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By Harry F. Weaver

WHEN 1 was assigned by the Director of the United States Bureau of Mines to present a paper at this annual meeting of the Mining Society of Nova Scotia, 1 was grateful, honoured, and elated to realize finally a life-long desire to see your beautiful land and visit with you who have the good fortune to live and work here. Naturally, in preparing for this important event, 1 wanted to give you something of special interest within the limits of the subject so I chose an area dose to my heart -the operation of our Federal coal mine inspection service, which has, as its fundamental purpose, the prevention of accidents in and around ?Coal mines. In 1957 the United States had 10,879 active coal mines scattered throughout 28 States and the Territory of Alaska. The production of coal for the year was about 515,472,000 tons, including 2.5,472,000 tons of anthracite and 490,000,000 tons of bituminous coal and Hgnite. Anthracite is mined principally in a comparatively small area of one State. AU the 28 States and the Territory produce bituminons coal and/or lignite. The beds mined range from 18 inches to more than 100 feet in thickness and from the horizontal to the perpendicular.

Jan 1, 1958

By A Campbell

Open pit blasting at Ernest Henry Mining has the potential to cause damage to nearby underground workings. This paper is a case study of the blast vibration management project that was conducted to ensure open pit blasting did not adversely affect the stability of upper production levels or cause damage to the underground primary fan units. The two upper levels of the underground mine surround the lower portion of the open pit mine. The remaining underground mine workings are directly below the open pit mine. This paper details the process developed to prevent open pit blasting causing excess vibration in the underground mine. Measurement of test blasts combined with historic blast monitoring data was used to determine site specific blast vibration parameters. Threshold vibration levels for blast-induced damage to underground drives and the fan chambers were developed from benchmarking and non-linear numerical modelling. A Monte Carlo simulation model was used to predict vibration levels in critical underground areas. Blasts predicted to exceed maximum vibration levels could then be redesigned to avoid damage.A scale distance law for determining peak particle velocity (PPV) from the distance and charge weight of blasts was developed. Underground observations were used to develop a site-specific relationship between PPV and ground support/rock mass damage. A Monte Carlo superposition prediction model was developed and compared to measured data to refine input parameters. Standards for redesigning open pit blasts in order to reduce blast vibrations whilst minimising impacts on productivity are described. Non-linear numerical modelling was used to establish the dynamic capacity of the fan chambers, and set a PPV of 250 mm/s as a threshold for damage. The numerical model captured the full dynamic behaviour of the fan chambers and installed support, including transient stresses, strains and induced damage, when subjected to a simulated open pit blast.This case study also outlines a procedure for monitoring and predicting blast vibrations at other mine sites where open pit blasting has the potential to impact on a nearby underground mine.

Nov 8, 2011

By Xiaojie Yang, Gang Yang, Zhenli Hao, Manchao He, Ruifeng Huang, Zheng Wang, Chaowen Hu

Preventing the spontaneous combustion of remnant coal, which is indicated by carbon monoxide (CO), is a significant issue for coal mining safety. The N00 longwall mining method with Z-type ventilation is advantageous for the prevention and control of CO; however, research regarding this topic is limited. To investigate the distribution of CO in a goaf and working face, a sealing material and technique for blocking the goaf were introduced after proposing a forming method for a Z-type ventilation system; furthermore, a monitoring method was designed and applied in the field. The results demonstrated that the CO concentration during mining in the upper corner and return airway ranged between 4–6 ppm and 3–7 ppm, respectively. More importantly, no CO was generated in the goaf. The results indicate that the advantages and mechanisms regarding the prevention of spontaneous ignition using the N00 longwall mining method with Z-type ventilation are as follows: (1) The adoption of the downward ventilation technique is not only beneficial for reducing the air pressure difference between both ends of the working face, but also prevents CO accumulation in the upper corner. (2) The basis of a spontaneous combustion disaster is eliminated owing to the absence of coal pillars reserved in the goaf. This study proposes a superior method for mitigating spontaneous combustion disasters related to remnant coal in the goaf in a coal mining field and contributes to the better understanding of the N00 longwall mining method for coal mining safety.

Nov 28, 2022

By Mario SINNAEVE, Olivier LEMAIRE, Gisèle WALMAG, Sébastien FLAMENT

Many hot rolling mills worldwide face nowadays bonding zone fatigue problems before reaching scrap diameter of the work rolls. This phenomenon is nowadays known to occur in reversing roughing mills both in stainless steel and in carbon steel rolling. The phenomenon can be explained through longer rolling campaigns, inadequate backup or work roll maintenance, harder steel grades or increased throughput by reduced amount of passes to achieve the same thickness. In order to help users in optimizing the roll use, we developed a numerical tool to evaluate and optimize roll maintenance. This paper will review the influence of roll geometries on stresses generated at the roll surface but also at the bonding zone. We will also show how roll geometries can decrease contact fatigue damages by modifying crowning and chamfering procedures, shell thickness, material design or campaign length

Oct 1, 2019

By L. Salnais

"Aluminum alloy structural components f or aircraft designed prior to the early 1970s, were machined from 2024, 7075 and 7079 plate, bar and forgings in either the T3xxx of the T6xxx tempers. Protective treatments for these parts consisted of chromic acid anodizing and alkyd zinc chromate primer, plus a nitrocellulose lacquer for exterior parts.The major service problem with these parts was the frequent occurrence of exfoliation corrosion and stress corrosion cracking (S. C. C.). Therefore, 2024 and 7079 alloys, with min or exceptions, were not used in aircraft designed after the early 1970s. Replacement materials were 7075 and 7050 alloys in the overaged, exfoliation corrosion and S. C. C. resistant, T73xxx tempers.The use of improved materials together with the upgrading to chromated epoxy primers, polyurethane enamels and the introduction of water displacing corrosion inhibiting compounds have significantly reduced corrosion in aircraft. IntroductionThe prevention of corrosion in aircraft has been a challenge to aircraft designers for many decades. With the design of the first all-metal aircraft, the designer and builder were thrust into the relatively new field of protective treatments as corrosion started to become more prevalent. This resulted from the continually increasing importance and wider utilization of aircraft, and their exposure to a wider variety of ho stile environments such as urban industrial pollution, high humidity tropical areas and salt ladened marine environments.Corrosion advanced another significant step when, after World War II, designs of new and larger aircraft utilized larger and thicker metal sections in the manufacture of structural components. With thicker mill products came higher residual heat treat, fabrication and assembly stresses resulting in an increased number of stress corrosion and exfoliation corrosion problems.Apart from the exterior environment, aircraft interior s can be exposed to a number of fluids which are either directly or indirectly responsible for corrosion. The most common of the fluids is water which is usually introduced as a result of condensation, especially in pressurized fuselages, and spillage from lavatories, galley s and electrolytes from batteries. These fluid s have a degrading effect on protective treatments and are also corrosive to the substrate metal. Fluids such as phosphate ester hydraulic fluids and ester based turbine engine lubricating oil s are not corrosive to the substrate metal, albeit they do contribute to corrosion by the degrading effect on protective treatments."

Jan 1, 1988

By E. Ghali, B. Arsenault

Aluminum alloys play an important role in the manufacturing of air and ground vehicles. However, with such alloys, corrosion damage is often found on structural components subjected to fatigue loading. The alloying provides large benefit in terms of the high specific tensile strength (ultimate strength/density ratio) to the aluminum alloy but causes the aluminum alloy to be more sensitive to localized corrosion due to complex microscopic heterogeneities such as secondary phases. This paper investigates thermal spray coating namely arc spraying to evaluate the protection against environmentally assisted cracking (EAC) and localized corrosion on Aircraft structural 7075 T651 aluminum alloys. In particular, EAC and pitting corrosion at the interface coating-substrate are a challenge for thermal spray protective coatings on aluminum alloys under cyclic load and immersion. To address these issues, different surface preparation techniques prior to arc spraying were considered such as chemical de-oxidation, laser ablation, shot peening and grit blasting. Results indicate that surface preparation and improved coating process parameters play an important role to provide a coating conferring a protection against both localized corrosion and EAC.

Jan 1, 2006

By S. Abe

An extensive study has been carried out to determine the true cause of floating slimes precipitation which sometimes occurs and badly affects the quality of copper cathodes. Soluhilities of floating slime compounds systematically measured for the ternary system As-Sb-Ri added solely or in combination with conventional copper electrolyte (63°C) and bench scale electrorefining experiments done by varying electrolyte composition, have shown conclusively that the level of Sb(V) ions plays a substantial role in the precipitation mechanism. It was, therefore, speculated that controlling the level of the less soluble S b ( V ) ions below a certain critical level should result in a complete elimination of the undesirable precipitation. This can be easily achieved, for instance, by the addition of a reducing agent such as SO2 gas and the simultaneous employment of a certain type of cheating agent that effectively removes excessive Sb and Bi from the contaminated electrolyte. Long-term pilot testing conducted in line with the above speculation has confirmed the SO2/chelating resin scheme to be industrially very attractive and feasible.

Jan 1, 1987

By W. G. Courtney

The prevention of frictional ignition with a ripper-type continuous mining machine using conical bits was investigated in the laboratory using cutter-drum-mounted water sprays. Results indicated that frictional ignition during dry cutting of sandstone with conical bits was readily obtained even at low drum rpm, while wet cutting with a carefully-designed water spray nozzle located behind the bit substantially reduced the likelihood of frictional ignition. However, the orientation and operation of the spray nozzle is critical and involves almost no margin for error. A Lee-Norse 265 ripper drum has been modified to include durable water seals and is presently being field tested underground.

Jan 1, 1987

By P. C. Thakur

Frictional ignitions (also called face ignitions) is defined as the rapid oxidation of a mixture of methane and air with a visible flame that could last from a few seconds to several minutes. These ignitions have a potential to turn into a mine explosion and eventually a large-scale mine fire. Over the last 22 years, U.S. coalmines have had 1566 frictional ignitions. There were no fatalities but serious injuries have occurred. Every effort, therefore, should be made to prevent frictional ignitions. The preventative measures fall under four categories: (a) degasification of coal seams prior to mining, (b) adequate ventilation, (c) wet cutting or water-jet assisted cutting and (d) machine design to minimize ignitions. The paper discusses each of these techniques in detail.

Jan 1, 2006

By A. J. Lanza

THE prevention of illness among the employees of the mining industry is especially important in view of the importance of the industry, the unsettled conditions of labor, which emphasize the economic necessity for conservation of labor, and for humanitarian reasons. The burden of chronic illness is altogether unwarranted and unnecessary. If the industry is to maintain its labor supply in an efficient manner and keep the standard high, it is essential that it make every effort to keep its labor in good physical condition. The basic principles underlying health conservation are the same for any industry, but they are here applied especially to the mining industry, and more particularly, perhaps, to metal mining, as it is with this phase of the industry that the writer is most familiar, and as it is conceded that metal mining presents more health hazards than coal mining. The first step in the prevention of illness lies in securing employees who are in sound health and free from organic disease. I do not mean that all men who go underground should be physically perfect, but they should be free from organic defects of the heart, lungs, and other organs, or from anatomical defects that would- markedly increase their liability to accident. The number of men working underground in mines in this country whose physical, condition totally unfits them for such work presents-a situation that should not be allowed to continue, and which I believe is 'not equalled in any other, industry in the country. There is but one way to secure men who come up to the required standard, . and that is by a thorough physical examination before employment. I am fully aware of the objections felt toward such a procedure by many employers and employees. There is much to he said on both sides, but to any one who is at all familiar with the mining industry as it is today in this country, and who approaches the matter with an unbiased mind, there can be absolutely no doubt as to the necessity for physical examination. As a purely logical proposition this is self-evident, but there remains the further necessity of placing physical examinations on such a

Jan 2, 1919

CHARLES F. WILLIS,* Bisbee, Ariz.-(written discussion?).-The consensus of the discussion of the paper of Dr. Lanza indicates that the physical examination, while it is probably a good thing, is fought by the workingman, and that, because of this fact, it has been proved unsuccessful. The physical examination standing alone is worth but little, and could easily be made a subject both of ridicule and dissension unless the company having such examination shows its own good faith in promoting a thoroughly better health program. It is easily seen why a workman would resent his employer expecting him to be physically fit, if at the same time the employer provides un-healthful, unsanitary, working conditions, or if the town in which the employees are expected to live is dirty and unkempt. One mocks the other. The employer cannot say, "You must remain healthy so that I can get by with unhealthy conditions." But if working- conditions are as good as can be obtained to keep men well, the employer can ask his men to be in a healthy condition. A State examination and standard would have many difficulties, owing to the fact that a man would pass or would not pass the standard set, thus eliminating the discretion on the part of the employer in placing men whose physical condition might well permit working in one place and not another. Any physical examination that is run for the purpose of eliminating the physically unfit is unjust, both to the worker and to the nation as a whole; a State examination would make a distinct dividing line, whereas examination by the employer is conducted with a vision of the positions available. The workman's opposition to the physical examination comes from the fact that he has been taught to believe that it is an interference in his personal affairs, that he can be clean or dirty as he chooses, that he can he healthy or unhealthy, and that it is nobody's business but his own. The war has taught us, however, that the individual is no longer the unit and that all such propositions must be based on the greatest good for the greatest number.

Jan 6, 1919

By K. V. Konigsmann

"Mattagami Lake Mines Ltd operate a zinc-copper mine with an annual output of about 200,000 tons of zinc and 30,000 tons of copper concentrates. Zinc concentrates arc shipped to a company owned smelter in Valleyfield (a distance of 690 miles), for Export to Quebec City and also to Josephtown, Pennsylvania (1,060 miles, Figure 1.)The protection of concentrates in open gondola rail shipments has been a matter of concern since operations commenced. Considerable financial losses did occur at times because of wind erosion. Operating difficulties were also encountered by customers because of excessive moisture accummulation in the concentrates. Test shipments made in 1969 established the magnitude of losses in open cars. The results and subsequent investigations at our mines and elsewhere confirmed that load protection is an economic necessity.Many types of covers were experimented with, more or less successfully. In 1972 we agreed on a joint program with Dupont of Canada Limited. A new type of cover was developed by early 1973. It has been in use since, undergoing several improvements as experience accumulates."

Jan 1, 1975

By C. Droun

"Low back pains account for about 13 per cent of all compensation claims made to the Quebec Workmen's Compensation Commission and cost the employers a sum exceeding ten million dollars. The frequency and cost of these health problems in Quebec metal mines are proportional to the provincial trends. An elaborate review of the literature on the causes, nature and prevention of low back pain is made in this presentation. A prevention program for low back pain has been designed in cooperation with a team of seven medical specialists and two physiotherapists for the Quebec metal mines. The program is especially designed for persons who have had low back pain, in order to prevent a recurrence, and for persons beginning to feel chronic difficulties. It is based on existing programs at the Hawthorne Plant of Western Electric Company and at Minnesota Mining and Manufacturing, but it requires a much different approach because of the nature of medical care available at the mining sites. The program is difficult because it involves a change of attitude for every employee and every supervisor. The program, so far, is beneficial because several men are now seriously engaged in an active program of reconditioning and because the problem of low back pain ie beginning to be seen from a new angle."

Jan 1, 1973

By D. C. Van Aken, O. J. Rajtora

A research effort sponsored by the Department of Energy (DOE) and several steel producers, is investigating the benefits of coating steelcasting nozzles with various materials. Coatings were applied to casting simulation nozzles made from industrial tundish nozzles (primarily of magnesia) and industrial submerged entry nozzles (SEN's) (primarily of alumina-graphite) in order to extend casting time prior to nozzle clogging. Nozzles were coated by air plasma spray (APS) using a 9M series APS system from Sulzer-Metco. The ability of these coatings to provide protection from clogging was evaluated using a steel casting simulation. Substrate-coating compatibility was characterized using optical and SEM microscopy.

Jan 1, 2004

By Jian Yang

The mechanism of resulfurization in the desulfurization process with magnesium vapor produced in situ by aluminothermic reduction of magnesium oxide was clarified in the present work. The influences of various operating parameters on the resulfurization were studied and the methods that could prevent resulfurization were proposed. There are two kinds of mechanisms of resulfurization in the desulfurization process with magnesium. One is decomposition of the desulfurization product of MgS under the inert atmosphere. The other is oxidation of MgS under the oxidative atmosphere. Under the present experimental conditions, lowering operating temperature and oxygen partial pressure in the atmosphere could effectively prevent the resulfurization. Adding CaO onto the melt surface was an effective method for preventing the resulfurization due to transformation of the desulfurization product of MgS into the more stable compound of CaS. Since addition of the activated charcoal powders greatly decreased the transfer rate of oxygen in the atmosphere to the melt surface, it also reduced the resulfurization remarkably.

Jan 1, 2006

Scale build-up in titanium palladium alloy spent electrolyte heat exchangers in the residue treatment plant commissioned at Risdon, Tasmania in 1971 was shown to be a mixture of manganese dioxide and anhydrite (CaSO4). The manganese dioxide was deposited as a result of thermal decomposition of permanganate ions present in the spent electrolyte. It was shown that deposition of manganese dioxide and associated anhydrite scale could be prevented by prior reduction of permanganate ions to the manganous (Mn++) state by the addition of ferrous ions. In the plant this was conveniently accomplished by injecting into the inlet line to the heat exchangers sufficient zinc plant solution containing ferrous sulfate to decolourise the spent electrolyte. This action prevented deposition of such scale for another 21 years, until the heaters were finally decommissioned in March 1992. Measurements indicated that addition of the reducing solution lowered the anodic potential of the titanium alloy by 200 - 300 mV (depending on the solution resistance), but that it was still +300 to 400 mV with respect to a standard calomel electrode. It was shown that, if necessary, a small impressed current could be applied to provide anodic protection. Before scale deposition was overcome by the addition of ferrous sulfate solution, badly scaled heat exchangers were cleaned by recirculating a solution of hydrogen peroxide in spent electrolyte or dilute aqueous sulfuric acid, after laboratory testing of a variety of possible solvents for the scale. Corrosion tests indicated that attack on the titanium alloy by the acidic peroxide cleaning solution was insignificant.

Jan 1, 2005

By G. Van Weert

Refractory ores and concentrates containing silver tend to form Ag-jarosite during autoclave oxidation. Silver extraction from the oxidation products is therefore low, unless a hot lime treatment step to decompose Ag-jarosite precedes cyanidation. Since silver iodide is very stable but soluble in cyanide solutions, the formation and decomposition of Ag-jarosite in the presence of iodine species was studied. Results indicate that Ag-jarosite formation could be prevented in favour of H3O-jarosite and AgI while oxidizing Ag2S under industrial autoclaving conditions, when the total iodine species to Ag mole ratio exceeded 5. Lower ratios gave proportionally more Ag-jarosite and less AgI. Under these conditions existing Ag-jarosite was also found to decompose in H30-jarosite and AgI.

Jan 1, 1993

By G. G. Lambert

The paper traces the pattern of spontaneous combustion in the workings of what was originally Hemsworth Colliery, but since July 1967 is now part of South Kirby Colliery. Examination is made of the Barnsley Seam sections and the part played by the top section of the seam as it comes in close proximity to the main seam. In this area of the colliery nine mechanised faces were set away between the years 1953 and 1968, every one "fired" at the pillar edge and six "fired" at the face line when production had ceased. The paper deals with the different preventative measures used, from sandbag walls, cement injections, spraying with polyurethane, until finally using Mandoseal as a sealant. Since the latter method was first used, the last three faces worked in this particular area were all salvaged completely, without any sign of a heating developing.

May 23, 1905

By V. V. Nazimko

Abandoned coal mines cause subsidence and structural damages. Shallow abandoned mines induce the most severe and harmful damages. In addition, they produce time-dependent subsidence which is difficult to predict. Backfilling of underground cavities with waste materials have been used to prevent the time-dependent subsidence or to mitigate its effect. However, this procedure is expensive. A new drill and blast technique has recently been proposed to prevent surface damage from time¬dependent subsidence over abandoned mines. It utilizes the principle that blasting in the caved rock and roof in the vicinity of a cavity will dilate the ground and create a self-supporting effect owing to increase in the volume. Physical modeling has demonstrated that artificial dilation of caved rock using the drill & blast technique creates positive effects due to the following sequence of events: the dilated rock creates a supporting effect for the suspended rock strata and reduces its span which decelerates 3.4 times the process of caving. The roof span is reduced by the next caved layer, which causes the hole boundaries to incline to each other. This effect converts the process of caving from a developing mode to a reduction mode. Finally, the sinkhole zone assumes a triangular shape with a negative angle of draw 64-700 in contrast to a rectangular shape of the chimney zone for natural caving. Vertical dimension of the triangular zone is 3.87 times of the room height. Final surface subsidence decreases at least 2.09 times; displacement 1.31 times, slope 2 27 times; curvature 3.42 times, horizontal strain 1 21 times in comparison to natural caving of the ground over an abandoned mine.

Jan 1, 1999

By Henry Howe

THAT the quiescence of a liquid while it is solidifying should favor the formation of columnar crystals, normal of the cooling surface, is seen readily on considering the mechanism of solidification. First; each particle of any composite liquid, whether it be an aqueous solution or a molten metal; in solidifying splits up into two parts, different in composition and hence in fusibility. One part is infusible at the, existing temperature, - and hence solidifies, and in general attaches itself to the inclosing walls of metal which have already, solidified; A, Fig. 1. The other part is, fusible at the existing temperature and hence remains molten. In the case of carbon Open steel, the part. of each drop which actually j; Sea solidifies is poorer, in carbon than the drop itself was before it began to solidify, and this impoverishment of the solidifying,. half-drop enriches . the other, half-drop in carbon, and Layer of Liquid thus. makes it unfreezable at the existing tem- Fig. 1.MECHANISM OF perature. SOLIDIFICATION. By this- mechanism there arises during solidification a " littoral" or shore layer- of liquid, B, Fig. 1, bathing the already solidified. walls, and more fusible than either those walls or the great remaining central mass of liquid or "deep sea," C, from which it separates them. It is essential that we grasp clearly this conception of a fusible littoral molten layer coating the already solidified walls and separating them from the deep sea. Meanwhile. heat is flowing rapidly outward through these walls, its escape cooling them, so that if any given particle of the deep sea metal

Jan 2, 1919