Search Documents

By W. G. Woolnough

There has been no noteworthy increase in production during 1935; but, on the other hand, there have been ample manifestations of a considerable increase in interest and activity in connection with petroleum prospecting. The Lakes Entrance field, in the State of Victoria, on the coast some 120 miles east of Melbourne, remains the only actual producer; and this production, consisting of lubricating stock devoid of light fractions, is very small in amount. Arrangements have been completed under which a series of "scout bores" for structure testing in the region of Lakes Entrance will be sunk by the Government of the State of Victoria, assisted by a subsidy from the Federal Government. Prospecting In the State of New South Wales, brilliant geological research in very difficult country, carried out by geologists of Oil Search Ltd., has revealed several previously unsuspected domal structures in the Sydney-Newcastle coal basin. These have been mapped in detail, and a test well is being sunk at Kulnura, 10 miles west of Wyong and 40 miles north of Sydney. At the date of writing this well has reached a depth of 1250 ft., 10-in. casing having been set at 1248 feet. Superficial formations consist of the Hawkesbury sandstone and Narrabeen beds of the Hawkes-bury system (fresh-water Triassic). It is anticipated that the upper coal measures of the Kamilaroi (Permo-Carboniferous) will be entered almost immediately. The objectives of the drilling are the upper and lower marine beds of the Kamilaroi system, which are regarded as promising as potential source—and reservoir—beds for oil. At Mulgoa, 30 miles west of Sydney, a bore is being sunk by the same company, Oil Search Ltd., to test for natural gas on a well defined structure located by the company's geologists. Noteworthy flows of gas have been encountered, but nothing approaching a commercial supply has been struck. It is considered probable that the gas has been derived

Jan 1, 1936

By S. R. Gilbert, B. W. Burdett, L. B. Hales

INTRODUCTION Grinding control is currently the most publicized control subject in the minerals industry. Flotation control and crushing control have not as yet received the widespread attention that grinding control has. The primary reasons for this center around the high capital costs of grinding equipment and the fact that grinding mills are extremely energy inefficient. In a typical copper concentrator the energy requirements to produce refined copper are: (1) [Total Energy Distribution (Kw-hr/yr)% Mining4.93 x 10817.3 Mineral Processing9.63 x 10833.8 Smelting and Refining13.9 x 10848.9] One-third of the total energy used for copper production is for mineral processing. A breakdown of this energy into process steps yields the following: [Total Energy Distribution (Kw-hr/yr)% Crushing and Grinding 7.16 x 108 73.8 Flotation 0.76 x 108 7.8 Materials Handling1.78 x 10818.4] It is apparent that comminution operations consume the largest proportion of the energy for processing and as such become major targets for improvements in efficiency. Unfortunately, size reduction operations are extremely inefficient. Efficiency calculations for grinding range from less than 0.1% to about 5% depending on the evaluation criteria. Because of these facts, grinding control has been and will continue to be the focus of major process control efforts. OBJECTIVES AND BENEFITS All benefits achieved as the result of grinding control are derived from modifying physical parameters which improve the efficiency of the grinding mill. These parameters include:

Jan 1, 1982

By Albert Walcott

THE success of various operations in the manufacture of optical glass depends, in a large measure, on the ability to maintain proper heat control. A good pyrometer system is, therefore, a very necessary part of the equipment needed. Men of long experience in dealing with high temperatures, who have acquired through constant practice the ability of judging approximate temperatures by means of color, are undoubtedly valuable, but even the most competent are not as reliable as a good pyrometer system. They admit that their ability to judge accurately varies from day to day and that their judgment is affected considerably by the condition of the sky, whether it is clear or cloudy. Besides, where it is a matter of only a few weeks to train a man to operate a pyrometer system, it takes about as many years to train him to judge temperatures by the state of incandescence. The pyrometer outfit in use in the glass plant of the Bausch & Lomb Optical Co. consists of the following: Platinum elements, optical pyrometers; base-metal elements, indicators, potentiometers, and recording pyrometers. Platinum Elements and Optical Pyrometers.-Temperature control in - the melting operation is of such great importance that it is very desirable to know the exact temperatures, relative temperatures being of little value. The use of the platinum element is to determine the rate of heating or cooling of the furnace. The platinum couple is installed in either the crown or the wall of the furnace. It is placed first in a porcelain protecting tube and this is placed in a permanently fixed fireclay tube projecting from 1 1/2 to 2 in. into the fire-chamber. It has been found impractical to use the platinum couple for determining exact temperatures of the melting furnace, for the platinum element deteriorates rather rapidly at the high temperatures used, 2500° to 2700° F. (1371° to 1482° C.). When protected and installed as described, though,

Jan 9, 1919

By Henry Howe

THE data which are collected in Table 1 show that the ferrite of low-carbon steel and of electrolytic iron, like the network of hypo- and hyper-eutectoid carbon steel, inherits, either absolutely or relatively, the, grain size of the mother austenite from which it is born in cooling through the transformation range. This evidence is so abundant and concordant as to cast doubt on Prof. Jeffries' 1 hypothesis of what might be called reversed inheritance, by which he explains Mr. Ruder's observation2 that the grains of a "slug of pressed pure electrolytic iron powder"were coarser, perhaps 12,000,000µ2, after a 3-hr. exposure to 1000° C. than after a 3-hr. exposure to 1250-1300°, when they were about 35,000µs. His explanation implies a natural tendency of coarser austenite grains to yield finer ferrite ones than spring from finer austenite grains, so that the inheritance is reversed. What seems to me a simpler explanation is that the enormous grains which followed the 1000° heating were not inherited from the mother austenite, but were formed by the process of natal coarsening, by means of which Stead and Carpenter developed grains of this same order of magnitude in this same kind of material, on heating to 950° or to 1000°, the temperature used by Mr. Ruder, provided the exposure was not unduly prolonged, and it does not seem to have been in Mr. Ruder's case. That their coarsening was natal and not through inheritance is shown first by the fact that their grain coarseness was out of all proportion to their relatively low temperatures and short periods, and hence was very far in excess of the grain size which the mother austenite must have had, and second and more cogently by the fact that the shape of these coarsened grains was evidently determined by the temperature distribution which existed during and immediately after the Ar3 transformation, that during the passage from the gamma to the non-gamma state.

Jan 9, 1917

By Julian Kennedy

THINKING that it may prove of interest to the Institute, 1 have prepared a short; account of the blowing in and subsequent working of the "A" furnace of the Edgar Thomson Steel Works. This furnace was built for the purpose of making spiegel, but has been started and is now running on Bessemer iron. The shape and size of the furnace are shown in the accompanying drawing. It will be seen that the section is formed of lines making very small angles with each other. In fact, an arc of a circle can be drawn, from the top to the tuyeres, which will nowhere deviate more than two inches from the lines given. In building, also, great pains were taken to gradually round the angles, so that the most careful observer, standing in the crucible and looking upward, could not tell at what points the slopes changed. It will also be seen that the widest part of the furnace is almost exactly midway between the bottom and the stock line. The flattest slope is maintained for 20 feet above the crucible, and is about 18 inch to the foot from the perpendicular. The furnace is lined with small brick throughout, and has six tuyeres four inches in diameter, which project seven inches inside of crucible. There are three Siemens-Cowper-Cochrane stoves, each 15 feet in diameter by 50 feet high. Blast is furnished by an upright engine with 32-inch steam cylinder, 84-inch air cylinder, and 48-inch stroke. The steam cylinder has balanced poppet valves, working horizontally. The steam valves are worked by a Porter link-movement in order to obtain a variable cut-off. The exhaust valves are worked by a separate eccentric. It is intended to attach a governor to the cut-off, but at present it is set by hand. The steam cylinder is

Jan 1, 1880

By J. H. Scaff, J. E. Kunzler

The measurement of the electrical, thermal, and magnetic properties of metals at low temperatures, primarily in the range of liquid helium below 4.2°K, is a powerful tool for investigating many of the fundamental properties of the metallic state. Such measurements also have many practical applications, particularly as an analytical tool. One example of the practical utility of such measurements is illustrated by a short study we have made of the low-temperature resistance of copper used in preparing varistors. Copper-oxide varistors are prepared by the thermal oxidation of copper. This results in the

Jan 1, 1959

By W. N. Logan

THE petroleum industry of Indiana made somewhat notable progress during the year 1923, considering the number of handicaps it encountered. The price of labor and materials continued to have an upward slant while the price of crude oil took a decidedly downward course. In spite of these adverse conditions, the quantity production will closely approximate that of 1922, when it passed the million-barrel mark. The progress of the industry in Indiana should be considered fairly satisfactory as long as the present production is maintained. In other words, if the loss of production from the waning old wells can be offset by the production from the new for a period of 10 or 15 years longer, the industry may have cause for congratulation. SUB-TRENTON INVESTIGATIONS In recent years a number of tests of strata lying below the Trenton limestone have been made in Indiana. Several of these tests were completed in 1923. Indications of oil were reported by drillers from several horizons below the Trenton. The most satisfactory of these came from the St. Peter sandstone lying immediately below the Trenton limestone, but no production has yet been obtained from any of the Sub-Trenton horizons. Glen Valley Wells.-Two wells in Marion County were drilled into the St. Peter sandstone, 1 mi. north of Glen Valley and 9 mi. south of Indianapolis. About 30 ft. of sand saturated with a dense asphaltic oil was found in the upper part of the St. Peter sandstone in one of the wells, which contained about 10 per cent. of the light oils, or more easily volatile constituents, and about 90 per cent. of a dark, dense, asphaltic residue. The oil resembled the residue of an asphaltic petroleum from which the more volatile oils had disappeared.

Jan 3, 1924

By B. W. Gandrud, R. G. Meara, O&apos

In 1034 the Southern Experiment Station of the U.S. Bureau of Mines in cooperation with the University of Alabama began an investigation of the availability of kyanite ores as a source of raw material for the manufacture of refractories. Under this program, gravity concentration and flotation tests have been made on two varieties of Georgia kyariite ore, mica schist and massive. Most of the attention has been directed to the mica schist ores, as they are more widely distributed and seem to offer greater economic possibilities than the massive ores. It is evident that the preparation of kyanite for use as a refractory material involves other considerations than the mere elimination of impurities. A concentration process that eliminates impurities satisfactorily may have to be followed by some additional treatment, since the final product must be of a coarseness and size ratio that will make it suitable for refractories manufacture. So far in the investigation at the Southern Experiment Station of the U.S. Bureau of Mines only the concentration problem has been considered, and this paper is intended as an interim report. Ores The schist ores contain 1 to 9 per cent of kyanite crystals embedded in mica and quartz, with smaller amounts of graphite, garnet and iron oxide and minor amounts of other heavy minerals. The garnet content varies from a trace to a few per cent. The minerals are easily released by moderate grinding. The size of the kyanite ranges from fine needles to crystals 1 1/2 in. long, 1/2 in. wide and 1/4 in. thick. The garnet, quartz and iron oxide grains have a smaller mean mesh than most of the kyanite. The maximum size of the garnet crystals corresponds to about 14 mesh and that of the sand grains is considerably less. Most of the iron oxide is still finer, for the minus 100-mesh size is greatly enriched in Fe²O3. The massive ore consists of radiating masses of kyanite interlocked with quartz, mica, corundum and small amounts of other heavy minerals.

Jan 1, 1938

By John C. Holtz

Hostility is a characteristic of the environment in underground mines. Nature opposes man's efforts to remove mineral deposits, and this condition is recognized when mining is described as winning minerals from the earth. Evidence of this conflict is the action of natural forces to close excavated passageways. In many mines, this behavior of the surrounding environment is an ever-present and ever-changing problem despite much research and empirical study. Geological conditions change abruptly and may result in rock bursts, the inrush of water, or variations in rock hardness. Although aspects of these problems will become intensified as the rate of mining increases, they are not considered in this discussion. Emphasis herein will be on the changes in the atmospheric environment. Men underground work in an ever-changing, alien, ambient atmosphere. Many conditions are encountered that will affect their health and safety unless properly controlled. Potentially explosive gases are released from minerals as they are mined or enter from the surrounding earth. Some mining methods generate noxious gases. Natural processes and diesel equipment can steal life-sustaining oxygen. Airborne dust may cause lung diseases when breathed by miners in excessive amounts and by affecting visibility, introduce safety hazards. Deep mines pose heat problems that may be aggravated by high-speed mining. The deleterious effects caused by these changes, and their mitigation, are subjects of this discussion. THE UNDERGROUND ATMOSPHERE Health and safety problems from changes in the underground atmosphere have been apparent since the beginning of mining. Alleviation of these problems has been by ventilation with normal air from the earth's surface that flushes away the vitiated mine atmosphere. The objective is to provide atmospheric conditions essentially similar to those that man is accustomed to on the surface.

Jan 1, 1970

By M. E. Volin, D. W. Fuerstenau, A. L. Mular

This paper presents the results of an investigation of the effect of feed size on the integral rate at which feed material is dry ground in a laboratory rod mill. The data are interpreted in terms of the Gaudin-Meloy distribution equation. The equation, Mo — Mt/t = Aoxo r-1, is found to hold for feed sizes smaller than some critical size or for grinding times larger than some critical time. It is shown that a feed grindability is related to this critical size, which appears to be the transition between predominately impact and predominately attrition grinding. Detailed research on feed size effects in comminution has been rather limited. Gaudin1 ground single-sieve fractions of quartz for extended time periods (four hours) in a laboratory ball mill. His work, which was designed to study the nature of size distributions, showed that there is a critical feed size above which comminution occurs primarily by attrition. For his system, the critical size was about 2-mm when using 22-mm balls. In a more recent investigation2 single-sieve fractions of quartz were ground in a laboratory rod mill for constant time periods (15 min) to determine how feed size affects the grindability of the material. This work showed that grindability is essentially independent of feed size in the rod mill after this moderately long grinding period. To further clarify this observation, a study in which feed size and grinding times are varied over a fairly wide range, and particularly, a study of the dependence of the integral rate of grinding on feed size during the initial stages of rod milling is necessary. For an analysis of such data, it is desirable to use a parameter which is very sensitive to change during the initial grinding period when reduction ratios are

Jan 1, 1964

By Richard A. Brown

The direct precipitation of uranium with hydrogen peroxide has been known since 1877. Commercial use of the process began in the 1960s. During 1967 the US Bureau of Mines (USBM) assisted the Climax Uranium Co., Grand Junction, CO in the development of a uranyl peroxide precipitation process to control a molybdenum impurity problem (Shabbir and Tame, 1978). Atlas Minerals, Moab, UT has used hydrogen peroxide to control vanadium and sodium levels in uranium concentrates since 1969 (Caropresso and Badger, 1973). Recently, the use of hydrogen peroxide by the uranium industry has grown, particularly since the increased demand for uranium has led to the processing of low grade ores. Impurities present in low-grade ores can be concentrated with the uranium during milling and will substantially complicate the refining of uranium yellowcake concentrates. Consequently, commercial nuclear fuel processors have imposed stringent specifications and penalties to control these impurities. The ability to produce a pure uranium yellowcake can eliminate penalty or reprocessing costs. Hydrogen peroxide precipitation of uranium is specific and quantitative, producing a very high purity product. Although the hydrogen peroxide precipitation of uranium has, and continues to be used primarily as means of producing a high purity yellowcake, it has also become an important process due to the superior physical properties of the precipitate. Under normal operating conditions, the precipitate produced by the reaction of hydrogen peroxide and uranium is dense, easily filtered and dried. The final dry yellowcake is pure, high U308 assay product. Consequently, processing costs such as filtering, drying and/or calcining and drumming, can be reduced compared to ammonia, caustic or Mag-Ox precipitation.

Jan 1, 1982

By R. T. Rometti, C. A. Bossard

INTRODUCTION Whenever a new mining property is developed or a new concentrator is built, considerable time, money, and planning are invested for the exploration, engineering, and construction of the required facilities. Yet, when these facilities are ready for startup, all too often insufficient time, money, and planning are invested in this critical phase of the project. Failure to plan for this phase results in untimely personnel mobilization, insufficient operator training, and inadequately prepared budget estimates, which combine to create excessive costs, lack of communication, unclear responsibility divisions, unnecessary delays, and poor production levels. Insufficient or excessive leadership, due to unclear assignment of responsibility, results in irrevocable problems within the startup team. A carefully planned and budgeted startup phase can avoid many of these problems. SCHEDULING A key element in properly planning the startup phase lies within the area of scheduling. Once the schedule has been established, planning can be greatly simplified through the expansion of each specified item. The overall project schedule should specify the date when the startup and initial operating management team will be brought onto the project. This team should be mobilized at least two years prior to the anticipated startup date, to allow sufficient time to begin to plan, assemble the startup groups for the various areas of the plant, initiate a workable communications system, and implement the development of the training program. This team is responsible for the preparation of a startup schedule, which would detail the dates for all key items associated with this phase of the project. These key items would include training program development, personnel hiring dates, prestartup plant checkout, etc.

Jan 1, 1982

By John A. Mathews

During the prosecution of the aircraft-production program in 1917 and 1918, the writer visited many plants engaged in the manufacture of motors, planes and parts, in carrying out his duties as chairman of the Committee on Aircraft-engine Forgings. On several occasions, when the question of expansion was discussed, it was noted that there was confusion in the use of the terms: the true coefficient of expansion, a physical constant, and distortion in hardening. One engineer, referring to a steel shown in the accompanying table, stated that he could not consider it for crankshafts because of its excessive coefficient of expansion, while another steel, also Iisted in the table, was said to be especially good because it had no coefficient of expansion, since it came out of the oil bath perfectly straight. Many years ago one of our employees designed a new oil furnace; when asked what became of the products of combustion, he replied: "There ain't any, we burn them all up." While the coefficient of expansion is not without its effect in volume changes in hardened steel, it is not a determining factor in the matter of distortion and going out of shape. Irregular heating, uneven furnace bottoms, and carelessness in withdrawing the part from the furnace, as well as the manner in which the part enters the quenching bath are of greater moment. Generally speaking, also, steels of relatively low hardening temperature will distort less than those requiring higher hardening heats. The coefficient of expansion must be considered in engineering design most frequently when different metals or alloys are used in the same construction. For example, the difference of expansion between a steel crankshaft and an aluminum crank case might be of real importance and a steel with no coefficient of expansion would be much less desirable than one with the normal coefficient. About 15 years ago, the writer made many determinations of the coefficient of expansion at low temperature ranges, usually between 20' and 100" C. Among the materials tested were: Pure forged electrolytic iron, 11.73 parts per million for l° C.; cast aluminum (99.93 per cent. AI.),

Jan 1, 1922

Dubbed "Freeport's Mission Impossible" by the trade press, the company's Ertsberg mine in West Irian nevertheless shipped its first concentrates in December 1972, ahead of schedule. This is a new and great chapter in the history of Freeport Minerals Co. and its contractors. Exploration and construction were only possible by moving equipment and supplies by helicopters. This work was carried out by Petroleum Helicopters, Inc., of Lafayette, La. At the peak of operations six machines were in service manned by 11 pilots and supported by 10 mechanics. During the month of August, with work in full swing 1,604 tons were moved, including 3 DC-6 tractors requiring 18 trips each; flying hours for the month were 636.

Jan 1, 1973

By Dewitt T. Ring

Oil development in 1934 has been largely restricted to drilling offset and lease requirement wells. Practically no effort has been made to discover new fields, chiefly because of price structure and proration allowance. A summary of developments during 1934 of necessity is brief. No state agency is maintained for the collection of data. The State Bureau of Mines issues permits for drilling and inspects the plugging of wells in coal-bearing measures only. Therefore data are not in existence with which to compile tables similar to those in other papers of this symposium. Forty-seven counties in the state produce oil, productive depths ranging from 100 to 5300 ft. Approximately 35 different formations in Ohio have produced either oil or gas. These reservoir rocks occur through a stratigraphic interval ranging in age from the shallow Goose Run sand of the Upper Pennsylvanian in Washington County to the St. Peter sand of Lower Ordovician in Seneca County. However, 75 per cent of these formations are unimportant from the standpoint of real production. Most of the oil and gas in Ohio has been produced from the Clinton, Oriskany, Berea and Big Injun sands and the Trenton Lime. Of these, the Clinton is first and Berea second in importance. Fields The oil and gas-producing territory of the state can be grouped into five fields or districts, made up of a series of "pools" usually separated by nonproductive areas, and is in no sense a belt of continuous production. Trenton Field of northwestern Ohio, is scattered through 15 counties. Development began in 1885. This field reached its peak in 1896 with a production of 20,575,138 bbl. for the year. For 1934, production had declined to 990,000 bbl. The oil is classified as Lima grade. Clinton Field extends from the Ohio River in Lawrence County to Lake Erie in Lorain, Cuyahoga and Ashtabula counties. First Clinton-

Jan 1, 1935

By Lyman H. Hart

Some of the significant facts that will affect the supply and demand for metals during the next few decades are given in this presentation. This is important because the only hope for intelligent guidance of the national destiny depends upon presenting a consistent and accurate picture of basic problems. The metals problems now fomenting are only slightly less important than those precipitating the energy crisis. Admittedly, it is difficult to generate serious thinking on this subject when the world is enjoying easy access to all metals at modest prices. This is possible because of the current world capacity to overproduce, and United States credit standing, at least up to now, has permitted buying freely on world markets. Although both these vital conditions are subject to change, there is little doubt that if the U.S. financial house is kept in order, we can muddle along for a while on a generally expanding, metalbased economy. But should our credit standing be permitted to collapse, or should there be a tightening of world supplies of metals, the nation would immediately find itself in trouble. Unfortunately, clear signals indicate that both of these conditions are threatening.

Jan 4, 1973

By G. G. Gunther, C. L. Boeke

THE zinc deleading processes at the Parral and Santa Barbara mills are described separately to provide a basis for comparison. Although the two procedures are fundamentally alike, there are some differences in application to meet specific conditions. The Asarco mill at Parral in the State of Chihuahua is a flotation plant treating 1450 metric tons per day of complex sulphide copper-lead-zinc ores. In general, the procedure used for selective separation of the minerals into a copper, a lead, and a zinc concentrate follows the usual practice. First, a bulk copper-lead concentrate is floated and then separated into a final copper and a final lead concentrate by the sulphurous acid process. A small tonnage of high grade gravity lead concentrate is tabled from the bulk copper-lead cleaner tailing before it is reground so as to avoid undesirable over-grinding and sliming of this portion of the lead mineral. Next, a zinc concentrate is floated from the lead rougher tailing and, as described later, is separated into a final lead product and a final zinc concentrate. Finally, the zinc rougher tailing receives a strong scavenger float to remove all recoverable middling values for regrinding and return to the flotation circuits. The slime is separated from the scavenger flotation product, and only the sand portion goes to the regrind section. The minerals in the separated slime are extremely resistant to all methods of selective separation and pose one of the major problems awaiting solution. Nevertheless, the slime shows a profit when mixed with either the lead or the zinc concentrate, except when metal prices are very low, so it is accepted as a final product for lack of a more profitable method of handling it. In contrast, the minerals in the reground sands of the

Jan 1, 1953

By Michael J. Fiannnaca, Michael M. Easdon

Disseminated epithermal gold metallization occurs within a breccia unit interpreted to be a submarine debris flow. Gold is associated with oxidized pyrite, fluorite, and jasperoidal silica. A minimum of 8 Mt (9 million st) of open-pittable mining reserves will be cyanide heap leached as run-of-mine ore at a rate of 0.9 Mt (1.0 million stpy 1. Careful evaluation of the combined results of successive sampling projects has established the pit plan, minable reserves, and process metallurgy of the operation. The sampling procedure utilized for a given test depended upon geological interpretation as well as the procedures, successes, and failures of previous tests. This paper summarizes the sampling and testing procedures of the development effort in light of the project goals and attendant problems in achieving them.

Jan 1, 1985

Greater automation of facilities is probably the best hope of the mining industry in its efforts to surmount continually rising labor costs. Underground mining, with its inherently low unit labor output, is especially vulnerable to rising costs, and here maximum automation is becoming increasingly important. One area of such operations that has been receiving a great deal of investigation is that of ore haulage and hoisting, two steps that often account for 10-35% of underground operating costs. Innovations and experimentation by mining firms and manufacturers over the past few years have resulted in larger, faster and more efficient tramming and hoisting equipment, but the White Pine Copper Co., at its operation in the Upper Peninsula of Michigan, is preparing to start up an entirely new concept in haulage later this summer. Known as the Dashaveyor System, it consists of individually powered modules (cars) that run on tracks inside a rectangular tube or on an open trackway at predetermined speeds up to 50 mph. At White Pine the Dashaveyor will be used to carry ore (crushed underground to -10 in.) from the mine to the concentrator. Dr. James Boyd, president of Copper Range Co., which is a 25% shareholder in The Dashaveyor Co., has indicated that if the Dashaveyor meets the expectations for surface operation, it will also be used underground for ore transport in place of the several miles of conveyor belts currently in use (Business Week, July 29, 1967).

Jan 7, 1968

By John P. Ashby

Mine production blasting is a process of destruction of rock masses in order that ore may be extracted. Many open pit operations are faced with the apparently conflicting requirements of providing large quantities of fragmented rock for the processing plant and of minimizing the damage inflicted upon the surrounding pit slopes. A reasonable compromise between these two conflicting demands may often be found by means of simple engineering of production blasts. Many operations tend to rely too heavily upon traditional wall control techniques to alleviate a problem already created by the production blasts. Various production trends including use of larger blastholes and patterns have tended to aggravate the situation. These practices only serve to emphasize the need for engineered improvements. Central to blasting engineering is the process of systematic trial and evaluation. Changes to the blasting system should be made singly, starting with the simplest. This paper discusses simple changes involving drill pattern control, effective use of blastholes and explosives, adequate delaying including use of down-the-hole sequential techniques, effective utilization of free faces, and avoidance of "choked" situations. By directing explosive effort where it is needed, such changes generally result in a significant improvement of slope conditions and of production blasting cost and performance.

Jan 1, 1983