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By W. A. Naismith

On 16 July 2004, at 07:10 a collapse of about 1.8 million m3 (about 4 ½ million tons) took place on the north wall on Nchanga Open Pit. This collapse was the result of a developing instability that was first identified when the benches in this area were exposed during September 2002. The NOP geotechnical and survey departments closely monitored the development of the failure. Control measures were implemented to reduce risk to men and equipment. These measures were continually improved and adjusted in reaction to observations and changing conditions. The purpose of this paper is to describe in detail the monitoring results that were obtained both by traditional methods and the novel slope stability radar system (SSR). Difficulties encountered in establishing critical deformation levels and deformation rates that can be used to predict the onset of collapse are described. Details of the monitoring and control measures, which led to the successful completion of mining in the area, are also described in this paper.

Jan 1, 2005

By T. F. Oliveira, E. B. Zanelato, J. Alexandre, L. J. T. Petrucci, A. R. G. Azevedo

The paper and cellulose industry is responsible for generating large amounts of solid waste, which are produced during various stages of the production process. Currently this material goes to places like landfills and other generating costs for the company. Furthermore, cement, mortar and concrete represent a significant economic and environmental cost. This study aims to determine the pozzolanic activity index in the residue studied to verify its viability in the incorporation of the same in cement. It will be used Luxan method for this determination. The data found show that the material has the possibility of being incorporated in the mortar due to its pozzolanic activity index.

Mar 1, 2017

By L. J. Ebert, G. Sachs, W. F. Brown

Isothermal transformation, or "aus-tempering," of a carbon-containing aus-tenite at elevated temperatures yields so-called "intermediate products." Their structure and properties are, for a given hardness, rather different from those of "tempered martensite" obtained on conventional quenching and tempering.' Several investigators2,3 have found that for high carbon and slightly alloyed steels the intermediate products formed at temperatures close to that of the martensite reaction possess strength properties superior to those of tempered martensite. The structure of these low temperature, intermediate products is generally acicular (bainite) but clearly different from that of martensite. However, at higher austempering temperatures, between 1000 and 1300°F (540 and 700°C) carbon steels were found to exhibit a rather low ductility.4,5 Thus notch bar tensile tests showed the ratio between notch strength and regular tensile strength to decrease with increasing austempering temperature. For ductilities below a few percent this notch strength ratio is a measure of ductility, according to investigations on low alloy steels.637 Furthermore the presence of intermediate products formed unintentionally on quenching was considered as responsible for the low ductility and impact energy of some heat treated steels,8 These intermediate products could result from partial transformation at the so-called "nose-temperature" where the rate of the transformation is a maximum. Tempering improved such mixtures of martensite and intermediate products, their properties approaching those of tempered martensite of equal hardness. The following investigation constitutes an attempt to determine certain strength properties of a partially austempered and subsequently quenched low alloy steel, namely, a chromium steel (SAE 5140) The structures formed by such a treatment should consist of a mixture of intermediate products formed on austempering and a martensite formed on oil quenching from the austempering temperature. It was intended, by varying the austempering time, to vary the quantity of the intermediate products between zero and 100 pct. The austempering temperature of 860°F was selected after extensive preliminary tests close to the nose-temperature. Austempering at this temperature yielded an acicular intermediate product. .Additional tests under less exacting conditions were made for an austempering temperature of 950°F where the intermediate product appeared to be very fine pearlite. To determine the effects of tempering on structures containing various amounts of

Jan 1, 1949

By Frank Miller

THE lower cost of producing oil from naturally flowing wells compared with pro-duction costs accruing from artificial lifting methods has stimulated much research, with the joint purpose of extending the natural flowing life of wells and of increas-ing the productivity of small wells. The laboratory investigation described herein was made to determine the effect of a slotted liner on the pressure gradient in the vicinity of the wall of a flowing well. Flow restrictions caused by the liner induce energy losses between the oil-bearing for-mation and the inside of the liner, which may be reduced by improved liner design, and thereby the flow capacity of wells may be increased. These losses have been evalu-ated for rectangular slots of different sizes, and means are suggested for reducing them. The dearth of information concerning the nature of the flow of fluids from uncon-solidated sands through small openings in the walls of pipes-as represented by the flow of oil from an oil sand into a slotted liner-is acknowledged. Although the bene-fits to be realized by operators through the use of optimum liners is just beginning to be recognized generally, Coberly1 in 1937 pointed out that the functioning of screen casing is an important factor in the pro-duction of oil. From his study on the selection of size of oil strings for wells in California, Parks2 concluded, in part, that the perforated section of the oil string de-serves continued study, especially with respect to the selection of perforations. The growing use of gravel packing result-ing from certain research findings lends even more significance to the problem of selecting optimum liners, as the application of these methods usually requires slotted liners or other kinds of perforated liners. The present study was made to obtain further information for the guidance of engineers and operators in selecting slotted liners and to develop a laboratory method that may be used in analyzing possible pressure conditions surrounding most types of perforated casings used in producing oil wells, so that the present inadequate fund of knowledge on this important subject may be expanded.

Jan 1, 1940

By G. Sachs, L. J. Ebert, W. F. Brown

Isothermal transformation, or "aus-tempering," of a carbon-containing aus-tenite at elevated temperatures yields so-called "intermediate products." Their structure and properties are, for a given hardness, rather different from those of "tempered martensite" obtained on conventional quenching and tempering.' Several investigators2,3 have found that for high carbon and slightly alloyed steels the intermediate products formed at temperatures close to that of the martensite reaction possess strength properties superior to those of tempered martensite. The structure of these low temperature, intermediate products is generally acicular (bainite) but clearly different from that of martensite. However, at higher austempering temperatures, between 1000 and 1300°F (540 and 700°C) carbon steels were found to exhibit a rather low ductility.4,5 Thus notch bar tensile tests showed the ratio between notch strength and regular tensile strength to decrease with increasing austempering temperature. For ductilities below a few percent this notch strength ratio is a measure of ductility, according to investigations on low alloy steels.637 Furthermore the presence of intermediate products formed unintentionally on quenching was considered as responsible for the low ductility and impact energy of some heat treated steels,8 These intermediate products could result from partial transformation at the so-called "nose-temperature" where the rate of the transformation is a maximum. Tempering improved such mixtures of martensite and intermediate products, their properties approaching those of tempered martensite of equal hardness. The following investigation constitutes an attempt to determine certain strength properties of a partially austempered and subsequently quenched low alloy steel, namely, a chromium steel (SAE 5140) The structures formed by such a treatment should consist of a mixture of intermediate products formed on austempering and a martensite formed on oil quenching from the austempering temperature. It was intended, by varying the austempering time, to vary the quantity of the intermediate products between zero and 100 pct. The austempering temperature of 860°F was selected after extensive preliminary tests close to the nose-temperature. Austempering at this temperature yielded an acicular intermediate product. .Additional tests under less exacting conditions were made for an austempering temperature of 950°F where the intermediate product appeared to be very fine pearlite. To determine the effects of tempering on structures containing various amounts of

Jan 1, 1949

By William Skinner, Ishmael Quaicoe, Jonas Addai-Mensah, Ataollah Nosrati

To date, intractable ore specific operational challenges such as poor heap geotechnical stability, permeability and high acid consumption rates associated with low grade (~1 wt%) nickel (Ni) laterites still makes the adoption of heap leaching processing unattractive. This paper presents some highlights of drum agglomeration, column leaching and characterization studies undertaken to foster the understanding and knowledge of some of the desirable product attributes of -2 mm and -15 mm, low grade saprolitic (SAP) and goethitic (G) Ni laterite feed ores and their blends (SAP/G). For column leaching, 5-40 mm agglomerate beds were continuously irrigated with 200 g/dm3 H2SO4 solution at 8.5 dm3/m2/h rate over 100 days. Ni, Co, Fe, Al and Mn extraction rates, free acid concentration, agglomerate bed slump and structural changes were determined as a function of time. The results show that at equivalent feed masses, except -15 mm G which displayed slower, pseudo-layering based behaviour, all the feeds (single and blends) displayed coalescence controlled agglomeration behaviour at varying binder dosages. Whilst the agglomerate compressive strength of the G ore was markedly higher than that of SAP ore, those of the blends were substantially similar. At fixed column leaching conditions, the Ni/Co extractions and acid consumption were higher for SAP ore whilst the agglomerate bed slump was lower than those for G ore. The bed of agglomerates produced from -2 mm G/-15 mm SAP blend was more stable than that for the -2 mm G/-2 mm SAP blend agglomerate, the latter experiencing blockage within 24 h of acid irrigation due to agglomerates breakdown. The Ni/Co extractions and acid consumption rates obtained for agglomerates of -15 mm G/-2 mm SAP blend were lower than expected based on the ratios of the SAP and G ores within the blend composition. The findings suggest that judicious saprolitic and limonitic ores’ blending could reduce acid consumption rate, improve the agglomerate bed robustness and enhance bed percolation behaviour under prolonged acid irrigation periods during heap leaching of lateritic ores of variable mineralogy.

Jan 1, 2014

By C. O. Brawner

INTRODUCTION Tailings dams up to about 200 ft. high are proposed to store tailings for a major mining operation on Marinduque Island in the Philippines. The original design of the dam utilized a compacted laterite starter dam followed by hydraulic placement of cycloned sands to form slime retaining dykes along the outer face of the dam. The upstream method of construction was proposed. In view of the failure of numerous tailings dams in Chile during the EL Cobre earthquake (I), an investigation was performed to assess the earthquake stability of the proposed dam. This included a soil investigation on the first cycloned sand dyke, which had been built to a height of 45 ft. Results indicated that the density of the sand was much lower than existing empirical criteria consider to be necessary for resistance to liquefaction. As a result, the dam was redesigned. The downstream method of construction was selected and a yearly construction program was developed to make use of sand available by cycloning. To increase shear strength, improve resistance to liquefaction, and to utilize steeper slopes, compaction of all sand in the dam was specified. A special underdrainage layer and toe drains were incorporated in the design. Details of the decant system and surface erosion alternatives are described. SITE CONDITIONS The mining project is located in the Philippine Islands. At the present annual rate of production, about 4,230,000 cu.m. of tailings will be produced yearly. The volume requirements for tailings storage design for the first 10 years of operation are in the order of 45,000,000 cu.m. The topography near the mine is mountainous with many gullies and canyons carved out by high intensity rainfall and runoff. The bedrock, which is generally shallow and weathered for a considerable depth, is overlain by laterite soils. Vegetation is comprised largely of palms, banana trees, and tropical shrubs and grasses. Precipitation is heavy. The average yearly rainfall over 24 years is 65.2 in. and the maximum recorded 24 hour rainfall is 9.0 in. High intensity rainfall is associated with typhoon storms, which are a seasonal threat inthe Philippines. Fig. 1 shows a summary of monthly precipitation.

Jan 1, 1972

By E. B. Hunt, T. M. Geffen, C. R. Stewart, V. J. Berry

Laboratory data .show that the gas-oil ratio performance of non-uniform porosity limestones produced by solution gas drive is sensitive to producing rate and to fluid properties. Nan-uniform porosity limestones are those for which laboratcry solution and external gas drive tests yield considerably different relative permeability ratio characterislics. The oil recovery performance by solution gas drive depends directly on the number of gas bubbles formed. Laboratory rates of pressure decline, which are 100 to 10,000 times greater than normal field rates. cause the formation of an unusually large number of gas bubbles. This results in abnormally high oil recovery efficiencies. Since it is impractical to reproduce the number of bubbles formed under field conditions, laboratory solution gas drive data on non-uniform porosity limestones are therefore not directly applicable to field operations. However, certain laboratory data can be used to make a conservative estimate of field performance. The concepts presented in this paper indicate the possibility that increased field oil recoveries may he obtained from non-uniform porosity limestones by rap- idly reducing reservoir pressure for a short interval of time. It has yet to be established that significant improvements in oil recovery from such reservoirs can he realized by varying the pressure decline rate within limits possible in the field. However, the possibility that recovery may be increased in this manner warrants further study. INTRODUCTION Limestone reservoir rocks can be divided into two general classes according to the nature of their pore space. One class has a comparatively uniform pore system composed mainly of voids between grains of the rock (intergranular type porosity). The other class, in addition to having intergranular porosity, has a secondary pore system composed of combinations of solution cavities, fractures, etc., and is considered to have non-uniform porosity. It has been shown in a previous publication' that the laboratory measured gas-oil flow behavior of uniform type porosity limestones is essentially the same for a test simulating a field solution gas drive as for one simulating an external gas drive. For non-uniform porosity type limestones a significant difference in gas-oil flow behavior was found. More efficient behavior was

Jan 1, 1955

By William L. Husk

Stockpiles have always been a necessary part of coal mining except, perhaps, when a person was mining only for the needs of his family from a seam on his home place or coal mined for the use of a small hamlet and carried to each man's house as it was mined. Then it may have been stockpiled at each man's place for several days or on the village common. Mining with this limited production required waste stockpiling. Stockpiling of the products of coal mining, both coal and waste material, has always been a necessity. Very little coal has ever been moved directly or immediately from the working face to the point of consumption and burned. It has always been expedient to stockpile the coal some- where and store the waste.

Jan 1, 1981

By J. L. Dion

"A study of the techniques to integrally cast copper tubes in copper tuyeres for use in blast furnaces has been carried out. The work has been performed in support of current efforts to produce two-compartment tuyeres having improved water-cooling capacity. A test pattern corresponding to a vertical section of a two-compartment tuyere, and including a cast-in-place copper tube, was used to investigate such variables as tube preparation, tube coolant, pouring temperature, pouring rate and gating design. Successful castings, either with a good metalfurgical bond or good intimate contact between the tube and the casting, were produced, with all combinations of gating system and position of the tube tried. However, the pouring temperature, the pouring rate and the effectiveness of the coolant are interrelated and must be controlled to produce a good metallurgical bond.IntroductionAs part of its contribution to, and in collaboration with, the Copper Casting for the Steel Industry Committee, CANMET has undertaken research into the methods and techniques needed for the integral casting of copper tubes into high-conductivity copper castings.The objective was to produce two-compartment copper blast furnace tuyeres in which the water-cooled nose compartment consists of a copper tube metallurgically bonded to the wall of the high-conductivity copper casting. This design, developed in the UK, has demonstrated a much extended service life with attendant economies; unscheduled shutdown of blast furnaces due to tuyere failure is a significant problem in the steel industry. The Canadian steel industry believes that this design will replace the currently used single-compartment tuyere in blast furnaces within a few years.The technology to produce these tuyeres does not exist in Canada. One of the main features is the inclusion of a smooth-walled cooling channel in the nose, which permits high velocity cooling water to be employed. A second compartment acts as a reservoir backup, should failure in the nose occur. This would allow continued use of the tuyere for a period of time, permitting a scheduled shutdown for repair s. To assist the Canadian producers of tuyeres to maintain their market, and the Canadian steel industry to have a reliable domestic supply, it is important that the necessary technology for the production of two-compartment tuyeres be developed and transferred to industry."

Jan 1, 1982

By Steven J. Page

Researchers have developed a model to describe airborne respirable dust (ARD) generation on surface coal mine drills. By measuring a few basic parameters and using a graph, a drill operator or engi­neer can estimate the relative severity of drill dust emissions as well as how much of a reduction in ARD can be obtained by changing any given parameter. Geometric parameters include: drill deck cross-sectional area, shroud leakage associated with the deck shroud as well as the operational parameters of bailing air­flow, and dust collector airflow. The rela­tionships yield predictive ARD values which fall in the range measured on oper­ating drills for collector/bailing air flow ratios greater than 2. Overexposure to airborne respirable crystalline silica dust can cause serious or fatal respiratory disease. Exposures of sur­face coal mine rock drillers to respirable crystalline silica are of particular concern. In a 1992 alert on silicosis in rock drillers, the National Institute for Occupational Safety and Health (NIOSH) reported on 23 cases of advanced silicosis (acute, acceler­ated, and chronic) ranging in ages from 25 to 60 with drilling tenures ranging between three and 20 years.1 Most of the cases involved drill operators in their 30?s and 40?s, indicating high silica exposure levels are associated with their occupation. A more recent lung x-ray surveillance study of a 664 volunteer population of surface coal miners showed that the prevalence of silicosis-like abnormalities was 9%.2 The two most significant factors associated with these abnormalities were increasing age and years of drilling experience.

Jan 1, 2008

By W. H. Cheung

Nickel (Ni) plays a major role in the production of steel and other major alloys. There are two sources of Ni: laterite and sulphide ores. Global reserves of sulphide ores are being rapidly depleted, while there are enormous reserves of Ni laterite, much of it in Australia. As well as being present in huge amounts, Ni laterites have the advantage of containing cobalt (Co), a valuable mineral. Over the past decade, these factors have been driving the industry to explore the processing of Ni laterite. A route that has been used commercially in processing nickel laterite ore involves the thermal activation of the minerals by pre-reduction followed by ammoniacal leaching (Caron). Although this process has been effective in processing the goethite rich laterite minerals, the higher-grade serpentine-based minerals have been shown to be less susceptible to this process. This has been attributed to the formation of inert olivine phases. In this study, we examined the use of an alternative lixiviant, sulphuric acid, in leaching pre-reduced limonite and weathered saprolite nickel laterite ores. The specific aim of this study was to examine the sulphuric acid leaching of Ni and Co from pre-reduced laterite minerals, and to understand the role of mineral transformations in this metal dissolution. Synchrotron based X-ray diffraction was used to examine the transformation of goethite (FeOOH) to spinels and serpentine mineral ((Mg,Fe)3Si2O5(OH)4) to olivine. Reduction tests were carried out using CO and CO2 reducing gas mixtures and temperatures from 400 °C to 700 °C. The rate of formation and disappearance of specific Bragg peaks during reduction of specific minerals were used to derive an understanding of these solid-state reactions. Laboratory based reduction tests and leaching in sulphuric acid were used to validate the effect of these mineral transformations. The results suggest the versatility of sulphuric acid in leaching nickel from spinels and olivine, which was achieved at the expense of lower selectivity. Cobalt dissolution was found to be dependent on the nature of ferro-cobalt alloy formed during reduction.

Jan 1, 2014

By R. G. Hall

WHEN we want to interpret some problem which faces us at the present, if that problem be a social or political movement, we turn to the pages of history for 'information. If the problem be one of science or of industry we turn to the library of the subject and endeavor to translate the present from the experience of the past. I wonder if you would bear with me for a few minutes as I look back to the time when I was going through mining school and looking forward with hope, it is true and with confidence also, but still with some trepidation and an occasional qualm, to the month of June when the class of 1897 would be hunting jobs. Those were the years 1893 to 1897. Those years saw the Treasury of the United States so empty of gold that the President had to appeal to financiers to accept the country's promises to pay in return for $100,000,000 in gold. And the invectives that were hurled at both their heads for such a betrayal of the people sound strangely similar to those you read today being daily written and screamed at another President for taking us into the League of Nations or for not issuing bonds in huge amounts for unemployment relief, or for not adopting somebody else's particular specific for the relief of hard times.

Jan 1, 1931

By Fred E. Beasley

Metallurgists have, in the last ten years, overcome many difficulties of high zinc in lead blast-furnace slags. This problem was brought to the front at the close of the war, by the price obtained for lead and the high cost of labor, fuel, and flux. The Port Pirie plant of the Broken Hill Associated Smelters, Australia, early in 1919 had increased the zinc oxide in its blast-furnace slags from 13.5 to 20 per cent., at the same time reducing the iron oxide in the slag from 33.5 to 25.6 per cent. These results were obtained by the addition of 10 to 12 per cent. granulated slag to the roaster charge, improved conditions of the crushing, mixing, and roasting of the constituents of the sinter. By experiments and improvements, the practice at this plant has developed a normal slag that carries 22 per cent. zinc oxide, and at times runs as high as 33 per cent. zinc oxide, with only slight furnace trouble. The granulated slag is used not only as a diluent to the sulfur in the roaster charge, but on account of its value as a slag-forming material and the physical properties it imparts to the finished sinter. The ore is mixed with flux and given a double roast. All the first roasting is by sintering with the Dwight & Lloyd machines. The final roasting is performed partly by Dwight & Lloyd machines and partly by H. & H. pots. The charge to the blast furnace consists chiefly of the final sinter, slag shells, siliceous and non-bearing sulfur lead ores. High blast and ore columns are the practice. The greatest care is taken to obtain in the final sinter as low a sulfur content as possible. Attracted by the success of the Port Pirie plant, The Consolidated Mining & Smelting Co. of Canada, at Trail, B. C., in 1920 treated its crushed primary sinter with about 15 per cent. granulated slag. The Trail smelter at this time was short of ore and a large part of the charge to the roasters consisted of the zinc-plant residue having the following analysis: 12 to 16 per cent. lead, 12 to 16 per cent. zinc, and 25 to 30 per cent. iron. The lead in the final sinter was low and the physical condition was so bad that all the sinter had to be screened before it could be charged to the blast furnace. Also it disintegrated on being trammed and dumped

Jan 1, 1925

By S. Kang, D. G. C. Robertson

Slag cleaning furnaces require extensive wall cooling because they involve the use of a superheated slag bath. This is in direct contrast to smelting furnaces, where the wall is usually (but not always) protected by "banks" of solid charge. In order to understand the heat transfer and flow in slag cleaning furnaces a number of model studies have been carried out using molten wax to simulate the slag. Wax is a good model fluid because, like slag, it has a high Prandtl number. Wax models cannot simulate the behavior close to the electrodes (DC arc or AC submerged), but they can and do give a good simulation of the flow and heat transfer at the wall. An understanding of these phenomena is of great importance for the design of cooling panels in the walls of the furnace. Since superheated molten slag will eventually wear away any refractory bricks over time, the wall cooling must be designed to form a frozen layer of slag, referred to as a "freeze lining". The heat flux density (Q/A) required to do this is given by Q/A = h* ?T, where h is the heat transfer coefficient in the slag phase at the wall, and Li T is the superheat (bulk slag temperature - liquidus temperature). Both Q/A and h vary greatly with position and both are usually a maximum at the slag line. In the experimental work, molten wax baths were heated by block heaters to provide similar energy densities to those encountered in commercial slag cleaning furnaces. This procedure was considered to be valid since most of the electrical energy into a furnace bath is dissipated as heat. Gas stirring was used to simulate the gas evolved at the electrode in real furnaces - the quantity of this gas could be estimated from a knowledge of electrode consumption. The similarity criterion was equal gas flow per unit area of surface, in model and prototype. Heat transfer coefficients were measured in the models as a function of power density, gas stirring, superheat, etc., and could be related to the full-scale operations by the use of dimensional analysis.

Jan 1, 1999

By J. T. Dunham

The Bureau of Mines studied by dilatometry the effect of titanium on the thermal expansivity of hot-rolled zinc and Zn-l percent Cu alloy. The titanium content of the alloys was varied up to 0.3 percent. Expansion coefficients were determined from measurements made both parallel and perpendicular to the plane of the rolled sheet. Titanium reduced expansion parallel to the plane of the sheet, especially in the rolling direction, but increased expansion perpendicular to the sheet. Basal-plane pole figures showed that the degree of preferred orientation increased with the titanium content in the alloy, and that anisotropic expansion can be correlated to sheet texture.

Jan 1, 1965

By Arkady Senchenko, Yury Kulikov

"Basic theoretical grounds of the methods applied for crushing and grinding parameters determination according to international standards are given in this paper. Statistical data about crushability and grindability research are shown. The potential relationship between the values of Fred Bond Work indices and John Starkey indices (Crushing index, Ball mill index, Rod mill index and AG/SAG index) are discussed in this paper. In order to establish correlation between the crushability and grindability indices the analysis of over 2 500 tests for 165 deposits located in different parts of the world was performed. The relationships among different types of energy consumed for crushing and grinding were determined. A method for preliminary estimation of energy consumption in semiautogenous + ball mill grinding circuit is suggested for its application in preliminary technological solutions development and technical-and-economic assessment."

Jan 1, 2014

By G. R. Chaudhury

Many base metals, such as copper, lead and zinc, are commercially extracted by thermal processing of sulphide concentrates. However, owing to the depletion of high grade sulphide ore reserves and to environmental legislation, efforts have been in progress for some years to develop methods for the extraction of metals from lower-grade oxide ores and secondary resources, and there are now examples of commercial-scale operations.

Dec 1, 1995

By M. W. Von Bernewitz, J. J. Forbes

"In the United States there are hundreds of underground and surface (inside and outside) inclines at coal mines on which trips of cars are continually being run with coal, rock, supplies, and men. The safety of the men and prevention of damage to the slopes depend, excluding the personal element of the hoist-man, on the strength and condition of the wire cable, draw bars, and the couplings, and on the links of chains and pins as well. Within a recent period of four weeks there have been two runaway trips, one on the surface and one underground; it seems desirable to call attention of mechanical engineers and others at coal mines to the need for closer and more frequent inspection of the cable, draw bars, coupling links and pins, derailing devices, wheels, brakes, and other parts of cars or trips on which men are hauled on inclines. This bureau has never published anything on this class of accident heretofore.How frequently runaway trips occur is not known. If no serious injury or fatalit has to be reported to the State authorities, a number of such happenings may occur and not be mentioned outside of the immediate vicinity of the mine.Runaway trips can and do result in considerable loss of life, in injuries, and damage, either at or near the place of the break, or throughout a mine by causing an explosion of gas or coal-dust or both, This report is restricted to a study of the mechanical and physical phases of car trip construction and of the metal of couplings and ropes; derailed trips are not included and may be the subject of another paper. There is no need to mention gas accumulations, coal-dust and rock-dusting, open lights, protected power lines, and permissible equipment, because these have all been well covered in Bureau of Mines publications which have been widely distributed and partly or wholly reprinted by others.Most of the items regarding the runaway trips tabulated have been abstracted from reports made respectively by Clarence Hall, W.O. Snelling, and J. W. Paul; D. Harrington and J. J. Forbes; H. C, Howarth and G. S. McCaa; K. L. Marshall and E. H. Denny; J. J. Forbes, G. W.- Grove, and R. D. Currie; S, P .Howell and K. L. Marshall; and .J. W. Paul, H. D. Mason, and G. E. McElroy, all of the mining and safety divisions; and C. H. Herty, jr., and G. R. Fitterer of the metallurgical section of the Bureau of Mines. W. J. Fene, K. L. Marshall, and S. P. Howell of the safety division, and J. F. Lessig, mechanical engineer, and G. St. J. Perrott, superintendent, Pittsburgh Experiment Station, read the text and offered sugges¬tions. W. J. McGregor, coroner for Allegheny County, and P. F. Nairn, State Mine Inspector of Pennsylvania, contributed valuable information."

Mar 1, 1931

By S. J. Schatzel, V. Gangrade

A ventilation research study was conducted by the U.S. National Institute for Occupational Safety and Health (NIOSH) and a cooperating longwall trona mine in the Green River basin of Wyoming in the United States. The objective of the study was to evaluate the movement of longwall face air and exchanges between the face and worked-out areas to document the presence or absence of face airflow pathways between these locations. Tracer gas experiments using sulfur hexafluoride (SF6  ) were conducted to describe air movement on the face and in the mined portion of the active panel. Maintaining adequate ventilation air on longwall faces is important for worker safety and for the dilution of gases emitted from the face and caved gob.