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By A. L. Holley

The intention of this paper is not to discuss this important subject in all its bearings, but merely to point out why mechanical tests of steel, as ordinarily made, are not, alone, of any special value to engineers—certainly not to general mechanical engineers. The agents of the Barrow Hematite Steel Company, one of the largest and most successful Bessemer establishments in England, have recently distributed a report, made by Sir William Fairbairn,

By Allen McComas, Frank Chase, Phyllip Worley

Longwall mining has gained the reputation as being the safest extraction method in underground coal mines. However, one of the most difficult tasks associated with longwall mining is moving the face once a panel is completed. Based on Mine Safety and Health Administration (MSHA) fatality reports since 1996, longwall face recovery operations have claimed the lives of 5 U.S. miners and have resulted in numerous injuries. Recovery operations can be hazardous because they involve moving large pieces of equipment in very confined spaces. They are also conducted in highly stressed ground conditions due to front abutment loads generated by panel extraction. Shield removal is the most hazardous operation during face recovery because miners are constantly exposed to the unpredictable gob edge. To protect the miners, one or more walking shields, cribbing and/or other supplemental roof and standing supports are typically employed as breaker line supports as each shield is removed. At the Harris No. 1 Mine in southern WV, mobile roof supports (MRS’s) have been used in lieu of traditional walking shields on 17 face moves since 1997. MRS’s are shield-like support units mounted on crawler tracks and are commonly used during room-and-pillar retreat mining operations. For longwall recovery, the two biggest advantages that MRS’s have over traditional walking shields are that they are remotely controlled and are highly maneuverable. MRS’s have contributed to safer shield recovery and shorter move times at the Harris No. 1 Mine. This paper will address both the safety and the operational issues associated with MRS usage during shield recovery. It will also discuss new developments, including the use of the inherently safer battery powered MRS’s, which have been recently certified by the Mine Safety and Health Administration.

By R. W. Nelson

Methods for determining permeability presented by W. D. Kruger3 in a paper entitled "Determining Areal Permeability Distribution by Calculation" have considerable merit. They can be expected to contribute significantly to analysis of flow in heterogeneous systems. Some rather subtle yet important conditions must be met, however, to assure that the computed permeabilities are correct. The conditions which insure a unique permeability distribution may have been overlooked in the method as proposed and presented in the subject paper. The subtlety of the special requirements may permit good agreement between computed and measured pressures in the reservoir; but the computed permeability may still be in error. The general theory and discussion of the requirements for a unique determination of the permeability distribution are presented elsewhere in more detail.7'8 Accordingly, only major features will be presented here in the notation of Kruger. GENERAL DESCRIPTION OF REQUIREMENTS A brief mention of the route to be followed in showing the special requirements may be helpful. The equation to be solved is a quasilinear, first-order, partial differential equation in the unknown permeability. This equation can be solved through an extension of Lagrange's method by reduction to a system of subsidiary ordinary differential equations. Through consideration of the identity of one of the Lagrange subsidiary differential equations with the stream function, a special interrelationship can be shown. The interrelationship has special significance with respect to the boundary condition. If the boundary function satisfies part of the subsidiary differential equation, no unique solution for the permeability distribution exists. In the physical problem this requirement for uniqueness indicates that the permeability measurements used as a boundary condition can not be along a stream tube. The boundary condition must be along a line, or series of lines, which completely traverse the region and pass through every stream tube.

By Richard Mainiero, Donald A. Hurd, James H. Rowland

In previous conferences the authors have reported on toxic fumes generated by the detonation of ANFO. The research reported here extends the earlier work to include an emulsion blasting agent and ANFO/emulsion blends. Explosive mixtures were shot in 4-inch Schedule 80 steel pipe in a chamber in the experimental mine at the Pittsburgh Research Laboratory (PRL). Following each shot, the fumes in the chamber were analyzed using on-line instrumentation. A major goal of the research was to gain a better understanding of the factors that lead to the generation of toxic fumes in blasting operations. Earlier studies have suggested that the high nitrogen dioxide and nitric oxide concentrations in product clouds might be the result of the poor confinement provided by relatively weak ground strata or the exposure of the explosive to ground water prior to shooting the shot. Various mixtures of ANFO and emulsion were detonated in schedule 80 steel pipe and galvanized sheet metal pipe to evaluate the effect of confinement. Explosive mixtures were also allowed to soak in water for less than one day, one week, one month, and two months to determine which explosive mixtures would be degraded and observe what effect this degradation had on fume production. Results indicated that the production of nitrogen dioxide increased with low confinement of the detonating explosive and with exposure of the explosive to water.

By Thomas M. Barczak

Roof support technology for longwall tailgates has changed dramatically during the past decade. Filling tailgates with conventional wood cribs is becoming the exception rather than the rule. Modern engineered timber support systems and a host of other alternative support products provide far greater capacity as well as stiffer response, thereby allowing the supports to resist roof movement with much less displacement than the soft wood cribbing used in the past. For these reasons, these products can provide superior roof control. In addition, the material handling requirements for support installation have now become a major consideration in the support design and selection process. Products such as conventional wood cribbing that require piece-meal construction of bulky, heavy components have diminished, while prop-type supports and products that can be installed with machinery and pumpable support technologies have grown in use resulting in fewer injuries to mine workers. Now, the opportunity exists to provide the safest, most cost effective support system, through engineering design rather than by trial and error and to optimize the use of the support system chosen. Yet this is rarely done. The key to accomplishing this task is to understand the interaction of the support system with the ground conditions at the installation site. A major focus of the paper is to conceptualize the support and interaction through the use of a ground reaction curve which relates the support resistance to the convergence of the longwall tailgate. The goal of any roof support design is to control the ground deformations and maintain the structural integrity of damaged or broken ground to the extent possible to provide a stable mine opening. In general, deformations will be a function of the stress environment and inherent strength of the surrounding rock mass. However, if the deformations are intimately linked to the stress changes such that the deformation can be controlled by the load resistance or reinforcement provided by a roof support system, then the loading behavior can be described as load-controlled. Conversely, if the deformation occurs irrespective of the installed support (assuming practical limitations), then the loading behavior is described as displacement-controlled. In this case, the deformation can be considered irresistible from a practical standpoint. In this context, the nature of the loading has significant consequences on the support design requirements. Finally, examples using the NIOSH Support Technology Optimization Program (STOP) to develop design criteria using ground reaction data from underground studies and ways to include uncontrolled convergence as part of the design criteria for standing roof supports will also be discussed.

By W. H. Schiffbauer

NIOSH has developed an active proximity warning system called HASARD (Hazardous Area Signaling and Ranging Device) for warning workers as they approach known dangerous areas around heavy mining equipment and other dangerous work zones. HASARD is composed of a transmitter and a receiver. The transmitter generates a 60-kHz magnetic field using one or more wire loop antennas. Each antenna is adjusted to establish a magnetic field pattern for each hazardous area. The receiver, worn by the worker, is a magnetic field strength meter. The received signal is compared against preset levels which are calibrated to identify levels of danger. The receiver outputs can include visual, audible, and vibratory indicators and it can also be made to disable machine functions. HASARD was field tested on a Joy 12 continuous miner, a Komatsu 210 M Haulpak, and on a highwall launch vehicle. Slight modifications were made for each application. HASARD provided warnings as designed and proved to be rugged enough to withstand the harshest of production environments.

By David Coleman

This paper presents a case history involving the installation of drilled in piles with rock sockets for the Bicycle and Pedestrian Path project located west of the Henry Hudson Parkway within the Riverside Park between 83rd Street and 91st Street at the Hudson River in New York, NY. The paper specifically addresses access and construction procedures for a marine installation when working in an urban and environmentally sensitive setting.

The February General Meeting of the Branch was held in the St. Helena Club at 8.00 p.m. on the 10th February, 1971. Mr G. Y. Nisbet (Chairman, O.F.S. Branch) was in the chair. There were also present: Seven Fellows: Messrs. N. A. Honnet, C. J. Isaac, J. M' Meyer, I. Thomas (Committee Members), J. Lorenzen, S. L. S. Swart and D. Waterman. Six Members: Messrs. R. Campbell, D. J. Couperthwaite, R. Cross, A. H. Edwards, C. G. J. Vermeulen and G. J. C. Young. Two Graduates: Messrs. J. McLuskie and M. H. Smith. Six Associates: Messrs. J. Dean, W. F. de Lange, J. S. Freer, A. Hooper, A. Paschalides and L. Vorster. One Student: Mr D. J. Hammond and nine visitors, a total attendance of thirty-two. Minutes As the minutes of the General Meeting held on the 17th November, 1970 had not yet been published in the Journal, the Chairman moved that the adoption and discussion thereof be deferred to the next General Meeting. This motion was adopted unanimously. Office-bearers The Chairman informed the meeting that this branch had received the resignation of Mr J. N. Saunders. Following his resignation the Committee elected the following office-bearers: Chairman - Mr G. Y. Nisbet Vice Chairman - Mr J. M. Meyer The Chairman also announced that Messrs. J. M. Meyer and G. J. C. Young had been co-opted onto the Committee. General Members were advised that arrangements had been made for the Cookhouse Tunnel visit towards the end of March. Talk by J. Freer The Chairman called on Mr J. Freer to deliver his talk on "Uranium Extraction, Processing and Conversion for Fuel Element Manufacture". The presentation of this talk, illustrated by sketches, proved very interesting and entertaining and was received with applause from all present. Mr I. Thomas proposed a vote of thanks to Mr Freer on behalf of all members of the O.F.S. Branch. After thanking Mr Freer for his talk and all present for their attendance, the Chairman declared the meeting closed at 9.30 p.m.

By Jasper Johnson

Taken in all its bearings there is, perhaps, no more interesting coal-field than that locally known and designated as " Wilmington," both on account of the superior qualities of its product as a household and steam fuel, when compared with other Illinois coal, and its geological position. The territory underlaid with coal, to which this name was originally given, embraced a very small area, including only the south half of sections 31 and 32 (township 33 north, range 9 east) in Wilmington township, and sections 5, 6, 7, 8, 17, 18, 19, 30, and 31, with occasional outliers in sections 3, 4, and 9, and, possibly, in sections 20, 28, 29, 30, and 32 (township 32 north, range 9 east) of Reed township, in Will County, comprising eleven square miles of workable coal within the known basin. Borings indicate the presence of coal on sections 30 and 33 in Wilmington

By J. H. Tonking, O. H. Kuschke

A description is given of the general geology, structure and minerals of economic significance of the Loolekop copper orebody at Phalaborwa. The open pit mining method is described with details of drilling, blasting, loading, hauling and primary crushing operations. A brief description is given of mine planning and its relationship to the control of the mining operation.

By Ed D. Thimons, Douglas E. Pollock, Andrew B. Cecala, Gregory J. Chekan, Jay F. Colinet, John A. Organiscak

Researchers at the Pittsburgh Research Laboratory (PRL) of the National Institute for Occupational Safety and Health (NIOSH) work to reduce respirable dust exposures in mining operations. One focus of this research is silica dust control for surface and underground operations in the metal/nonmetal mining industry. PRL researchers analyze dust sampling results from the Mine Safety and Health Administration (MSHA) to identify high-risk occupations to guide research efforts. Research is then conducted in an effort to improve existing technologies and/or develop new controls for reducing worker exposure to airborne silica dust. During the last few years, PRL researchers have conducted research related to the following goals: improving protection provided by enclosed cabs on mobile surface mining equipment, reducing dust generation from surface drills, reducing dust levels in iron ore operations, and developing a new method to clean dust from workers’ soiled clothes. A description of each of these controls and subsequent dust reductions quantified through site surveys will be provided.

By Vijia K. Karra

The goal of aggregates producing companies across the United States is to ensure their workers go home safely each day. At the National Institute for Occupational Safety and Health (NIOSH), researchers are pursuing this vision of safety and health through a fact-finding approach for reducing injury illness in various mineral sectors. Surveillance data from Mine Safety and Health Administration (MSHA) has been the source for such analyses. It helps to focus research efforts on key machinery, workers, and their tasks. The second installment of this two-part series follows last month's focus on crushed stone.

The President: We are very fortunate tonight to have with us Professor Franz Pawlek, Head of the Institute of Extractive Metallurgy for Non-Ferrous Metals of the Technical University, Berlin. In him we have a representative from one of the few mining and metallurgical universities in Western Germany, since I understand there are only three such universities, Berlin, Aachen and Kassel. The latter is represented by Mr Schmelling who has accompanied Professor Pawlek here tonight. The famous Freiberg University is on the other side of the Iron Curtain, and so is Breslau. Professor Pawlek was born in Vienna many, many years ago, and he obtained his diploma and then later his Doctor's Degree in metallurgy, in Vienna. For four years he worked for an Austrian company, and then moved to Berlin and joined the A.E.G. Company. After the war, he joined the Institute, which had been very heavily damaged, and he was closely associated with the rebuilding and re-equipping of the faculty of mining and metallurgy. He has written numerous papers, and I am sure we are going to have a most entertaining and interesting evening's talk. The President: Gentlemen, I am sure you would like me to thank Professor Pawlek for his talk tonight. My knowledge of pressure leaching is particularly small, limited to a friendship with Professor Frank Forward, to whose original work at Fort Saskatchewan reference has been made by Professor Pawlek. I enjoyed Professor Pawlek's talk, and as a mining engineer I managed to follow most of the argument, mainly because it was so lucidly presented, aided by these informative slides; but I never realised how complicated a problem this process can be. I am taking the liberty of asking Professor Howat to express our thanks from a more technical point of view. After Professor Howat has spoken, and possibly posed a few questions, I shall throw the meeting open in the hope that various people here will be prepared to ask questions. I see one or two gentlemen who have been over in Canada studying pressure leaching lately, and I hope they will ask questions, informally if they so wish. We will not record the full proceedings of this meeting tonight, in the hope that there will be more questions of a general nature. Thank you. Professor Howat: Mr President, Professor Pawlek, I am afraid I am up here under false pretences, because the matter that I thought I was asked to do was to propose a word of thanks, and I usually thought that a word of thanks was taken at the end,-however. It is always very intriguing to think that for all these thousands of years that have passed, pyrometallurgical processes have provided the main methods of extracting metals from their ores. Within the last 100 years, hydro metallurgical processes have become of increasing importance, and it is quite interesting to speculate that the largest single hydrometallurgical process is the one that we operate in this country,-which was devised by two distinguished countrymen of mine,-namely, McArthur and Forrest.

Ninth International Symposium TECHNIQUES FOR DECISION MAKING IN THE MINERAL INDUSTRY The Symposium which is to be held in Montreal during the week of 14th to 19th June, 1970, follows the Computer Symposium held in Salt Lake City in September, 1969. The purpose of the Symposium is to define the role of decision-making techniques within the mineral industry and to stimulate the development of specific applications. The subject of the Symposium-mathematics, operations research and computers as applied to the mineral industry-have permitted us to structure it in such a way that a complete picture of the mineral industry in its public policy, corporate, financial and technological environment emerges. Topics for the sessions are: . The Public Policy Environment;. The role of Decision Making Techniques in the Mining Company; . Information Storage and Retrieval; . Markets-Forecasting, Patterns and Strategies;. Search for Mineral Deposits;. Quantification of Geological Variables;. The Mine Development Decision; Production Systems;. Planning, Scheduling and Control Systems. The sessions will be directed energetically by chairmen who have been in continuous contact with the authors, providing them with information about related papers and sessions. This symposium is sponsored by the Canadian Institute of Mining and Metallurgy, McGill University and Ecole Polytechnique. Further information may be obtained from: The 9th International Symposium. W. H. Gauvin, General Chairman, J. Elbrond, Programme Chairman. Department of Mining Engineering, Ecole Poly technique, P.O. Box 501, Snowdon, Montreal 248, Quebec, Canada. ACHEMA 1970 The European meeting of Chemical Engineering and the Achema Congress 1970 is being held at Frankfurt/Maine, from 17th to 24th June, 1970. The programme includes some 110 plenary and specialised lectures, numerous technical films, excursions, and technical discussions in front of the exhibits which form the central feature of the Achema-Exhibition Congress. Further information may be obtained from the honorary representative of Achema in South Africa, Mr F. Schilling, P.O. Box 31274, Braamfontein, Johannesburg. NINTH COMMONWEALTH CONGRESS PROCEEDINGS Publication of the proceedings of the Ninth Commonwealth Mining and Metallurgical Congress, 1969, is being undertaken by the Institution of Mining and Metallurgy, London. There will be four volumes covering papers presented at the Congress together with the discussion and author's replies, and the addresses by Sir Duncan and Sir Ronald Prain. These will be available April-June 1970. Special pre-publication prices apply to orders received before 1st April, 1970. Order forms may be obtained from Secretary S.A.I.M.M., P.O. Box 1183, Johannesburg. 6th World Congress on the Prevention of Occupational Risks This Congress, dealing with industrial accidents and occupational diseases, will be held in Vienna from 10th to 15th May, 1971. Further information may be obtained from: VI Weltkongress für Unfallverhütung, Postfach 745, A-1015 Wien, ÖSTERREICH. International Vacuum Metallurgy Conference 1970 The Vacuum Metallurgy Division of the American Vacuum Society is organizing an international meeting that will be held at the Convention Center in Aanaheim, California from 15th to 19th June, 1970. Enquiries should be directed to the Arrangement's Chairman, L. M. Bianchi, TRW Inc., 23555 Euclid Avenue, Cleveland, Ohio 44117, Tel. No. (216) 383-2111. AIME WORLD LEAD-ZINC SYMPOSIUM This symposium is being held from 21st to 23rd October, 1970, in St. Louis, Missouri, U.S.A., in conjunction with the Fall Meeting of the Society of Mining Engineers, and a Rapid Excavation Conference. In addition to local field trips to smelter and refinery operations there will be a number of extended trips of six to eight days. Information may be obtained from: Mr. John C. Fox, Secretary, Society of Mining Engineers of AI.M.E., 354 East 47th Street, New York, N.Y. 10017, U.S.A. NEW SUBSCRIPTION RATE TO THE JOURNAL As from 1st JANUARY, 1970, the subscription rate for the Journal has been increased from R12.00 to R18.00 per annum, i.e. R1.50 per issue instead of R1.00. The discount to booksellers is 15 per cent. COURSEOF THE THEORYOF THE UNIT OPERATION OF GRINDING The South African Institute of Chemical Engineers is arranging for Prof. L. G. Austen to conduct a course on the above subject in September, 1970. Interested persons should contact Dr G. S. Harrison, S.A. Institution of Chemical Engineers, A.E. & C.I., 15 Anderson Street, Johannesburg. METRICATION The S.A. Bureau of Standards has published a document entitled "Metric Scales and Units for use in the Building and Construction Industry." It has been compiled by the Metrication Committee of the National Building and Construction Advisory Council and is the first of the series of informatory documents relating to the programme for the metrication of the Building Act Construction Industry. This document is obtainable from the South African Bureau of Standards, Private Bag 191, Pretoria at 50c per copy.

By C. O. Karacan, S. J. Schatzel, W. P. Diamond

In coal mining, longwall mining is a preferred method to maximize production by extracting large blocks of coal that have been outlined with a set of development entries. In U.S. mines, longwall panels are typically 305 m (1,000ft) wide (with a continual trend towards even wider panels), and usually over 3,050 m (10,000ft) in length. The increasing size of longwall panels, while helping to increase coal production, may also increase methane emissions due to the exposure of the mining environment to a larger area of fractured, gas-bearing strata. Thus, understanding the impact of increased panel widths on methane emissions, and designing gob gas ventholes and bleeder systems accordingly, can enhance the safety of the underground workforce by reducing their exposure to potentially explosive accumulations of methane/air mixtures. As part of its mine safety research program, NIOSH’s Pittsburgh Research Laboratory has initiated a reservoir modeling effort to better understand the interaction of the various geotechnical factors influencing gas flow within and to the underground longwall mining environment. A focus of this modeling effort has been 1) the prediction of the incremental amount of methane emissions to be expected due to increasing longwall panel widths, and 2) optimizing gob gas venthole completion practices to capture more of the gas in the subsided strata above longwall panels before it can enter the ventilation system of the underground workplace. The history matching phase of the study has been carried out on a 381-m (1,250ft) wide panel in the Pittsburgh Coalbed. Simulations have also been completed for a 442 m (1,450ft) wide panel to estimate the incremental increase in methane emissions and the performance of current gob gas venthole placement configurations. Additional venthole placement configurations were simulated to investigate options for optimizing methane capture from the subsided strata above the wider longwall panel.

By John A. Church

In the year 1874, when the price of pig-iron was still high, that staple product became the subject of discussion in the newspapers and among those philosophers who are determined to know the "reason why" for all things. The object of the inquiry was to find out Why iron did not fall in price as much as some other things had fallen. Indeed, there seemed to be an impression that iron and gold ought to move on nearly parallel lines, for the fact was constantly brought forward that iron then cost twice as much as it did before the war, though gold had returned to within twelve or fifteen per cent. of its former value. After some time the papers, by what seemed to be nearly unanimous consent, reached the conclusion that the maintenance of high prices was the work of the furnace proprietors, who, as the result of their shrewdness, were pocketing enormous profits. No proof was given to support this opinion, and the figures of cost and sale that were produced were of the most general kind, and used in the most vague manner. Visiting the president of the Thomas Iron Company, whose great works at Hokendaqua and Catasauqua, in Pennsylvania, are so well known as the largest and among the best conducted in America, I found him quite willing to meet the vague suspicions of the newspaper wiseacres, by a publication of the figures contained in the furnace-books of his company. These were accordingly given to the world through the Engineering and Mining Journal, and attracted the general attention they so well deserve. Though my own name became connected with these statistics, from the fact that I used them as the basis for the first attempt ever made to calcalate the furnace economy of an American works, I can, without the suspicion of egotism, say that the statistics referred to are the most valuable contribution the literature of American blast-furnace work has yet received, for their interest is independent of personal considerations, and due entirely to the fact that they represent faithfully the details of practice in one of the most prominent American works. They are an exact transcript of the furnace-books, and form a body of accurate information of the greatest value to the metullurgical student. Their importance is shown by the fact that though the theoretical conclusions which I based upon them have been several times attacked, not one of my critics has made the slightest contribution to

The Institute assembled in the library of the Sheffield Scientific School at 8 o'clock, Tuesday evening, February 23d. Prof. G. J. Brush greeted the members present on behalf of the Government of the Sheffield School in a few words of cordial welcome, to which President Raymond responded. Dr. Raymond then delivered an address on the History of the Relative Values of Gold and Silver. The Council presented, through the President, a list of names of persons duly proposed for members and associates, with recommendation for election. The following gentlemen were unanimously elected: *Prof. George J. Brush,. .. New Haven, Conn. *Prof. Oscar D. Allen,. .. New Haven, Conn. *C. Constable,.....New York City. *Leven S Goodrich,.... Oxmoor, Jefferson Co., Ala. *Charles J. Nourse,.... Columbia, Lancaster Co., Pa. *J. W. Mickley,.....Hockendauqua, Pa. *Hugh Alex. Crawford,. ..St. Louis, No. *General Ario Pardee,. .. Hazleton, Luzerne Co., Pa. N. W. Lord,.....New Pork City. J. Holme Maghee,.... New York City. *George E. B. Jackson,. .. Portland, Me. *Charles W. Watkis,.... Salt Lake City, Utah. *Charles E. Hall,....Philadelphia. *Charles J. Duval,.... San Francisco, Cal. Joseph Gorlinski,.... Salt Lake City, Utah. * Alfred Wartenweiler,. .. Salt Lake City, Utah. Wilmot J. Bowen,.... Salt Lake City, Utah. *Joseph Stokes,..... Trenton, N. J. Jason P. Brown,.... Boston, Mass. *William Davis Hartshorne,. . Bethlehem, Hunterdon Co., N. J. *Henry Williams,.... Spanish Bar, Clear Creek Co., Cot. *Robert Forsyth ,....Chicago, Ill. *S. T. Wellman,.....Cleveland, Ohio. *H. C. Walton,.....Chicago, 111. *Andrew Roy,.....Columbus, Ohio. *James H. Rittenhonse,. .. Providence, Pa.

By A. J. Teplitz, R. J. Goodwin

A new type water shut-off for use in air drilling has been developed. The method has been 99 to 100 per rent effective in several different formations of inter-ranular-type porosity. Since costs for materials, time and equipment used are relatively small, the process should extend economies of air drilling to many new areas. The treatment involves a new technique for forming a water-inroluble precipitate within the pores of a rock. Advantage it taken of the difference in mobility of a liquid and a gas in porous media to achieve the greatest volume of precipitate in a given pore. Reactants selected for the laboratory (2nd field tests were aluminum sulfate solution and gaseous ammonia. This process has been tested in both intergranular and fractured-type porosities. It has consistently shut-of between 99 and 100 per cent of the water flowing from formations having intergranular-type porosity and perrlreuhilities ranging from a few millidarcise to over a darcy The treatment is not particularly suitable for shutting-off water from fractured formations although plugging of the order of 50 per cent or greater has been achieved in all such applications. Among advantages of the treatment are: (I) no reaction waiting rime after a relatively short placement time, (2) a low mate-rials cost of about $3/f1 of hole treated, (3) use of common service-type equipment for treatment, and (4) no unusual requirements for mixing and placement. INTRODUCTION In rotary drilling with air or gas it has been possible to increase bit life by tenfold and more than double rate of penetration over corresponding performance when drilling with mud. These factors have amounted to as much as 22 per cent savings on total cost of drilling a well. However, these advantages are rapidly lost when water is encountered in an air- or gas-drilled well because water interferes with the removal of cuttings from the hole and also gives rise to other difficulties. In attempting to combat water troubles, operators have commonly resorted to such measures as mist drilling, treatment with cement or chemicals, converting to conventional mud drilling, or setting casing. In many cases these measures have either been costly or ineffective. In an effort to overcome this problem, studies were undertaken to develop an effective and economical water shut-off technique for use in formations possessing inter-granular-type porosity. Extensive laboratory experimentation finally led to a unique method for producing a water-insoluble precipitate within the pores of a sandstone. The unique part of the treatment is use of a liquid and a gas to form the precipitate, and in this case the reactants used were aluminum sulfate solution and gaseous ammonia. The reaction between these two materials is shown in the following equation. Al2 (SO1)3 - 18 H20 6NH2? saturated Water- Solution Cat 2A1(OH)3 . n H20 3(NH4)2SO • n H20 Solid Solid That is, a solid precipitate consisting of aluminum hydroxide and ammonium sulfate is formed when ammonia reacts with aqueous aluminum sulfate. The aluminum hydroxide is insoluble in water and the ammonium sulfate, though soluble, can only be removed from the formation pores by diffusion—an extremely slow process. Although the precipitate formed by the reaction is not particularly firm, great strength is not needed for a precipitate to bridge and plug intergran-ular-type porosity. A flow path in such a system is extremely tortuous and involves a great variety of pore

By Allan MacRae

Freeport-McMoRan Inc. operates an ISASMELTTM furnace for the smelting of copper concentrate at the Miami Smelter in Claypool, Arizona. In May 2017, the furnace was restarted after incorporating newly designed copper cooling elements from just above the tap hole to the underside of the roof. The objective of the improved cooling design was to extend campaign life by eliminating existing failure mechanisms with the wall refractory. In addition to upgraded bathline coolers and complete coverage of the gas offtake transition, or ‘kettle’, with plate coolers, a novel arrangement of coolers was installed in the remaining freeboard area. The shell required significant cutting and re-stiffening, as well as extensive modification of the cooling water piping. Based on performance observed to date, it is expected that smelter throughput will be increased due to extended ISASMELTTM refractory campaign life.