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By E. Topuz

Mining equipment, like all other equipment, is subject to failure. Since most failures occur at random and are unexpected, corrective maintenance is usually more expensive and causes more down-time than preventive maintenance. In order to reduce the number of failures and thereby increase the availability of an equipment or system, preventive maintenance can be scheduled at predetermined points of time. The preventive maintenance scheduling policies presented in this paper utilize reliability and probability theories. They can be applied to various production bottlenecks where high cost equipment precludes having sufficient quantities of stand-by units.

Jan 1, 1982

By S. J. Jung, F. Lock

This research came about because of the recognized need for a safe, easy way to line small-diameter bored raises (less than 150 cm). Currently, an operator must go down the raise and apply the concrete lining manually, using the shotcrete method of application. With an automated system, there would be no man positioned in the bore itself. All control functions could be commanded from a central location. Shotcreting in the confined space of a small-diameter bored raise presents problems that can be overcome by the application of shotcrete using a remote system.

Jan 1, 1995

By L. W. Saperstein, MJ. Carlson

With the goal of improving the strength characteristics of pneumatically emplaced material used for localized subsidence control, the binding additives fly ash, bentonite, and portland cement were examined for their effect on the support capabilities of coal refuse. It was found that, within certain concentration ranges, all three offered some increase in the ultimate strength of the backfilling mixture. However, portland cement gave the greatest percentage increases. Selection of the appropriate backfilling mixture will allow for the most economical and efficient subsidence control when pneumatic stowing is employed.

Jan 1, 1990

By R. E. Blair

The economics of the producer-consumer interface - the route from mine to market - impact much more severely on specialty industrial minerals, extender/fillers that have to be sold, than on commodity industrial minerals that are basically supplied. Working capital costs for inventories and accounts receivable, fixed capital costs for storage/ warehousing/distribution, and sales and marketing costs all make the extender/filler producer much more of a marketer than a miner. The future survival of an extender/filler producer will primarily depend on the skill he has in the economics of the interface.

Jan 1, 1981

By James R. Arnold

Gold Fields Mining Corporation started processing ore from it's Chimney Creek operation in northern Nevada in November, 1987. Since that time production has averaged about 200,000 ounces per year from the milling and dump leaching circuits combined. The events that led up to commissioning of the plant started in January of 1985 when the Gold Fields exploration team drilled their first hole in an area now known as Discovery Hill. The major orebody was located later in the year in what is currently the major focus of activity, the North Pit. Subsequent drilling since plant startup has found another 14 million tons of ore two miles south of the original orebody. This South Pit orebody is currently being stripped and metallurgical testing is underway. Engineering Engineering on the Chimney Creek plant started in earnest in May, 1986. Davy McKee Corporation from San Ramon, California, did both the engineering and the construction management. Before engineering began the entire senior staff of the Plant Department was hired and assigned to the project. Senior staff included the Plant Superintendent, Plant General Foreman, Maintenance General Foreman and Chief Metallurgist. Gold Fields does not employ an internal central engineering staff to design their plants. We feel that the people who design the plant should be the ones who will be required to run it once it has been commissioned. This philosophy affords a continuous accountability from start of design through commissioning and operations. All four of the senior staff spent the most critical phase of the engineering stage at Davy McKee, so the plant is truly a reflection of all four disciplines. In bringing on the Maintenance General Foreman from the start, there was a focus placed on ease of maintaining the plant. Another philosophy that was adopted from the start was that the plant be easy to work in and maintain for both operators and maintenance personnel. Numerous design criteria were given to Davy McKee to ensure this. For example, we required that every piece of equipment could be reached easily with a crane or fork lift. All conveyors were required to have walkways on both sides for ease of maintenance and a minimum of 30 inches of clearance under them for ease of cleanup. Visibility for operators was considered very important and the control rooms and general plant layout were designed with this in mind. A list of about 100 general rules were given to Davy McKee during the early layout meetings and these were held as the general design criteria throughout engineering and construction. While engineering was progressing in San Ramon, California, dump leach test work was being done at the site. Three 6 foot diameter fiberglass columns were constructed and filled to a 20 foot height with low grade ore. Leaching characteristics were determined and the dump leach design was based on information collected from these columns. Construction The major contractors on the project were The Industrial Company for the bulk of the piping and structural, EMKO on the electrical/ instrumentation and Hunewill for most of the earth work and leach pad construction. All plant operating and maintenance personnel were employed eight weeks before startup for intensive training. Instructors were Gold Fields personnel, including foremen, and Davy McKee engineers. On occasion, selected suppliers representatives were brought in to discuss major pieces of equipment. Project completion was targeted for January, 1988 at a projected cost of 78.9 million dollars. Actual startup was about 1 1/2 months ahead of schedule and slightly under budget. Full design capacity was achieved the first full month of operation. Crushing Run of mine ore is delivered to the crusher and dumped into a 90 ton hopper which is topped with a 30" X 30" opening stationary grizzly. Ore is fed to a 50" X 60" Telsmith jaw crusher with a 5' wide apron feeder. The closed size setting of the

Jan 1, 1989

By James N. Grassby

Metal production has traditionally been a cyclical industry. 1977 in the base metals industry has highlighted that fact with a steady decline in the market place for base metals. Corporate aggregate planning is based on good forecasting and when changing conditions make that forecasting inaccurate, alternate analysis of schedules must be accomplished quickly. The computer is the only medium powerful enough to answer management's questions within an acceptable time frame. Worldwide communications networks now make it possible for the many multinational mining companies to arrive at coordinated corporate production plans based on similar basic data from several producing divisions. The Ontario Div. of Inco Metals Co., a unit of Inco Ltd., encompassed during 1977 14 producing mines, 2 nonproducing mines, 1 nonproducing open pit, 5 flotation mills, I smelter, 2 nickel refineries, 1 copper refinery, and an iron ore recovery plant. Several new mines are under development. Mine production approximates 63 500 tpd (70,000 stpd) from some 1000 workplaces. The need for longrange mine planning and scheduling is obvious and until recently has been satisfied by manual methods. However, while manual methods are often quite practical for a small number of mines, or for mines with relatively short lives, or for mines with only one mining method, the situation in the Ontario Div. is too complex and long-term to allow effective, timely planning by such methods. In 1967, a year after the first computer was installed in the division, work was begun on the computerization of the more than 30,000 borehole logs kept in the mines exploration files with a view to speeding up the assessment of mineral resources. Also in 1967 one of the first substantial systems developed on the main business systems computer was the monthly scheduling of development and production for all mines. This system encompassed tons productions per workplace, feet development per workplace, auxiliary and service activities and the requisite labor for each of these. These two dates are mentioned to show that concurrently with the acquisition of computers in the division there was an early understanding of the importance of automating mine scheduling and planning and of the potential for effective and useful computerization of such activities. In 1970, a pilot program was developed in one of the mines containing a large number of workplaces (350) to schedule the production on a network basis. Varying degrees of interest were shown by the individual mine engineers based on the complexity of the production planning problem at each mine. In an evolutionary process, mines were added to the system as its value became obvious in terms of time saving, flexibility, and accuracy. In 1975, the central mine engineering department decided that the system should be extended to all mines so that a complete division-wide long-range scheduling system would be available upon which to base development and production planning. This system would use basic ore data, allow the addition of scheduling commands, and calculate a schedule for the life of the mine. Many reports could be produced for each mine and all-mine summaries would also be available. The significance of the system can be stated in one phrase-speed, accuracy, and flexibility. Whereas in the past a long-range all mines schedule might have been done once a year, taking from two to three months, now it can be done in a day. The chief mines engineer can incorporate changes in input data and external constraints and call for a "new look" at the long-range schedule to assist him and mines production management in their decision-making processes. Using previous manual methods this could not be done quickly enough to be useful.

Jan 1, 1979

By H. D. Sharma

INTRODUCTION Uranium mill tailings, by-products from the mining and milling of uranium oxide contain all decay products of uranium-238, uranium-235 and all the Th-232. The ore containing all daughter products of the parents U-238, U-235 and Th-232 is ground to approximately 50% under 200 mesh particle size and after extraction of uranium, the residue, described as tailings, is discharged into natural depressions confined by dams. These deposition sites are referred to as tailings ponds. Tailings ponds are located in two mining districts, Bancroft and Elliot Lake in the Province of Ontario, Canada. Some parts of tailings ponds are dry up to a depth of several meters, whereas other parts have a water table very close to the surface and still others are covered with water. The extent to which the daughters of uranium isotopes are in equilibrium with the parents U-238 and U-235 is dependent on the age of the deposit in which uranium occurs and the extent to which the decay products are removed by geochemical processes. In the mining district of Bancroft, the deposit is known to be approximately 1 billion years old, whereas in Elliot Lake, the deposit is considered to be approximately 2 billion years old. The ratio of radiogenic lead isotopes Pb-206 and Pb-207, can provide some estimates concerning the age of the deposits. If the tailings are not affected by geochemical processes, the tailings would contain all the daughters of the 4n+2 and 4n+3 series in equilibrium concentrations. The equilibrium activities of some members of the 4n+2 series are calculated in Table 1. [ ] The amount of radiogenic stable lead isotopes depends on the age of the ore deposits. If the deposit in each district is of the same age, a definite relationship is expected with respect to the activity of Pb-210 and the radiogenic stable isotopes. Approximately 33 million tons of the tailings have been deposited in the early 1960's, approximately 20 years ago. During this period of storage, the segregation of uranium daughters, like radium, the diffusion of gaseous product, Rn-222, and removal of precursors by geochemical processes, can cause dis-equilibrium. Earlier work concerned with the uptake of Ra-226 and Pb-210 by plants (Kalin and Sharma, 1981), indicated that the concentrations of Pb-210,in samples of the tailings taken, were lower than the expected equilibrium. The diffusion of radon from a variety of matrices has been studied (Tanner, 1964). It has been shown that the diffusion coefficient is dependent on the particle size in which its precursor is present, the moisture content and the surface conditions. The direct measurement of radon concentrations in the environment near the ponds is dependent on the metereological conditions. Kramer, Schroeder and Evans, 1964, have examined the variations in the concentration of radon near the ground level with respect to atmospheric variables, such as changes in barometric pressure, precipitation, wind velocities, thermal atmospheric instability. It is difficult to relate the total release of radon from the ponds to the atmosphere over an extended period. Our measurements of Pb-210 and total lead on tailings samples taken from 16 sites indicate that the ratios of the activity of Pb-210 to the mass of total lead can provide parameters which are helpful in the estimation of the total amount of radon and its decay products diffusing from the tailings ponds. In this paper, we present the results of measurements of activities of Ra-226, Pb-210 and total lead in samples from various ponds situated in both mining districts. The measurements were confined to samples taken at 0-25 cm depth from the surface.

Jan 1, 1981

By R. J. Weege

Conventional underground mapping methods and diamond drilling are being applied in a study to determine the nature of the copper ore occurrences near the footwall of the Osceola lava flow top, commonly referred to as the Osceola Amygdaloid. Our work to date suggests that structures formed by relatively impermeable barriers, created by flowage and injection of still-molten lava from the interior of the flow into the solidified, brecciated crust, acted as the ore receptacles. Ascending hydrothermal fluids traveling near the footwall contact were trapped and confined in these barriers which retarded the direct upward movement of the ore fluids and caused deposition of copper. Oreshoots located near the footwall appear to have been formed spatially' independently from the hanging-wall oreshoots by fluids traveling simultaneously, but along different channelways. The barrier concept as advanced by earlier writers to explain the concentration of the ore-bearing, fluids into broad shoots con¬stituting entire ore bodies is found to be equally as applicable for the localization of smaller oreshoots within the Osceola ore body.

Jan 1, 1962

By R. H. Olson

Pigments are used in two segments of papermaking, as the major component in paper coating formulations and, in small percentages, as fillers in the paper web. Historically, the dominant use has been in coating, however, recent developments have fostered a multifaceted effort to substantially increase the pigment component in the paper furnish. Factors responsible for these developments together with their relationship to recent and forecast changes in papermaking technology are reviewed. Finally, some thoughts are presented on the probable timing and extent of these changes as well as their expected impact on the future demand for the common paper pigments.

Jan 1, 1985

By Joseph R. Wojcik

Introduction Placer deposits account for one-half to two-thirds of the total gold produced worldwide. As many as 311 t (10 million oz) have been produced from some major districts. Several others are credited with 155 t (5 million oz). All the major districts and many lesser ones have similar characteristics. Consideration of these characteristics offers insight into the origin of gold in the deposit. Knowing the gold deposit's geologic history leads to useful conclusions in exploring for placer deposits and for deposits in consolidated areas. Placer Deposit Characteristics Table 1 lists 17 placer gold districts around the world and their characteristics. These include type and age of, mineralized source rocks, associated intrusive rocks, and age of intermediate sedimentary cycles. Although quartzite or sandstone occurs in the bedrock sequence in four of the 17 districts, slates, phyllites, or schists are present in all of the districts. Additionally, in all but three, the slates are pre-Mesozoic. And, in six of the remaining 14, the slates are Precambrian. Rocks intrusive into the slates are all of intermediate to acidic composition and are emplaced as stocks, dikes, or sills, rather than being batholithic in proportions. Intermediate interceptors have not been recognized in only three of the 17 districts. Data from China and Mongolia are inconclusive as to this characteristic. Black Shale Gold Higher than average gold values are found in modern sedimentary rocks in coarse granulites, conglomerates, sandstones, and gray-wackes. Not so predictably, higher than average gold values also occur in black shales and carbonaceous argillities. Li and Shokena (1974) found that, in the Proterozoic sedimentary and equivalent metamorphic rocks of the Enisei Ridge, carbonaceous and graphitic phyllites and schists were particularly enriched in gold. Korotayeva and Polikarpochkin (1969) reported gold content in organic rocks to be enriched up to 15 times more than the organic free shales and siltstones of the Nerchinsk Zavod region of eastern Transbaikal. Black shales can be gold interceptors as are rocks of the granulite facies. Gold occurs in shales in particulate, free form, in pyrite, adsorbed on clays, and precipitated on carbon. In copper-bearing shales of Poland's Fore-Sudetic monocline, Kucha (1973) reported gold present in organic compounds as well as in silver bearing minerals. Anoshin (1969) found a strong correlation between gold and the pelitic fraction of sediments in certain rocks of the Atlantic Ocean basin. Heavy metal absorption on clays results in agglomeration to the extent that the particles settle with the heavy mineral fraction in enriched strata. Piper and Graef (1974) think that gold in sediments on the flank of the East Pacific rise is of lithogenic origin. Crockett (1973), however, proposed a volcanogenic exhalative origin. A strong correlation between gold and volcanic activity exists in rocks of the Canadian Shield where tuffaceous sediments and porphyries are more frequently enriched in gold than rocks with no volcanic components. Volcanic rocks of intermediate to acidic composition are considered here to be the primary source of gold in black shales. Gold is concentrated in shales as detrital free grains with diameters less than 50 µm (270 mesh), as precipitates, and in pyrite or other sulfide minerals. This is the first step in the history of gold placer deposits. Grain Size Modification Gold, as free grains with diameters less than 50 µm (270 mesh), is too light to be concentrated hydraulically into placer deposits. Some process has increased the average size of the gold grains. Mobilization during regional metamorphism converts most of the gold into particulate grains or entrains it in microfractures in the sulfide minerals. With moderate folding, small, white, vitreous quartz veins develop. As deformation continues, larger, more conspicuous quartz veins are formed. The larger veins are folded and faulted and contain native gold as minute specks and flakes not visi-

Jan 11, 1984

By Richard Klimpel

The laboratory ball mill grinding of coal/water slurries is described for three coals. Emphasis is placed on the measurement of specific rates of breakage for various operating conditions. Corresponding rheological information is also presented based on data collected using a rotational viscometer. A rheological explanation of the influence of various slurry fluidity conditions on the specific rates of breakage is presented. This rheological approach has proved useful In both the identification of suitable chemicals for increasing breakage rates in coal/mineral slurry grinding and in the plant scale implementation of dense slurry grinding systems.

Jan 1, 1982

By Vytas Svalbonas

Sophisticated computer analysis methods such as finite elements, finite differences, and numerical integration have become tools in the mineral processing industry for design of large mill shells. While use of such methods allows the analyst-designer to take new freedoms with his designed structure, there are also pitfalls and dangers which must be recognized for the proper use of such sophisticated tools. One of the worst of these is treating any computer answers as "gospel truth". The present paper discusses the knowledge required by the analyst-designer for proper use of computer analysis, as well as explaining to the layman how to identify questionable areas in such structural analyses.

Jan 1, 1979

By L. Adler

When systematically compared to other engineering fields, mining engineering is distinctive in 1) having a total systems concern. 2) dealing with encumbered space and 3) requiring full spectrum practice. The total systems concern results from having to design and then co-ordinate in space and time several major systems: excavating and bulk handling, ground control, life support and normal support. This requirement favors a generalist rather than a specialist approach. In coping with encumbered space especially in underground coal mining, the uncertainties of geologic conditions are compounded by tightness, roughness, remoteness and hazards. Into this difficult setting the total systems * complex is "stuffed," adding congestion and interference. Because of significant ground deterioration a flexible "rapid in-out" approach is usually vital to mining. Full spectrum practice arises from the need to manage, as well as to plan and design, a labor intensive operation. Since market conditions can also fluctuate most aspects of administration are needed in many respects, mining engineering functions relative to civil engineering in a way similar to industrial to mechanical engineering, with encumbered space being crucial. On this basis stress is placed on: 1) personal relations, 2) field work and 3) entrepreneurship, viewing time as money. Specific recommendations for improving engineering, safety and management and leadership are made. Since most new deposits are marginal, by applying these recommendations with high technology they could possibly now be mined on a widespread basis.

Jan 1, 1985

By R. A. Matuszak

In recent years, a new concept in the control of electrically powered excavators has come into existence. The new type of control system has come to be known as "static" control. The use of the name "static" to describe this system is somewhat misleading since this term refers only to one of the many advantages of this very important advance in excavator control systems. In 1959, the first truly "static" control for Ward-Leonard equipped electric excavators was designed, developed and placed in service. The control system, originally intended only as a more modern electronic type of alternate to the tried and proven rotating amplifier control system then in use, has since proven to be much more.

Jan 1, 1964

By Richard C. Marshall

The heightened concern over the environment which has developed in recent years has caused activities on National Forest lands to come under more intense public scrutiny. This has been especially true for activities oriented toward the production of commodities. Cattle grazing, mining, timber harvesting, and oil and gas leasing and drilling have all been increasingly subject to appeal and litigation. As a result, environmental analyses being conducted by the Forest Service have become more comprehensive, and measures to reduce or eliminate adverse impacts on resources have been given more attention. The costs of such environmental mitigation measures can be significant even when viewed in the context of the millions of dollars a company may spend, for example, to develop a mine. Using the Montanore Project in northwestern Montana as a case study, this paper examines the costs of alleviating some of the detrimental effects which may occur as a result of a mining operation. Although many of the general issues that have been raised about Montanore are common to other mineral projects, the scale of the project, as well as the fact that the ore body is within a wilderness area, the site is in grizzly bear habitat, and the surface waters are considered to be pristine, all combine to make Montanore particularly challenging from an environ- mental standpoint. Much of the information which follows is contained in the most recent version of the Draft Environmental Impact Statement (DEIS) which is scheduled to be published in several weeks. Based on agency and public comments, some of the information presented in the paper will change before the Final Environmental Impact Statement is issued in 1991.

Jan 1, 1991

By Gerhardt A. Bennewitz

The mechanism shown here (Fig. 1) may not be all that it appears to be. To many of you it may look like a hopper car, a thing of mobility, in which you would ship coal, ores, limestone, or other bulk materials. It is approximately 50 feet long, 12 feet high, and can be placed on tracks which are on approximate 14 foot centers. But far too often in the past, and all too often today, this mechanism has been made to serve as an immobile storage box, with its primary role -- the transportation of products, seemingly incidental to the storage function. Our engineering training teaches us to conserve resources, despite some of the popular and misconceived philosophies being advanced these days. Those of you who work for companies with traffic departments know that they are always striving to reduce the price which is paid to move your mine products. Today, let's consider and analyze the ways in which the cost of transporting your mine products might be reduced, based on particular reference to coal. Bear in mind that in this context, cost and price are not necessarily synonymous. Until a few years ago, most coal and other bulk materials handled by railroads moved under standard tariff rules. These rules, which still exist today, provided transportation vehicles (railroad cars) for extended periods at no added price to the shipper or receiver. "Normal" free time rules would permit a car to be held for a maximum of 48 hours without charge; however, in the case of coal, there is a rule which, subject to liberal rules as to the

Jan 1, 1972

By John S. Owens

The National Steel Pellet Project and the Butler Taconite Project are operated by The Hanna Mining Company in the vicinity of the towns of Keewatin and Nashwauk, on the western Mesabi Range. Production began in 1967, after seven years of exploratory and development diamond drilling and reconnaissance magnetic surveys, Previously, direct shipping hematitegoethite ores and gravity concentrates had been produced in the area from numerous open pits and several underground mines since the start of the century. Total shipments of these oxidized ores amounted to more than 200 million tons, but at the present time such reserves are nearly exhausted, and there are no mining operations in the Keewatin-Nashwauk area except at the two taconite projects. The locations of all of the present taconite operations on the Mesabi Range are shown in Figure 1, extending for a distance of about seventy miles from the Butler plant to the Dunka River area. The Butler and National plants have a combined rated capacity of 4.4 million tons of pellets. Their reserves cover a combined strike length of about eight miles on the Biwabik iron formation. All of the intervals between present taconite operations on the Mesabi are potential sources of additional magnetic taconite; in particular, exploration and economic studies have been carried out by Jones and Laughlin Steel Corporation in the Biwabik area between Aurora and Virginia, and by Pickands Mather and Company in the Hibbing area. However, west of the Henna and Butler holdings, it appears unlikely that magnetic taconite exists in commerical quantities at economic depths due to extensive oxidation of magnetite to hematite.

Jan 1, 1968

By George J. Thompson

Almost all persons connected with mining industry have had an exasperating experience like the following: 'On a cold and frosty morning in mid-January, you find yourself quite happy with the world. Production is up and the mine has been running smoothly. All at once the radio cracks up your tranquility -- 'so and so' piece of equip¬ment has broken its 'whatzit'. Now the iron is in the fire, and things have to be fixed quick.!' This can be a major failure which will bring the whole operation to a grinding halt or just one of the numerous maintenance headaches on an auxiliary piece of equipment. After one has experienced a major or minor catastrophe, he has to wonder whether some other methods with respect to design and maintenance would help prevent these unexpected calamities. The objective of this paper is to gain an insight into the charac¬teristics of steel at cold temperatures so that better decisions can be made with respect to maintenance and repair of mining equipment. Most machinery and their structures are exposed to cold temperatures. Even in locations as far south as Alabama and Arizona, brief periods of cold in winter months can adversely affect the ability of mach¬ines to do their work. To understand the background of cold temperature brittle fracture, jet us examine its basic elements. First, when steel gets cold, it gets brittle. This is best described by Figure 1. This graph shows a typical stress/strain curve of a mild or medium grade steel at room temperature. Stress is defined simply as the amount of force acting on one square inch of

Jan 1, 1972

By L. G. Wilson

In order to comply with time limitations imposed by this symposium, a very narrow but nonetheless interesting segment of the market has been chosen for discussion of the preparation of a tailor-made product to meet a specific need, and in view of the fact that the barite market is one of the oldest and one of the broadest non-metallic mineral markets in the world, it is necessary that we place this in perspective. Of a recent world annual production; (i.e., 1966 figures released last year in MINERALS YEARBOOK), of some four million tons, the United States consumed over 1/2 million tons, of which approximately 950,000 tons were produced domestically and approximately 700,000 tons were imported. Of this total, something approaching 90% was used for drilling-mud weighting, and of the balance, all but about 60,000 tone is consumed in the production of glass, barium chemicals, aggregates, and other minor uses; thus we are really taking a look at a very minute, however important, and very selective, portion of the total barite-market. The real meat of this paper, after eliminating all irrelevant uses of barite, and delineating the area of discussion, resolves itself into the approach to a favorable marketing area and a specific attack on that area. Cost, to the user, has been, patently, a function of distance, as the basic price of barite has varied very little over the years until recently, and freight rates have been the governing factor. Conversely, the seller of barytes must make concession in the plant price to compensate for distance, if he is to successfully compete.

Jan 1, 1969

By I. J. Dowdeswell

Perspective Man is a model maker. Throughout recorded history man has-used models both to provide insights into the workings of the processes which surround him and as a step towards the eventual control of those processes. These models have covered the field from extremely large systems (solar and celestial. models) to infinitesimally small systems (sub-atomic .and atomic models). Models have been developed for social systems, ecological systems, biological systems and economic systems: all fields of human endeavour contain the fruits of this restless model-making. The Role of Models Since the evidence of mans' industry in formulating models is so abundant, it is worthwhile stating some of the reasons. Based on the simple definition that "a model is a convenient and useful representation of some facet of the 'real' world", then a model provides a means for: 1. Understanding the thing being studied. 2. Communicating that understanding to others. 3. Manipulating the thing being modelled. The common denominator implicit in these reasons is that- improved control is the. objective off all modelling or simulation work. Improved control shows itself either directly by the development of devices which perform the control functions or indirectly by improvement in the decision making process itself. For example, in a process plant, a suitable model of part of the process could lead either to the use of automatic control devices such as set-point controllers or to the implementation of instructions (pre-defined decisions) which permit the operator to better control the process. Typical process control systems use both of these since fully automatic control is restricted to processes where the required information can be effectively measured.

Jan 1, 1972