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By Boryong Lee, Heedong Sung, Minho Park, Sunyoung Choi

Recently, the demand for ultra-thin steel plate with high hardness and strength has been increasing in various industries. In order to satisfy this requirement, steel company designs the chemistry with low CEQ and obtains the required characteristics through quenching and tempering process. Especially, these steels are accompanied by low temperature tempering as a necessary process. Unlike ordinary high temperature tempering steels, it is impossible to improve the flatness after low temperature tempering. Therefore, shape control in the quenching process is very important for securing the excellent quality flatness. In order to obtain flatness in the quenching process, uniform cooling inside the plate should be accompanied. However, the quenching process has limitations in estimating the temperature behavior during cooling because the plate temperature is lowered to room temperature. In this study, a thermocouple was installed inside the actual quenching plate to measure the temperature behavior during cooling and to establish the manufacturing conditions of the quenching plate to ensure excellent flatness quality.

Oct 1, 2019

By O. Cermak, F. Degonld

Although 3D fragmentation analysis is a relatively new technology, it is rapidly gaining popularity among mid-sized mining operations and quarries. The results provided by this technology are adequate, but like other picture analytic methods, it mainly focuses on the surface of the muck-pile. These results are incomplete or incorrect as falling rocks and boulders from the stemming zone are constantly influencing the muck-pile surface. This obstacle can be overcome by collecting a large amount of data and analyzing it over time. However, this is not always an ideal solution, as companies prefer to receive results immediately after the blast to make resource allocation decisions, production planning, and plan for the next blast. Over the past year and a half, we have conducted a study on various muck-pile fragmentation analysis results from 3D modeling in Central Europe, comparing the results between the surface and inside of the muck-pile. By analyzing multiple shot results, we were able to determine the percentage difference between the top and inside fragment sizes and calculate the range of correction coefficients for different rock types. Applying these coefficients to a single muck-pile surface fragmentation analysis allows us to determine the actual fragment sizes inside the muck-pile. This enables us to make informed decisions regarding loading, hauling, material mixing, and proper crushing or milling. By overcoming the limitation of surface-based analysis, we can now accurately evaluate blast performance, which leads to better processes optimization and increase efficiency. As 3D fragmentation analysis becomes more widespread, we expect to see even more benefits for the mining and quarrying industry

Jan 1, 2024

By D. S. Scovira, T. Gustavsson

Exiting WW2 (mid-1940s), the potential of nitrates (ammonium nitrate, calcium nitrate, sodium nitrate) and hydrogen peroxide for application as a commercial explosives for mining, construction, and other industrial purposes both became known. The technology stream advanced the development and uptake of nitrate based explosives to the point that they are the current global standard for blasting. Today, environmental issues are shaping the strategic agenda across various industries. Most global mineral resource, construction houses, and explosive manufacturers have publicly announced ESG carbon reduction commitments in support of COP26 Net Zero 2050. The mid-2010s saw a renewed interest in hydrogen peroxide explosives to eliminate NOx fume. Carbon reduction initiatives in the early 2020s provided additional impetus to investigate hydrogen peroxide based explosives for industrial use. Hypex Bio has recently pioneered the formulation, manufacture, and end-use delivery of a Hydrogen Peroxide Emulsion (HPE) on an industrial scale. The HPE is composed primarily of hydrogen peroxide (H2O2) plus a lesser amount of fuel and emulsifier phase. The base HPE is produced in a low energy intensity modular plant using industry proven mixing techniques. The base HPE is a white, highly viscous emulsion that is similar in consistency to base nitrate emulsions. To enable end blasting use, a mobile charging unit gases the base HPE to a detonable density. The HPE is compatible with current priming and initiation systems. Hydrogen peroxide explosives offer a significant reduction in total carbon emission as compared to nitrate based explosives. The production of ammonium nitrate (AN) emulsion is energy-intensive and not carbon neutral. Based on the EU Average and for the oxidizer phase only, 1 kg [2.2 lb] of AN emulsion emits 2.3 kg [5.1 lb] of CO2 as compared to the production of hydrogen peroxide emulsion that results in 0.23 kg [0.5 lb] of CO2. This is a difference of 90%. HPE contains no nitrates and does not generate post blast nitrous oxides (NOx). HPE generates no aqueous nitrate or ammonia pollution and is a solution to meeting increasingly regulated mine site water discharge limits. Hypex Bio recently conducted a successful underground HPE evaluation with a major mining company in Sweden. HPE blast designs were the same as those done with nitrate based emulsions. Rock breakage, advance, muck displacement, and excavator performance were equivalent. Ventilation and re-entry times were reduced. The mining company has expressed further interest in assessing HPE and is demonstrating industrial leadership by exploring this transformative explosive technology

Jan 1, 2024

By E. Líder, J. Pavez, J. Rivera

The application of new technologies, methodologies, and the use of new products in mining operations is a practice that is becoming more common in the industry every day, added to the new challenges and restrictions found in the operation. In the city of Tierra Amarilla, the interaction between mining operations and the community presents a constant challenge given the proximity to the community and the limitations that this presents. Explosive charge mass, in conventional blasting using traditional explosives (ANFOs, packaged explosives for example) limits the explosive charge lengths (they are reduced), impacting the explosive charge productivity. To improve the productivity of explosive charge and fragmentation, the use of low-density explosives was proposed, allowing the increase of the explosive charge length, trying to maintain the vibration levels within the established limits (2mm/s), preserving the fragmentation of the rock in the required sizes. The present study shows the results obtained from the application of low-density bulk emulsion for production blasting charges using upward and downward fan drillings. During this process, 18 blasting events were carried out, of which 8 were Up-hole loading (average density of 0.75 gr/cc) and 10 with Down-Hole loading (average density of 0.95 gr/cc). In summary, a total of 110,760 tons of ore have been broken, using low density emulsion, meeting the proposed objectives such as: 33% reduction of vibrations, 12% overbreak (within the theoretical design), P80 of 11in and 4.6% in fines.

Jan 1, 2024

By J. Sanchidrián, A. Fernández, P. Segarra

The combination of chemical analysis techniques as XRF and measurement-while-drilling (MWD) technology in underground mining is a novel approach to gather comprehensive on-line information about physical and mineralogical data. In this work their integration is investigated aiming to delineate the ore/waste boundary. The input data analyzed come from a narrow vein underground mine, where the ore correspond to fluorite, and gathered in two production levels with complex mineralogical characteristics. Two approaches are followed to build a generalizable classification methodology and a site-specific model: a k-means clustering heuristic algorithm to define rock classes based on their physicochemical features, and a machine learning (ML) ensemble model trained with drilling parameters. For an imbalance class problem, a good recognition is obtained for the ore when is related to a high content of silica and for the waste. To predict the ore with low silica content it is necessary to integrate an analysis-while-drilling method to recognize the fluorite content when this mineral is embedded in different rocks. MWD can be employing for the lithologies recognition when representing different structural and mechanical properties between them.

Jan 1, 2024

By J. Silva, T. Worsey

The Worsey-Silva equation determines the optimal row timing for the smallest fragmentation and allows fragmentation models to be adjusted due to row timing. The equation utilizes the concept of dynamic confinement to determine when the best time to fire the next row or sequence series would be if the smallest fragmentation is desired. Full-scale testing was conducted at an aggregate quarry in Ontario to support the theory and equation. The full-scale testing comprised six (6) blasts, two (2) different contractors, and three (3) different sequences. The test parameters were kept consistent, besides changing the timing between sequential charges to explore the timing sequence’s influences on fragmentation. From this research, the theory of dynamic confinement relating to row timing was discovered, and the equation to determine the optimal timing for the smallest fragmentation was derived. An equation to adjust fragmentation based on row timing was derived from the full-scale testing and literature review. The Worsey-Silva equation can be used with other fragmentation models as it takes the fragmentation results from the other models and adjusts them based on the row timing used. The paper explains the theory behind the equation, the research supporting the findings, and the developed Worsey-Silva equation for row timing

Jan 1, 2024

By M. Gebhardt, J. Johnson, S. Rosenthal

The use of presplitting applications in an underground mine setting is a method of reducing overbreak in the rib and back when blasting occurs. Presplitting performed at the Underground Mine Education Center (UMEC) on Montana Technological University’s campus in Butte, Montana showed a dramatic decrease in the amount of overbreak incurred in the blasting process. Application of the presplitting technique occurred after presplitting presentations at ISEE in San Antonio. Presplit testing consisted of drilling perimeter holes closer together than production holes and loading perimeter holes with a combination of specialized presplit explosive and packaged emulsion with electronic detonator initiation. The ideology was to shoot the perimeter row first, to create a fracture around the perimeter, so when the main production round is shot there is less shock exerted on the surrounding walls due to the pre-fractured perimeter rock. For the test performed, the back ended up with 83% of total holes resulting in half barrels representing a remarkable result. The right rib ended up with one half barrel visible before muck was removed while the left rib did not have any half barrels visible due to a clay seam being in very close vicinity to the perimeter row. The first test blast was a great start encouraging future work on presplitting applications in the UMEC. Additional testing will continue with different combinations of perimeter hole spacing, the addition of a buffer row along the ribs, and varying loading techniques to determine the most effective presplit method for the rock type of the UMEC. Detailed test results and loading configurations will be provided in the paper.

Jan 1, 2024

By S. Mansfield, A. Sharma

At a large open cut copper mine, in pit crushing and conveying is used to shorten haul routes and minimise stockpiling of ore. This strategy decreases capital expenditure by reducing the number of haul trucks and excavators required and reduces the need to rehandle ore from stockpiles with a secondary load and haul fleet, with an overall goal of lowering operating costs and carbon emissions. As the mine has developed and expanded, it was necessary to extend the conveying network and install a fourth, semi-mobile crusher to increase the output of the operation, while maintaining the operational efficiencies. This required the blasting of a new tipping bench and pocket for the installation of one of the largest and most powerful semi-mobile, crushing plants. Fed by 360 tonne (396 ton) ultra-heavy class haul trucks, the KB 63-130 Pro gyratory crusher is the highest capacity available in the market. This paper describes the holistic process that was applied to model, design and execute the blasts required to create the pocket for the semi-mobile crusher, the surrounding tipping bench, plus the conveyor corridor and access ramp used by the ultra-heavy class trucks.

Jan 1, 2024

By P. Lozada

The objective currently demanded from controlled blasting techniques is to minimize damage to the remaining rock mass while protecting the integrity of mine walls and ensuring the quality of the fragmented material for easier extraction. Finding this balance represents one of the three main challenges faced by large open-pit mines. They must achieve mine stability by complying with slope designs while also maintaining good results in terms of fragmentation and equipment productivity. The main constraints are related to unfavorable geological conditions, water presence, limited drilling diameters and available explosive products, as well as managing drilling times and blast scheduling, among others. For slope control, in addition to presplitting, blasting designs generally include buffered rows, drilled with smaller diameters, and loaded with fewer kilograms of explosives than production holes. The objective is to reduce the powder factor (kg/t) to minimize the energetic influence on the walls and attenuate damage. However, this often requires using very short charge lengths compared to the bench height (one-third or less) and reducing the pattern geometry, which increases the number of holes per ton and drilling costs. This traditional technique of reducing powder factor in the buffered rows has the main limitation of not being able to distribute the explosive energy throughout the entire column, leading to fragmentation issues mainly in the steaming area. Measurements conducted by Orica in their operations indicate at least a 30% increase in P80 particle size in the buffer zone associated with this condition. To improve energy distribution, techniques such as decking, or vertically decoupled charges can be employed. However, these techniques cannot be applied under wet conditions, and strict control over implementation quality is required to avoid deviations, which increases loading operational times and resource required. In this sense, the use of less energetic and lower-density explosives is a better alternative. On one hand, they allow for complete charge columns in the buffered rows, ensuring homogeneous fragmentation, and on the other hand, they reduce the energetic influence on the slopes, significantly decreasing vibration levels. With less energy per kilogram of explosive (MJ/kg) and less charge per linear meter (kg/m), it becomes possible to handle higher specific charges and longer explosive columns, providing flexibility in drilling and loading design options without compromising slope stability.

Jan 1, 2024

By C. Breeds, K. Jeremiah, E. Jennings

Washington State has a well developed set of blasting regulations which have been promulgated by the Department of Labor using extensive stakeholder input, not only from citizens but also from manufacturers and representatives of IME, blasters in charge, blasting engineers, blasting companies, local and federal law enforcement agencies, fire officials, and local and state government representatives. WAC 296-52 therefore provides a foundation or platform for developing city ordinances for Washington State cities should a City wish to do so. On the other hand, Oregon’s code is based on OSHA 1926, Subdivision U, Blasting and the Use of Explosives which provides scant direction regarding the modern use of explosives. Reference is also made to ODOT Section 00335 - Blasting Methods and Protection of Excavation Backslopes. This paper examines two separate programs that have been developed by two Cities, one in Washington State and one in Oregon to further regulate blasting inside City limits and discusses why the lack of a regulatory foundation made one approach more difficult than the other. One of the authors was retained by the City of Kennewick, WA to develop their ordinance and has more recently followed and reacted to a pending ordinance for the City of Redmond, Oregon. The paper will compare and contrast the different approaches and comment on the reaction from both Blasters and the public. We also present a case study that involved blasting in an urban area of Oregon to prepare a foundation for a water tank. Controlled Blasting was carried out within 70-ft of residencies and within a community that had expressed reservations regarding blasting even though the work would make a significant contribution to the betterment of the community. Pre-construction surveys of residencies located in a large area surrounding the site were performed and a well-planned blasting program was carried out. Residencies were subject to vibration levels that were monitored using six seismographs that surrounded the site and these units measured vibration levels that were significantly lower than allowed by statute. There were complaints triggered by individuals reactions to blast vibrations which validated commonly held models of human perception but no damage was caused by the Blasting.

Jan 1, 2024

By J. Pizarro

Any organization that subjects its activities to a continuous improvement methodology, aiming to optimize their processes and services, must be able to adequately measure the results of the implemented changes to pursue better outcomes. This is no different for mining companies. When it comes to blasting, an accurate fragmentation analysis can correlate blast design and rock mass parameters to particle size distribution, enabling us to further analyze the correspondence of specific design patterns, applied to specific rock mass properties and the result in measured fragmentation indicators. Over time, many tools were developed for us to obtain PSD data, albeit each of them had their own shortcomings. The first ones to be developed involved photographing the muck pile including a scale object, uploading those photos to a PC, and using specialized software to analyze each one. As a result, analysts would get a PSD curve that served as reference for the performance of the blast. This method, which is still used, has major shortcomings. The most obvious one is that it is only able to capture a slice of the blast, which corresponds to the exposed section of the muck pile the analyst has access to, and even there its reach is limited to the areas that are safe for getting close enough for placing the scale, which are not many. Consequently, this is a very limited way to get a fragmentation performance assess for a blast. Currently, autonomous systems are capable of taking continuous pictures of the muck pile. Installed on a shovel, conveyor belt or crusher feed, these systems can take a continuous stream of pictures that are later analyzed automatically without the need of human intervention. These systems greatly increase the volume of data and, consequently, we have a PSD curve that is more representative of the blast performance. However, this technology still had issues when trying to sample front end loaders mining operations or getting results from underground blasting due to the inherent difficulties of these operations. New algorithms used for capturing and processing data for front end loaders can overcome the harsh environment of their operations and produce PSD data in high vibration environments and difficult mining angles. For underground mining, algorithms can be used to sample each truck exiting the mine, giving a reliable source of fragmentation analysis that can be traced back to their stope of origin. The development of this technology extends the existing system’s capabilities and helps us in our efforts to improve fragmentation results with each blast.

Jan 1, 2024

By P. Couceiro, J. Navarro

A new methodology to perform selective blast designs by adapting the explosive energy, hole by hole (or in the hole), to the rock properties as a combination of their strength properties through the X-Rock model has been developed based on drill-monitoring data from both autonomous and manual rotary drilling modes. For that, a thorough normalization process has been developed to minimize external influences in the data induced by the different rig system and the operator interventions during manual drilling operation. Principal component analysis has been used to combine drill monitoring information. Data from 48,385 blastholes, comprised in 102 production blasts at 7 different levels in one expansion of the mine have been used for the analysis. The methodology, called X-Energy, combines the X-Rock model outputs with actual blast design parameters (drill pattern, stemming and borehole length, explosive mass/density and others) and a constant variable obtained from a machine learning algorithm, to estimate size distribution and percentage of fines and coarse material, hole by hole, by combining and recalibrating the Kuznetsov (Cunningham, 1987) based equation. From it, a new shovel-independent diggability model has been developed as combination of the P80 size, the rock properties (from the X-Rock) and a constant variable obtained from a machine learning algorithm. The X-Energy application presented in this study have been implemented in Minera Escondida Limitada (MEL), to design and operate production blasts with the goal of varying the explosive density to the rock properties to obtain a more uniform size distribution and digging rates, hole by hole, based on a target size and rate, and improving slope care, preventing active faults to fail. The methodology has been applied and validated in 17 production blast (8,277 blasthole), unlocking an average of 12.8% reduction in explosives costs (explosive consumption), by combining a pattern expansion strategy and a better distribution of the explosive density within the blast. The results demonstrate how a better distribution of the explosive energy by varying its density in the hole according to the rock and blast geometry variables can reduce powder factor (explosive consumption) while improving or maintaining blasting and digging results.

Jan 1, 2024

By M. Araos

Non-ideal explosives can be characterised by different methods like velocity of detonation measurement, double pipe tests, underwater tests, aquarium tests, etc., to name a few. Both aquarium and velocity of detonation tests were selected to characterise a non-ideal explosive that is based on hydrogen peroxide, fuel, and void sensitisation. The detonation process in an aquarium of this sensitised explosive was captured at 80,000 frames per second using a high-speed camera. The explosive product was detonated using 51mm (2inches) diameter acrylic pipe charges. The product was detonated at different densities in an aquarium (cube box containing water). An aquarium provides a homogenous confinement for the detonation of explosives and more importantly, allows observing the shock wave as it changes the refraction index of water. The analysis of the video footage allowed the calculation of the velocity of detonation, pressure, gas rate release, and how the shock wave's shape in water changes with densities. It is suggested that the calculation of the rate of gas release could be related to the bubble data obtained from underwater tests.

Jan 1, 2024

By A. Gontijo, A. Matos, P. Lincoln, L. Fonsecail

This paper investigates how to manage and model the vibrations caused by rock blasting in a Brazilian underground mine. Considering the frequent detonations and the previous lack of effective vibration control, understanding, and reducing the impact of these seismic waves is critical. We emphasize the use of the near field model technique, which considers the varied physical properties of different rocks, optimizes blasting plans, and minimizes damage to the rock mass. We detail a case study that demonstrates a comprehensive approach to vibration control. The discussion includes the creation of a monitoring plan, the methodology used, results and the specific challenges and solutions found during the blasting process. This study provides a practical guide for similar future projects. Finally, we present a predictive model based on the collected data, offering insights into the vibrations caused by blasting. This model helps decision-makers minimize the risk of displacing rock blocks in the blasting area, improving safety and operational efficiency

Jan 1, 2024

By Janaina da Silva Vieira

Nos últimos anos, especialmente fibras naturais extraídas de plantas lignocelulósico, ganharam atenção devido ao seu desempenho como engenharia de reforço. Uma de suas aplicações mais importantes é como reforço de compósitos poliméricos na substituição de fibras sintéticas, que não são ambientalmente corretas. Todavia, as fibras ligoncelulósicas com Malva, Juta dentre outras possuem algumas características negativas para sua incorporação em matrizes poliméricas, como por exemplo, o fato dessas não possuírem boa aderência aos polímeros, pelo seu caráter hidrofílico e do caráter hidrofóbico das resinas. Esse trabalho estudou a incorporação de manta hibrida de fibras de malva e juta em compósitos epoxy DGEBA/TETA para testes de impacto Izod. Os corpos de prova foram feitos sob pressão para que houvesse uma melhora na aderência. O aumento do volume da manta incorporado gerou um aumento da resistência apresentado que pode ser justificado pelo fato da manta atuar como um bloqueador de trincas.

Oct 30, 2017

By Anna Carolina Cerqueira Neves

As fibras sintéticas vêm sendo gradualmente substituídas por fibras naturais. Em comparação com a fibra sintética, fibra natural demonstrou vantagens econômicas e ambientais. Visto que apresenta características interfaciais com matrizes poliméricas que favorecem a absorção de energia de alto impacto pela estrutura. No entanto, até agora pouco foi avaliado sobre a fibra de cânhamo incorporada em matrizes poliméricas. Este estudo tem o objetivo de avaliar a resistência ao impacto deste tipo de compósito com matriz de poliéster reforçada com diferentes porcentagens de fibras de cânhamo. A resistência ao impacto aumenta proporcionalmente com a quantidade relativa de fibras incorporadas como reforço na matriz polimérica. Este desempenho foi relacionado com a dificuldade de ruptura imposta pelas fibras, resultante da interação da matriz de fibra de cânhamo / poliéster de forma a ajudar a absorção da energia de impacto.

Aug 17, 2017

By Lidia Rangel Roveta

O processo de aciaria da ArcelorMittal Aços Planos América do Sul tem um abastecimento de diário de Cal em torno de 420 ton. O processo de abastecimento deste produto, que consiste da programação, liberação de portaria e descarregamento não estava satisfatório, considerando o tempo de permanência de caminhões na portaria aguardando liberação e consequentemente custos com diárias e alimentação. Visando otimizar este processo, a partir do resultado da analise dos procedimentos de descarga, utilizado atualmente, foi implementado como plano de ação um sistema automatizado de agendamento de descarga de Cal que, após 15 dias de implantação resultou na redução de 66% no custo de pagamento de diária, além de previsão de ganho futuro em frete.

Aug 16, 2017

By Marcus Vinicius Laudares Mendonça

SMS calculates and improves tooth and flank profiles individually to realise a homogeneous pressure distribution over the complete load flank. With a tooth profile and flank profile according to AGMA, ISO or DIN standard the contact pressure varies along the load flank. To realize a homogeneous distribution of the contact pressure and to avoid a premature mesh, SMS improves the tooth profile and flank profile in three steps. First SMS is doing a preliminary calculation and design according ISO, DIN or AGMA standard, with safety factors based on more than 125 years of experience. Second SMS calculates and checks the local contact pressure at the load flank under consideration of shaft, gearing and housing deformation, as well as the bearing behaviour. Finally SMS calculates and designs an improved tooth profile and flank profile to receive a homogeneous contact pressure at the load flank. The result is an increase of the torque transmitting capacity of up to 30% of the SMS advanced gears with the same outer dimensions than traditional gears.

Aug 17, 2017

During 1990-1999, a total of 458 fires occurred in all coal mining categories; 157 of those fires caused 164 injuries and 2 fatalities. The greatest number of fues and fire injuries occurred at surface mines, whch also had the highest risk rate values. A total of 66 fuefighting interventions were required. Of these, there were 25 mine rescue team interventions in underground mines, including 5 mobile equipment firefighting interventions, and 41 fire brigade and fire department interventions at all surface operations, including 19 mobile equipment interventions. In all, 50 fires destroyed or heavily damaged equipment (including 16 pieces of mobile equipment) because of failure of other firefighting methods, late fire detection, undetected fires, or fire size. A total of 1 14 fires were detected late by smoke, and 42 fires were not detected.

By Janusz S. Laskowski

"Frothers offered by different manufacturers are marketed with some information on their chemical and physical properties (e.g. density, viscosity, color, water-solubility, safety/toxicity, etc.). But frothers are used in flotation to generate fine bubbles and to stabilize the forth, and this information is only provided in a very qualitative description of the visual appearance of bubbles and froths. The terms “powerful” and “selective”, which have been commonly used to characterize frothers, have intuitive rather than scientific meaning.This paper introduces the DFI (Dynamic Foamability Index) plotted vs. CCC (Critical Coalescence Concentration) diagrams to classify flotation frothers (Fig. 1). The frothers characterized by low CCC and high DFI values have properties of strong flotation frothers, while those with high CCC and low DFI values are more selective. The proposed frother classification system, based on simple CCC and DFI measurements, provides, for the first time, a solid ground-work for characterization of the flotation frothers."

Jan 1, 2003