, with its attendant influx of additional capital and technological expertise, enabled WMCF to increase both efficiency and output at the mine during 1984. Higher output was obtained owing to an increase in underground ore production, which was partly offset by a reduction in opencut tonnage, as well as to modifications in the recovery circuit. Rate of recovery increased from about 15% to over 82% of the gold contained in the ore and from about 40% to 45% of the contained silver.

Jan 1, 1986

Impermeable geologic faults in the coal seam can cause intermittent production problems or can cause unexpected amounts of water or gas to issue from degasification boreholes. These faults also can impact methane emissions into the mine workings, especially if they hinder proper and effective degasification of the coal bed. They may also act as barriers for methane flow in the coal seam. Although this might seem beneficial for advancing mine workings, faulting may also cause gas pressure buildups and result in compartmentalization of the gassy regions from which large quantities of water and methane may rush into mine workings. This study uses reservoir simulations to illustrate the effects of impermeable faults, with and without throws, on the production performance of vertical and horizontal degasification boreholes. These boreholes were drilled from the surface to intercept the coal layer and fault and were assumed to produce methane two years prior to mining of the coal seam. Longwall advances and face position related emissions and reservoir properties were characterized using sector definitions along the path of the panel grids. This work numerically evaluates water and gas productions of each borehole and presents the effects and the impacts of impermeable faults on methane emissions due to an advancing coal face. The results can be used to understand the effects of impermeable faults on borehole productions and face emissions due to these coal seam anomalies.

Jan 1, 2008

By Martin Hertzberg

The Bureau of Mines 8-liter flammability system was used to study the effectiveness of a variety of powdered inhibitors in preventing the propagation of explosions of coal dust or methane in air. Over 35 different chemical additives were evaluated against Pittsburgh seam pulverized coal. The least effective inhibitors were the carbonates, which required mass additions in the range of two to three parts inhibitor to one part of coal dust in order to prevent propagation. The most effective inhibitors were the derivatives of ammonium phosphate, which were effective quenching agents at additions of only one part inhibitor to four parts of coal dust. Alkali halide powders were of intermediate effectiveness. These laboratory-scale results are in good agreement with full-scale mine experiments in all cases where detailed comparisons have been made. Data were also obtained for the effectiveness of several of the same powdered inhibitors against methane-air explosions. Their relative order of effectiveness and the concentration ranges required for quenching the gas explosion are comparable to those measured for coal dust explosions. Data are also presented for the effectiveness of N2 and CF3Br addition. Some preliminary data are also presented for powder addition to methane burner flames. Those data are compared with other burner data and evaluated in terms of their relevance to explosion tests.

Jan 1, 1982

By C. W. Owings

When explosions have occurred in mines where rock dust has been used to some extent, generally to a very limited extent, the press has immediately characterized those mines as "rock-dusted." To persons familiar with the method of rock-dusting, it is apparent that if rock-dusting is done properly, if all mine surfaces are rock-dusted to within at least 40 feet of the faces of rooms and entries, and if the incombustible content of the dust is more than 65 per cent, there is little likelihood that an explosion of coal-dust will occur. The report that an explosion has occurred in a "rock-dusted" mine immediately conveys to the mind of the alert safety advocate the information that the mine is inadequately rock-dusted or that either dust sampling of the rock-dusted surfaces has not been done or, if done, the mine has not been redusted with sufficient promptness. Rules for Collection of Samples Collection of dust samples is by no means intricate, but a few simple rules must be kept in mind if the results are to be dependable. A sample must represent the true average conditions of the dust in the section or zone in which it is taken, and therefore 'the point at which the sample is to be collected must be selected with care. During an explosion much if not all of the dust on the ribs, roof, timber, and road in the affected region is blown into the air; the sample, therefore, should contain all loose dust and material on: the surfaces to a depth of about 1 inch, if that amount is present. If there is considerable sand locally along the track, care must be taken not to include enough of this material to vitiate the sale and distort the results; however, if the sand is distributed throughout the region being sampled it should be included. Dust should not be collected from recesses in the ribs, such as hitches cut for timber, as the character of the dust in such places is often different from that on the ribs proper. Samples should not be collected at points where the dusting machine has been loaded or at a point where the machine has stopped and discharged for a longer period than at other points on the entry or in the rooms. In short, the sample must represent AVERAGE CONDITIONS, and if there is any doubt as to the character of the dust it is far better to have too much combustible matter than too much incombustible matter in the sample, as it is best to err on the side of safety if it is necessary to err.

Jan 1, 1929

By Joseph P. Flick, Kathleen M. Kowalski, Lynn L. Rethi, Roberta A. Calhoun

Many miners are involved in tasks at the mine site that are similar to those sub-tasks performed in general construction, maintenance and repair (CMR) type work activities. As a result, many of the injuries in the mining industry today can be traced to employees performing these CMR type work activities. Indeed, a recent analysis of a major aggregate company revealed that 65% of all injuries documented originated from performing such CMR activities. It is hypothesized that the number of injuries to miners performing construction, maintenance and repair (CMR) work activities on mine property may be reduced through improved training that focuses on better hazard recognition using the numerous visual and other cues that are available for evaluating workplace health and safety hazards. To this end, researchers at NIOSH’s Pittsburgh Research Laboratory have merged two proven methods of training miners to recognize hazards, stereoscopic (3-D) slides and the concept of degraded images, into this training program. Stereoscopic (3-D) slides have been shown in earlier NIOSH and U.S. Bureau of Mines research to be an effective training aid for improving the ability of miners to recognize various geologic and mining-induced irregularities that can cause groundfalls.3 They realistically portray the natural mine environment, and thus are an excellent training aid for teaching miners to recognize such visual cues. The degraded image concept, originally developed by the military and used for target detection training, describes scenes where the target is partially hidden by cloud cover, dust, rain, natural barriers, buildings, or other obstructions that can camouflage or confuse the target. Research had shown that flight observers who were trained with less than ideal (or degraded) pictures were more successful in subsequent identification of targets than those trained using ideal (or highlighted) pictures of targets. In order to investigate this concept for training miners to recognize hazards, NIOSH researchers developed a prototype hazard recognition training program using such mining scenes. A control program based on traditional highlighted mining scenes was also developed. Both programs were applied to subjects in a field experiment. Results indicated that miners trained with the degraded images did significantly better on a follow-up test of hazard recognition.4 This hazard recognition program teaches trainees to look for hazards in a more realistic manner than that of the control program. This specific training program for CMR activities involves using the degraded image concept and 3-D slides. The module is designed to educate workers on hazard identification techniques and safe work practices. It focuses on teaching miners techniques for recognizing visual (sight) cues, and then uses these cues to evaluate mining conditions. It should be stressed that other senses, such as sound can also play an important role in hazard detection.

Jan 1, 1999

By L. C. IlsLey, E. J. Gleim

It is the firm belief of the Bureau's engineers that the introduction of electrical mining machines has done much to increase safety in mining as a whole . There can be no doubt but that the substitution of machine mining together with permissible powder for the method of " shooting from the solid " has been the means of saving the lives of many shot- firers . Machine mining also leaves the roof in a better condition as lighter charges of powder are required to bring down the coal . Thus the danger from falls of roof are lessened . It is recognized that every effort should be made to prevent all accidents due to the use of electrical machinery but it is felt that any action tending to limit the use of such machinery would be a backward rather than a forward step in the safety measures laid out to decrease the hazards in coal mining .

May 1, 1920

This chapter defines light as a type of energy, and tells how different features of light are measured. It 1s important to understand the units of light measurement because they are used throughout the rest of the book. But more Important, this will help you to understand the "regs" and how to get the best out of the lighting you have available! By the time you complete this chapter, you should know what candle-power, foot-candle, and foot-lambert refer to, and you will also be able to tell why the helmet that the new miner wears appears orange to human eyes. Light that you "see" is really radiant energy that hits the retina of the eye. Radiant energy moves out from a light source much like a series of bullets from a number of machine guns being fired at the same time in all directions.

Jan 1, 1976

As technology evolves, accidents may occur because human-system interactions were not considered adequately in the process. A systematic methodology can be used to evaluate the causes of mishaps and to develop recommendations that will enhance safety. A recent trend observed in underground coal mining is used to illustrate this principle because an underground mine is a dynamic work environment. Mining is characterized not only by frequent geologic changes but by technological evolution that can seriously degrade human performance and compromise worker health and safety The case exemplified in this paper involves implementation of remotely controlled equipment for extended cut mining. Extended cut mining technology evolved with minimal ergonomic consideration even though the change from on¬board to remote machine operation dramatically modified the role of the human component. In response to concern that system interactions should be examined more closely. a methodology was developed to identify hazards.

Jan 1, 1998

By G. T. Lineberry, W. J. Wiehagen

This paper discusses a practical method for enhancing the performance of mining work crews. The method, described as the Work Crew Performance Model (WCPM), seeks to define performance variability within similar tasks of an underground work crew. Key components of the WCPM include: (I) job definition through task analyses; (2) the ranking of job elements by perceived cost consequence; (3) observational techniques to establish performance baselines; and (4) cost linkages between adherence to task procedures and measures of consequence for noncompliance. The components of this model emphasize a reliance on learning from a veteran work force and using that information to reinvest in strategies to enhance safety and efficiency. These strategies are not limited to technologic efforts but include consideration of the so-called "soft-skill technologies" aimed at reducing variability in individual performance and at effecting a continuous improvement in overall system effectiveness.

By George J. Conroy, Angel G. Jordan, Eugene W. Bartel

Time-domain reflectometry has long been an accepted and used method for locating electrical faults in electrical cables. The process has, however, required the use of equipment that is somewhat complex and difficult to use. The skill level needed to operate such equipment is high. Therefore, the use of the time-domain reflectometry process has been limited to selected locations and controlled environments. The process, however, has great potential for mine system applications. The ability to locate and repair trailing power cable without removing it from the mine would result in great savings in cost and employee-hours. Therefore, an automatic microprocessor-controlled time- domain reflectometry system was developed to reduce process complexity and skill level needed to operate the unit. The theory of operations is discussed along with the computer analogies used in the unit. The present unit capabilities are presented and future areas of application and research are discussed.

Jan 1, 1979

By Stephen A. Hare, O&apos

The melting, casting, and welding of the Raney nickel alloy (42 pct Ni-58 pct A1), a methanation catalyst useful in coal gasification, were investigated. Melting was done in graphite crucibles by heating aluminum and adding nickel using a cryolite slag cover. Casting conditions were found to be optimum when the melt temperature ranged from 1,125° to 1,200° C and the mold temperature ranged from ambient to 250° C. Suitable mold materials were found to be quartz, heat-resistant glassware, olivine, and zircon. Welding of the alloy can be accomplished using tungsten inert gas process. Tensile strength of the alloy, in the as-cast condition, was found to be 2,000 1b/sq in with an impact strength of less than 1 ft-1b. The coefficient of thermal expansion was determined to be 18.4 x 10-6/° C after heat treatment.

Jan 1, 1977