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Canadian mining giant Teck Resources Ltd. will be the exclusive supplier of the metals used in the production of the more than 1,000 medals to be awarded at the Vancouver 2010 Olympic and Paralympic Winter Games. Teck, the diversified resource company headquartered in Vancouver, B.C., is providing 2.05 kg (4.5 lbs) of gold, 1,950 kg (4,300 lbs) of silver and 903 kg (2,000 lbs) of copper sourced from its operations around the world. In addition to the raw materials mines, this year?s medals will make Olympic history as they will be the first to contain metals recovered from processing the circuit boards from end-of-life electronics (e-waste) that would have otherwise been destined for a landfill. After mining or production through a variety of smelting and recovery processes, each metal has been refined to enhance the metal purity.

Jan 1, 2010

In 2011, the value of mineral production increased in the United States for the second consecutive year (Table 1). Production increased modestly for most mineral commodities mined in the United States, and price increases, especially for precious metals, resulted in increases in the value of production. Minerals remained fundamental to the U.S. economy, contributing to the real gross domestic product (GDP) at several levels, including mining, processing and manufacturing finished products. Minerals? contribution to the GDP increased for the second consecutive year. Trends in other sectors of the domestic economy were similar to those in mineral production and consumption rates. U.S. apparent mineral consumption (industrial) of 11 mineral commodities decreased substantially from 2005 to 2010 (aluminum, cadmium, cement, copper, iron, lead, salt, soda ash, steel, tin and zinc). Data for 2011 were not calculated, but the data show a sustained decrease (especially for the metals) preceding the recession through 2010, so consumption seems to be behaving differently than production and GDP. After continued decline following the 2008?2009 recession, the construction industry began to show signs of improvement during 2011, with increased production and consumption of cement, construction sand and gravel, and gypsum ? mineral commodities that are used almost exclusively in construction. Crushed stone production, however, continued to decline.

Jan 1, 2012

By T. M. “Mike” Gurr

"U. S. marketable phosphate rock production for the 2018 crop year (July 1, 2017 to June 30, 2018) showed an increase to 27.7 Mt (30.5 million st) from the 2017 crop year production of 27.1 Mt (29.8 million st), as reported to the U. S. Department of the Interior by the mining companies operating in the United States during crop year 2018 (Table 1). Domestic consumption decreased in the 2018 crop year to 23.9 Mt (26.3 million st), as compared to the 27.2 Mt (30 million st) consumed in crop year 2017. U.S. imports of phosphate rock increased to 3 Mt (3.3 million st) for the 2018 crop year from the 1.81 Mt (1.9 million st) for crop year 2017. Imports of phosphate rock were from Peru and Morocco. There was an increase of 2.85 Mt (3.1 million st) in producers’ stocks from 7.45 Mt (8.2 million st) in crop year 2017 to 10.3 Mt (11.3 million st) in crop year 2018 (Table I).For calendar year 2018, Florida and North Carolina phosphate rock production accounted for 75 percent of the total U.S. production, with the balance being produced in Idaho and Utah. The Florida and North Carolina percent of U.S. production is declining. U.S. production of 25.7 Mt (28.3 million st) in calendar year 2018 was produced by five companies at 10 mines in four states and accounted for approximately 9.6 percent of the world production of 267.7 Mt (295 million st) for calendar year 2018 (Table 2).In calendar year 2018, U.S. phosphate production decreased by 2.2 Mt (2.4 million st), while companies increased stocks of phosphate rock by 1.7 Mt (1.9 million st). The domestic production for calendar year 2018 of 25.7 Mt (28.3 million st) represents 78.4 percent of the domestic production capacity of 32.8 Mt (36.1 million st).At present, China reportedly produces more than 50 percent of the world’s phosphate rock. As a result of planned expansions, Morocco production has increased from 27 Mt (30 million st) in 2017 to 33 Mt/a (36 million stpy), which is approximately 12.3 percent of the world’s production, moving ahead of the U.S. production. In calendar year 2018, the U.S. phosphate rock production was 25.7 Mt (28.3 million st), which is less than 10 percent of the world’s production of phosphate rock (Fig. 1)."

Aug 1, 2019

By CHRISTOPHER D. HEBERT, SCOTT W. HOFFMAN

All Rights Reserved. Printed in the United States of America. Information contained in this work has been obtained by SME, Inc. from sources believed to be reliable. However, neither SME nor its authors guarantee the accuracy or completeness of any information published herein, and neither SME nor its authors shall be responsible for any errors, omissions, or damages arising out of use of this information. This work is published with the understanding that SME and its authors are supplying information but are not attempting to render engineering or other professional services. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of the publisher. Any statement or views presented here are those of individual authors and are not necessarily those of the SME. The mention of trade names for commercial products does not imply the approval or endorsement of SME.

Dec 1, 2019

By William H. Langer

The annual consumption of sand and gravel aggregate in 2006 in the Phoenix, AZ metropolitan area was about 76 Mt (84 million st) (USGS, 2009), or about 18 t (20 st) per capita. Quaternary alluvial deposits in the modern stream channel of the Agua Fria River west of Phoenix are mined and processed to provide some of this aggregate to the greater Phoenix area. The Agua Fria drainage basin (Fig. 1) is characterized by rugged mountains with high elevations and steep stream gradients in the north, and by broad alluvial filled basins separated by elongated fault-block mountain ranges in the south. The Agua Fria River, the basin?s main drainage, flows south from Prescott, AZ and west of Phoenix to the Gila River. The Waddel Dam impounds Lake Pleasant and greatly limits the flow of the Agua Fria River south of the lake. The southern portion of the watershed, south of Lake Pleasant, opens out into a broad valley where the river flows through urban and agricultural lands to its confluence with the Gila River, a tributary of the Colorado River.

Jan 2, 2010

Smart defense: that?s what the industry needs to play for the next four years, according to panelists at the 118th Annual Meeting of the Northwest Mining Association (NWMA), which met December 2-7 in Spokane, WA. The conference was well attended, with approximately 2,200 attendees, 244 booths in the two packed exhibition halls, and a rich offering of short courses, field trips, social events and technical sessions. Speakers at the packed legislative session articulated many of the frustrations felt by members of the mining community after the U.S. elections in November, and offered words of advice. Matthew Ellsworth, the new Government Affairs hire at NWMA, stated it best: ?Elections are like Christmas: you find out who?s naughty and nice ? and it?s always going to come again.?

Jan 1, 2013

By C. Geier

Previous mine incidents show weaknesses in mine rescue preparedness from poor training in decision making, leadership and incident command center (ICC) protocols. Computer simulations offer a larger range of training opportunities for mine rescue teams focusing on exploration and communications. The mine rescue simulator developed by the Colorado School of Mines and Rite Solutions Inc. utilizes four computers for the instructor and team, with the instructor monitoring the team?s progress. As the team explores, it relays information back to the Fresh Air Base, which then reports to the ICC. This forces a three-step communication procedure, enhancing the team?s overall communication skills and developing ICC protocols. The simulator is decision-based, demanding team decisions be made quickly. Upon completion, teams commented positively. Generally, participants said that the simulator is useful for learning how to communicate and make decisions during mine rescue emergencies. This mine rescue simulator improves team training, providing effective communications practice with an easy setup and no production interruption.

Feb 1, 2014

By Ronald L. Gibbs

IN THE BEGINNING Contrary to popular myth, the personal computer can trace its roots back to a time before 1981 and the IBM PC. The seeds of the personal computer revolution were probably founded in 1975 with the release of the Altair (kit) personal computer, first advertised in Popular Electronics. June of 1975 marked the beginning of the Homebrew Computer Club in San Francisco. The founding membership list of the Homebrew Club now reads like a "Who's Who" of those involved in the early development of the personal computer industry. The Apple I computer was created by Steve Wozniak in early 1976 from the newly manufactured MOS Technology 6502 chip. It had 4,000 bytes (4K) of Random Access Memory (RAM] memory, a revolutionary amount of memory in 1976. Another early pioneer, the Commodore Pet computer, was another 6502 machine, but with 8K of memory. Tandy Corporation made its name in the hobby industry with leather kits. They embarked on a new path with the production of the TRS-80 line of personal computers. Most were based on the Z-80 chip, but again, were memory limited. A number of other Z-80 based systems followed later, including the Osbourne and the KayPro Computers. These systems were based on the Digital Research CP/M operating system and had a maximum of 64,000 bytes of memory (64K). The Apple I1 Computer appeared in 1977. Newer models of the original Commodore Pet and an Atari computer followed. These machines were also limited to 64K of memory addressing, and the early models typically shipped with only 16K, 32K, or 48K of memory. The Z-80 and the 6502 were the first truly commercialized CPU chips touting boxes with key- boards, monitors (sometimes a TV), and the ability to expand (peripheral slots for serial communications, centronics parallel communications, etc.1. They all shared one technology, audio tape as a storage media. The use of a portable tape recorder provided inexpensive, if not always reliable, magnetic storage. The tape recorders were typically finicky and required patience to use. Adjustments to the volume control were often needed to find "just-the-right" setting for loading or saving information. This kept the personal computer from being accepted in many markets, and gave it a reputation as a hobbyist or experimenters' toy. In early 1979, Steve Wozniak finished the design of a floppy disk drive and controller. This was a revolutionary design which reduced the "then" standard number of controller chips from fifty-plus, to just eight. With the advent of an affordable floppy disk drive mechanism, the personal computer was about to gain respectability. From a business standpoint, it was now possible to save and reliably retrieve business information. It also provided a superior means of distribution for commercially created software. Commercial software became a commodity rather than an oddity.

Jan 1, 1993

By M. Westendorf, T. Banerjee, S. Kaushik, D. Tinney

"Cyclones are one of the most extensively used pieces of equipment within the mineral processing industry because of their simplistic operating and maintenance philosophies. They are commonly used as classifiers within the comminution circuit to control the grinding product particle size for satisfactory performance of downstream operations.Cyclones are a key contributor to the effective operation of the plant and have a significant impact on the mineral processing plant operations. If the cyclones are not performing as they should, the results are often a combination of lost recovery, grade, capacity and reduced throughput. Similarly, an inefficient cyclone operation may also lead to low or high recirculating loads that impact the efficiency of the comminution circuit. This highlights the importance of having proper stability in cyclone operation while implementing any plant-wide optimization strategy.One of the key challenges in cyclone operation is that cyclones are highly sensitive to changes in operating conditions and are affected by process fluctuations such as feed pressure, solids concentration and flow rates. Fluctuations in cyclone feed characteristics lead to unstable cyclone performance which affects mineral liberation. For such an impactful unit operation, cyclones have historically been under-instrumented in an otherwise highly instrumented process plant. Traditionally, mill operators have relied on visual observations of the apex discharge to determine the operating state of the cyclones. Visual cues corresponding to the different cyclone operating conditions have been discussed by Neesse et al. (2004) as shown in Fig. 1."

Jan 1, 2014

By R. Heiser, J. Vendetti, B. P. Connor, E. J. Haas

Health and safety indicators help mine sites predict the likelihood of an event, advance initiatives to control risks, and track progress. Although useful to encourage individuals within the mining companies to work together to identify such indicators, executing risk assessments comes with challenges. Specifically, varying or inaccurate perceptions of risk, in addition to trust and buy-in of a risk management system, contribute to inconsistent levels of participation in risk programs. This paper focuses on one trona mine’s experience in the development and implementation of a field-level risk assessment program to help its organization understand and manage risk to an acceptable level. Through a transformational process of ongoing leadership development, support and communication, Solvay Green River fostered a culture grounded in risk assessment, safety interactions and hazard correction. The application of consistent risk assessment tools was critical to create a participatory workforce that not only talks about safety but actively identifies factors that contribute to hazards and potential incidents. In this paper, reflecting on the mine’s previous process of risk-assessment implementation provides examples of likely barriers that sites may encounter when trying to document and manage risks, as well as a variety of mini case examples that showcase how the organization worked through these barriers to facilitate the identification of leading indicators to ultimately reduce incidents.

Jan 1, 2018

By R. Heiser, J. Vendetti, B. P. Connor, E. J. Haas

Health and safety indicators help mine sites predict the likelihood of an event, advance initiatives to control risks, and track progress. Although useful to encourage individuals within the mining companies to work together to identify such indicators, executing risk assessments comes with challenges. Specifically, varying or inaccurate perceptions of risk, in addition to trust and buy-in of a risk management system, contribute to inconsistent levels of participation in risk programs. This paper focuses on one trona mine’s experience in the development and implementation of a field-level risk assessment program to help its organization understand and manage risk to an acceptable level. Through a transformational process of ongoing leadership development, support and communication, Solvay Green River fostered a culture grounded in risk assessment, safety interactions and hazard correction. The application of consistent risk assessment tools was critical to create a participatory workforce that not only talks about safety but actively identifies factors that contribute to hazards and potential incidents. In this paper, reflecting on the mine’s previous process of risk-assessment implementation provides examples of likely barriers that sites may encounter when trying to document and manage risks, as well as a variety of mini case examples that showcase how the organization worked through these barriers to facilitate the identification of leading indicators to ultimately reduce incidents.

Jan 1, 2017

By Elza Burch

Introduction The feeding to zero concept involves feeding 600 µm x 0 (28 mesh x 0) size raw coal to heavy media (magnetite) cyclones along with the +600 µm (+28 mesh) size coal. Traditional circuits employ desliming or removing the 600 µm x 0 (28 mesh x 0) size fraction and feeding the cyclones +600 µm (+28 mesh) size coal. The feeding to zero concept recirculates 600 µm x 0 (28 mesh x 0) fines in the circuit. At the same time, a portion of the fine material is continuously withdrawn and recovered. This, in turn, prevents a fines buildup. This concept eliminates desliming screens and secondary fines circuitry for recovery of 600 x 150 µm (28 mesh x 100 mesh) coal. The result is a very simple circuit. Feeding to zero at Island Creek Island Creek Corp. was the first involved with the new concept in 1976. The company needed a temporary plant for the 9.5 mm x 0 (0.4 in. x 0) raw coal at its Pond Fork mine, near Madison, WV, while a full-scale plant was being designed and built. At that time, the Childress Corp., of Beckley, WV, became interested in the feeding to zero concept. Island Creek awarded a contract to Childress to build a single cyclone modular plant, incorporating this feeding to zero concept. The plant was erected in three months. The Pond Fork modular plant proved successful in attaining the desired feed rate of about 63.5 t/h (70 stph), while maintaining good separating efficiencies and low magnetite consumption rates. The 9.5 mm x 150 µm (0.4 in. x 100 mesh) clean coal was recovered and the 150 µm x 0 (100 mesh x 0) size was disposed of to waste. The full-scale plant was completed about two years later and the Pond Fork modular plant was moved to Holden, WV. There, it was incorporated into the Holden 29 preparation plant as a separate circuit for cleaning -25 mm (-1 in.) coal. In 1976, a similar plant was installed in Virginia by another company. These two plants are believed to be the first two operational plants in the United States incorporating the feeding to zero concept. Island Creek subsequently contracted with Childress for an identical plant at the Coal Mountain operation in West Virginia. The plant operated for three years before the mine was closed. The unit was then moved to the Spurlock mine near Martin, KY where it continues to operate. The successful operation of the Pond Fork and Coal Mountain plants before and after relocation proved both the performance and moveability of this type of circuit when constructed in a modular fashion. Since the first two plants were built, Island Creek has incorporated the feeding to zero circuit in nine additional plants. A grand total of 33 cyclones have been installed using this concept. One is the Providence mine, near Providence. Providence preparation plant Island Creek contracted with J.O. Lively Corp. of Glen White, WV in July 1978 for the construction of the Providence preparation plant. The plant began operation in February 1979. The construction period was about halved by building the plant with modular design concepts. Prefabricated sections, floors, and sides were brought in as units and then bolted in place. The Providence plant has a good track record of processing coal at a feed rate of 454 kt/h (500 stph). Feed coal to the plant has an average ash content of about 18% and sulfur content of about 4.5%. It contains about 22% refuse. The coal product has an average ash content of about 8% and sulfur content is about 3%. Raw West Kentucky No. 9 seam coal is conveyed from a box cut in the Providence mine to a rotary breaker. The breaker is fitted with 74 mm-diam (3 in.-diam) opening breaker plates. Therefore, it is well suited for removing trash, roof bolts, wood, and pyritic balls that are common in Illinois Basin coal. The -75 mm (-3 in.) coal is conveyed from the rotary breaker to

Jan 8, 1987

By Tim O’Neil

Nearly 4,800 mining professionals and exhibitors occupying 580 booths attended the 2000 SME Annual Meeting and Exhibit, Feb. 28-March 1, in Salt Lake City, UT. The technical program included80 sessions and four specialty symposia: bulk material handling, control 2000, minor elements 2000 and plant operaters. Meeting highlights included the keynote session. Executive shared their perspectives on pivotal issues and approaches to address the challenges of the new millennium. SME has begun planning for its 2001 Annual Meeting, Feb. 26-28, in Denver, CO. The meeting carries the theme “2001 — A Mining Odyssey.” A call for papers has been issued and exhibit space is 80% reserved. For information, visit SME’s website, www.sme-net.org. Or write Box 625002, Littleton, CO 80162-5002,ph 800 763 3132 or 303 973 9550, fax 303 979 3461, or email meetings@smenet.org.

Jan 1, 2000

By J. Navoyski, B. Macdonald, W. J. Helfrich, J. L. Bellanca, B. Demich

DISCLAIMER The findings and conclusions in this paper are those of the authors and do not necessarily represent the official position of the National Institute for Occupational Safety and Health, Centers for Disease Control and Prevention. Mention of company names or products does not constitute endorsement by NIOSH. ABSTRACT Recent advances in computing, rendering, and display technologies have generated increased accessibility for virtual reality (VR). VR allows the creation of dynamic, high-fidelity environments to simulate dangerous situations, test conditions, and visualize concepts. Consequently, numerous products have been developed, but many of these are limited in scope. Therefore, National Institute for Occupational Safety and Health researchers developed a VR framework, called VR Mine, to rapidly create an underground mine for human data collection, simulation, visualization, and training. This paper describes the features of VR Mine using self-escape and proximity detection as case studies. Features include mine generation, simulated networks, proximity detection systems, and the integration and visualization of real-time ventilation models. INTRODUCTION There are many definitions of virtual reality (VR) that include various levels of immersion and features [1]. Some definitions refer to specific technologies [2], while others are limited to visualization [3]. For this paper, a more general definition of VR will be adopted. VR is defined as the collection of hardware and software that interactively engages users and stimulates their senses within a synthetic or virtual environment. From a hardware standpoint, this can include anything from a phone to a head-mounted display (HMD) to a large-scale theater as well as speakers, microphones, haptic sensors, and interaction devices. The software used to create virtual environments (VEs) generally includes a game engine, custom software components and libraries, and two-dimensional and three-dimensional graphical assets. Recent hardware and software advances have increased the fidelity and availability of VR. New and improved technologies including HMDs and high-resolution monitors and projectors can display sharper, more detailed visualizations. For example, in the past five years between the release of the Oculus Rift DK1 (2013) and the HTC Vive Pro (2018), there was a three-fold increase in resolution along with a 50% increase in the refresh rate. Furthermore, despite early claims that low-cost VR technology was readily available [4], computational power has not been sufficient to handle the large amount of data generated by these systems [5]. In the past five years, however, rendering speeds have more than doubled and memory has more than tripled [6], allowing these visualizations to be incorporated into higher-complexity and -fidelity VEs that more closely mirror the real world. Similarly, software capabilities have also significantly improved through game engine advancements and feature development. In the past several years, game engines have added and improved features such as physics, lighting, platform support (e.g. Android), and asset development integration. Some of the current leading commercial game engines are Amazon Lumberyard, CryEngine, Unreal, and Unity, but this can quickly change as is evident in the literature [7, 8].

Jan 1, 2019

By Nick Rose, Mathieu Veillette, Matthew King

"The Teck Highland Valley copper (THVC) mine is located approximately 55 km (34 miles) southwest of Kamloops and approximately 20 km (12 miles) west of Logan Lake, BC, Canada (Fig. 1). Mining at THVC is conducted at three openpit operations comprised of Valley, Lornex and Highmont with a total annual output on the order of 300 kt (330,000 st) copper concentrate and 5 kt (5,500 st) of molybdenum concentrate. The Phase 8 pushback in the Valley Pit (Fig. 2) was mined from 2011 to 2016. Successful slope steepening occurred in the later stage of the pushback with the implementation of presplit blasting in 2015 and 2016.This article summarizes the investigation and design approach including: structural analysis, kinematic assessments of bench breakback potential, development of discrete fracture networks (DFNs) to characterize discontinuity fabric, rockfall modelling, 2D anisotropic limit equilibrium and 2D distinct element modelling, assessment of potential kinematic failure modes affecting double benches with 3D distinct element modelling and improved blasting techniques using e-dets. THVC is currently undertaking a mine life expansion involving the pushback of the west wall of the Valley Pit above Phase 8 to extend the mine life to 2029. Engineering geologyThe east wall slope in the Valley Pit is comprised of a 350-m (1,148-ft) thick sequence of glacial valley sediments that occur along the Highland Valley (Fig. 2), exposing an overburden slope up to about 225-m (740-ft) high below the crest of the ultimate east wall. The glacial overburden units consist of pro-glacial outwash and glaciofluvial deposits, glacial outwash sands and gravels interbedded with till and alluvial fans consisting of cross-bedded sands and sandy-gravels. Lacustrine sediments occur within the mid to lower portion of the glacial sequence and contain intervals of low-shear-strength clays and silts. Two large (1.3 and 7 Mt or 1.4 and 7.7 million st) waste rock buttresses were required to maintain slope stability using slot-cut and fill mining methods, as described in Fortin et al. (2011).The Valley porphyry deposit occurs in the central portion of the late Upper Triassic Guichon Creek Batholith, which intrudes assemblages of the Permian Cache Creek and Upper Triassic Nicola groups. The Valley deposit occurs in an area of intense fracturing near the intersection of the northerly trending Lornex Fault and the northwest to westerly trending Highland Valley Fault."

Apr 1, 2019

By F. Mendaña

The characteristics of the igneous and metamorphic bedrock, extra-hard and abrasive, of the Guadarrama Tunnels, a bi-tube project of length 28.4 km without any intermediate attack, are first commented upon. Next, a detailed discussion is given of the most relevant aspects of the performance of the four double shield type TBMs. The experience of this leads to various recommendations to be borne in mind in future designs of TBM having to work in rock of similar characteristics.

Jan 1, 2007

By Allan E. Koski

Ceveland-Cliffs uses a specialized software package in mine planning at the Empire Mine, an iron ore mine it manages on Michigan’s Marquette Iron Range. The application puts together years of mining experience that began in the early 1960s on the eastern end of the Marquette Range. The Empire Mine is in its 38th year of production. It uses the software to model a complex and highly variable low-grade magnetite ore body, capturing the economics of mining and processing to the final product. With special attention given to geostatistical methods, the software is used for all geologic modeling, ore reserve estimation, ore control, pit design and short- and long-range planning.

Jan 1, 2000

By W. C. Yates

Lack of visibility from large, open-pit haulage truck cabs has become a serious safety problem. Anaconda conducted a research program to develop a low cost system to alert haulage truck operators to small vehicles present in blind areas. Several systems were developed and tested. As open-pit haulage truck size has increased, so has the size of the blind areas. Mine utility vehicles, pickup trucks, and cars are concealed within these blind areas and become safety hazards. Figure 1 shows the typical blind areas of a 136 t (150-ton) haulage truck. The areas of greatest concern are at the rear center and front right corner of the truck. In these "no visibility" areas many small vehicles have been crushed by large haulage trucks at various mine sites. In most instances, the occupants escaped the vehicle before it was destroyed. But injuries and death have occurred. In most cases, the accidents were attributed to negligence or carelessness by the small vehicle driver. The limited visibility problem still exists, though, and a solution is needed. Initial Solution The usual plane mirror on the driver's side and the convex mirror on the right front of the haulage truck allow only limited rear visibility. The typical, right side convex mirror is generally small and difficult to locate at a glance. This convex mirror also presents an image that distorts distance perception. These mirrors are of¬ten broken and immediate replacement not demanded or made. The US Bureau of Mines, in a contract with M.B. Associates, San Ramon, CA, developed an improved visibility system. It consisted of a larger, left view mirror and unique, blind area viewer. The large 230 x 690 mm (9 x 27 in.) left mirror has a small convex spot mirror near the bottom. The entire unit can be quickly replaced if broken. The large size provides a full view of driver orientation features such as the rear tire and the top of the load bed. The right 300 x 410 mm (12 x 16 in.) mirror has a convex surface and is quite rugged. The 510 mm (20 in.) spherical radius presents the operator with some distance distortion, but objects in its view are easily seen. The "blind area viewer" consists of a modified fresnel lens that allows the driver to "look around the corner." Installation of three of these lenses on the front of each haulage truck is rec¬ommended for adequate blind area coverage. This system significantly increases an operator's field of view and allows viewing of objects within about 3 m (9.8 ft of the truck. Many open-pit mines are nor mounting on smaller vehicles a long whip with a flag and lamp or both. This increases vehicle visibility to haulage truck operators. The whip is permanently attached to the mine vehicle. It can also be magnetically attached to transient vehicles. The whip system. though, is inadequate for visibility in the critical rear and right front blind areas. Alternate Solutions All of these visibility aids as¬sume an attentive driver. In addi¬tion, areas such as the rear blinc, area are not covered. Based on the inadequacy of existing visibility systems, Anaconda made a com mitment to further the truck de¬tection technology. The best ap¬proach was considered to be ar active system. It would notify the haulage truck operator that an en¬croaching vehicle is present. Sev¬eral systems were considered, in¬cluding ultrasonics and elec¬tromagnetics. For the ultrasonic system, com mercial and in-house design were looked at. Designing an( building transducers with the spe cific beam shape to match the haulage truck blind spots re¬quired a major technological breakthrough. False alarms ap¬peared difficult to prevent en¬tirely. They were caused by pass¬ing, trailing, or leading vehicles a., well as nonthreatening objects. As a result of these problems, the ul¬trasonic technique was not pur sued. An alternative, an electro

Jan 7, 1982

By G. M. Rao, P. N. Deo

Graphite is soft and easily floatable but it is quite difficult to obtain high purity concentrate at coarse sizes. Chemical treatment can produce high grade concentrate but it is an expensive process. Graphite containing plus 96% fixed carbon (FC) with coarse flakes commands high price in international market. Such graphite concentrate containing plus 96% FC was produced in Indian Bureau of Mines (IBM) by using newly developed reagent (mixture of different hydrocarbons and terpenes, IBM/D7) instead of commonly used frothers viz. pine oil, MIBC, kerosine etc. and regrinding in a special type of mill with special grinding media instead of grinding in a conventional ball/ rod mill followed by cleaning. Both the new reagent (frother) and special grinding media are inexpensive and readily available. The process is under patenting. This paper focuses application of this new grinding methodology for flake size protection, and the new reagent for selective flotation of high purity graphite.

Jan 1, 1995

By Matthew S. Sanchez, Richard J. Lee, Matthew D. Zock, Drew R. Van Orden, Yumi Kamiya, Edward B. Ilgren

In many developing countries, asbestos is still used for friction products, insulation, and asbestoscement products. However, there is very limited modern data evaluating the airborne concentrations of asbestos fibers in operating asbestos plants. We have conducted an Industrial Hygiene survey, using state of the art PCM and TEM analysis, of a Bolivian asbestos cement plant that uses crocidolite during the production of roofing shingles and water tanks. The study is the first to use modern analytical measurements in an uncontrolled asbestos environment. Thus, this study offers insight into the historical airborne exposures at asbestos plants operating before modern dust control measures were introduced or airborne fiber levels regulated. The results suggest that fiber concentrations are far in excess of those for which current models would predict the onset of asbestos disease and mesothelioma. Significantly, the plant and community do not have an elevated incidence of asbestos disease or mesothelioma. Airborne fiber levels during comminution and fiber sizing ranged from 100 to as much as 1,000 f/cc. Fiber levels in the mixing, forming and finishing areas ranged from 0.5 to 9 f/cc. Based on the number of overloaded samples and estimates of their concentration, historical estimates of exposure may be underestimated by an order of magnitude. Also, an excellent correlation (1:1) between the PCM and TEM fiber concentrations (for fibers _0.25 um diameter) were obtained, raising questions about the conventional wisdom that the PCM systematically undercounts fibers. The results of this study further indicate that current models may overestimate the risk of asbestos disease and mesothelioma.

Jan 1, 2012