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By Fred Leonard

This report is principally concerned with the engineering and economic feasibility of area surface coal mining systems other than draglines. This analysis evaluates shovel/ trucks, shovel/crusher/conveyors, and shovel/rail excavation and haulage systems for an assortment of geologic environments and production rates in the Powder River Basin (PRB). Shovel/trucks, front-end loaders trucks, and shovel/crusher/conveyors were studied in a multi-seam, dipping geologic area of the Four Corners Region. The Texas lignite engineering and economic research involved bucket-wheel excavators (BWE), BWE/backhoes, and scraper/backhoe combinations for overburden and coal excavation. The PRB truck/shovel study utilized the most recent computer simulation available in both the design and cost analyses. Detailed engineering analysis, followed by in-depth operating costs (operating and depreciation), result in a complete evaluation of each mining system. Cost comparisons of the different mining systems under similar geologic and production constraints are presented in the report to illustrate the estimated capital investment and production costs per ton of coal and bank cubic yard of overburden.

Jan 1, 1980

By Lijun Xu, Jan M. Mutmansky

"Mutmansky, J.M. and· Lijun Xu, 1989. Some observations on particulates collected in underground coal mines using diesel and non-diesel equipment. Min. Sci. Technol., 9: 207-218.The results obtained when sampling twenty underground coal mine sections, each in a different mine, are outlined. The sampling effort was oriented toward a detailed characterization of coal mine dusts and thus eight-stage Anderson Model 298 impactors were used as the primary collection instrument. This instrument allowed a fairly detailed size distribution for each of the particulates sampled. Because four of the mines used diesel outby equipment and/or diesel shuttle cars at the face, it is possible to make some comparisons of the particulate distributions in diesel versus non-diesel mines.One of the more interesting results is the pattern that exists in mines lising diesels only for outby utility haulage. Particulates in these mines seem to be consistently heavy in the fine size ranges, perhaps being of significant concern to the industry. While no definite conclusions can be drawn from the limited data, a more detailed study of particulates may provide a better picture of particulate loadings.IntroductionThe subject of particulate emiss1ons from underground diesel equipment is currently a very important topic as health concerns and regulation of diesel particulate emissions have created new environmental problems for mine operators. The amount of particulate matter originating from diesels has not been extensively measured and problems of differentiating coal and mineral dust from diesel particulates make existing data questionable.However, it is necessary to make an assessment of the problem in order to solve it. It is known that particulates from diesel engines are solid aerosols formed in the combustion process. Technically, this places the particles in the category of fumes. It is also known from tests where no mineral dust could be a factor in the measurements that about 90% of diesel particles are less than 1 µm in aerodynamic diameter [3]. To measure the diesel component of a coal/diesel particulate to measure, Johnson et al. [2] have developed procedures for utilizing laser Raman spectroscopy. The determination of diesel content in a coal/diesel mixture is difficult due to the chemical similarity of the two organic materials. However, laser Raman spectroscopy, which is often used for identification of organic materials, has potential if the Raman spectra for the two materials are different and unique. The study concluded that an accuracy of ±~% could be achieved for mixtures containing up to 55% diesel particulate. The method is relatively complex and would need further development for routine application."

Jan 1, 1990

By Eugene T. Sheridan

The process of converting coal into coke is known as carbonization. Essentially, carbonization is destructive distillation in which the volatile matter of coal is released when coal is he ted above its decomposition temperature and passes through a plastic stage before solidifying and forming coke. The mechanics of coke formation are complex, and the specific properties of certain coals that tallow them to "cake" or form coke are still unknown. Coke is a hard, cellular, carbonaceous mass, formed by heating coal in the absence of air. It is porous, irregular in size and shape, and is similar in appearance to wood charcoal. Coke, however, is denser, more porous, and more abrasive than charcoal.

Jan 1, 1965

By Eugene T. Sheridan

The process of converting coal into coke is known as carbonization. Essentially, carbonization is destructive distillation in which the volatile matter of coal is released when coal is heated above its decomposition temperature and passes through a plastic stage before solidifying and forming coke. The mechanics of coke formation are complex, and the specific properties of certain coals that allow them to "cake" or form coke are still unknown. Coke is a hard, cellular, carbonaceous mass, formed by heating coal in the absence of air. It is porous, irregular in size and shape, and is similar in appearance to wood charcoal. Coke, however, is denser, more porous, and more abrasive than charcoal.

Jan 1, 1965

By Charles H. Foreman

This paper describing the mining practice of the Hecla and Star mines, both located at Burke, Idaho, is one of a series being prepared by the Bureau of Mines on mining practices, methods, and costs in the various mining districts of the United States. It is partly a revision of articles by the author appearing in volume 72 of the Transactions of the American Institute of Mining Engineers, published in 1925, and in the June 1928, issue of the American Mining Congress Journal. About 26,000 tons per month of lead ore is produced at the Hecla mine. Costs at the mine are given for the year 1928. Stoping operations in the Star mine have covered such a short period, during which time the abnormal expenses of starting were incurred, that they are not given in this paper.

Jan 1, 1930

By S. H. Ash

THE MAGNITUDE of the anthracite industry's drainage problem in the Northern field of Pennsylvania is realized when it is known that, for the 8-year period 1944-51, all pumping plants in this region pumped an average volume of 112.5 billion gallons of water from the mines to the surface each year. This is over 214,000 gallons per minute pumped against an average hydrostatic head of 400 feet each year for that period (12).4 By comparison, Lake Wallenpaupack, the largest artificial body of water lying wholly in Pennsylvania, contains 71 billion gallons of water in its 24-square-mile area; the average volume of water pumped from the mines in the Northern field each year during the 8-year period was 58 percent more than the volume impounded in Lake Wallenpaupack. The natural configuration of the drainage area overlying the Northern field subdivides the total area into two major drainage areas-the Lackawanna River drainage area and the Susquehanna River drainage area overlying the Wyoming Basin. Although the 169-square-mile drainage area overlying the Wyoming Basin is slightly less than half that of the Lackawanna River drainage area (10), the total volume of water pumped to the surface from mines in the Wyoming Basin is 21 percent more than the total volume pumped to the surface from mines in the Lackawanna Basin. From this, it is apparent that the Susquehanna River and the pervious deposits in the buried valley over which it flows in its course across the coal measures of Wyoming Valley is the greatest single source of mine water affecting mines in this area. Because of its relatively flat terrain, the wide flood plain of Wyoming Valley does not facilitate rapid runoff; consequently, much of the surface water seeps directly into the buried-valley deposits and eventually into the mine workings.

Jan 1, 1953

By Gerhard Braüner

The present knowledge on ground movements and mining damage is mainly based on observations made when mining seamlike deposits. The studies, rules, and regulations in different countries agree in that the differential ground movements, especially the strain, account for the damage to structures. Accordingly, large buildings are particularly susceptible. The opinions on what amount of ground deformation induces what degree of structural damage are not quite uniform. Mining damage can be reduced or prevented by structural and/or underground precautions. The latter comprise measures for generally reducing the ground movements (leaving pillars, filling, partial extraction) and for reducing temporary movements (rapid extraction, specially arranged workings). Because the differential movements decrease with increasing depth of mining, safety pillars are largely dispensable at greater depths. Shafts are mainly affected by the vertical derivatives of rock displacements, but extraction in the vicinity of shafts is feasible even under difficult conditions. The theoretical concept of the ground movement process established in part 1 of this work is in qualitative agreement with the facts herein observed. As a quantitative approach, it should be applied to calculating ground surface movements rather than rock movements about underground openings. It can be extended by introducing more detailed strata characteristics.

Jan 1, 1973

By R. Hogg

"Particles play an important role in our environment and in many aspects of human activity. Much of the Earth's surface - sand, soil, rocks - consists of particles, as do clouds in the atmosphere, smoke from fires, and dust in our homes. Many of the foods we eat - cereals, flour, instant coffee - and everyday items such as pharmaceuticals, cosmetics, detergents and other cleaning products are encountered in the form of particles. Inks and paints consist of very fine particles dispersed in liquids. Modem agriculture uses huge quantities of fertilizers and pesticides, largely in particulate form. The list could be extended almost indefinitely; particle systems are obviously an important part of our daily lives. But what do we know about them? For most people, the answer is probably: not much.We are all familiar with the three common states of matter: gas, liquid and solid. In many respects, particle systems should be regarded as a distinct class of their own. The particles themselves may be solid but we all know that a heap of sand is quite different from a solid rock. A cloud of liquid droplets - fog - has much more in common with a cloud of solid particles - smoke - than it does with a bucket of water. There are certain characteristics and properties which are unique to the particulate state. The behavior of any particle system is determined not only by the material from which the particles are made, but also by interactions among the particles and with their environment. These interactions become increasingly important as the size of the particles decreases, and for exceedingly fine particles, smaller than about one micrometer (0.000001 meters or 0.00004 inches), these interactions dominate and we enter the realm of colloidal systems.Particle SystemsA system in which discrete entities - particles -are dispersed in a continuous medium can be regarded as a particulate system. The particles and the medium can consist of a solid, liquid or gas. The various combinations and some common examples are listed in Table 1. The properties and behavior of these systems depend on the characteristics of the particles, the nature of the medium, and the relative abundance of the two phases. In general, it is the latter which determines the kind of behavior exhibited by the system.As a general rule, the behavior of particle systems follows that of the dispersed phase (the particles) at high concentration, and that of the continuous phase (the medium) at low concentration. For example, both powders and smokes consist of solid particles in a gaseous medium. However, in a powder the solids typically occupy over one half of the total volume; in many respects powders behave like solids. In a smoke, on the other hand, the particles may take up only a few parts per million of volume, so that these systems generally behave like gases."

Jan 1, 1989

This report summarizes the results of the Narragansett Win Projec't's activities during the U.S. Bureau of Mines (BOM) Phase 1, which was transitional from and which followed the National Science Foundation (NSF) Phase which initiated the investigation of New England's potential roil resource. The 960 sq. mile basin is structural and topographic lowland containing 12,000 to 20,000 ft. of terrigenous clastic sediments of late Pennsylvanian age, and which rests on an upper Precambrian and Cambrian basement. The Rhode Island Formation, which is the coal-bearing unit, comprising the bulk of the Pennsylvanian rocks consists, in order of decreasing abundance, of sandstone, conglomerate, silts tone, shale, and coal. In the NSF Phase, 24 drill-holes yielded 17,900 ft, of core; in the BOM Phase I study, 4 drillholes yielded 2,100 ft. of core. Anthracite and semi-anthracite was encountered in beds Up to 30 ft. thick in widely spaced parts of the Basin. The coal, typically very low in sulfur, and a high ash anthracite, won mined in substantial volumes from 1808 to 1959 from shaft and open lit in Portsmouth and Cranston, R.I., and in lesser volumes in Mansfield, Mass. Currently coal is now being mined in Plainville, Mass. as a fuel in the manufacturing of light-weight aggregate from the same quarry that serves as the source of the rock being processed. The structurally complex Narragansett Basin is now known to have a greater extent than earlier since recent drilling by others (Chapter 2) has confirmed our interpretation that the Basin extended offshore south A Boston. The, Basin also extends into Rhode Island Sound to the south. The geological structure is more complex in the southern part of the Basin than in the northern part. Three episodes of folding have been documented on Aquidneck Island and four episodes of faulting have been demonstrated for the Basin as a whole. Relatively less well exposed rock in the northern part of the Basin, increases the difficulty of recognizing and correlating structural episodes in the northern part of the Basin. The Basin his hewn subdivided into six structural domains which appear to have distinctive structural, metamorphic, paleontological and sedimentological differences that mw assist in isolating important events in the evolution of the Basin and its component parts. The tentative structural model recently developed in POP Phase I has important implications for exploration and mining. In the first and second folding stages the coal is mobilized and thickened in the crests and troughs of folds whose axes are horizontal to subhorizontal. While conventional coal exploration and mining methods are not applicable, great thickening in the crests and troughs of large scale structures, which can he defined by geology, geophysics and drilling, may provide compensating advantages. Bedrock over most of the Basin is 0-50 ft., but thicknesses of glacial deposits up to 150 ft. are present locally. Pro-Pleistocene topographic trends are controlled by structure and rock hardness; Pleistocene deposits aligned to the S. F. are superimposed on earlier trends. The southern part of the Basin is mainly dominated by high grade Barrovian metamorphism and plutonism of Permian age, related to the Alleghanian Orogeny. About 300 sq. miles of the 960 sq. mile Basin has been affected. The remaining 660 sq. miles, in the chlorite and subchlorite zones of metamorphism are compatible with the presence of high quality anthracite and semi-anthracite. Illite crystallinity studies begun in the NSF Phase, have been carried out in the BOM Phase l with important results. About ME of the northern Basin is now known to be in the diagenetic (unmetamorphosed) or subchlorite zone and the remainder in the chlorite zone of metamorphism. Mite studies, probably best recording temperature effects, show a generally progressive increase from the NW corner of the Basin near Plainville, Mass. toward the south and southeast. Reflectivity and coal petrography studies, probably best recording pressure and effects related to shearing, indicate a generally opposite pattern. Thus these methods provide powerful tools for the ultimate solution of problems important to coal exploration for coals of higher combustible volatile content and exploitation of these. Due to the complex nature of the coal, chemical data may not he easily used to determine rank. The coals have been tectonically deformed and mineralized. This deformation plus thermal metamorphism have altered the coals, in some cases by producing natural coke. Brecciated coal is often coated with a secondary depositional carbon. The coals' hydroscopic nature and high ash contents are due to the deformed nature of the coal and the presence of this secondary carbon. The stratigraphy and sedimentology of the coal-bearing Rhode Island Formation is similar to described alluvial fan deposits. The non-geological studies al-low three conclusions to be made: 1. A substantial number of areas have been identified in the Narragansett Basin in which mining could be carried out without undue difficulty from a land use point of view. 2. Substantially more than two hundred instances of past or current- mining activities have been identified in the Basin. Many of those are in areas defined as geologically interesting, and may be advantageous From the point of view of future exploration. 3. The map synthesis technique developed for this contract is successful and may easily be adapted to future exploration in its current form and also in its expandable form dealing with unit measurements of one-tenth mile. We recommend that BOM Phase 2 exploration should accomplish the intent of the Congressional language in House Report No. 95-1251, to continue a substantial drilling and geophysics program: "The Committee expects the Bureau to continue studies involved in ascertaining the extent and quality of low sulfur coal reserves in the Narragansett Basin in New England including necessary drilling and geophysical studies. The knowledge of the extent of such deposits is of great importance to this 'energy pour' area".

Jan 1, 1979

By L. C. IlsLey, H. B. Freeman

In connection with the approval of coal-cutting machines for service in gaseous mines , the engineers of the Bureau of Mines have been somewhat concerned as to the type of trailing cables that could safely be used on permissible outfits . While no final action has been taken on this question ( tentative approvals having been granted pending investigations ) , the Bureau has been endeavoring to collect data and information on this question which would permit a fair , yet safe , ruling to be made . For this purpose cooperative arrangements were made with three coal companies to visit certain of their mines , making inspections inside the mines to observe the cables and cutting machines in operation . In all , twenty mines were visited . A questionnaire covering the operations of trailing cables was filled out at each of these mines . In a few instances no personal inspection was made , the information being supplied by mine officials after conferences with the Bureau's engineer . At other mines the information given by mine officials was supplemented by personal observation inside the mines , usually at a time when the cutting machines were in operation .

Jul 1, 1923

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Jan 1, 2012

By Michael G. Zabetakis

THIS is a summary of the available limit of flammability, autoignition, and burning-rate data for more than 200 combustible gases and vapors in air and other oxidants, as well as of empirical rules and graphs that can be used to predict similar data for thousands of other combustibles under a variety of environmental conditions. Specific data are presented on the paraffinic, unsaturated, aromatic, and alicyclic hydrocarbons, alcohols, ethers, aldehydes, ketones, and sulfur compounds, and an assortment of fuels, fuel blends, hydraulic fluids, engine oils, and miscellaneous combustible gases and vapors.

Jan 1, 1965

By A. B. Needham

This paper, which describes mining practices at a mine in the Cave- in-Rock, Illinois, fluorspar district, is one of a series being prepared by the Bureau of Mines on mining practices, methods, and costs in the various mining districts of the United States. Ore deposits in the southern Illinois-western Kentucky fluorspar dis- trict are of two general types (1) the flat-bedded, lenticular replacement and (2) the relatively narrow, rather steeply dipping fault or fissure filling. This paper describes production methods used and results obtained in mining one of the bedded lenticular ore bodies that are prevalent in the northeast portion of the district near Cave-in-Rock.

Aug 1, 1949

By Robert W. Waytulonis

The mining regulations of all 50 States were reviewed by the Bureau of Mines, and those parts pertaining to the use of internal combustion (IC) engines (particularly diesel engines) in underground mines or confined spaces were extracted. Also extracted were subjects associated with the use of IC engines; for example, storage and handling of flammable liquids, maintenance, and ventilation requirements. As the laws now stand, 29 States have specific regulations that affect the operation of diesel engines in underground coal and/or metal and nonmetal mines. The other States have no regulations because either they have no mining activities or they defer to Federal regulations. Six states have regulations expressly prohibiting the use of diesels in underground coal mines. Specific contacts (addresses and phone numbers) precede each State's regulations to facilitate inquiries about regulation revisions and interpretation.

Jan 1, 1981

By Sean Gallagher

The vast majority of ergonomics research has addressed the demands of work in standing or sitting postures, and understandably so. However, many workers (for example, underground miners, aircraft baggage handlers, plumbers, agricultural workers, mechanics, and others) are often required to adopt postures such as kneeling, stooping, squatting, or lying down for significant periods of the work day.

Jan 1, 2005

By Rudolf Kudlich

"SUMMARYThe Ringelmann Smoke Chart fulfills an important need in smoke abatement work and certain problems in the combustion of fuels. A knowledge of its history and method of preparation is, therefore, of interest to many. Since instructions on its use are not shown on the recent edition of the chart, those included in this revision of the previous information circular, by Rudolf Kudlich, now are a necessary complement to the chart. More detail regarding the use of the chart is included than was given in the earlier manuscript.INTRODUCTIONThe Ringelmann Smoke Chart, giving shades of gray by which the density of columns of smoke rising from stacks may be compared, was developed by a Professor Ringelmann of Paris. Maximilian Ringelmann, born in 1861, was professor of agricultural engineering at l'Institute National Agronomique and Director de la Station d'Essais de Machines in Paris in 1888, and held those positions for many years thereafter.The chart apparently was introduced into the United States by William Kent in an article published in ""Engineering News"" of November 11, 1897, with a comment that he had learned of it in a private communication from a Bryan Donkin of London. It was said to have come into somewhat extensive use in Europe by that time. Kent proposed in 1899 that it be accepted as the standard measure of smoke density in the standard code for power-plant testing that was being formulated by the American Society of Mechanical Engineers.The Ringelmann Chart was used by the engineers of the Technologic Branch of the Federal Geological Survey (which later formed the nucleus of the present Bureau of Mines) in their studies of smokeless combustion beginning at St. Louis in 1904, and by 1910 had been recognized officially in the smoke ordinance for Boston passed by the Massachusetts Legislature."

Apr 1, 1955

By T. M. Romslo

"INTRODUCTION This report presents factual data obtained by the Bureau of Mines in the course of an investigation of the Antler mine in the Cedar Valley mining district, Mohave County, Ariz.The Antler property was first examined by Thomas L. Chapman, mining engineer, Bureau of Mines, on December 18, 1943, and January 28, 1944. In June 1945, A. H. Wadsworth, Jr., and R. L. Griggs, geologists, Federal Geo¬logical Survey, examined the Antler mine and several other mines in the district. Both Chapman and Wadsworth recommended diamond drilling of the Antler property to determine the character and extent of ore deposition.In October 1946, the surface and underground workings were surveyed by George Huseman, Mining engineer, and T. M. Romslo, project engineer. The following month Eldred. D. Wilson, geologist of the Arizona Bureau of Mines, assisted by the project engineer, mapped the geology. Subsequently trails were built to drilling sites and diamond drilling started January 16, 1947. The project was completed April 25, 1947.ACKNOWLEDGMENTSIn its program of investigation of mineral deposits, the Bureau of Mines has as its primary objective the more effective utilization of our mineral resources to the end that they make the greatest possible contribution to national security and economy. It is the policy of the Bureau to publish the facts developed by each project as soon as practicable after its conclusion. The Mining Division, Lowell B. Moon, chief, conducts preliminary examinations, does the actual investigative work, and prepares the final report. The Metallurgical Division, O. C. Ralston, chief, analyzes samples and takes beneficiation tests."

Mar 1, 1948

By M. L. Whisman

Three samples of waste lubricating oil were re-refined by processes developed by the Bureau of Mines and reformulated with additives to meet designated requirements for viscosity and service. Quality-defining bench-scale tests were used to compare and evaluate the quality of these three motor oils, eight commercially re-refined lubricating oils, and three new lubricating oils. Most of the re-refined oils studied could not be distinguished from new oils by the bench tests used to define quality. There was some evidence, however, that one and perhaps more of the re-refined products investigated might not meet all of the quality standards of new lubricating oil, suggesting the need for better quality controls by re-refiners.

Jan 1, 1974

By C. S. ROBINSON, T. M. Romslo

This investigation was conducted jointly by the Bureau of Mines and the Geological Survey to obtain further information on the source and economic possibilities of the copper mineralization exposed on the Copper Giant group of claims, Ajo mining district, Pima County, Ariz. The Copper Giant group of claims was first brought to the attention of the Bureau of Mines by Joseph Hunter (deceased), Phoenix, Ariz., part owner of the claims. In December 1942 these claims, and an adjoining group, were investigated by T. C. Denton, mining engineer, formerly with the Bureau of Mines, and Nels P. Peterson, geologist, Federal Geological Survey. It was concluded the area could not be considered as a source of copper for immed- iate emergency needs and that further investigation of the area, at the time, was not warranted. In the spring of 1948 the lessee, J. H. Greenway Albert, requested Bureau of Mines assistance in developing the property. J. H. Hedges, former chief, Tucson Branch, Mining Division, and Lincoln A. Stewart, mining engineer, Bureau of Mines, made a cursory examination of the property and noted that at numerous places, low-grade copper mineralization appeared on fractures and bedding of the Locomotive fanglomerate and Ajo volcanics, which are thought to be of Tertiary age. During the period of May 11 through 14, 1949, Bureau of Mines engineers3 mapped and sampled two areas of mineral- ization. On June 2 and 3, 1949, the areas selected by the Bureau and three other nearby mineralized areas were investigated by C. A. Anderson and R. S. Cannon, Jr., of the Federal Geological Survey. As a result of these examina- tions, further investigation of certain areas was believed to be merited. The Copper Giant area was selected as the most favorable in which to carry out exploratory and development work. The field work on the project was started in October 1949 and completed in December 1949. It consisted of road building, trenching, sampling, topo- graphic and geologic mapping, diamond drilling, and logging of core. Samples taken on the project and during preliminary examinations totaled 64, of which 63 were surface samples. Diamond drilling, started October 10 and completed December 7, consisted of two holes for a total depth of 1,542 feet.

Mar 1, 1952

By John H. Johnson

Diesel tailpipe CO, C02, NO, and N02 concentrations by the Emissions Measurement Apparatus (EMA) were found to compare satisfactorily with simultaneous concentrations by instruments in the MSHA engine certification laboratory in Bruceton, Pa. The EMA was then applied to the measurement of LHD vehicle diesel tailpipe gases and smoke opacity in the White Pine and Brushy Creek Mines. A general experimental approach was developed by which instruments could be compared for the measurement of diesel exhaust pollutant concentrations in the 1/2 to 5TLV range. The concentrations are changed by varying engine speed, dynamometer load, and the portion of the exhaust which enters the dilution tunnel. Dräger detector tube diluted exhaust CO, CO2, NO, and NO2 measurements were compared with simultaneously taken portable instrument measurements. Diesel exhaust interference inaccuracies were separated from inaccuracies due to detector tube calibration by comparing the instrument readings with both actual detector tube readings and detector tube readings corrected by recalibration of the detector tubes alongside NBS traceable calibration gases. The detector tubes' accuracy was found to be only slightly affected by diesel exhaust interferences and it was concluded that most measure within certification limits established by the National Institute for Occupational Safety and Health. The effects of 2 exhaust system configurations on the pollutant concentrations in a dead-end heading were studied. Both of the configurations exhausted the gases near the roof, directing them toward the crosscut, and both improved the stratification of the air in the heading, due to the bouyancy of the hot exhaust gases. One of the configurations was a pair of Fume Diluters which diluted the exhaust with air by a 10:1 ratio, and the second system was simply a pair of exhaust pipes, bent to direct the exhaust similarly to the fume dilutors. By redirecting the exhaust, the concentration of C02 measured on the LHD vehicle was reduced by as much as 507, in dead-end headings up to 200 ft long. The Fume Diluters showed no improvement over the simple redesign of the exhaust system.

Jan 1, 1980