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By B. Denby

Paper presented at a meeting on: Artificial intelligence in the minerals sector, held in Nottingham, UK, 20 April 1993. The design and scheduling of open pit operations are consistent problems encountered by the surface mining industry. Numerous techniques and algorithms have been developed to assist the mining engineer in the creation of optimum development strategies. Virtually all the practical techniques that have been produced have concentrated on one of the aspects (limit definition or scheduling) at the expense of the other. It has long been recognised, however, that the two activities are intrinsically linked and thus solving either problem independently of the other can only ever produce sub-optimal results as a whole. This has been termed the "circular reasoning problem". It has also been recognised that, for all practical-sized situations, solving both problems simultaneously is virtually impossible using conventional techniques due to the massive size of the search space involved. A technique is presented which is based on a self-learning genetic algorithm, which provides a combined pit limit and extraction schedule simultaneously in order to maximise the NPV (net present value) of the extraction. The theory is developed in two-dimensions and a number of examples of its application are presented. It is proposed that this approach is a highly efficient, heuristic technique offering the potential to transcend the circular reasoning difficulties of separate pit limit and extraction scheduling systems. Extension of the technique into three-dimensions and its application to realistic problem sizes are discussed

Apr 1, 1994

By I. D. Nock, R. M. Parkin

Paper presented at a meeting on: Artificial intelligence in the minerals sector, held in Nottingham, UK, 20 April 1993 (original title: Knowledge-based condition monitoring of cone crushers). A large proportion of the electricity used by the quarrying industry is consumed in the comminution and sizing process. In most cases aggregate processing plants operate with minimum control features resulting in limited operational efficiency. Improved control is required to increase operational efficiency with concomitant savings associated with reduction in re-circulating load and improved resource utilisation. Development work has suggested that a combination of adaptive control and process condition monitoring could improve control of comminution plants. Many commercial process control and condition monitoring systems are available, but none were deemed suitable due to the domain specific characteristics of the application. An assessment of the particular characteristics of cone crushing concluded that the application was best suited to the use of small domain specific process control combined with bespoke condition monitoring. The processing power of the control system for the project is a function not of the academic requirement, but rather the economic and practical constraints imposed by the application. As a result of the constraints a high-end PC system has been designed in preference to a workstation. Within the research project work packages are sub-divided into novel wear sensor development, knowledge based control/condition monitoring and the investigation and mathematical modelling of the wear mechanisms inherent in cone crushing. Numerous strategies were considered to implement the control system outlined. The system currently under development is a modular design which utilises intelligent novel sensors to provide a variety of data inputs

Apr 1, 1994

By A. P. Gize, J. F. W. Bowles, D. J. Vaughan, S. J. Norris

Paper presented at the IAGOD international symposium on mineralization related to mafic and ultramafic rocks held in Orleans, France, 1-3 September 1993. Geological evidence from tropical laterites indicates clearly that platinum group metals are taken into solution and precipitated to form grains larger than those in the source rocks. Platinum and palladium move differentially in the surface environment, with Pt partitioning into soils and eluvial or alluvial deposits while Pd remains more mobile in natural waters. Natural organic acids, particularly humic acid, can interact with platinum-group elements and concentrate them even in areas where their content in rocks is very low. Experimental work has confirmed that Pt and Pd can be taken into solution by humic acid at room temperature and in geologically short time-spans. Solubility and deposition may be controlled by physicochemical conditions, reaction kinetics or an adsorption effect, or there may be two competing reactions, solubilisation assisted by organic matter and a kinetically slower metal precipitation

Apr 1, 1994

By P. J. Rowsell, M. D. Waller

Paper presented at a meeting on: Artificial intelligence in the minerals sector, held in Nottingham, UK, 20 April 1993. The applications of artificial intelligence systems in the upstream petroleum industry are reviewed. Particular emphasis is placed on current and potential applications in drilling engineering. Several recent advances in drilling technology have led to a large increase in the quality and volume of data available. This combined with the escalating cost, particularly of off-shore operations, is testing the traditional reliance on the skill and judgement of rig operators. AI systems offer enormous scope in enhancing and aiding the performance of these operations

Apr 1, 1994

By O. R. Eckstrand, M. Asif, P. L. Schwann, A. J. Naldrett, R. J. F. Scoates

Paper presented at the IAGOD international symposium on mineralisation related to mafic and ultramafic rocks, held in Orleans, France, 1-3 September 1993. PGE-bearing sulphide mineralisation is contained in the lower 600 m of the Upper Central Layered Zone of the intrusion. There are four regimes with distinctive crystallisation characteristics. PGE content is low, both in bulk rock and in terms of metal in 100% sulphides, in the sulphide-rich cumulates but increases sharply in the sulphide-poor cumulates at the base of regime 1. Increases in regime 2 have no such clear relationship with incoming cumulus sulphides. PGE contents are low throughout regime 3, but regime 4 has sulphides with high PGE content, decreasing rapidly upwards, at the base of many of its cyclic units. The observations are interpreted as indicating that sulphide saturation occurred in the middle of a cyclic unit in regime 1, after which fractional segregation of sulphide caused a systematic decrease in PGE content. The resulting contrast between 40 000 ppb PGE in sulphides below the mineralised zone and less than 1 000 ppb above is of practical importance in exploration for such zones. In regime 2 the magma chamber was open to fresh influxes and PGE content was not so sensitive to sulphide saturation. In many regime 4 units influxes of new magma caused immediate sulphide saturation and PGE depletion, so that PGE-rich cumulates do not underlie PGE-bearing sulphide zones. Theoretical analysis indicates that regime 1-type behaviour is likely to characterise intrusions below the level at which plagioclase has entered as a cumulus phase and regime 4-type behaviour above

Apr 1, 1994

By S. Henley

Paper presented at a meeting on: Artificial intelligence in the minerals sector, held in Nottingham, UK, 20 April 1993 (original title: The database: a pre-requisite for large-scale use of AI in mining). Artificial intelligence is a term which has been widely applied to different techniques including rule-based systems using inductive and deductive logic algorithms, neural networks, learning systems and genetic algorithms. In principle it should be applied to adaptive statistical techniques. Some of these applications have been coded in languages which are specifically suited to the novel requirements of AI but are not easy to integrate with more traditional computing methods. Efforts have been made to bridge the gaps, particularly with database management systems and such efforts at integration should provide the key to future success in the application of AI. A field which has been termed "knowledge engineering" cannot be credible as such if it fails to provide easy access to raw materials of "knowledge" i.e. the data residing in databases. In the mining industry there are a number of significant areas in which AI could usefully be applied throughout the industry, but its advance is slow because of the lack or inefficiency of such database links. Current development of object-oriented database systems for geology and mining holds out hope for such integration in the foreseeable future

Apr 1, 1994

By D. M. Evans, D. L. Buchanan

Paper presented at the IAGOD international symposium on mineralisation related to mafic and ultramafic rocks, held in Orleans, France, 1-3 September 1993. The Zinca area was chosen as a suitable location for an investigation of the weathering and secondary dispersion of platinum group metals from the Zone. It was concluded that platinum is immobile while within weathered rock, its mineral phases tending to alter from primary sulphides and tellurides to secondary Pt-Fe alloys. Palladium is variably mobile in weathered rock. In stream sediments Pt occurs mainly as small, dense, discrete particles, giving rise to a nugget effect, whereas Pd probably occurs as much finer particles or chemically adsorbed on to a suitable substrate. Pt shows a rapid decrease in sediments downstream from mineralisation, whereas Pd has a much slower downstream decay

Apr 1, 1994

By I. Gaballah

Decontamination of synthetic solutions of PbC12 containing 10, 100 and 1000 ppm of lead, using chemically treated barks had been studied. The percentage of !cad cations' removal from solutions depends upon the pH and the initial concentration. About 99 % of the initial lead content can be removed at pH of about 3.5, 5.5 and 6.5 for initial concentrations of 10, 100 and 1000 ppm respectively. The maximum retention capacity of the treated bark is about 83 mg of lead per gram of modified bark. Bark loaded with lead had been analyzed by Infra Red spectroscopy. It seems that lead reacts with hydroxyl groups of the phenolic constituents of the bark. On the other hand, the removal of a lead cation by the bark leads to the release of two H+. This seems to show that the removal of lead could be interpreted as an ion exchange with hydrogen belonging to the hydroxyl groups of the modified bark.

Jan 1, 1994

By J. E. Sallee

An experimental study has been conducted on the level of arsenic contamination in samples of zinc oxide when the zinc oxide is contacted with gas mixtures containing As4O6(g). This contamination has been determined as a function of A4O6 saturation pressure, temperature, zinc oxide sample surface area, impurities, and oxygen level in the gas mixture. The results indicated a rather clean separation can be achieved between condensed zinc oxide and gaseous arsenic oxide as long as attention is given to temperature control, and the final zinc oxide surface area. For a 300°C operation temperature and an AqOg saturation pressure of 0.38 TORR (or 0.05% As406 by volume), the contamination level is expected to be approximately 100 ppm. This suggests that arsenical dusts can be treated in the HRD flame reactor process and a reasonable purity zinc oxideproduct produced. The results also show no evidence of zinc arsenite or zinc arsenate formation.

Jan 1, 1994

By Deepak Gupta, R. Kageyamat, J. W. Evans

"In electromagnetic casting, a liquid metal pool is partly supported by electromagnetic forces resulting from the interaction between induced currents and an alternating magnetic field. Stability of the metal surface is of paramount importance if the cast ingot is to be free from surface defects. Prior work by Garnier and Moreau had suggested that the magnetic field has no influence on the surface stability, but a more complete analysis at Berkeley suggested that surface perturbations are destabilized by the magnetic field once a critical magnetic field is exceeded. More recently we have employed a modified version of the software SOLA to compute the behaviour of a melt surface in the presence of an alternating field. The computed results support the theoretical analysis in predicting an unstable surface. Experimental work is now in progress to examine the stability of a mercury pool in the presence of an alternating field. Introduction and Previous InvestigationsElectromagnetic casting (EMC) is a technique widely employed in the aluminum industry to produce ingot for subsequent rolling. It is a ""continuous"" casting technique (illustrated in Fig. 1) producing ingots several meters high (and perhaps 1m by 2m in horizontal dimensions) at a casting speed of one or two mm. per second. The technology has gained acceptance because the metal is solidified without contact with a mold. Consequently the surface finish of the ingot is usually smooth and the ingot can be fed directly to rolling without machining, the surface (""scalping""). Scalping is necessary with alternative technologies (e.g., DC casting) where a mold is used. Consequently any disturbances that result in surface imperfections of EMC ingot are a serious matter. One type of imperfection is waviness on the surface of the ingot; a line drawn along the crest of a wave would run horizontally around the ingot. This imperfection may be caused by waves on the surface of the metal pool. As the waves reach the solidification line at the periphery of the metal they cause alternate outward and inward bowing of the meniscus at that point with attendant small (but significant) changes in ingot width. Elimination of building vibrations and similar disturbances minimize the occurrence of these surface waves but it is interesting to speculate whether there are disturbances of the metal pool that arise from the electromagnetic forces supporting the liquid metal. These forces are generated by the interaction of currents induced in the melt and the magnetic field produced by the current imposed on the inductor surrounding the melt. The present investigation has been concerned with whether the alternating magnetic field destabilizes the melt surface."

Jan 1, 1994

By H. E. Frimmel

Abstract - Most of the gold in the Late Archean Witwatersrand Basin is of detrital origin but, in its present form, it is metamorphosed. The only relict detrital features preserved are the morpho­logical characteristics of some placer gold particles. Regional burial metamorphism in the shallower and deeper levels of the Witwatersrand Supergroup reached temperatures around 300°C and 350°C at pressures between 2 kbar and 3 kbar, respectively , estimated from phase relations, chlorite-chloritoid exchange thermometry and chlorite thermometry . Metamorphism of the gold involved compositional homogenization of individual gold particles and partial recrystallization. Various infiltration events caused the partial mobilization of the gold at slightly lower temperatures, between 240°C and 300°C. These infiltrations can be related to crustal extension during the deposition of massive carbonate sequences of the Transvaal Supergroup (around 2.5 Ga), and later to the emplacement of the Bushveld Complex, and to the Vredefort event around 2.0 Ga ago. The mobility of the gold was dependent on the sulfur fugacity prevailing in a particular horizon which, in turn, was deter­ mined by the amount of pyrite (and other sulfides) present in that horizon. With the sulfur fugacity being controlled by stratigraphy, low fluid:rock ratios in a pyrite-rich horizon were most conducive for the mobilization of the gold. Thus, long-range gold mobilization in the Witwatersrand Basin can be expected to be the exception rather than the rule.

Jan 1, 1994

By Moore A. J, Evans R

Blast vibration control and assessment techniques have been developed which supplement traditional charge mass scaling methods. The improved techniques, which can be used to predict air and ground vibration levels at the planning stage, and to assist in the control of blasting operations, have reduced the level of operating risk concerning blast vibration. In addition to such factors as charge mass, distance and blast vibration levels, these additional techniques take account of orientation of the blasting face, topographic shielding, wavefront reinforcement, and meteorological conditions. They have assisted in compliance with specified blast vibration levels for environmental licence and mining lease conditions, the reduction of blast vibration nuisance to residents in the area surrounding a mine, and control of building and rock structure response in adjacent areas on the mine lease area.

Jan 1, 1994

By P. T. Velu

Solubility of metal oxides in the molten salt electrblytes is an important parameter in the electrochemical processing of metals and alloys. The efficiency of an electrochemical process primarily depends on the quantity of metal oxide present in the electrolyte in the dissolved form and its thermodynamic properties. The activity of CeO2 was calculated using the free energy of fusion of CeO2,{ AG°m, CeO2. The AGOm,CeO2 }was deduced from the values of enthalpy, heat of fusion and melting point of Ce02. The activity coefficients of CeO2 as a function of temperature and melt composition were calculated. The thermodynamic data such as integral molar enthalpy, entropy and Gibbs energy of formation were calculated as a function of composition and temperature.

Jan 1, 1994

By X. Nie

A new one-step process was developed to completely eliminate iron and directly obtain pure Ni, Co, and Cu chloride catholyte from nickel rich matte by low temperature (400 0c) chlorination roasting of Ni, Co, and Cu with HCl and leaching with water (PH 7). The effects of roasting temperature, time, oxygen potential and HCI addition and leaching temperature, pH, H2S04 addition and residue sulphur on the recovery of metals and purity of leaching solution were investigated. More than 99 % of Ni and Co and 95 % of Cu in the matte was directly extracted into the solution while 99.995 % of Fe remained in the residue. The iron concentration in the leaching solution was less than 3.6 X 10-5 mol/L.

Jan 1, 1994

By J. W. A. Morris

To investigate the use of centrifugal fields in fused salt electrowinning cells, a high temperature rig has been designed, constructed and commissioned. Initially, the cell has been applied to the fused salt electrowinning of zinc. Current efficiencies of 93% have been obtained for inter electrode gaps as small as 8mm for 70mm diameter electrodes rotating at 100rpm. The construction of a semi-rigorous physical model has shown the potential exists to extend the use of centrifugal fields to the electrowinning of light metals.

Jan 1, 1994

By the courtesy of Metropolitana Milanese (Milan Underground), roost of the delegates visited on April 12, 1991 the tunnel of "PORTA VENEZIA" STATION of MILANO RAILWAY LINK. The "PORTA VENEZIA" STATION will be the most important in the link and it will he also the largest underground project of the whole railway transport network in Lomhardy. The particular conditions of the soil and the collocation of site in the center of Milano have required new technologies and the technical solution applied to this job is called "Cellular Arch Method" by its designer Prof. P. Lunardi. Our sincere thanks go to Prof. P. Lunardi and Eng. E.M. Pizzarotti of Rocksoil, Milano who have kindly furnished us a technical description of this method. Eng. Pizzarotti was the guide during the visit and gave all the technical explanations to the delegates. THE "VENEZIA" STATION IN THE 2PB SECTION OF THE RAILWAY LINK The excavation of cavities in loose ground, exceeding a certain dimension and at shallow depth, is not feasible using traditional methods: in fact it is not possible to consolidate the ground around the cavity in such a way that homogeneity and resistance is sufficiently guaranteed.

Jan 1, 1994

By L. Xu, R. Bhaskar

The trends in dust exposure levels and longwall production over the last 20 years were examined. The study was conducted for nine major underground coal mining states: Alabama, Colorado, Illinois, Kentucky, Ohio. Pennsylvania, Utah, Virginia and West Virginia. The dust exposure and shift production data were obtained from the Mine Safety and Health Administration (MSHA). Trends were identified and analyzed for the headgate, tailgate, jack setter and shearer operator positions. The relationships between average scam height and dust exposure levels as well as the percentage of dust samples exceeding the dust standard for the four occupations were examined. The concentration to production ratio, a better indicator of the success of dust control measures, was calculated for the 20-Year period. The data show that, in general, dust exposures over the last two decades hare decreased. However, it appears that much of the decrease was in states that had significantly high dust exposure levels (such as Alabama and Utah), while for states such as Virginia, West Virginia and Pennsylvania, the decrease was not as dramatic. Major reductions were made in the period starting in 1982, when a host of longwall dust control techniques was introduced. However, nearly 35% of jack setter and shearer operator dust exposures were still above 2 mg/m3 in 1990, with nearly 20% of tailgate operator exposures and 8% of headgate operator exposures being above the federal standard. The concentration/production ratio has shown a remarkable decrease since 1981. This indicates that long wall operators have been able to meet increased production as well as, to a large extent, control chest production at the face. An analysis of the relationship between average seam height and dust concentration for the years 1984 and 1990 shows that while in 1984, the dust concentration could be correlated to seam height, in 1990 the relationship was less definitive. This indicates that technological factors may be more important than seam height.

Jan 1, 1994

By Karan S. Keith, Haydn H. Murray

The sorptive and impervious nature of clay materials was recognized long before modem technology allowed us to understand the physiochemistry of clays. In Cyprus, around 5000 BC, sorbent clays were used for fulling woolen cloth. One of the earliest recorded uses of clays as an impervious liner was more than 3200 years ago in the construction of a bitumen-sand-gravel-clay liner built along the embankment of the Tigris River at Assur. Today one of the most common applications for clay minerals in the environmental industry is for use as impermeable barriers to fluid transport. Clay minerals are fine in particle size and thus have large surface areas, which, as a result of intermolecular forces and ionic substitutions, make them excellent materials for both ion exchange and ion sorption. Therefore it was logical to consider certain clay materials for applications in the environmental industry, where they can act as physical and chemical traps for potential contaminants. Certain bentonites have historically been used as sealants for fluids (Grim, 1962), and other clays have been used as sorbents for both water and oil (Haden, Jr., 1972). Prior to the 1980s, disposal of the nation's municipal, commercial, chemical, and nuclear wastes was largely indiscriminate and poorly regulated. This created environmental pollution problems, especially with respect to groundwater contamination. Promulgation of federal regulations like the Resource Conservation and Recovery Act (RCRA) and the Comprehensive Environmental Response, Compensation and Liability Act (CERCLA - commonly known as Superfund) have forced a more careful and costly approach to waste disposal. The US Environmental Protection Agency (EPA) is the government body charged with enforcing and ensuring compliance with federal regulations governing toxic waste production, storage, and disposal. Widespread application of geotechnology to the design and construction of waste containment systems and to pollution remediation has become necessary due to such laws and because of increasing use of the subsurface environment for the disposal of hazardous wastes. In the United States nearly 1.8 kg of trash is disposed of per person per day, which amounts to nearly 181 Mt per year. This amount is more than double the waste produced in 1960, and these numbers are expected to continue to increase. Canada produces approximately 1.68 kg of waste per person per day. The EPA estimates that in the United States 64% of our garbage is landfilled, 18% recycled, and 18% incinerated. Even with continued increases in recycling and incineration efforts, the EPA projects that the United States will still need 82% of today's landfill capacity in the year 2000. Data on the exact number of landfills in the United States and Canada is conflicting in part because of changing definitions of what constitutes a landfill and because of inadequate record- keeping by some states and provinces. An estimate of the number of municipal solid waste (MSW) landfills in the United States in 1990 to 1991 ranged from 4 462 to 10 467 with an average estimate of 6 600. In Canada the number of MSW landfills reported varied from 5 493 in a 1982 survey to 1 766 reported in a 1991 National Solid Wastes Management Association (NSWMA) survey (Repa and Sheets, 1992b). A properly operated MSW landfill on average requires 1 hectare of land per year per 25 000 people (Coates, 198 1). In addition to MSW facilities, there are also waste disposal facilities needed for hazardous waste and low level and high level radioactive waste. In 1983, approximately 266 Mt of hazardous waste was generated in the United States, almost 50% of this by industrial production. About 68% of the hazardous waste generated in the United States and Canada and almost 50% generated in Europe are still landfilled (Egger, 1987). In 1985, approximately 51 000 m3 of commercially produced low level radioactive waste was disposed of in radioactive waste disposal sites across the United States (Jungling and Greeves, 1989). By 1987, the US defense program had produced approximately 10 000 t of high level nuclear waste. In addition, there were approximately 14 000 t of spent fuel assemblies from commercial nuclear power plants in temporary storage; the amount is expected to nearly triple by the year 2000. Presently most commercial spent fuel assemblies are stored in water-filled pools at nuclear power plants. Defense waste is stored on federal reservations in surface and underground steel tanks (Anon., 1987). Under federal law nearly all waste disposal and containment sites are required to have a liner or barrier and a cover system design that meets federal- or state-approved hydraulic conductivity requirements for the type of waste that the site will receive. When approved materials, necessary for constructing the waste containment structure, are not available on site, one of the most economical ways to meet these requirements is through the use of clay, soil/clay, or clay/geotextile materials. In a 1991 survey by NSWMA of its members and other select private sector facilities, 81% of the surveyed landfills had some type of liner system. About 75% of these liners were clay materials (either recompacted or natural). The remaining 30% were using flexible membrane liners as part of a liner system. Clay liner materials are most commonly used in the South, Midwest, West-central, and South-central regions of the United States. About 93% of the landfill facilities had closure plans, and of these 91 % were using clay materials in some way for the final cover material (Repa and Sheets, 1992a). Waste barriers and containment structures take several basic forms, and they are used in a variety of different applications: 1) cutoff walls, 2) soil or soil/clay-admix liners, 3) geosynthetic bentonite-clay/geotextile membranes, 4) radioactive waste containment barriers, and 5) synthetic geomembranes. This chapter will discuss the first four of these categories. The field of synthetic geomembranes, although a related topic, is beyond the scope of

Jan 1, 1994

By A. D. Davis

The disposal of spent ore from cyanide heap-leach processing facilities is of concern to the mining industry, regulatory agencies, and the public. Disposal of several hundred million tons of additional spent ore is planned in the western United States during the next decade, with increased amounts likely if gold prices rise. In the past decade, more than fifteen million tons of spent ore have been disposed of in the Black Hills. South Dakota's off-loading criterion for cyanide has been set by the state's Department of Environment and Natural Resources at 0.5 parts per million (ppm) as weak acid dissociable (WAD) cyanide. Nitrate off-loading limits vary for each mine in the state, depending on ore type and other factors. Nitrate concentrations in leachate from spent ore depositories could be caused by conversion from other nitrogen-containing species. One likely source of nitrate is residual explosives from blasting of ore. Previous work on the combustion products of nitrogen explosives has shown incomplete 3xidation (Johansson and Persson, 1970). Another likely nitrate source is degradation of cyanide to ammonia, followed by oxidation to nitrite and nitrate.

Jan 1, 1994

By Andre Vien, D. H. Hendriks, D. Willet, B. C. Flintoff

"For many years the training of mill operators was an informal process which involved senior operators training junior operators on an as-needed basis. Recognizing the needs and benefits of better training some companies, and even some provinces through legislation, have moved to ensure that a formalized training program exists in the plants. These programs tend to focus on basic safety and operations. Much remains to be done. With the more rapid incorporation of new processing and information technologies, and the goal to keep labour costs to a minimum by doing more with less, operator training has become a critical issue. This paper briefly examines the evolution of training programs, provides some measure of their effectiveness, and explores some recent developments which could have a very significant impact on the industry.PreambleOne can draw an analogy between operator training and the mechanical support of production equipment. When we buy a piece of process equipment it is critical that the mechanical installation be done properly to ensure that the device will operate at peak performance on start-up. Once the equipment is running, some form of preventive maintenance is required to ensure continued efficient operation. The operators and the equipment are both elements of the processing system, yet the former do not seem to get the same ""start-up"" or ""operating"" support. Are they not seen as critical to efficient operation? Why is this so? What impact does it have? How can we improve?These are all very logical and important questions, although the answers are not nearly so obvious. In the mineral processing industry, progress in operator training over the past thirty years has been limited and quite variable. To address the perceived need for a more coherent and consistent approach, some provinces have moved to incorporate basic training requirements in their legislation. Some plants have gone a few steps further by building integrated training programs into their operating culture. One conclusion which can be easily reached is that there are no standards, and that the range of training activity is great. In other words, a flotation operator is not a flotation operator is not a flotation operator. Their knowledge and skills are very much a function of training and experience, which are clearly corporate and site specific."

Jan 1, 1994