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By F. G. Crack, R. V. Ramani, R. L. Frantz

Management for mine construction and development differs from that needed for routine mine production and maintenance. An integrated approach to managing mine development projects must consider contract documents; management organization of a project; the project manager's role and the field supervisor's responsibility; and the use of scientific techniques for planning, scheduling, executing, and controlling projects. Professional project management encompasses the following: • Preparing contract documents that establish technical and financial schedules, and detail the responsibility for the physical work commitment. • Developing a project's organizational structure, to clearly define the roles of the project manager and the field supervisors. • Establishing project management and field supervisor relationships, to avoid ambiguity in assigning responsibility and to ensure desired project progress. • Using management science techniques, particularly networking techniques such as the critical path method for planning scheduling, executing, and controlling projects. Project Versus Production Management Project management differs from routine production management in the following ways: • Uniqueness: A project is unique. Production operations tend to be repetitive. The magnitude of one-time capital expenditures for many facets of mine development warrant special skills and attention. These professional project development skills must already be available by prior experience in the management team. • Personnel: In projects, personnel are usually assigned on a specialty basis and frequently change with the project activity. On the other hand, production personnel work together, more or less permanently. • Management Structure: In a project there may be several staff-line relationships that are not clearly defined and change with changing project activities. In a production situation, the lines of communication and authority are usually well defined. • Time Frame: A difference between project and routine production management is that project activities have comparatively less well defined durations and often tend to be relatively short-term. Production usually has both long-term and short-term plans and well defined long-term and shor-term goals. In project management, formal, critical, short-term reviews are frequently required. In production management, five year plans can be formally adjusted quarterly and annually. Short-term weekly or daily reviews can be informal. • Response to Delays: Delays in a development project may occur without anyone being immediately aware of their existence or suspecting the magnitude of consequence. In contrast, any delays in the production process can be easily identified from prior results comparison. Additionally, the response is quick, usually in a set routine. This can be traced back to the management structure and personnel. • Control Techniques: Measurements of project progress for control are not easily made due to the variety of activities that are carried on at the same time by different work groups. The yard-sticks of performance measurement for individual activities, let alone for the total project, are not easily established. However, due to the difficulty in detecting project delays, a workable control system is vitally important to a project manager. To apply a scientific project control technique such as "management by exception" requires specific planning and monitoring from the project manager for each activity in the project. Production and productivity are quick and effective yard-sticks of measuring performance in a routine operation. Control techniques required in production management usually revolve around these measures. Construction Contracts The construction contract is an important document that establishes contract scope, technical and financial details of the work, and achievement deadlines. It may also serve as the contract document to pay for work done and to verify field progress with planned progress. In practice, it is a good idea to develop a job-specific contract. This whole area is replete with legal precedence and procedures, and it is not the intent here to deal with the intricacies of establishing a contract document. But it is necessary to have an understanding of major contract types. Construction contracts are extremely important legal documents. They may vary in work specifications and enforcement of the provisions. Due to their nature, they must be composed with legal help and will take some time to compile. Even with all the precautions and provisions, it is not uncommon to find owner and contractor disagreeing. Therefore, it is important to include a way to resolve any difference quickly and to incorporate aspects of the contract as part of an overall management control tool for efficient project management.

Jan 7, 1982

By Bhawani Singh, A. K. Dube, B. Singh

At least three hydroelectric tunnels constructed during the last decade through the lower Himalayan region in India have met with serious problems of supporting in squeezing ground conditions. Steel ribs under went intolerable deformations requiring rectification to provide space for concrete lining which delayed the projects inordinately. In an attempt to choose a rational method of predicting rock load, the authors have compared rock loads estimated from various classification systems and elasto-plastic theory with observed values. The deficiencies of the classification systems have been highlighted to show that the combination of elastoplastic theory and tunnel instrumentation programme provides better guidelines for the design of tunnel supports in squeezing ground conditions.

Jan 1, 1981

By Steve Kral

Amax Coal Industries Inc.'s Delta Mine is a medium-sized. high-sulfur coal producer that has lived up to the challenges posed by nearly six decades of a highly competitive domestic coal market. The mine now faces one of its biggest challenges - the same one staring at the dozens of other high-sulfur producers in the Midwest - the Clean Air Act Amendments of 1990. The 59-year-old mine, located in the coal fields of southern Illinois, has remained one of the state's oldest continuously operating mines by rolling with the ups and downs of the coal market and by incorporating new technologies and innovative productivity improvements into its operation.

Jan 1, 1993

By Frank P. Frandina, Michael J. Loehr, Paul E. Gabryszak

The Heartland Corridor Clearance Improvement Project is part of a regional Public-Private initiative to allow double stack container trains a direct route from the Port of Norfolk through Virginia, West Virginia, Eastern Kentucky and into Central Ohio. In the Preliminary Engineering stage, 30 existing tunnels were assessed and 28 were found to need clearance improvements to allow the use of double stack trains. Alternative tunnel enlargement methods were developed to achieve the desired clearance improvements, while maintaining structural integrity and minimizing disruption to train traffic. This paper summarizes the geometric and condition investigations of the existing tunnels, as well as describes the preferred methodologies to achieve the desired clearance. The clearance improvements will be implemented beginning in the summer of 2007.

Jan 1, 2007

By E. Petrakis, K. Komnitsas

The main objective of batch grinding modeling is the estimation of the product particle size distribution over time or specific energy input to the mill. So far, the developed analytical methods require often complicated calculations which are timeconsuming. Thus, more simple approaches that allow the reliable prediction of the complete product size distribution need to be developed. In the present paper, an approach, based on the population balance model (PBM), that reliably predicts the product size distribution is proposed. In order to enable this, the simplified form of the fundamental batch grinding equation was transformed into the well-known Rosin–Rammler (R-R) distribution, thus allowing the determination of the breakage rate for each grinding period. A time-dependent breakage rate framework was developed where the traditional linear theory of the PBM is considered a partial case. This approach allows the deviations from the linear theory to be categorized and the degree of the acceleration-deceleration of the breakage rate to be predicted. Modeling results were validated by laboratory grinding studies using two homogeneous materials, quartz and marble, and one heterogeneous, a limonitic laterite. The experimental data revealed that grinding exhibits non-first-order behavior and the degree of deviation from the linear theory depends on the tested material. The reliability of the proposed model was validated with the use of the distribution modulus n, the a value of the breakage rate parameter, and the optimum n values that minimize the sum of the differences between the experimental and estimated particle size distributions.

Feb 8, 2021

By Russell Clough

The Pacheco Pumping Plant is situated on the west end of San Luis Reservoir in western Merced County, California. It is designed to draw water from the reservoir and pump it into a 3,500,000 gallon regulating tank. The water then flows entirely by gravity to the Coyote Pump Station in Morgan Hill, a distance of 40 miles, where it is pumped into Anderson Reservoir. This water is used to recharge the depleted groundwater table in the Santa Clara Valley. Eventually, some of the water will be diverted to Hollister in San Benito County and to Watsonville and Santa Cruz in Santa Cruz County. The owner is the United States Bureau of Reclamation. The underground work consisted of a fifteen foot finished diameter surge shaft 250 feet deep to the crown of the pump chamber; a twenty foot finished diameter pump chamber which declined from the shaft at 14.2% for ninety feet and then ran horizontally for 180 feet; and twelve each five foot diameter steel lined intake shafts 240 feet deep which intersect the pump chamber in the horizontal section. (Figure 1) Upon completion of the pump chamber, the contractor had to dewater the existing tunnel under the reservoir, excavate the remaining fifteen foot plug, and concrete the transition. The low bidder for this contract was Underground - Continental-Heller at 414,456,000. Excavation of the open cut for the pumping plant and surge shaft began on April 14, 1983. This was performed using a Koehring 1066D backhoe, dozer, trucks, and two Cat 631 scrapers. The excavation was started at the surge shaft so that the grouting could begin

Jan 1, 1985

By Rushikesh Battulwar, Javad Sattarvand, Joseph Seamons, Masoud Zare

In the last decade, new developments took place in the area of indoor positioning (or localization). Since the Global Navigation Satellite System (GNSS) cannot be used in underground mines, other technologies are needed for localization. Positioning and communication options today primarily include Wi-Fi, Bluetooth Low Energy (BLE), Ultra-Wideband (UWB), Radio Frequency Identification Device (RFID), etc. Smartphones and tablets currently have an array of sensors and radios, which can provide valuable information to allow indoor localization via various methods. Where mineworkers could keep smartphones with them, they can be highly effective at enabling localization and navigation. Recent applications of these technologies in underground mines have been thoroughly reviewed and examined for the likelihood of their utility for accurate localization where no other means exist. Some critical challenges and gaps that need to be addressed in future research have been identified.

Sep 5, 2021

By Angela Binder, Mareike Schubert, Yichen Jiang, Sandra Nowosad, Oliver Langefeld

GermanyINTRODUCTIONThe mining industry is currently characterized by various factors such as environmental impact, resource scarcity, social responsibility and geopolitical uncertainty. The production of minerals required to meet the demand for renewable energy is expected to increase by 500 % by 2050, particularly for critical minerals such as graphite, lithium and cobalt 1. Easily accessible deposits are often depleted, meaning that deeper and more complex deposits need to be developed. Furthermore, investors’ value systems have shifted towards more sustainable practices. Alternative approaches to solving this problem are therefore currently being developed, such as the Modular Mining Systems concept for scalable and adaptable mining projects 2. Many mining companies have also taken important steps to become more sustainable, implementing measures such as proactive closure strategies, restoration programs and the development of renewable energy projects. In the European Union, laws such as the Critical Raw Materials Act and the Net Zero Industry Act support the mining industry 3,4. They see it as important for the energy transition and promote more sustainable ways of working in the industry Particularly negative environmental impacts such as land degradation, scarcity of local water resources, water pollution and greenhouse gas emissions are ingrained in society’s memory. Despite these efforts, the public image has not yet changed. To change this perception, the industry must strive to better communicate its sustainable practices and the steps it is taking towards a more responsible and sustainable future, promote transparency and build trust.Digitalization, automation and electrification are driving the digital transformation in mining. However, their implementation can lead to higher capital expenditure, limiting their adoption across the industry. Furthermore, implementing new technologies can be a daunting task for any organization. Change management comes into play when introducing such disruptive technologies. It involves preparing an organization for change, potential resistance and establishing effective communication. This helps to ensure that the implementation is successful and the benefits of the new technology are maximized. Digital transformation requires well-trained, young mining, electrical, mechatronic and software engineers with a deep understanding of information systems. Unfortunately, the industry faces the enormous challenge of attracting this younger generation, who have little interest in the extraction of raw materials. The need for action is compounded by an aging active workforce heading into retirement and the forecast of increasing demand for critical minerals.In this challenging environment, the concept of Blue Mining with its constant further developments represents a promising approach. This implies a shift from a linear to a sustainably oriented circular economy. For the mining industry, this specifically means the introduction of innovative technologies, the increased recovery of materials from waste and the consistent questioning and application of circular principles along the entire life cycle of a mine. Such a change can not only reduce the environmental impact, but also contribute to economic resilience and increased social acceptance of mining.

Feb 1, 2025

By Dan Witkowsky

For the 36th consecutive summer, the Colorado Mining Association Education Foundation and the Colorado School of Mines have sponsored “A Total Concept of the Mining Industry” for kindergarten through grade 12 teachers. Teachers from 34 states, plus the District of Columbia and two foreign countries, have graduated from the four-week course. They received six hours of recertification credit. This summer 31 teachers from Colorado, Kentucky, Virginia and Alaska completed the program. The course is unique from other shorter courses in that it solicits teachers of all disciplines from all K-12classes. In addition to the expected earth science and mathematics teachers, the Class of 2004 consisted of educators who teach music, chemistry, biology, social studies, history, basic English and world history. Others in the program included those who teach American history, physical and life science, remedial reading, consumer/family studies, “world of work,” language arts, engineering technology, environmental science, world geography, human anatomy and physiology, and business.

Jan 1, 2004

By Steve Kral

The Society for Mining, Metallurgy and Exploration’s origins can be traced back to 1871. This was when 22 Pennsylvania coal mining engineers founded the American Institute of Mining Engineers (AIME). The organization’s objective was to “promote the arts and sciences connected with economic production of the useful minerals and metals, and the welfare of those employed in those industries by all lawful means.” Metallurgy and Petroleum were added to the AIME name in 1919 and 1956, respectively. Divisions of AIME were formed throughout the following years in recognition of the increasing trend toward specialization among mineral industry engineers. At the time, SME’s divisions consisted of the Coal Division (1930, now known as the Coal and Energy Division), the Industrial Minerals Division (1935), the Mineral and Metallurgical Processing Division (1948) and the Mining and Exploration Division (1949). The Environmental Division was created in 1997.

Jan 1, 2007

By Ji Fang, Chong Fan, Fengrui Wang, Dongxin Bai

Unmanned mining technology in underground mines offers high efficiency, safety, and low cost. However, ground operators face challenges in accurately perceiving the underground environment through videos. This paper presents an augmented reality (AR) platform developed to enhance the unmanned mining process. The platform uses cameras and 5G technology to transmit high-fidelity video streams to the ground, where key targets are identified and virtual models are registered in the video to enhance the real scene. Tests in the Xinli stope of the Sanshandao gold mine showed the platform’s effectiveness in improving ground operators’ perception and production efficiency.

Jan 30, 2022

By Dale Matthews

The Getchell Mine, near Winnemucca, NR, was discovered in the 1930s and was initially mined to recover gold from oxide ores. During the 1940s and 1950s, gold was recovered from the highly refractory arsenic sulfide ores using horizontal kilns to roast the ores. During the 1960s, fluid bed roasters were used to oxidize the ore and recover the gold. The mine was shut down from 1968 through 1985. In 1985, heap leaching was started on the low-grade oxide ores that were available. In 1989, a pressure oxidation circuit was started to recover gold from the higher grade sulfide ores. Flowsheet The basic plant flowsheet of the Getchell Mine are shown in Figs. 1 and 2. The plant was designed to process a nominal 2.7 kt/d (3000 stpd) of ore with about an 85% onstream availability and a gold production of 15.5 kg/d (500 oz/ day). Run-of-mine (ROM) ore is fed directly to a wet semiautogenuous grinding (SAG) mill after the +457-µm (+18in.) rock is removed on a stationary grizzly. From the SAG mill, the ore goes to a ball mill where it is ground to 80% -75 µm (-200 mesh) and is then sent to a thickener. The SAG and ball mill operate in closed circuit using cyclones.

Jan 1, 1994

By Y. C. Kim, I. S. Roditis, P. K. Medhi

P. Mousset-Jones I found the article most interesting and timely. I consider it imperative that mine case studies like this one are undertaken and published so that the practicing mining engineer and geologist can obtain a better idea of what is the preferred estimation and grade control technique to use, given the site-specific geology, grade distribution, etc. Mining companies, with operating gold mines, need to be encouraged to either initiate such a study in-house or support a research project by financing a graduate student at a local university. The latter method is preferable since it not only provides research support but also an excellent training opportunity for young mining engineers and geologists. Ideally, what is needed is exploration drill-hole, blasthole, and mine production data that can then be used to assess the efficiency of different estimation and grade control methods by comparing the results obtained using the drill/blasthole data with the actual production data. It is hoped that more mining companies will realize that the rewards from this kind of research greatly outweigh the sometimes perceived problem with releasing data to a university. I noticed that the authors used the blasthole data to represent the actual values, the validity of which relies heavily on the two key assumptions with regards to blasthole assays and in-pit ore-waste selection procedures. Could the authors comment in more detail on these assumptions and what criteria they used to check the validity of the assumptions? Since the article was published, have the authors had the opportunity to compare their estimates with the actual production data? It would be interesting to compare other estimation methods with OK and IK. For example, how well did the polygonal method used at the mine compare with the results given in the paper? I would like to mention that B.L. Kwa completed a similar study (Kwa and Mousset-Jones, 1986) using exploration drill-hole, blasthole, and production data from the Alligator Ridge mine in Nevada. The study compared a variety of estimation methods, including IK, and the final results are shown in Fig. 1. The IK method exhibits the smallest difference between estimated and production results and is closely followed by the indicator moving window (Ind MW) method. Reference Kwa, B.L., and Mousset-Jones, P., 1986, "Indicator Kriging Applied to a Gold Deposit in Nevada," Proceedings, Symposium on Ore Reserve Estimation Methods, Models, and Reality, CIMM Annual Meeting, Montreal, Quebec, Canada, May, pp. 185194. Reply by Y.C. Kim We do concur with Professor Mousset-Jones with respect to the merit of such case studies performed at a local university. In answer to his request for comment on the validity of the two key assumptions made in our paper, we can only say that these are reasonable assumptions that are very difficult to validate. The assumption of blasthole assays being accurate can be partially validated by a careful analysis of the nugget component of blasthole variograms. The assumption that the in-pit ore-waste selection procedure in use was an effective one can only be validated through comparison between the mine estimates of ounces of gold versus the actual recovered ounces of gold at the mill. Neither one of these two assumptions has been validated to date due to several reasons. For example, the mine went through a change in management since the study. Similarly, no compelling reasons have been presented to perform detailed variogram analysis of the blasthole data. We do, however, believe that the obtained results (i.e., indicator kriging performs better than OK in a highly skewed deposit) will remain the same in relative terms, regardless of how valid these two assumptions may be. The most recent comparative study by D. S. Lindsey of the Montana College of Mineral Science and Technology also shows a similar ranking between ordinary kriging versus probability kriging, which is an extended version of indicator kriging. Reference Lindsey, D.S., 1987, "A Comparative Study: Probability Kriging vs. Ordinary Kriging at the Golden Sunlight Mine," MS Thesis, Department of Mining Engineering, Montana College of Mineral Science and Technology, Butte, MT, May, 81 pp.

Jan 3, 1988

By D. F. Lillie

The milling plant of Bicroft Uranium Mines Limited has been in operation for a period of 2 years. During this time many changes, both physical and chemical, have been made in an effort to improve plant efficiency. Investigational work has been facilitated greatly by the fact that the Bicroft mill consists to a large extent of two parallel circuits; however, the number of inter-related variables is great, and it is difficult to measure, let alone control, all of them simultaneously. The Bicroft mill staff feel that much progress has been made, but there is much yet to be done and many questions still to be answered. The property of Bicroft Uranium Mines is located in Cardiff Township in the Highlands of Haliburton County, southeastern Ontario, some 140 miles northeast of the city of Toronto and 70 miles due north of Lake Ontario. The ore-bearing dikes are classed as mafic, non-segregated, syenite and granite pegmatites. Microline, microline perthite, quartz, uraninite, uranotharite, fluorite, titanite, cyrolite, calcite, pyrite, pyrrhotite and molybdenite as important accessories. The mill was designed for a nominal capacity of 1,000 tpd with all sections except grinding, leaching and clarification capable of 1,500 tons. Feed was entered to one mill unit on October 29, 1956 and to the second parallel line on November 13. The total feed rate was at 1,000 tpd on November 15. The first precipitate was produced on November 12. By August 1958 the average entry had been increased to 1,410 tpd without the installation of any additional major equipment. The overall recovery has been greater than 93,0 pet do several months, but a recovery of 92.5 pct appears to be most economical. Operating time for 8 months in 1958 has been 97.1 pet although all grinding mills were relined during this period.

Jan 1, 1959

By G. Montes-Atenas

Throughout the years, research studies have reached a consensus in acknowledging the relevancy of surface chemistry phenomena on minerals separation and metals extraction. Many techniques, and notably, scanning electron microscope-based technologies have revolutionised the entire mineral processing industry. Nevertheless, the comprehensive understanding on how surface chemistry properties influence the performance of many processes involving ores is still a challenge, a matter of controversy. The latter is mainly due to the fact that all interfacial processes do not necessarily require stoichiometric and well defined atomic structures. This is particularly true in the case of sulphide minerals which are well known to be superficially unstable in aerated media. When trying to measure any variable related to mineral-mineral or mineral-aqueous solution interfaces, there are too many unknowns regarding how sensitive the interface is when facing sampling protocols and sample handling. The aim of this research work is to make a case for improving future concentrators? survey protocols. It suggests a methodology to study effectively chemical changes at the outmost mineral surface layer at different stages of a mineral processing operation. The sampling protocol and sample handling is presented in details and it is applied to the regrinding stage of an industrial plant.

Feb 27, 2013

By Jean Habimana

Complex and distinct geological units spread along the 7-mile long 30-ft inside diameter Upper Rouge Tunnel CSO Control Project in Detroit, Michigan. Its construction is divided in two tunnel construction packages: The South Tunnel, to be driven in finely laminated weak TG Limy Shale, will be excavated by a shielded TBM with precast concrete segmental lining, while the North tunnel, predominantly in a relatively more competent geologic formation Antrim Shale, will be excavated by a main beam TBM with a two-pass lining system. The adits and deaeration chambers will be excavated by sequential excavation method. This paper addresses the process of selecting excavation methods and lining systems for shafts, tunnels, connecting adits, and deaeration chambers.

By Paul Richardson

This paper will review several projects completed during the period from 1976 through 1984 which have been carried out utilizing big hole drilling concepts. The projects discussed will be from various industries to demonstrate the extent that big hole drilling methods are being used along with the current state of development. There will be a discussion of projects planned for the future where big hole drilling methods are the only technology being considered. Also included in the discussions will be an overview of the most recently completed heavy oil recovery project. During the next decade, big hole drilling methods will be used more and more in all industries where underground access is required. The safety, speed and economics associated with shaft sinking using drilling methods are becoming more and more recognized and the technology is rapidly becoming an accepted shaft sinking method.

Jan 1, 1985

By A. Fred Gelding

Introduction In preparing this paper considerable time was spent attempting to find some upbeat data about the mining industry, so those of us in the field could feel somewhat better about future prospects. Much to my regret, I failed to uncover substantial evidence that our near-term or, for that matter, our long-term opportunities appear all that bright in North America. That is certainly not the kind of assessment anyone likes to hear or accept as even a possibility. Those remarks may, on the surface, appear far too pessimistic. This industry will experience a recovery and most likely will see conditions begin to improve later this year or early next. The kind and degree of recovery, however, will more than likely differ from those experienced in the past. Fundamental Changes Clearly, the fundamentals on a world scale of our business have undergone important changes. In recognizing these fundamental changes, mining authorities believe productivity advances are needed to change the direction mining has taken in recent years. The really tough question is whether increases in productivity will be enough to change the course of events that has dominated the mining sector for the past decade. Before one can provide an honest answer, an appraisal of what has and is happening now is necessary. Here are some changes and events that have taken place that effect domestic mining and will probably continue: • Mineral-rich lesser developed countries (LDCs) in Africa, South America, and Asia-Pacific have reached a point where they have developed the needed mining infrastructure to not only produce at a high rate, but in many instances, at a lower cost than fully developed countries. Just as importantly, these countries, even if they do not enjoy lower costs, will produce for world export with government subsidies because min¬ing products are key in obtaining badly needed foreign exchange. • These producing countries also have the distance advantage of lower labor, environmental, and other important regulatory costs. If that were not enough, these same countries have minerals with considerably higher grade ore and, in some cases, much lower cost accessibility. • Exporting North American commodities is impaired by a dollar that continues to strengthen against other important currencies around the world. There are other impediments to overcome, but these represent some of the realities our industry faces. Can those obstacles be overcome through improving productivity? In the past, this industry has offset the impact of these events to a sizeable degree through innovations of mining techniques, equipment and processes, and by increasing the size of its individual operations to reduce costs. Will further enhancements along these lines be enough to alter this changing balance in the future? While there is no answer, it is apparent that if we do not mount a full-scale assault in some key areas, our prospects will not be encouraging. Productivity improvements throughout the entire chain of the mining industry most certainly rates as a high priority. Every link in that chain from mine planning, equipment selections, and transportation considerations needs to be examined and reexamined to assure the lowest effective cost is developed. Quality, while oftentimes costing a little more initially, is still the most cost effective purchasing decision to make. Regulations Another area of concern is regulations, be they environmental or those that dictate what must or must not be done in running our business. Certainly, I do not suggest that we not protect our environment. However, there is an acceptable balance that has, over

Jan 11, 1983

By Edwin F. Shorey, Richard F. Coon, Steven B. Fradkin

Crosstown Interceptor Phase IA is the first deep tunnel element of the Milwaukee Inline Project. The tunnel contract includes 6,492 meters (m) of 9.1-m-diameter tunnel, two access shafts, and partial lining for structural purposes. The work also includes grouting to be performed as directed by the engineer to provide groundwater infiltration control in lined and unlined reaches of the tunnel. This paper summarizes infiltration observations, progress of the grouting work, and its potential application to the remainder of the Milwaukee project.

Jan 1, 1987

By Les Gutzwiller

Fan applications in the mining industry have changed during the last 70 years. In 1922, J.R. Robinson authored a technical volume entitled Practical Mine Ventilation. At that time, atmospheric control had only recently shifted from natural to mechanical. The large, mechanical draft fans that were used then were centrifugal. The fans ran at low speeds, about300 rpm. Most were steam-engine driven. In the late 1920s and early 1930s, mines became larger, increasing the pressure and volume requirements of the fan equipment. Axial fans were designed to run at much higher speeds (710 to 880 rpm) and were driven by electric motors. They were also smaller and less expensive to install than the cumbersome centrifugal units. However, changes in mining have resulted in progressively higher static-pressure requirements. So centrifugal fans are once again proving to be a good choice.

Jan 1, 1999