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By John C. Edwards, Gerald S. Morrow

The U.S. Bureau of Mines has constructed a smoke chamber and developed sensitivity tests for smoke detectors. Response of ionization- and optical-type commercially available smoke detectors have been investigated. Six smoke detectors were measured with respect to visually obscuring smoke characterized by a corresponding optical density for smoldering and flaming coal combustion in the smoke chamber. It was determined that for one type of ionization smoke detector the alarm time was nearly equivalent to that of an odor monitor's alarm for smoldering coal combustion experiments and earlier for flaming coal combustion experiments. The experiments showed that an average CO concentration of 5 ppm corresponded to an optical density of 0.022 m for smoldering and flaming-1coal combustion. Two of the commercially available ionization-type smoke detectors were more responsive to flaming than smoldering coal combustion at an optical density of 0.022 m, whereas the optical smoke detectors-1showed the opposite trend. The responsive characteristics of the detectors evaluated with respect to known smoke conditions in the smoke chamber shows their potential for use as mine fire sensors or part of a mine atmospheric monitoring system to improve mine safety.

Jan 1, 1995

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

To enhance safety and efficiency when moving large mining equipment under energized trolley lines, and to assist in compliance with Section 75.1003.2, 30 CFR. Approach A system was designed, using established technology, that permits a remotely located circuit breaker to be controlled from the cab of a mine locomotive moving large mining equipment under energized trolley lines. This control consists of setting the desired trip current, automatic or manual tripping, resetting, and voice communications between the locomotive and a remote Circuit breaker location. How It Works According to 75.1003.2, 30 CFR, whenever a piece of off-track equipment (such as a longwall chock or a continuous miner) is moved by rail under energized trolley or feeder lines, power for the locomotive that is moving the equipment must come from only one' circuit breaker. This circuit breaker must be adjusted to permit no more than one-half its rated short-circuit current to flow. The intent is to lessen the danger if an accident should occur, and if the equipment contacts the trolley line. Even so, the danger is great. This half setting can still represent many hundreds or even thousands of amperes, enough to endanger personnel, the equipment, or the mine. The Remote Control System reduces this danger substantially by giving the personnel associated with the move total control over the associated circuit breaker. The system as designed, is intended to be used with portable circuit breakers that are pulled on a small flat car by a mine jeep, and either precede or follow the equipment, depending on the direction of the power. This portable circuit breaker is equipped with a commercially available solid state overcurrent relay and associated shunt. This circuit breaker is connected via heavy duty clamps around an open trolley line tie breaker such that the current through the shunt is also the current in the trolley line. A receiver, interfaced with the overcurrent relay and shunt, completes the remote system.

Jan 1, 1981

"Fire fighting in metal mines under the best of conditions is a dangerous, a slow, and a difficult task. Certain gases generated from combustible material burning in restricted areas are poisonous, even in small quantities, and can not be breathed without serious and often fatal results. In addition to poisonous gases, smoke is given off which obscures the vision of the fire fighter and frequently prevents him from gaining access to the fire area. Many fire-fighting crews have had to turn back because their vision was so impaired by the dense smoke that the fire area could not be located and there was danger of them becoming lost in the mine.In mines having mechanically controlled ventilation - that is, mines not dependent entirely upon natural air currents - the gas and smoke can be forced ahead of the fire-fighting crews, thereby facilitating exploration of the mine and saving the time, energy and oxygen of the mine rescue apparatus crews.Where currents of fresh air can be circulated up to points near the fire without danger of seriously spreading the fire, fresh air bases can be established in the immediate vicinity, and a more intelligent campaign for fighting or controlling the fire can be mapped out.Positive air currents through forced ventilation may also result in saving the lives of miners who otherwise might have been trapped in smoke and poisonous gases.It is generally known that comparatively few metal mines have attempted to regulate or control air currents, with the result that when a fire occurs underground, the normal ventilation may be reversed, short circuited, or the air current may be in one direction one minute and in the opposite direction the next; or, generally speaking, the ventilation can not be depended upon, and smoke and poisonous gases may accumulate in any part of the mine or ""drift"" on the fire-fighters or on the miners endeavoring to escape."

Apr 1, 1921

By W. R. Reed

Dust dispersion modeling is a subject that has had a large amount of research activity. Much of the research has focused on large-scale global or regional dispersion models. Other models have been created for industry-specific purposes. Furthermore, some of the past research has focused on dust dispersion modeling in the mining industry. This report presents the various dust dispersion models that have been developed specifically for the mining industry. The report first gives a brief background of the regulatory environment that helped to promote development of such models. It then presents an overview of the mathematical concepts used in this dispersion modeling. Finally, each of the various models developed for the mining industry are described, along with their associated mathematical algorithms and any field validation conducted on the different models.

Jan 9, 2005

By W. W. Adams

Fatal accidents at coal mines throughout the United States numbered 170 during May , 1923 , according to reports received by the Bureau of Mines of the Department of the Interior from State mine inspectors . The production of coal during the month was 54,649,000 tons ; hence , the fatality rate was 3.11 per million tons . In May last year the fatality rate was 4.22 , based upon an output of 20,636,000 tons , including 35,000 tons of anthracite . Because of the miners ' suspension of work last year, the production of fresh-mined anthracite in May 1922 was completely stopped ; in May 1923 the anthracite output was 9,573,000 tons . For bituminous mines alone , the fatality rate in May 1923 was 2.67 per million tons as compared with 4.17 in May a year ago . During the first five months of the present year , the fatality rate for bituminous mines was 3.55 per million tons , based on 809 deaths , as against a rate of 3.70 for the corresponding months last year, based on 611 deaths . The rate for 1923 represents a reduction of 4 per cent . For anthracite mines alone the five-month fatality rate for 1923 was 5.36 per million tons , based on 228 fatalities , as against a rate of 6.72 for the first five months of 1922 based on 147 fatalities . The rate for 1923 represents a reduction of 20 per cent . The average fatality rate for May during the past ten years ( 1913-1922 ) is 3.37 per million tons for bituminous coal mines and 6.02 per million tons for anthracite mines . A gas explosion , due to open light , occurred on May 6 at Aguila , Colorado , and resulted in the death of ten men . This explosion brought the number of "major disasters " in 1923 to 4 , with a loss of 145 lives . During the first five months of last year, there were 7 similar disasters with a loss of 82 lives . The year's record to date for all fatalities from all causes shows a reduction in the fatality rates per million tons from haulage accidents and from falls of roof and coal , an increase in explosions of gas and dust and in accidents due to electricity , and no change in the fatality rate from explosives . The reductions in haulage accidents and in falls of roof and coal are particularly gratifying, because these two classes of accidents usually cause about 65 per cent of all fatalities in the coal-mining industry . Reports of Investigations , Department of the Interior , Bureau of Mines .

Jun 1, 1923

By Rimas Pakalnis, Tom Brady, Lewis Martin

A major focus of ground control research presently being conducted by the Spokane Research Laboratory of the National Institute for Occupational Safety and Health (NIOSH) is to incorporate weak rock masses (such as are associated with operations in the Carlin Trend in Nevada) into existing design relationships. The original database that led to most of the empirical design relationships presently employed in hard-rock mining was derived from fair-to-good-quality rock. In this study, the relationship between weak rock quality and opening design (non-entry/entry methods) is being investigated. The common factor in all mines is a weak back or wall. This work attempts to provide tools that will enable a mine operator to make economic decisions that will also ensure a safe working environment. Tom Brady (for correspondence - E-mail- thb6@cdc.gov)and Lewis Martin are at the Spokane Research Laboratory, National Institute for Occupational Safety and Health, 315 East Montgomery Avenue, Spokane, WA 99207-2291, USA (E-mail• ljm8@cdcgov); Rimas Pakalnis is at the Mining Department, University of British Columbia, Vancouver, British Columbia, Canada (E-mail: rcp@mining.ubcca).

By R. F. Abernethy

The work discussed in this report was done by the Bureau of Mines to develop a method for determining trace amounts of fluorine in coal. Samples of coal mixed with calcium oxide as a fixative agent for fluorine were ashed at 600° C and the residue was fused with sodium carbonate. The melt was dissolved in phosphoric and sulfuric acids and distilled to separate the fluorine) which was determined in the distillate by a SPADNS-zirconium spectrophotometric method. Fluorine determinations of 83 commercial coals ranged from 0,001 to 0.019 percent.

Jan 1, 1967

By Dana Reinke, Launa Mallett

Interest in training evaluation in the mining industry was piqued with the promulgation of Title 30, Part 46, of the Code of Federal Regulations. Under Part 46.3, a training plan is considered to be approved if it contains certain information, including “The evaluation procedures used to determine the effectiveness of training.” The present paper is a broad overview of training evaluation and is intended to give trainers and decision-makers a framework for planning or assessing training evaluation strategies. It discusses questions to consider when starting an evaluation plan, Kirkpatrick’s model of evaluation categories, and various ways to collect data. It does not provide detailed instructions on how to develop evaluation methodologies, but reviews topics to consider when creating an evaluation plan. Training evaluation is a term that has many different meanings: assessing the quality of a course, effectiveness of materials used, teaching style of an instructor, or the comfort of a classroom. An evaluation can be done informally over lunch or with highly structured data-gathering tools. It can produce results that are useful to trainers, program administrators, corporate decision-makers, or no one. The key to a worthwhile evaluation is clearly defining why the evaluation is being conducted. Once the purpose is defined, planning the evaluation strategy can begin. For an evaluation to be effective, it should be incorporated into the development of the training activity itself. The training evaluation worksheet at the end of this paper can be used to guide evaluation planning.

Jan 1, 2002

By A. B. Hooker

Investigations at the Pittsburgh Experiment Station have shown that the satisfactory operation of aflame safety lamp depends not only upon proper design and assembly of the lamp but upon the kind of fuel used, and that much of the trouble experienced with permissible flame safety lamps at mines is due to the common use of motor gasolines, none of which is suitable in the present types of permissible flame safety laps. This report gives the results of a limited study to determine what satisfactory fuels are available, the specification limits of such fuels, and to suggest modifications of assembly and care of the lamps to improve performance with any satisfactory fuel.

Jan 1, 1938

By R. W. Crocker, H. H. Clark

The purpose of the investigation discussed in this bulletin, one of a series dealing with the use of electricity in mines, was to study the various means and methods used to confine the flashes that occur when a switch carrying electric current is opened. The flash result- ing from the opening of a 250-volt direct-current circuit carrying more than half an ampere will ignite explosive mixtures of mine gas and air. An equally dangerous flash may be produced by even less cur- rent from a 500-volt circuit. Few mine electric circuits carry less than half an ampere when in use. The need of protecting the switches of such circuits in places where gas is likely to be present is therefore obvious. Two general methods have been proposed for preventing switching flashes from igniting gas surrounding the switch. One method is to inclose the switch in a casing provided with openings that are covered with wire gauze or otherwise designed and equipped for preventing the passage of flames from the interior to the exterior of the switch casing. Switches so protected are called explosion-proof switches. The second method is to immerse the switch contacts in oil to a depth sufficient to quench any flash that may occur when the switch is operated. Switches so protected are called oil switches. The success of the first method of protection depends upon the proper design and construction of the switch casing. It is essential to the successful operation of the second method that the switch contacts be surrounded by the proper kind of oil in good condition. There are several ways in which an oil switch may be deprived of its protective feature. The oil tank may not be filled or, if filled, the oil may leak out or be spilled. The oil tank may be removed (in some designs) and not replaced or through neglect the condition of the oil may become such that it is no longer an efficient protection. While such contingencies are not likely to occur, and although oil switches may be so designed that the loss of oil is not probable, nevertheless, as compared with oil switches, explosion-proof switches seem to

Jan 1, 1913

By Edward F. Divers

The Bureau of Mines recently tested a sideboard device that is designed to act as an extension of conventional brattice, thus improving face ventilation of developing room-and-pillar-type coal mining. In these laboratory tests, an 8-foot-long rigid sideboard was mounted vertically along the left fender of a full-scale-model ripper-type continuous mining machine, rising to the mine roof to provide an air seal. It extended from the auger support frame pivot point outby along the fender. A novel water spray manifold was used to form an air seal between the sideboard and brattice. Tests showed improvement in face ventilation with the prototype device, and also demonstrated that water sprays can form an effective air seal over a fairly wide pressure range. Based on this preliminary study, subsequent improvements may make the sideboard concept much more effective, thus affording a simple, inexpensive technique to improve the effectiveness of face ventilation.

Jan 1, 1979

By Robert L. Lagace, N. Albert Moussa

The objective of this project was to perform a preliminary study to determine the desirability/practicality of burying the communication cables in underground mines in order to protect then from the effects of fires and explosions We conducted discussions with Government and industry specialists on the physics of mine fires and explosions, mine disaster fighting, rescue, and investigation activities, and on nine operations. In addition we examined published experimental work and selected detailed NSHA accident reports on fires and explosions in underground mines. We found the overall desirability /practicality of cable burial must be regarded at this time as highly questionable, because of its benefit limitations to special sceneries, its practical operational shortcomings, and the availability of alternative cable protection options.

Jan 2, 1982

By Launa G. Mallett, Kathleen Kowalski-Trakofler, Robert H. Peters, Charles PH. D. Vaught, Peter Keating, William J. Wiehagen

On-the-job training is a common means of training or retraining workers and the practice may seem simple and straightforward. Doing it effectively however requires more thought and preparation than simply having someone follow an experienced worker around and watch what they're doing. Over the years, various techniques and practices have evolved that pass on the skills and knowledge of a trainer or coach in a manner that leads an inexperienced trainee to really absorb the information being taught. On-the-job training thus becomes less a haphazard show-and-tell and more a real transfer of information. The goal of this document is to describe how to develop or manage an on-the-job training program so that information is passed on from trainer/coach to trainee efficiently and effectively. By efficient is meant the best use of time and resources of all those involved in the training process, and by effective is meant that the trainee truly learns the skills and internalizes the knowledge needed to perform the job well. The first part of the document discusses topics to think about when developing a formal on- the-job training program. A structure based on coaching is suggested. Then a workshop designed to prepare trainers as coaches is described. Workshop materials include an instructor’s guide and trainee workbook. These materials can be used to train coaches and to assist trainees as they go through the learning process. Content related to specific jobs can be added to these materials to create targeted on-the job-training manuals. Structuring a formal on-the-job training program It is likely that some form of on-the-job training (OJT) is being conducted at your workplace. The formality of that training can range from a structured program to an informal “follow Joe around” method. If your program is completely unstructured, it may not be meeting current training needs. Worse, it may perpetuate bad habits and create “trained” employees who are not given the same information or evaluated to the same standards. Wiehagen et al. comment that, “Success in using unplanned OJT is usually dependent on the luck of the draw, that is, whether the informal trainer is competent at the task he or she is teaching, is motivated to teach, can organize the job into logical components, and knows something about good practices in teaching and evaluating” (2002, p. 27). It is only through planning a structured OJT program that consistency can be created and maintained. At the least, all trainees who have successfully completed such a program can be expected to perform at an established level—they will know what they must do to be successful.

Jan 7, 2005

Simplify the spraying of sealants onto coal mine roofs. Approach A nonclogging system in which dry-fed sealant is mixed with water down-stream of the spray nozzle, has been developed and tested. How It Works The two-channel nozzle of this spray discharges two separate flows, a mixture of air and dry sealant from a central cylinder, and an encircling spray of water from a concentrically mounted water ring (a ring-shaped manifold). Downstream of the nozzle, the water mixes with the air and sealant to form a wet sealant spray that adheres to mine surfaces with very little rebound. (See photograph.) Extensively modified commercial spray machines are used to feed the sealant to the spray nozzle smoothly, without raising dust. Plugging of the nozzle is practically eliminated by two self-cleaning design features of the nozzle. These are the air gap and the tapered bore of the cylinder, (See drawing.)

Jan 1, 1979

Protect rescue workers fighting fires or mine personnel temporarily working in hot environments from heat stress. Approach A specially designed ice-cooled vest is worn while working in hot environments where cooling the mine air is not possible. How It Works The vest holds a total of 44 individual ice cells in packets that are firmly held near the wearer's skin. These ice cells remove heat from the wearer, reducing heat stress and increasing comfort. The locations of the ice cells and packets are shown in the diagram. The vest is constructed in three layers with the outer layer being aluminzed fiberglass cloth. Its aluminized surface reflects radiated heat, and its fiberglass cloth provides fire resistance and strength.

Jan 1, 1979

Dec 1, 2007

By L. J. Prosser, A. T. Iannacchione

From 1991 through 1995, 44 miners out of a total workforce of less than 2,000 were fatally injured in the stone industry. Of these, 12 occurred at underground mining operations with nine deaths resulting from roof or rib falls. A safer environment can be achieved by evaluating the nature of the hazardous ground and by developing more efficient and effective ground-control strategies Roof and rib conditions were observed and assessed in 33 underground stone mines in Illinois, Indiana, Kentucky, Maryland, Missouri, Pennsylvania and West Virginia (Fig. 1). Hazard assessment indicated that the ground failures that occurred under moderate to substantial overburden. i.e., >30 at (100 ft), were caused by stress concentrations and geologic strictures. Ground failures near the surface are caused by solution (water) processes. Selection of the mining horizon and mine-layout decisions tremendously influence ground stability.

Assure fail-safe stopping of a mining vehicle immediately following a loss of electric power. Approach A separate emergency brake system which actuates when electrical power is interrupted, was installed on several mining vehicles and tested in a long-term underground mining demonstration. How It Works Separate, spring-actuated brakes, which press against brake discs, are used to stop the vehicle following power failure. To allow norm al movement of the vehicle, hydraulic oil under pres? sure from the vehicle's hydraulic system is directed to a spring? loaded piston in each emergency brake housing. That pressure causes the piston to compress the spring and relieves the spring pressure against the puck, thereby allowing the brake disc to turn freely. See Figure 1 A. If the electrical power fails or if the machine is turned off, a valve in the hydraulic line to the emergency brakes opens. That valve, shown as ?Solenoid Valve (automatic)" in Figure 1, which is normally held closed by its electrical solenoid while the vehicle is electrically powered, is opened by the spring in the valve assembly. The pressure in the hydraulic line which is connected to the emergency brakes then drops to

Jan 1, 1978

By Martin H. Stanczyk

Two methods of recovering zinc from zinc ammonia complex solutions were investigated. One method studied was distillation of the ammonia from the solutions to recover a basic zinc sulfate, which after calcining to zinc oxide was reduced to metallic zinc using hydrogen at 900° C. The second method tested was electrolysis. The tests were made of synthetic and leach solutions analyzing about 80, 100, and 115 gpl (grams per liter) of Zn, NH3, and SO4, respectively. The leach solutions were prepared by oxidation leaching of a sphalerite flotation concentrate, assaying 55 pct zinc at elevated temperature and pressure. The distillation method recovered about 98 pct of the zinc in a product analyzing 97 pct zinc. Ammonia losses incurred during the leaching and distillation operations were about 0.1 lb per lb (pound per pound) of metallic zinc produced. Electrolysis of the solutions at a cathode current density of 25 amp per sq ft (ampere per square foot) yielded zinc deposits assaying in excess of 99.9 pct zinc. About 1.5 kwhr (kilowatt-hour) of power were consumed per pound of zinc deposited; the current efficiency was 72 pct. Other electrodeposition tests revealed that small amounts of ferric iron in the cell liquor were deleterious to electrolysis unless about 5 lb of glue per ton of zinc were present in the electrolyte. The use of glue and vigorous agitation of the electrolyte gave smooth zinc deposits from solutions containing as much as 0.1 gpl iron.

Jan 1, 1962