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By J. J. Cilliers, J-A. Lamamy, J. N. Rasera, K. Hadler

Production of oxygen on the moon can be achieved by reduction of lunar soil. One such reduction technology, hydrogen reduction, favours a high proportion of ilmenite in the feedstock. Ilmenite is present in lunar soil as a minor mineral phase, but it can be upgraded using electrostatic separation. This study presents the results of a preliminary investigation into the operating parameters and sensitivities of a free-fall electrostatic mineral separator for lunar applications. Samples of ballotini and ilmenite as well as simple binary mixtures of the two were tribocharged on copper and passed through a uniform electrostatic field. The field is varied to change the electrostatic force acting on the particles. The proportion of material reporting to the positive electrode collectors, negative electrode collectors or the central collector was measured to determine the separation performance. The data confirmed that the charge transferred from the tribocharger to each species is in agreement with the triboelectric series; ballotini was found to charge positively on copper and ilmenite negatively. Particle-particle contacts were dominant, however, resulting in a somewhat symmetrical particle distribution in the collectors. These findings indicate that the copper tribocharger design requires optimisation in order to substantially increase particle-wall contacts. Four binary mixtures with feed grades of ilmenite ranging from 5% to 20% were prepared and tested. This study found that a higher ilmenite head grade resulted in a higher concentrate grade (26.3% from a head grade of 20%) with low recovery (3.4%). In contrast, the lower feed grade resulted in a low concentrate grade but higher recovery. The mass yield of ilmenite was 1.4 times greater for the highest-grade feed than for the lowest. A subsequent study into the reprocessing of middling fraction found a nearly constant relationship between cumulative grade and recovery. This is the first investigation into the effect of feed grade on the concentrate grade and recovery for lunar mineral processing. Keywords: Lunar resources, beneficiation, electrostatic, SRU, ISRU

Jan 1, 2020

By S. Burks

This paper develops the themes explored by the authors at the Fourth International Platinum Conference,. Optimization techniques can be used to significantly increase the value of mining businesses by enabling better long-term planning decisions. Open pit and underground mine design, mine scheduling, cut-off grade and blending, stockpiling, and the linking of these to flexible elements of the metallurgical recovery processes are all evaluated together. Transport or sale of intermediate products and the requirements of the product metal markets can also be considered. Experience shows that net present value (NPV) can potentially be increased by 5-35 per cent or more, usually even before the expenditure of significant amounts of project capital. The case studies presented include: > An existing operation with multiple open pits and PGM concentrators linked to offsite downstream processing facilities, and with infrastructure constraints for which the scheduling of current operations and the potential for expansion were investigated > An existing operation with an integrated portfolio of mines, concentrators, smelter, and refinery, for which the various possible sources of ore for processing were prioritized to match the downstream process plant constraints and the product markets > An underground operation in Zimbabwe for which the optimum mining width was calculated and expansion plans were evaluated > An underground mine with many separate mining sections, for which a revised schedule was developed aiming to keep the shaft system and processing plant at capacity with the highest net value material available at any time throughout the life of mine. In the concluding section of the paper, a few brief notes are included suggesting how the strategic recommendations from enterprise optimization studies may be implemented by the owner's team.

Jan 1, 2013

By J. Nell

An overview is given of the matte melting process used for the beneficiation of South African platinum group metal (PGM) ores. Most producers use six-electrode furnaces to melt the concentrate and Pierce Smith converters to oxidize excess iron sulphide from the furnace matte. Concentrates from two reef types (the so-called Merensky and UG-2 reefs) dominate the feedstock supply. Concentrate from the Merensky Reef is low in chromium and does not pose significant melting problems. Concentrates from the UG-2reef contain much higher levels of chromium, which results in the formation of chromium-rich spinels during melting. This is attributed to the low solubility of chromium in furnace slag under typical operating conditions (an oxygen partial pressure of 10-8?10-9bar at temperatures of 1550°C to 1600°C). During the converting process, care is needed to avoid excessively oxidizing conditions, which result in cobalt, nickel and copper losses to the slag. High nickel losses result in the formation of Fe2NiO4 (trevorite), which often forms solid solutions with FeCr2O4and Fe3O4. In future, the main challenge in the processing of South African PGM ores will be to cope with ever-increasing levels of chromium in the concentrate. A short-term solution to the problem would be to melt the concentrate under slightly reducing conditions to promote the formation of CrO, which is more soluble in the slag than Cr2O3.A longer-term solution to the problem would be to abandon the current matte-smelting process in favour of an alloy-based process, which would offer total flexibility with respect to the amount of chromium that can be tolerated in the feed. Keywords: Merensky, UG-2, furnace, slag, matte, converting, spinel, chromium

Jan 1, 2004

By S. Ngidi

Palabora Mining Company operates a low grade underground copper mine situated in the Limpopo Province, South Africa. Full production was first reached in May 2005 after a successful transition from an open pit operation to an underground block cave operation. The operation faces a number of technical and operational challenges, not the least being fragmentation of a competent rock mass and external dilution. The cave is subdivided into three main sectors being the east, the west and the central sectors. Caving was initiated from the weaker central sector, which has the majority of its drawpoints located directly under the open pit bottom currently filled with about 130 million tons of waste material from the pit wall failure incurred in 2004. About 48% of the ore reserve has to be extracted from the western sector, which has a much courser fragmentation compared to the other two sectors and only 25% from the central sector with the finest fragmentation. The main constraint during the ramp-up stage has been secondary breaking of drawpoint blockages. Ground-breaking secondary breaking and cave management initiatives and practices have made it possible for Palabora to realize and sustain high production rates.

Jan 1, 2007

By D. D. Munro

Finsch Mine is a kimberlite diamond mine located at Lime Acres in the Northern Cape Province of South Africa. The mine was founded in 1961 and started surface mining in 1964. Underground production commenced in 1990 using a modified blast-hole open stoping method for the mining of Blocks 1, 2 and 3. Block 4 is currently being mined as a block cave. The process of identifying and optimizing a method to mine the Block 5 orebody started in 1991, and in 2006 incline caving was identified as being technically feasible. This paper aims to document the process employed in developing this method by the Block 5 prefeasibility team as well as discuss the technical challenges encountered during this process. The paper commences with a history of Finsch Mine and highlights the complex geology and threat of sidewall failure that prompted the decision to use block caving as the mining method for Block 4. A literature study of mines that implemented mining methods upon which the incline cave was conceptualized is then presented. These practices were then used to form the basis for the designs on which the initial geotechnical modelling was done and built upon through an iterative process of modelling and design changes. The ventilation of the mining area, initial productivity simulation results, and the applicability of automation and comminution processes in the incline cave are also presented. The paper concludes with an investigation into some of the challenges of the mining method, and shows that that incline caving is a technical option available for further investigation in determining the optimal mining method to be employed at Block 5, Finsch Diamond Mine. Keywords massive mining, incline caving, geotechnical modelling.

Jul 1, 2013

By N. N. Malila, N. R. Shoko

The ever-increasing pressure on the profit margins of ferro-chrome producers and the gradual depletion of deposits of rich hard lumpy chrome ores calls for the ferrochrome industry to maximise the use of fine fractions of concentrates and friable chromite ores. Zimbabwe is endowed with huge deposits of refractory and friable ores that occur on and off the Great Dyke complex. The conventional metallurgical process of smelting of chromite ores in submerged arc furnaces is favoured by the use of refractory hard lumpy ores. The requirement to use all lumpy ore has been circumvented to a large extent at Zimbabwe Alloys. The use of briquetted chrome ore fines in the production of Ferrosilicon Chrome and High Carbon Ferrochrome has yielded positive results over a period in excess of twenty-five years. Of the three industrially used methods of agglomeration of chromite ores; sintering, pelletisation and briquetting, briquetting is preferred because the other two are associated with higher capital and operational cost. Zimbabwe Alloys has developed operational and technical expertise on the briquetting and utilisation of chromite ore fines and concentrates. Variations in the quality of available chromite ore fines imply that their amenability to briquetting is a dynamic problem. Appropriate briquetting parameters to guarantee quality briquettes are essential to the successful use of briquetted chromite ore fines. In developing a technology for briquetting of chromite ores, it is important not only to study the mineralogical and grain-size characteristics of the chromite ore fines but also to make an informed choice of the type and quantity of the binder and the conditions for producing a physically and chemically competent green and cured briquette. This paper discusses Zimbabwe Alloys' experience on the briquetting process and the advantages derived in the smelting of the briquetted chromite ore fines in comparison to the use of conventional lumpy chromite ore with respect to improvements in chromium recovery and as a consequence related efficiencies and unit cost of production.

Jan 1, 2004

By J. N. Van der Merwe

The data base of failed pillar cases as used by Salamon and Munro (1967) in their original analysis to determine the strength of coal pillars empirically, has been updated for this study. It is shown that the Vaal Basin and Klip River coal fields exhibit similar behaviour that differs from the failures in other areas, i.e. failure at high safety factors within a short period of time. Those collapse cases have been omitted from the new data base. Failures in the other areas that occurred after 1967 have been added. Using a technique to minimize the area of overlap between the populations of safety factors of failed and intact pillar cases, the new data base was re-analysed in conjunction with the original Salamon-Munro data base of intact pillar cases, from which the cases in the areas of weak coal were likewise eliminated. It was found that a linear formula reduced the overlap area by22%. The new formula predicts higher strength for pillars with a width-to-height ratio greater than approximately 2.0 to 3.0 and a lower strength for smaller pillars. It was also found that in order to obtain the same relative measure of stability as with the Salamon-Munro formula, the strength constant in the new formula should be within a range of 2.8 to 3.5 MPa. For most current South African coal mining conditions, using the new formula for pillar strength will result in leaving smaller pillars without sacrificing stability. The reason for this is that the Salamon-Munro formula under-estimated the strength of larger pillars and over-estimated the strength of smaller pillars. The new formula will thus result in improved reserve utilization without sacrificing stability.

Jan 1, 2003

The Centenary Distinguished Lecture was held on Thursday, 24th March, 1994 at the Convention Centre of the Sandton Sun, Johannesburg at 20:00. Herewith the proceedings that followed. P.R. Janisch: The South African Institute of Mining and Metalurgy began life one hundred years ago tonight, and eight years (almost to the day) after the 1886 discovery of gold, which has impacted so profoundly on the course of events in our country since then. The Early Years That discovery was a mater of fortune, but not in the sense of the conventional prospector's lucky strike. Canny explorers, such as the Strubens, had been around for some years and, if George Harrison had not stumbled over the Main Reef when he did, someone else would surely have done so within months. The element of luck was that the gold-bearing rocks of the Witwatersrand actually lay exposed to sight. We now know that they are something of the order of 2,5 billion years old. Rocks of that age are usually covered by younger formations. In fact, the bulk of the Witwatersrand Basin is covered by lava, dolomite, and Karoo measures. What, one wonders, would our history have been had the Karoo, which stops at the Vaal, extended no more than 60 kilometres further north. Dr H. Scot-Russell A piece of advice attributed to Paul Kruger, the who was President of the South African Republic one hundred years ago, was the following: 'Seek from the past that which is good, and build on it for the future'. It is advice that can be applied universally and, whether deliberately or not, it must have motivated my predecessors when this Institute celebrated its 40th, 50th, and 75th birthdays. Those milestones were each marked by retrospectives, as Peter Janisch has so ably presented tonight on our hundredth anniversary. The parallels do not end there. We find ourselves in times no less daunting than those our predecessors. Next month will see the birth of a new kind of South Africa; so did May 1902, May 1919, and May 1948.

Jan 1, 1994

By C. Nangolo

Mineral commodity prices comprise one of the key criteria in the selection of mining stocks. We contend that of the three principal elements of mineral commodity prices, spot price, forward price and long-term price, one has a greater impact on the share valuation processes used by investors. This research paper examines the extent to which each of these elements influences the valuation process. The intention is to provide investors in mining stocks with a greater understanding of how fluctuations of commodity prices over time affect the prices of the mining stocks they hold, or intend to sell or buy. Three mineral commodities, gold, silver, and copper, were used as case studies, since market data on these commodities is readily available in the public domain. Nine market indices covering all three mineral commodities were selected. These are based on clearly defined criteria with the intention of eliminating ambiguity and to test for correlation with the three sets of mineral commodity prices. Nine mining companies, which were not the primary drivers of the relevant indices employed in the study, were used to validate the results obtained from the indices in order to avoid duplication of the same correlation during cross-checking. Each commodity price was adjusted for operating costs. For each market index, an average operating cost was calculated from the companies comprising its basket, while each company?s annual operating costs were used for the stocks of the individual companies examined. The data was collected for the period January 2004 to October 2010. This period was further split up into three sub-periods to account for the Global Financial Crisis (GFC) period that started in mid-2008. We conclude that mining stock prices are correlated with mineral commodity prices, but with spot and forward prices exhibiting stronger correlations than long-term price. This finding should be useful for evaluation purposes. Where cash flow methodologies such as discounted cash flow or earnings per share are used to value ordinary shares and commodity prices are required to estimate future cash flows, the findings suggest that spot prices should be used as opposed to long-term prices. The work reported in this paper is part of a current MSc research study at the University of the Witwatersrand.

Jan 1, 2011

By P. S. Paul

Mine accidents/injuries are complex and generally characterized by several factors, from technical to social characteristics. In this paper, a sociotechnical model for work injury in mines was developed and tested through structural equation modelling with application to case study mines in India. In total 14 variables were considered in this study. Most of the variables are not directly quantifiable. Instruments were developed to quantify them through a questionnaire survey. Underground mineworkers were randomly selected for the survey. Responses of 300 participants were used for the analysis. The analysis was conducted in three parts. Firstly, high-low plots were constructed to explore the variations in responses to the questionnaires by the accident involved (AG) and non-involved (NAG) workers. Secondly, a t-test was conducted to see whether the responses were significantly different for the two groups or not. The chi-square results showed significant differences of responses among the two groups. Finally, how these difference scan cause accidents/injuries in mines was hypothesized and evaluated using structural equation modelling. The measurement model of the Linear Structural Relations (LISREL) program was used to identify the latent constructs of the sociotechnical model. The structural model of LISREL was used to estimate the interrelationships among the constructs. The case study results showed that there is a sequential interaction among the sociotechnical factors leading to accidents/injuries in mines. Work hazards induce more job stress in the workers while social support mitigates the same. Job stress and safety environment predict the workers? job involvement. A worker who is more job-involved exhibits better safety performance, which in turn reduces work injury. The safety environment is shown to have a direct mitigating effect on work-related injury. The findings of this study clearly revealed that job stress and safety environment are the two key factors influencing work-related injuries in mines that need to be addressed properly through effective safety programmes.

Jan 1, 2005

By H. W. Glen

In the hope of finding out what the readers of the SAIMM Journal want of our Journal, we sent out a questionnaire with the October 1979 issue. The 2500 copies of the questionnaire sent out elicited 228 responses, which represents a return of 8,8 per cent. The number of responses received from overseas was 24, i.e., approximately 10 per cent of the total. The following is an analysis of the responses received.

Jan 1, 1980

By E. Isokangas

A mine is essentially a series of operations, including drilling and blasting, crushing, milling, flotation, and leaching, that are interconnected and therefore interrelated, with the performance of one operation affecting the performance of another. Optimizing each stage separately without considering the whole system often causes potential economic benefits and energy savings to be missed. However, the PIO methodology is a thorough approach which considers these individual process activities within the context of the whole process. The basic principle is to optimize the process as a whole, rather than each process step in isolation from the others. Metso?s Process Technology and Innovation (PTI) group offers a global consulting service for the mining and construction industries. A significant amount of this consulting work involves process integration and optimization (PIO) studies. When conducting a PIO study, every aspect of the process is considered. In addition to drilling and blasting, transportation, handling and storage, crushing, screening, grinding, flotation, separation, and recovery, other aspects including equipment utilization and energy consumption and even greenhouse gas emissions are also included if necessary. In a PIO project, it is very important to understand what type of material is being processed at any point in time. That is, which domain or domains is the material part of? This is necessary in order to observe the effect of different ore sources (and the blending of sources) on concentrator performance. Linking the ore from the pit to the concentrator required the development of an ore tracking system. As a result, PTI developed a radio-frequency based material tracking system called SmartTag?. This system allows tracking of ore from its source through blasting, run-of-mine (ROM) pads, crushers, intermediate stockpiles, and finally into the concentrator. Using the SmartTag? system, definitive correlations can be made between the performance of the plant and the plant feed characteristics, including the domain from which the feed ore originated. Since its commercialization in 2007, SmartTag? has been used in the majority of PTI?s consulting projects and several permanent systems have been installed worldwide1. Successful applications of the SmartTag? system have encouraged development to allow the system to be used in a wider variety of plants, in particular plants with finer crushing and screening stages. This paper describes how the SmartTag? system is being utilized by PTI and the benefits being gained by its use in PIO projects, as well as presenting some case studies.

Jan 1, 2012

By M. D. Raganya

The Kriel Colliery is an Anglo Coal mine which is contracted with Eskom to produce No. 4 seam for Kriel power station. The mine previously found it uneconomical to mine No. 5 seam due to the low qualities and tonnages of the seam, both at the opencast and underground sections. An area has been encountered for the first time at Kriel Colliery opencast pit 5, where the tonnage and qualities of No. 5 seam warrant further investigation. The primary reason for the investi¬gation of No. 5 seam by Kriel Colliery is because of the advantage of the high selling price (R450/t) that the market is currently prepared to pay for the No. 5 seam. The aim of this project is to mine No. 5 seam economically without interrupting No. 4 seam mining operations. The problem is that the equipments that are currently being used at the mine belong to Eskom and are dedicated to mining No. 4 seam only, not No. 5 seam. Through geology investigation, it is found that the whole No. 5 seam (No. 5 seam upper and lower) has an average thickness of 1.8 m. It also contains a parting of carbonaceous shale which divides the seam into two parts. No. 5 seam upper contains less tonnage compared to No. 5 seam lower. The calorific value and ash content of No. 5 seam lower is far better than No. 5 seam upper, but would still require washing the coal. This makes No. 5 seam lower the preferred seam to mine because it meets the requirements of the customer which is Highveld Steel. It is a coincidence that the area containing No. 5 seam under investigation encounters high overburden problems. The problem of drilling to No. 4 seam was going to be encountered because the thickness of the overburden ranges from 35 to 39 m. The Gardner Denver at the mine can drill blastholes only to a depth of 34.5 m, meaning the full overburden will not be drilled at once. This means the mining of No. 5 seam will do favours for Eskom because the overburden thickness will be minimized. This then led to an agreement between Anglo Coal and Eskom to mine No. 5 seam because both companies benefit from the project. In order to identify a suitable mining method for No. 5 seam lower, literature studies took place. It is found that San Juan mine from the USA has similar geological features to Kriel Colliery's No. 5 seam. Through comparisons, it is found that truck and shovel mining would suit the geology of Kriel Colliery's No. 5 seam since San Juan mine is using it. The sequence of mining No. 5 seam lower allows for a clearance of two cuts between the truck and shovel operation and the dragline. The mining sequence of No. 5 and 4 seam will be in the order of top soil removal; soft overburden pre-stripping; pre-strip drilling; pre-strip hard overburden; No. 5 seam lower coaling; interburden drilling and blasting; interburden stripping and No. 4 seam coaling. Financial evaluation of the project shows that a contractor will charge Kriel Colliery (Anglo Coal) approximately R 102.2 million to mine No. 5 seam successfully. The sales of No. 5 seam lower will provide a profit of R99.4 million at a yield of 70% from the washing plant. The project is beneficial to both Eskom and Anglo Coal because Eskom will have eliminated the problem of pre-stripping and Anglo Coal will generate additional profit. Through investigation and analyses of the project, it is proven to be viable and should take place. This is after looking at the advantages that the project has for Anglo Coal and Eskom. Keywords No. 5 seam, truck and shovel mining, Kriel Colliery, No. 5 seam mining at Kriel Colliery opencast, Anglo Coal and Eskom, No. 5 seam upper and lower, top soil removal, soft overburden pre-stripping, pre-strip drilling, pre-strip hard overburden, No. 5 seam lower coaling, interburden drilling and blasting, interburden stripping, No. 4 seam coaling.

Jan 1, 2011

What is the role of The South African Institute of Mining and Metallurgy at a time when so much is developing and changing in South Africa? The minerals industry is represented through employers, employees, government, education, research, public views, and even pure political interests. The role of the Institute is to represent the mining and metallurgical profession. In this role the Institute has aligned itself with Associated Scientific and Technical Societies, the Council of Scientific Societies and the Engineering Association. The Institute is also active on the Engineering Council of South Africa.

Jan 1, 1996

By Manuel Rapiman, Ricardo Sepulveda

The feasibility study of Escondida Norte (ENorte), recommended a slope angle design for the Final Pit. But, according to the experience obtained with the slope adjacent to the West wall of ENorte, in which Compañia Minera Zaldívar (CMZ) gained in its phase 4, a slope of similar geotechnical characteristics will be exposed in the West Wall of Phase 1 (Premine) and of the Final Pit, with an interramp angle 53º and with very good stability results. In this regard, Minera Escondida Ltd. (MEL) performed a study of the slope angles for the phases mentioned and according to this delivered the results of this evaluation, the recommendations and/or the necessary conclusions in the design to ensure that the slopes are stable enough and may enable safe operational management of them.

Jan 1, 2006

"Chairman: Mr R. A. PLUMBRIDGE Rapporteur: Dr D. M. HAWKINSPapers:The relevance of computer methods to the economics of the mineral industry by R: A. PerlmanDynamic control of a mining enterprise by R. G. CoyleAn economic model of the mineral sands industry by G. P. A. HoweMr M. Splaine, in opening the discussion on Mr Perlman's paper, asked whether the model, as fitted by data up to 1963, predicted the rise in the price of copper in 1967, and whether the model could be used to capitalize on short-term price fluctuations.Answering the second question first, Mr Perlman said that the horizon used is six months to one year. In the very short term the activities of speculators obscured the effect of the fundamental econometric variables. This effect, however, was removed if one moved to a longer term, say, quarterly. In 1963 the model had predicted a price rise in 1964 and 1965 and a drop in price in 1966. The rise in 1967 had been caused by a strike, and imponderables such as large strikes were difficult to include in the model since they were unpredictable. Model simulation can be used to show the effect of strikes on price and the effect of small strikes is small.Mr B. R. van Rooyen said that because models are both calibrated and tested on historical data a bias was introduced which gave rise to an overoptimistic estimate of the accuracy of the forecasts. To this Mr Perlman replied that there seemed to be no alternative to the use of historical data for calibrating and testing models, and thus little hope of avoiding the bias. A second point made by Mr. van Rooyen was that manage¬ment tended to be suspicious of complex models and that frequently more heuristic models were sufficiently accurate and preferable for investment decisions. He added that if management were not involved in the model building the econometrician might easily go astray, Mr Perlman replied that symbiosis between data analysts and users of the model was essential and that the experience of the practitioner must be reflected in the model.Mr M. R. Fuller-Good remarked that a clear understanding of future price trends was essential for effective capital planning, and asked, first, how one went from the compiled data on supply and demand to the determination of their effect on price, record, whether necessary data, for example, capacities, could be obtained timeously, and, third, when strikes restricted supply, whether stockpiling by consumers induced large price fluctuations."

Jan 1, 2014

The Annual General Meeting of the Johannesburg Branch of The South African Institute of Mining and Metallurgy was held at the Johannesburg Country Club on Tuesday, 21st July, 1992. Big turnout at Lunchtime Lecture The re-introduction of Lunchtime Lectures by the Johannesburg Branch of the South African Institute of Mining and Metallurgy met with resounding success when more than 100 delegates packed the Standard Bank auditorium in Simmonds Street to hear Dr Zach de Beer, leader of the Democratic Party, give his views on the state of the nation.

Jan 1, 1992

By H. A. D. Kirsten

SYNOPSIS This paper describes simple calculations to evaluate the stability of hangingwall and footwall strata at the work¬ing face and in backfilled areas. It shows that the benefits of support provided by backfill can best be realized when the fill is placed as close to the face as possible. The main beneficial effects of fill are that it reduces the stope span, at the same time providing a damping effect on vibrations, and prevents the fall-out of blocks in filled areas, thus maintaining the competence of the strata.

Jan 1, 1988

By Brian Wyatt, Neil Webb, Marcel Roche, John Thirkettle

Recent developments in survey techniques and measuring equipment now allow for an accurate assessment of external coating condition and cathodic protection performance. These developments build on 20 years of experience of using Direct Current Voltage Gradient (DCVG) and Close Interval Potential Survey (CIPS) methods. The techniques use the latest advances in measurement systems coupled to a bespoke data processing system. The paper describes tests and trial surveys carried out on a hydrocarbon transmission pipeline in West Africa during 2005. The survey works described and conclusions drawn are from the data collected. Of particular interest are the apparent capacitance effects which are thought to occur under disbonded coating and the characteristics that these may show on the integrated CIPS and recorded DCVG profiles. This paper was originally presented at the Cefracor conference in Aix, France, in June 2006 The pipeline was originally installed on a phased basis between 1989 and 1994. The external coatings were three layer polyethylene factory coating and shrink sleeve field joint coating. An impressed current cathodic protection system was installed. The pipeline has subsequently been affected by disbondment of the coatings. It was a primary objective of the trials to attempt to identify such affected areas. In addition to a technically detailed account of the survey works undertaken and the results obtained the authors will consider the practical and commercial aspects of these surveys with input that provides a perspective from the specifier, pipeline surveyor, pipeline operations personnel and the pipeline owner. It is intended that the data presented will provide greater awareness of the benefits and limitations of the techniques used and their role for both stand-alone interpretation and the integration of the survey information with other inspection methods used for external corrosion assessment. The application of the described techniques is well developed and proven to locate and characterise through?coating defects and to provide a full audit of cathodic protection status. However, the possibility of the techniques being able to indicate disbonded coating is unproven and further tests and trials are planned which may allow a greater understanding of the electrical characteristics which are believed to be associated with disbonded coatings which may or may not be filled with an electrolyte. Further work is currently planned in West Africa, South Africa and Scotland in order to improve the understanding of this technique and to determine if the reported indications do actually represent a method of locating disbonded coatings. Keywords: External Coating, Cathodic Protection, DCVG, CIPS, corrosion assessment.

Jan 1, 2006

By K. Gharibi, A. Dehghani, S. Farrokhpay, M. Aghajanloo, M. Ostadrahimi

The effect of flotation operational parameters on froth stability and froth recovery was studied. Froth stability was measured using a special column. To determine the froth recovery, the froth height change model and froth height exponential model were used. It was found that since the interactions between the pulp and froth zones affect the time of froth formation, the exponential model is more suitable than the froth height change method for determining the froth recovery. The results showed that superficial air velocity and collector dosage have, respectively, the highest and lowest effect on the froth recovery, while froth recovery decreases sharply with increasing froth height.

Jan 1, 2021