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By R. V. Ramani, R. Stefanko, G. W. Luxbacher

1 9 THIS IS A DIGITAL COMPUTER SIMULATION OF THE VENTILATION SYSTEM OF A MINE LOCATED IN WASHINGTON COUNTY; PENNSYLVANIA. THE VENTILATION SURVEY ON WHICH THIS SIMULATION IS BASED WAS RUN FROM OCT. 27-30 AND ON NOV. 2;1976 IN THE ACTIVE PORTION OF THE MINE INBY COMBS SHAFT AND THE INACTIVE PORTION AROUND AND INBY DONAHOO SHAFT. FOLLOW-UP SURVEYS WERE THEN RUN ON FEB. 18 AND FROM MARCH 7-11;1977 TO INCLUDE THE MAIN HAULAGE SYSTEM OUTBY THE ACTIVE AREAS 0F THE MINE. ALL SURVEY DATA WAS NORMALIZED TO A STANDARD DENSITY OF 0.075 POUNDS/CU.FT. PRIOR TO THE CALCULATION OF INPUT PARAMETERS FOR THIS SIMULATION.

Jan 1, 1977

By Stephen L. Tillim

Tubular Handles can negatively affect the contents of the carpal tunnel. Years of injuries from grasping handles for tools and machines can cause carpal tunnel syndrome, tendonitis and wrist joint injuries. The can cause inability to use a hand and resulted in the longer absences from work than injuries from falls, accidents or fires.1 Cylindrical, tubular and rectangular handles are rolled flat structures. They place the hand on a rolled flat surface where the ends of the middle and ring fingers overlap the index and small fingers. They are pulled along a series of lines that contact the end joint of the index finger, the middle bones of the middle and ring fingers and the end bone of the small finger. Cylinders are pulled diagonally in the hand toward the carpal tunnel (CT) area. Gripping in this manner tenses asymmetric muscle groups in the forearm. Handles could work better if they do not place pressure on the CT and conform to the natural function or neutral hand position where the hand rests or dangles at the side of the body, the finger tips form a diagonal, the palm and fingers form a cup, the thumb rests between the index and middle fingers and the wrist is mildly extended. However, handles designed for the neutral position are pulled by diagonally oriented fingers into the valley between the thenar and hypothenar muscles where they can compress the median nerve and tendons exiting the CT. Seven principles for handles that do not place pressure on the carpal tunnel and employ optimal hand position are presented. First, handles should align the ends of the fingers parallel to the horizontal crease and not diagonally. Second, handles should extend from the cupped fingers to meet the muscles at the base of the thumb on the radial side of the hand and extend further on the other or ulnar side to meet a portion of the small muscles. Third, handles should have a recess on the proximal side to prevent contacting or placing pressure on the carpal tunnel. Fourth, handle design should be based on hand measurements in a position of function. Fifth, handles should come in sizes. Sixth, handles should be placed on tools to maintain the wrist and elbow in neutral position. The seventh is handles should support the maximum area of the hand and absorb, but not direct, vibration to the carpal tunnel. These principles led to prototypes and patents for handles for gripping, pinching and squeezing2,3,4 . The poster will illustrate and explain the principles Bonsil handles. Research, with existing tools, is needed to substantiate claims made for the Bonsil handle.

Jan 6, 2006

By Jeffery L. Kohler, Eric R. Bauer

Prolonged exposure to noise over a period of years generally causes permanent damage to the auditory nerve and/or its sensory components. This irreversible damage, known as noise-induced hearing loss (NIHL), is the most common occupational disease in the United States today. Workers suffering from NIHL have difficulty understanding human speech and hearing other workplace cues. Despite the use of regulations and efforts by government and industry to reduce NIHL, the problem today is as prevalent as it was more - than two decades ago. Recently, the Mine Safety and Health Administration (MSHA) promulgated a new regulation that is designed to reduce NIHL in the mining industry. One of the more significant provisions is the elimination of MSHA's past practice of giving "credit" for the use of personal hearing protection, thereby reestablishing the primacy of engineering and administrative controls. However, there is a knowledge gap that is impeding the development and implementation of engineering and administrative controls. Although significant data exist on the exposure to noise by occupational code, little is known about the noise sources that contribute the most to the worker's dose. This is problematic in a workplace with multiple noise sources and workers who travel among noise sources. Yet without this knowledge, it is difficult to focus control efforts in any practical manner. Thus, it is important to characterize noise sources sufficiently well so that the sources most hazardous to hearing are identified and those conditions of exposure that are most amenable to engineering controls are pinpointed as well. The Pittsburgh Research Laboratory (PRL) of the National Institute for Occupational Safety and Health (NIOSH) is conducting a cross-sectional survey of noise sources and worker noise exposures in the mining industry to address this deficiency. The initial effort, conducted at a coal preparation plant and results are described in this paper. Preliminary analyses indicate that the noise levels on all floors exceeds 90 dBA in most areas, and that levels as high as 115 dBA were recorded. In addition, the one worker whose responsibility is to monitor the equipment and "house clean" the plant is slightly overexposed, even though he spends only half the shift in the plant. General information on the hearing loss problem in mining, a review of hearing protection use and noise regulations in mining, and other background materials are also presented.

By D. Harringtong

"There has been much writing and argument on the subject of giving bonuses to miners, quarrymen, metallurgical and chemical workers, and others as a stimulus for safe work and for work safely done. Theoretically, everyone should be careful and should not need monetary or any other type of encouragement for the prevention of accidents; as a. fact, few people are careful, and this is primarily the reason way many if not most accidents occur. A bonus, however, is not simply money given away by an employer; it must be earned, so to speak, before it becomes due; in other words, if the standard established is not reached, no bonus is paid, and in many cases some disciplinary action is taken.The United States Bureau of Mines Is asked from time to time for suggestions for rewards to mine workers who have a good attitude toward working safely or who need some stimulus to cause them to make greater or more earnest efforts toward safety for themselves and their co-workers. A recent inquiry prompted the collection of data on some safety bonus systems from reports of this bureau's field engineers and others, and some of these Now given. Bonus practice at both coal and metal mines is included because a system used at metal mines is generally adaptable to coal mines; in fact, in numerous cases, bonus systems recently started at some coal mines are based on systems in vogue and giving satisfaction some metal mines; in-some instances, also, metal mines have been able to get good suggestions from coal mines or from the cement or petroleum industries. it .should be understood that a bonus, even as applied to the encouragement of safety, does not necessarily mean payment of money; in fact, some successful bonus systems have in them no direct money exchange; hence, the bonus as treated in this paper is that defined as ""Something given in addition to what is ordinarily received by, or strictly due to, the recipient.""Acknowledgment is given here to members of the safety division of the Bureau of Mines who sent in some of the information here presented; to the Engineering and Mining Journal and Mining Congress Journal, from which some items were abstracted; to various mining officials who gave data in one form or another; and to M. von Bernewitz, of the United. States Bureau of lines who aided in framing parts of this paper."

Jun 1, 1932

By W. D. Ryan

The American public has at all times been prone to discuss important questions that call for consideration and adjustment. Debatable subjects upon which sides may be taken always receive unusual prominence, but other questions equally important may be neglected. The real "paramount issue," calling for remedial action, is the ever-increasing number of deaths caused by preventable accidents. This matter demands the attention of the entire American people; the importance of accident prevention can not be overemphasized, and in many phases of American life, especially among the mining and allied industries, far too little real attention has been given the importance of conserving life and limb by accident prevention. ACCIDENTS COMPARED TO WAR AS A CAUSE OF DEATH Harry T. Hoffman, Wyoming labor commissioner, writes the following: It is one of the peculiar complexes of this rapidly moving age that we all stand aghast at the horrors of war and view with appar- ent indifference the greater havoc of industrial peace. Did you ever stop to think that approximately twice as many people were killed by accidents in the United States in 1929, as there were American soldiers killed in the entire period of the World War? Every employer and every worker should be thoroughly aroused over the tremendous toll levied against industrial forces by accidents which are largely preventable and develop a faith in safety efforts that will fire them with a zeal as pronounced as that of their religion or their patriotism. Let us remember safety-first to the end that the workman shall live to enjoy the fruits of his labor; that his mother shall have the comfort of his arm in her age; that his wife shall not be untimely a widow; that his children shall have a father; that crip- ples and helpless wrecks who were strong men shall no longer be a by-product of industry.

Apr 1, 1931

By T. R. Taubert, D. H. Carlson, J. H. Johnson

"ObjectiveDevelop a portable emissions measurement apparatus to sample and measure tailpipe concentrations of diesel particulate matter (DPM), carbon monoxide (CO), carbon dioxide (COJ, nitric oxide (NO), and nitrogen dioxide (NOJ under steady-state engine load and speed conditions during a 1-minute test.BackgroundThe U.S. Bureau of Mines (USBM) has a comprehensive research program to develop ways to reduce exposure of miners to diesel exhaust pollutants. Engine maintenance has been shown to have important effects on such exposure.Accurate measurements of tailpipe emissions are becoming an essential part of a good maintenance program for underground mines that use diesel-powered vehicles. Past studies of particulates in U.S. underground coal mines have shown that DPM alone may be present at concentrations greater than 1 milligram per cubic meter (mg/m3), half the 2-mg/m3 limit for respirable coal mine dust. A poorly tuned (smoking) diesel engine may be the sole cause for respirable dust concentrations exceeding the limit. Although there is currently no standard specifically for DPM in U.S. mines, regulatory steps are underway, and significant reductions of DPM levels in both coal and metal mines will most likely be required.Tailpipe emission measurements can provide diagnostic information to identify engine malfunctions such as clogged air cleaners, faulty injectors, or incorrect injection timing. In some cases, mine vehicle tailpipe DPM concentrations have been reduced up to 50 percent by engine maintenance and adjustments.An accurate measuring instrument would also be useful for determining the effects of exhaust control devices on tailpipe emissions. Little information is currently available about the overall effectiveness of exhaust controls after long-term use. Raw exhaust concentrations with and without the control device can be measured in underground mines, and from these data a control efficiency can be calculated. Knowledge of the effectiveness of exhaust control devices over time is needed to make intelligent decisions on bow to use and maintain these devices, and when to replace them."

Dec 1, 1995

By D. J. Parker

Since the introduction of electricity into the mines of the United States , the hazards incident to the industry have increased materially in both coal and metal mines . For economic reasons the tendency at present , particularly in coal mining , is decidedly toward the adoption of electrical mine machinery , including alternating current machinery , on a more extensive scale than ever before . Obviously, the growing use of such equipment will result in an ever -increasing number of underground transformer stations . The principal electrical hazards in mines are threefold ; fire , explosion, and contact . Of these , fire is the greatest hazard involved in the use of electricity underground , and several fires have originated in underground transformer and motor generator set stations . The fire hazard due to improperly installed and poorly maintained underground transformer stations is an ever-present one , and failure to take the necessariman remedial action is likely to result , sooner or later, in the destruction of life and property . Upon suggesting the necessary corrective measures with respect to such installations , one is often confronted with the statement to the effect that even though this particular hazard has existed over a period of years , there have been no unfavorable results therefrom thus far . Frequently , the desirability for action is not apparent to the mine management until it is too late . Because a mine has a record free from fires , explosions , etc. , over a number of years of operation during which these hazards existed , such good fortune should not be taken as a guarantee that this or any other mine is immune from these common dangers . When the elements of an existing hazard are properly balanced or in the right proportion, the unfortunate combination must of necessity culminate in misfortune of one kind or another. The fire hazard due to underground transformer installations can be very definitely minimized by proper installation and maintenance . In coal mines the transformer banks , connected to 2,300 and occasionally to 4,400 volt circuits , are often found located in open- ended crosscuts , mounted on concrete or timber foundations , and in nonfireproof surroundings .

Jul 1, 1930

By George D. Dub, FREDERICK G. MOSES

The Bureau of Mines, in connection with the investigations of war minerals it conducted, examined the graphite deposits of this country, studied the methods of mining and preparation used, and sought to devise more efficient methods for the preparation of do- mestic graphite, and to standardize the quality of the product. The graphite investigations covered three general phases, as follows: 1. An examination of the deposits in Alabama and other States, and a survey of the methods of mining and preparation used. In this connection methods of sampling and analysis were noted and ex- periments made to determine a standard method of sampling and a rapid but accurate method of analysis. 2. Experimental work on the concentration and refining of domes- tic crucible graphite to improve the quality of the product and to lessen waste. 3. Experimental work in crucible manufacture to determine the properties of domestic flake and the maximum proportions that might be used without impairing the quality of the crucibles. This work was accompanied by photomicrographic study of crucible structure. In this bulletin are presented the results obtained in the first two phases of the work outlined above. The bulletin is in two parts. The first part describes the methods of mining and milling used, suggests a standard method of sampling finished graphite, and de- scribes a rapid and convenient method of analysis developed at the Pittsburgh station of the Bureau of Mines, to which had been as- signed the analytical and microscopic work. The second part describes experiments on the concentration and milling of graphite, which were made at the Salt Lake City, Utah, station. As soon as the reports incorporated in this bulletin were ready, mimeograph copies were distributed to those persons most interested in order to make the results immediately available. The experimental work on crucible manufacture, assigned to the Columbus, Ohio, station, yielded results which were made known to the industry. Á report on this work will be published later as a separate bulletin.

Jan 1, 1920

By L. C. IlsLey

As part of its work for the improvement of safety conditions in mines , the Bureau of Mines has undertaken to establish a list of permissible storage - battery locomotives for use in gaseous mines , and , to this end , has issued Schedule 15 , "Procedure for Establishing a List of Permissible Storage -Battery Locomotives for Use in Gaseous Mines . " Up to the present time , two approvals * have been issued under this Schedule , and considerable testing work done on four other applications which have been made for approval . Prior to the publication of Schedule 15 , the Bureau conducted both field and laboratory investigations to determine the hazard from the batteries used in mine locomotives . ** These investigations indicated that the safety of the locomotive would depend largely on proper care of the battery , also on the use of a battery as mechanically rugged as possible . For this reason the Bureau staff , in testing locomotives submitted for approval , considered it advisable to subject the batteries to a jarring or bumping test to prove their adequacy as regards mechanical endurance and ruggedness . These tests on the batteries of the locomotives are described below.

May 1, 1922

Reduce injury to people or damage to equipment when a scheduled production blast is detonated. Approach The essential elements of an effective blast area security system were identified through case studies of five mining operations where the blast area guarding practices were considered to be superior to those generally found in the industry. These elements were used in making recommendations for improved blast area safeguarding practices. Background The blast area security system is a means by which the mine operator prevents injury to people or damage to equipment when blasting is performed. Analysis of blasting accidents showed that most blasting accidents occur during scheduled blasting and are due to inadequate blast-site security. Factors contributing to the system's breakdown are failure to clear the blast zone, inadequate guarding. and failure of personnel to follow instructions, retreat to a safe location, and/or take adequate cover. Mine personnel, visitors and even trespassers can inadvertently wander into a blasting zone unless proper procedures exist to ensure that all personnel are cleared from the blast zone and kept safely away until after blasting IS completed. Statistics show that the blaster is the miner most frequently injured In these accidents.

Jan 1, 1986

By Peter L. Swanson

NIOSH has developed an automated PC-based seismic monitoring system for use in mine ground control studies. The distribution and coordination of data acquisition and processing functions across a local area network (LAN) is a central feature of the system. Design requirements include (1) the use of lowcost, off-the-shelf, data acquisition and computer hardware, (2) the capability of automatically merging waveform data sets from different types of monitoring systems, (3) delivery of raw and processed data underground and on the surface, as well as to remote sites, and (4) automated data collection and processing over long periods of time without the need for human intervention. Current mine-wide installations utilize multiple, autonomous seismic networks located both underground and on the surface and provide 20 to 40 stations within a radius of several kilometers. Event locations, magnitude estimates, and other processed data are distributed for display and analysis on network nodes both underground and in the offices of mine engineers and managers. This paper describes the system's hardware and software components, examples of installations in hard-rock and coal mines, and a few observations from western U.S. longwall coal mines.

By David Hoadley, Kenneth R. Maser, Ashok B. Boghani, James E. Billar, D. Randolph Berry, Mackenzie Burnett, Robert H. Trent

Appendix B - Mine Evacuation Simulation Program - User's Manual B 1 Introduction Appendix B documents information necessary to use the emergency escape simulation program and to make modifications if necessary. For a user interested in using the program as it exists, Sections B 2, B 5 and B 6 are particularly useful. The program listing (B.6) can be used to prepare a card deck and the data cards can be punched from the directions given in Section B. 2. Typical input data and output printout summarized in B 5 provides guidelines for the program use. Sections B 3 (Program Nomenclature) and B 4 (Subroutine Description) describe, in detail, the inner workings of the program and are particularly useful for a user interested in modifying the program.

Jan 1, 1976

By Rimas Pakalnis, Catherine A. Dreesbach, Lewis A. Martin

Instrumented cable bolts developed at the Spokane Research Laboratory of the National Institute for Occupational Safety and Health were used in conjunction with existing ground control systems to monitor rock mass loads at Tg Soda Ash's trona mine, Granger, WY. Axial and shear loads were determined to levels of strain gauge accuracy of ±5 N or ±5 micro strain. These gauges were embedded in a remanufactured king wire that replaced the conventional king wire. Cable bolt performance, quality of grout, and installation techniques were also assessed. By using instrumented cables, a mine operator can determine axial load along the cable at predefined gauge locations. These data provide necessary input for an operator to design a safer working environment for miners.

Jan 10, 2000

By R. H. Kudlich

In order to assist the various Federal and State agencies using large quantities of coal to select coal best suited technically and economically to their use, the United States Bureau of Mines has placed at their disposal a fuel inspection service. As part of this service, inspections are made at the mines which propose to furnish coal to these agencies on contracts. Such inspections cover both the mine itself to ascertain its capacity to fur- nish the desired tonnage and quality of the coal, the preparation of the coal in the tipple, and the obtaining of samples for analysis to determine the quality of coal as shipped. To insure that the sample sent to the laboratory for analysis is representative of the average quality of the coal, increments are taken at intervals until a gross sample of about 1,000 pounds of coal has been collected from each of the sizes of coal shipped by the mine, while coal has been coming from all parts of the mine. In reducing this gross sample to the small sample which is sent to the laboratory for analysis it is necessary to crush and quarter the coal by a certain standardized method until only 5 or 6 pounds of coal small enough to pass through a 3/16-inch square-mesh screen remains. The ordinary method which the bureau has followed was to crush the coal by hand with a tamper, such as is used for tamping concrete, on some hare smooth surface and to reduce the volume by quartering and riffling. During the past few years the demands from various Federal and State agencies for this service have been increasing rapidly in respect to bituminous coals. In addition to this, which might be called the normal increase, numerous requests have been received for similar service in respect to anthracite. It was obvious that if this increased demand was to be met it would be necessary either to increase the force allotted to this work or to provide the present force with some means by which their work could be made more effective. A care- ful survey of the situation showed that the greatest amount of time was consumed in trans- porting the men and their equipment from mine to mine in the same district, and in reducing the gross sample to the small finely crushed sample which is to be sent to the laboratory. Both of these phases of the work could be greatly accelerated by providing a motor truck of suitable speed and capacity, carrying a power-operated crusher, and the proper auxiliary equipment to store the gross sample as collected and to reduce it in volume efficiently after it has been crushed. Such a truck has been provided and placed in service. In the eight months it has been in operation the desired results have been fully attained. About twice as many samples as usual have been taken during that time by the same 2-pan crew assigned to this work. Many of the mines in the eastern part of the United States are in hilly or mountainous regions and can be reached only over rough, practically unimproved roads. Hence the speci- fications for the truck were drawn to cover high-quality, long-life trucks, in order that

Nov 1, 1931

By R. V. Ramani, B. K. Belle

The increased effectiveness of a two-phase spray system (TPSS) over a single-phase spray system (SPSS) for dust suppression is reported in several laboratory studies. The dust collection efficiencies of SPSS and TPSS were studied in a model experimental longwall gallery facility at Pittsburgh Research Laboratory at NIOSH (USA). The experimental design consisted of two factors: pressure, and airflow. Each factor had three levels. SPSS experiments were conducted at only one pressure (1035 kPa) which is nearly 1.5 times higher than the highest air and water pressure for TPSS experiments. The results of the study are presented in this paper. While it appears that TPSS performed better than SPSS, the data is not sufficiently conclusive on this aspect. The differing spray characteristics of the chosen TPSS and SPSS nozzles did not allow a direct comparison of the two systems. In the TPSS arrangement, considerably greater turbulence in airflow is created around the shearer; it is likely that at least in the immediate vicinity of the tailgate drum, there is a roll back of the dust/mist cloud into the walkway. Therefore, positioning of the personnel upwind of the tailgate drum is necessary to avoid high dust exposures. The rate of decrease in concentration with TPSS is higher than that with SPSS. This may be due to the greater atomization of the water. The test set-up did not allow the study of conditions when coal is cut from tail to head where the potential for personal exposure is high. Changes in the experimental design are necessary to overcome some of the reasons expected for the inconclusive results.

By L. C. IlsLey

It is most unfortunate that a few must often suffer , and perhaps die , that many may benefit from a fuller appreciation of the dangers surrounding mining operations , and the proper use of safeguards designed to offset these dangers . This has been the case during the last few months in the anthracite field , where several explosions , resulting in burnings and fatalities , were undoubtedly caused by the use of defective or improperly assembled flame safety lamps . Had this same lack of understanding regarding the proper assembly of this safety device , and had the same indifference on the part of the user in keeping the lamps locked at all times and in proper condition , been permitted in a region where the coal dust was explosive , a terrible disaster would surely have resulted . In nearly every coal -mining country , including the United States , the Davy and Clanny type of lamp has been superseded , and rightly so , by some kind of bonneted lamp . Bonneted lamps , especially of the naphtha type , while much safer than the unbonneted , have more parts and need more care in assembling . For this reason the burden of responsibility for their being properly assembled rests with the lamp man ; therefore , it is extremely important that only competent , conscientious men be given this work .

Dec 1, 1921

By Sinisa M. Djordjevic, Isaac A. Zlochower, Kevin J. Liekhus, Cindy A. Loehr, Kenneth L. Cashdollar

An experimental program was conducted to evaluate the accuracy of some current methods for predicting the flammability of gas mixtures containing hydrogen and flammable or nonflammable volatile organic compounds (VOCs) in air The specific VOCs tested were toluene, 1,2-dichloroethane, 2-butanone, and carbon tetrachloride. The lower flammability limits (LFLs) of gas mixtures containing equal molar quantities of the components were determined in a 19.4-1 laboratory flammability chamber using a strong spark ignition source and a pressure criterion for flammability. All but one of the LFL values for the individual components were in agreement with earlier literature values. However, the LFL of l,2-dichlorocthane was found to be significantly lower than the range of values reported for previous determinations in smaller chambers. Two methods for calculating the LFL of mixtures were considered. The Group Factor (atomic) Contribution Method was determined to he generally more accurate than the LeChatelier Method for estimating the LFL of the gas mixtures reported here, although the LeChatelier Method was usually more conservative. The Group Factor Method predicted higher values (nonconservative) for the LFLs of several mixtures than were experimentally measured. For the case of a mixture of hydrogen and carbon tetrachloride, the Group Method estimation of the LFL was seriously in error.

By David Hoadley, Kenneth R. Maser, Ashok B. Boghani, James E. Billar, D. Randolph Berry, Mackenzie Burnett, Robert H. Trent

C. 7 Emergency Rescue Hoists There is a need, especially in mine development areas, for portable, on-call, man-rated equipment capable of lifting men through several hundred feet. Wire rope climbing equipment as shown in Figure 37 appears particularly suited to this need. It is portable, weighing approximately 100 lbs. , is currently man-rated for numerous above ground applications and can be electric or air powered. Commercial units currently have a lifting capacity of 1000 lbs. , and can be fitted with bosun' s chairs. Lifting speeds are in the 20-30 FPM range and the equipment is not depth limited. In a situation where miners are unable to climb to the top of a shaft this equipment could rapidly be anchored to the top of the shaft and lowered to them by hand. Since the self contained unit is controlled by the person travelling in the shaft he would be able to negotiate shaft obstruction himself. This would not be possible with other forms of easily deployed free-hanging equipment. Typical manufacturers of this type of equipment are Ohio Hoist Mfg, Co, 321 South Beaver St. Lisbon, Ohio 44432 216-424-7283 Sky Climber Inc. 17311 South Main St. Gardena, California 90248 213-321 -6414

Jan 1, 1976

By Victor J. Lynch

The Andover-Sulphur Hill mines are 12 miles northeast of Andover and 5 miles southeast of Newton, in Sussex County, N.J. The property is situated on the Lehigh Valley and Hudson River Railroad and half a mile east of U.S. Highway 206. It is connected with the main highway by a hard-surfaced county road. (See fig. 1.) Howard J. Hewitt of Lafayette, N.J., has under lease the Sulphur Hill tract, consisting of 28 acres, and has an option on the Tar Hill tract of 106 acres. The Tar Hill property adjoins the Sulphur Hill on the northeast. (See fig. 2.) The Andover-Sulphur Hill property is owned by the Lenape Corp. of Andover, N.J., while the Tar Hill tract is owned by the Crane Iron Co. of Phillipsburg, N.J. These mines produced iron ore during a period of about 100 years but have not been operated since 1880. Zinc and lead sulfides occur mixed with iron ores in the lower workings of the old mines. A diamond-drilling program was recommended to determine the extent of the sulfide mineralization in depth and also to explore further the iron-ore deposits on the property. The project was started October 6, 1942, and finished November 25, 1942.

Dec 1, 1947

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