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By Joseph B. Novak

In the last decade or so, the importance of effective preventive maintenance controls and practices has taken on a new and accelerated emphasis. Advances in technology and changes in equipment and product designs impose more precise and demanding standards of quality, productivity and customer service at a very rapid pace. Daily, it is becoming more apparent that in order to fulfill current requirements, existing manufacturing practices and associated control programs must also be upgraded and expanded. This is particularly true in the field of maintenance services. As production and quality standards become more demanding, effective equipment maintenance takes on more importance and becomes more difficult to sustain. In modern plants, the failure of a single equipment component can shutdown a complete production line causing interruptions to operating and shipping schedules that result in costly downtime, dissatisfied customers, and reduced profits. These costly experiences can be minimized with an effective maintenance program that provides maximum equipment reliability and minimum downtime and readily adapts to revision and change. A significant feature of an effective program is the provision of controls over activities generally identified as

Jan 1, 1971

By Ossi V. I. Hintikka

There are several limestone deposits around the Lohja area in southern Finland. Raw material for cement rock is mined from some of them. The formations are geologically complicated, and therefore selective mining is used whenever possible. One of these mines is the Tytyri underground limestone mine, which is divided into two parts; Törmä and Solhem. In addition to the selective mining system hand sorting or picking must be used at the Tytyri mine to improve the overall grade of the blended limestone. Some means were needed in order to improve the quality and to increase the feed rate by the elimination of hand sorting. Sorting machines were considered and eventually a Sortex 811MW was pilot plant tested at the Ojamo mine near Tytyri. This machine now continues to be used on production.

Jan 1, 1971

By A. B. Walker

The effects of the injection of dry limestone additives into boilers for the sorption of sulphur dioxide have been studied in pilot and full-scale systems. The effects of such injections on boiler mass particulate emissions as well as collectability characteristics of the fly ash and reaction products are presented. Implications of the effects on the design and economics of particulate collectors, in particular electrostatic precipitators, are discussed.

Jan 1, 1971

By H. D. Goodfellow, R. A. Elliott

"This paper covers the evolution of large mills and autogenous grinding and compares grinding practice in the iron ore industry with that in the base metal industries. Comments on novel methods of grinding are presented for discussion. Recent developments in the field of classification are briefly reviewed. A systems analysis approach to grinding circuits is discussed. Finally, a point is made for establishing a group within the industry with the purpose of developing a comprehensive evaluation of grinding research and development."

Jan 1, 1971

By E. R. Mitchell

When we grow up in an urban environment and choose to become a part of a way of life, it is sometimes difficult to appreciate the cost of this decision in terms of pollution. Explained in this article is our dependence on technology and the amount of pollution that technology produces. Inventories of air pollution on both a personal and a national basis are given so that the reader may judge the magnitude of the problem. In doing so, it is hoped that the reader will understand the need for a responsible attitude toward pollution by everyone and how he can make a personal contribution.

Jan 1, 1971

By W. C. Hellyer, R. A. Campbell

In single-stage autogenous grinding, the buildup of a critical size fraction in the media can be corrected by removing this material through pebble ports, crushing it below the critical size range, and recycling the crusher product back to the mill. The rate at which the critical sire fraction is crushed affects the size distribution of the grinding media and this in turn affects the sire distribution of the grate discharge. This provides a means for controlling the grind produced by a single-stage autogenous grinding unit. The pilot-plant investigations on a very hard copper ore were carried out at the facilities of the Institute of Mineral Research, Michigan Technological University. In an autogenous grinding circuit in which feed at approximately 9 in. top size is reduced to a size suitable for subsequent processing, the build-up of a "critical size" fraction in the media causes problems. A "critical size" fraction has been defined as, "media too small to effect reduction by impact grinding of ore coarser than a quarter of an inch and too large to be broken by the largest size of media in the charge."' The buildup of a critical size fraction reduces the capacity of the mill, increases the grinding power requirements per ton of finished product, and generally produces a finer grind than is desired. It is general practice to overcome this problem by the addition of large-diameter steel balls to the grinding charge. This has certain disadvantages, such as 1) an increase in mill liner wear, 2) wear on the steel balls, and 3) some loss in flexibility in grinding circuit opera-tions resulting from difficulties in removing the steel balls by means other than by grinding out. A number of investigators' have suggested the use of a small crusher as an alternative to the use of large steel balls for control of a critical size fraction. With this technique the critical size fraction is removed from the mill continuously through suitable-sized pebble ports, crushed below the critical size range, and returned to the mill. An external crusher would cause no increase in mill liner wear, the wear on the crusher would be less expensive than the wear on the steel balls, and the flexibility of the grinding circuit operations would be enhanced since the crusher can be cut into and out of the circuit at will. This paper describes an autogenous grinding pilot plant investigation on a very hard copper ore, which led to the selection of an autogenous grinding flowsheet incorporating a crusher in the circuit as the preferred method for grinding this ore. Further development of the technique demonstrated that the crusher could be employed to control the product produced by an autogenous grinding unit. Description of Pilot Plant These investigations were carried out at the pilot-plant facilities of the Institute of Mineral Research, Michigan Technological University, Houghton, Mich. The autogenous grinding unit was a 6-ft-diam by 2-ft-long Hardinge Cascade mill with %-in. slotted steel grates. Pebble ports cut into the grates allowed passage of pebbles having a top size of approximately 21/2 in. The grate and pebble-port discharge material passed over a 3/16-in, trommel screen with the trommel under -size being pumped to the classification device. DSM screens were employed for classification in the early investigations, but were replaced later by a small Dorr rake classifier. The trommel oversize material returned to the mill via scissor conveyors. When the crusher was incorporated into the circuit, the trommel oversize material passed to a double-deck vibrating screen fitted with 2-in. and 3/4-in. square mesh screen cloths. The $ 2-in. and the —2 +3/4-in. size fractions were combined and crushed to a nominal 1 in. in a 4 x 6-in. jaw crusher. The crusher discharge and the —3/4-in. screen undersize returned to the mill. In the final investigation, a flap gate fitted to the top deck of the screen directed the — 21/2 +2-in. size fraction to the crusher or back to the grinding mill. The flap gate operated manually on a 15-min cycle, with this material being crushed for so many minutes out of each cycle. This was found to be a more reliable method of controlling the amount of — 21/2 +2-in. material crushed than attempting to make a split of a small weight of material on a continuous basis. Operational Techniques: Each sample was sized into three fractions and the Cascade mill feed was reconstituted from these size fractions in the proportions existing in the original sample. Sufficient feed for 15 min operation was weighed out and fed by hand over a 15-min period. The gross mill power draft was recorded every 15 min, corrected for tare power and drive efficiency, and reported as net kilowatt-hours per ton. A recording kilo-watt-hour meter provided a continuous visual record of the power drawn by the mill. Pulp densities of the trommel undersize and the classifier overflow (or DSM undersize) were taken every 15 min. The classifier overflow was sampled automatically. Timed samples of the classifier sands were taken every 15 or 30 min, weighed, and returned to the circuit. After correcting for moisture content, the weights were converted into percent circulating load. Timed samples of the +2 in., the —2 + 3/4-in., —3/4-in. screen fractions, and the crusher discharge, were

Jan 1, 1971

By B. M. Monaghan

"The developments of the 1950s and 1960s have seen Canada become an international source of iron ore, trading in all geographical areas and hemispheres. Canada's production will significantly increase in the next decade. However, although the outlook is bright, iron ore producers cannot be complacent. Instead, we must weigh the factors that have brought about the development of the Canadian iron ore industry and examine the probable changes for the next decade that will affect its growth.Looking ahead in the 1970s, competition will be severe. Pressure on prices will continue as new sources of supply bid for long-term contracts and as steel producers continue to develop mines around the world. Rising costs will make these pressures more severe. We must balance the growth of the world's steel makers with the emergence of new supplies of iron ore. The iron ore industry is now part of a new era in which demand and supply are intermeshed, and the developments around the world are acting on the Canadian iron ore industry's future."

Jan 1, 1971

By A. L. Mular

Some specific cases of the collection of data from industrial grinding and classifying operations, and the development of models from the data so obtained, will be described. The problems encountered, the effort involved, and the value of the derived models in improving the plant efficiencies will be discussed and documented where possible.

Jan 1, 1971

By A. W. Maynard

Simple chemical spot tests for the identification of major alloying elements in aluminum-base alloys are described. The tests are suitable for use by nontechnical personnel working outside a laboratory. Tests for zinc, copper, manganese, and magnesium employ electrographic sampling methods and sample papers. Use of electrographic sampling in a test for magnesium in aluminum is made possible by using glass fiber filter paper. Differentiations between magnesium and magnesium-silicon alloys of aluminum and between aluminum-base and magnesium-base alloys are made by direct chemical solution tests. Description of a device for obtaining reliable electrographic samples is included. A sequence of testing for identification by alloy groups is given.

Jan 1, 1971

By David A. Summers, John Corwine, Li-King Chen

The results from fracturing plexiglas beams are combined in eight existing equations to determine the surface energy of the material. The reliability of each equation is tested, and the equation in use to determine fracture toughness is found to be the most exact. This equation is then used in determination of the surface energy of Barre Granite.

Jan 1, 1971

By Charles T. Holland

INTRODUCTION Insofar as I am aware, the term rock mechanics was not in the English dictionary in 1930 when I started my graduate program at West Virginia University. Hence, I never thought that I was undertaking studies in rock mechanics when I undertook to write a thesis on the physical properties of West Virginia coal. In this case, the subject was primarily concerned with the compressive strength of coal, the elasticity of the coal, the physical weathering properties of the coal and its friability. These days investigations of rocks pertaining to such properties are included in the term "rock mechanics". Other than this aspect, the principle interest in this part of my program was that I became interested in the strength of coal from the standpoint of structural purposes, and also became cognizant of its elastic properties as well as its energy storing properties. This research also tied in with a remark that Professor Lawall made in a Mining Methods class in 1928 when he remarked that a peculiar thing was happening in the southern part of West Virginia, namely, in the Pocahontas coal field. His remarks were to the effect that pillars were blowing up in the mines and when asked why he replied the cause was not known. The failure of three-inch coal specimens, especially those in stronger coal, in non-hydraulic actuated testing machines was reminiscent of his description of those pillar bursts or bumps.

Jan 1, 1971

By Larman J. Heath

Liquid incendiaries were burned within the interstices of several different types of sandstone cores to determine the technical feasibility of increasing sandstone permeability by this method. Fuel-oxidant mixtures were tested in 186 cores; six cores exploded when ignited. In virtually all instances, the explosion completely pulverized the sandstone cores. In addition n those cores damaged by explosions, 24 cores were fractured so severely that permeability tests were impossible. Although combustion gener¬ally increased the permeability, specific mixtures at given pressures were inconsistent in their ignition and burning behavior. Tests indicated that the heat of burning incendiaries significantly increased sandstone permeability. The improved permeability ratios were usually less than 2, but one was 10.3. Permeability alteration by other in situ methods was not as effective as that by flame propagation.

Jan 1, 1971

The past decade has seen remarkable progress by the railroads both in equipment and concepts in the handling of dry bulk. materials. While such shipments have always been an important part of the traffic handled by the railroads I little was done to improve the efficiency of handling or toward attempted optimization of equipment design before 1960. Several developments at about that time turned attention to this important segment of railroad traffic. One was the construction of a successful coal slurry pipe-line. Another was the promise of substantial economy in electric power transmission by ultrahigh voltage systems and finally, came the growing technological and economic feasibility of nuclear fuel electric generating plants. Each of these developments was a threat to the coal traffic of the railroads --the most important single commodity they handled in terms of revenue and tonnage. By the mid-1950's I Southern Railway management had become most concerned with its growing investment in freight car equipment and the declining revenue productivity of the capital employed. Additionally I there was substantial concern with the loss of business and potential losses in the area of the railroad's greatest economic advantage --bulk commodity movements. In 1958 a small team was established to study this problem. They arrived at two conclusions. The first conclusion was that within limits of maximum gross allowable weight on rail the lowest unit net capacity cost of investment came at maximum allowable gross weight per car unit. The second conclusion was that with a high degree of utilization costs per weight unit transported could be reduced to the pOint where

Jan 1, 1971

By Ralph M. Foecking

The disposal of the phosphate slimes produced by Florida beneficiation operations is perhaps the biggest single problem of the phosphate mining industry. This is an old problem which has not been solved and which is becoming increasingly severe. In a typical phosphate mining operation, the phosphate rock mined is initmately mixed with sand and clay, constituting what is known as matrix. During the beneficiation, the clay and other fine materials are separated usually at -150 mesh, and washed from the phosphate rock in a form of diluted slurry known as phosphate slimes. The quantity of slimes solids and their composition vary considerably with the location but usually represent from 25 to 35% of the ore mined. Because of the affinity that clays have for water, large volumes of water are required to separate the granular material in the matrix forming a dilute slime suspension (1.5 to 3% solids) of colloidal material, which settles very slowly, and thus requires immense impounding areas, which never becomes totally usable land. These ponds also contain about 25 to 35% of the total P205 values mined. The magnitude of the problem represented by the slimes can be appreciated better if we realize that there are around

Jan 1, 1971

By William G. Pariseau

A small displacement-small strain finite element technique utilizing the constant strain triangle and incremental constitutive equations for elastic-plastic media that are nonhardening and obey a Coulomb yield condition has been applied to the analysis of gravity flow initiation in a V-shaped hopper containing a powder under lunar environmental conditions. Three methods of loading were examined. Of the three, the method of computing the initial state of stress in a filled hopper prior to drawdown by adding material to the hopper layer-by-layer is superior (as expected). Results of the analysis of a typical hopper problem show that the initial state of stress, the elastic moduli, and the strength parameters have an important influence on material response subsequent to the opening of the hopper outlet.

Jan 1, 1971

By M. W. Bates, A. L. Mular

This paper, based on work carried out at Queen's University, describes the development and use of mathematical models of the parallel cyclone classifiers being used in the Strathcona mill of Falconbridge Nickel Min.es Ltd.

Jan 1, 1971

By V. E. Edlund

Laboratory batch flotation tests were conducted on copper converter slags to evaluate the relative merits of recovering copper from slow-cooled versus water-quenched slags. Three slags containing 1.6, 5.0, and 6.6 percent copper were used. More than 90 percent of the copper was recovered in a rougher concentrate leaving a 0.2- to 0.3-percent copper tailings when treating slow-cooled slag. Lower recoveries and higher copper tailings ranging from 0,5 to 0.6 percent copper were obtained from quenched slag. Grindability studies were made on the respective heat-treated slags. Quenched slags proved more difficult to grind than slow-cooled slags. Cost studies showed that (1) the cost of slow cooling and crushing off-sets any advantages of higher copper recoveries from slow-cooled slag, and (2) water-quenched slag, which requires no crushing preparatory to grinding, could be treated more economically. Costs based on processing 1,000 tons of slag per day would be $1.85 per ton for quenched slag versus $2.37 per ton for slow-cooled slag.

Jan 1, 1971

By David M. Lapham

In Pennsylvania, 310 sampled sites of clay and shale have been evaluated for: potential use, chiefly as structural clay products, refractories, and lightweight aggregate; lithology; physical properties tests; fired tests, both quick-fire and rotary kiln; major-element chemical analyses, and quantitative five-component X-ray mineralogy for quartz, mica, feldspar, kaolinite, and chlorite-vermiculite-montmoril-lonite. Approximately 80 percent of the samples are of some potential use. Of 220 shale samples, 84 were potential lightweight aggregate sources and 83 potential brick sources. Binary correlations of test data versus potential use indicate that certain empirically determined parameters may be critical. These are: lithology, particularly for medium to super-duty refractories and lightweight aggregate; kaol-finite content for refractories versus low-temperature fired product sources; quartz content illustrating that there is an apparently necessary minimum quantity for brick; quartz content, which is low in high grades of lightweight aggregate; mica content, which is low for refractories and possibly high for lightweight aggregate; total iron, which is low for refractories and shows a 40 percent minimum for lightweight aggregate; carbon dioxide, which is low for refractorfes, beneficial in lightweight aggregate, and probably restrictive for some tiles choroite yermicalite, which is low for refractoies and possibly beneficial in lightweight aggregate. In Pennsylvania, clay and shale materials constitute one of the state's major economic mineral resources. To date, the testing program indicates considerable development potential in brick, tile, and lightweight aggregate industries, and perhaps a future potential for aluminum from shales that exceed 20 percent A12Q3.

Jan 1, 1971

By S. Usui, I. Iwasaki

The adsorption mechanism of dodecylammonium acetate (DAA) on mercury in potassium fluoride solutions at natural, near neutral pH was investigated. Difler-ential capacity combined with electrocapillary measurements on a dropping mercury electrode were found to provide a sensitive and reliable approach. A shift in the electro capillary maximum (or the point-of-zero-charge) towards positive polarization of the surface due to the adsorption of amine indicated a specific affinity of dodecylammonium ion for mercury surfaces. The amine was shown to adsorb competitively with potassium ion on mercury. Through correlation of the adsorption density of the amine, calculated from the thermodynamic analyses of the electrocapillary curves, and of the diflerential capacity curves, the adsorbed state and the orientation of the amine at the interface were considered. The similarities and the differences in the adsorption behavior of the amine on mercury and on such ionic solids as quartz, silver sulfide, and silver iodide were evaluated. With the promise of flotation providing a cheap and large-scale process for the upgrading of low-grade ores and magnetic concentrates, the iron ore industry has made a sustained search over the years for a flotation reagent of general applicability and high selectivity. Having shelves full of commercial reagents already on hand and anticipating more, both the users and the suppliers are in need of an experimental approach sensitive enough to differentiate the individual characteristics in each group of reagents. Therefore, the adsorption behavior of various flotation reagents on mineral surfaces from aqueous solutions has been a subject of much investigation. The current view of adsorption based on the electrical double-layer theory is formulated on the assumption that certain ions in solution act as potential-determining ions. Their concentrations fix the potential drop across the double layer and their adsorptions govern the surface charge.' Two methods used to study the adsorption

Jan 1, 1971

By Owens S. Roberts

The drive selected for any piece of machinery must adequately satisfy the application requirements both during the starting interval and at running conditions, All loading possibilities of the drive must be known and allowances made for any adverse limiting conditions such as extreme cold, or perhaps an intermittent excessive loading situation etc. In general, the drive must be selected to provide the required operating characteristics with maximum reliability and at minimum cost. Simplicity of overall design is always an advantage and care must be exercised to insure that systems incorporating unnecessary complicated parts are not indiscriminantly provided. Important non-technical considerations such as equipment avail-ability (on an overseas project) as well as standardization details also play a role in the drive selection process. Additionally, an assessment of the potential capabilities of the personnel that will have to maintain the equipment can have some influence on the final choice. Several types of prime movers are available but this article will restrict itself to the use of induction motors operating from an available alternating current power source. Many drive arrangements are possible, the most common being the direct coupled single motor arrangement. It is sometimes desirable to use more than one motor per machine, but these designs are usually more

Jan 1, 1971