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By R Handfield, G Kary, Frieda Project

Recent exploration by the Cyprus Amax-Highlands Pacific-OMRD Joint Venture at the Frieda River project, PNG has demonstrated the extent of igneous phases, alteration and mineralisation, and the relationships between the various mineralisation styles in this major Cu-Au porphyry-epithermal system. The project area is in the obducted volcano-sedimentary section of the New Guinea mobile belt 78 km NE of Ok Tedi. It is between two major NNE dipping faults interpreted to have undergone thrusting then sinistral shear in the Late Miocene to Recent. The Frieda River Igneous Complex is a 15 km +7 km ovoid area with a central pod of basaltic andesite volcanics with cogenetic diorite to quartz diorite subvolcanic intrusions, and flanking clastic sediments. A series of late-stage, hornblende quartz diorite plugs ring the main igneous mass. The igneous rocks have a normal K calc-alkaline character with a very limited compositional variation. The intrusives are exposed on the eastern flank of the complex and have five mappable units and numerous defined phases. The southeastern quarter of the complex is host to a cluster of at least seven stockwork porphyry copper and skarn-hosted deposits within an area of 4.5 +3.5 km. The Horse-Ivaal and Koki deposits have identified resources totalling 804 mt @ 0.46 per cent Cu and 0.3 ppm Au, and the other deposits are in various stages of exploration. All these deposits are related to the Horse Microdiorite phase of the Complex and are outlined by a zone of potassic-propylitic-SCC alteration. Local overprinting argillic and advanced argillic alteration is related to a separate, post-porphyry mineralisation intrusive phase. The recent emphasis has been on the identification of higher-grade zones using ideas of structural control and specific intrusive-alteration-mineralisation relationships within the known resource areas. An elongate area 13 km x 4 km in the centre of the Complex has advanced argillic alteration in the volcanic rocks. This alteration zone hosts the Nena deposit (52.8 mt @ two per cent Cu and 0.7 ppm Au) and approximately 20 prospects of high sulphidation type. These deposits are distributed along two prominent NW-trending siliceous ridges interpreted as regional scale structures. Nena is a pod of vein and replacement sulphides hosted in a tectonically controlled multiphase breccia that overprints the advanced argillic alteration. The Nena deposit is 4 km from the nearest of the major porphyry occurrences. It is underlain by basemetal veins and minor porphyry mineralisation that are related to the Flimtem Trachyandesite intrusive phase. The recent search for additional Nena-type ore has focussed on the siliceous ridges using detailed structural and geochemical ore control criteria. Widespread, but poorly mineralised, basemetal-bearing carbonate and sulphate veins form a ring around the mineralised area. These veins have sericitic selvages, cut the porphyry mineralisation, but are cut by and locally underlie the silica-alunite phase of the advanced argillic alteration. The current model is that there are discrete intrusive phases responsible for each of major hydrothermal events at Frieda. These include from oldest to youngest:the Koki phase has no related alteration or mineralisation; the dominant Frieda phase has the hornfels, early skarn and minor magnetite-chalcopyrite mineralisation; the Horse phase has the bulk of porphyry copper and skarn-hosted mineralisation and minor basemetal veins; the peripheral Knob phase is barren; and the Flimtem phase has the high sulphidation epithermal deposits and minor porphyry and vein mineralisation. The intrusive phases span the interval 17 to 11.5 Ma and are co-magmatic. They represent discrete batches off the parent magma, rather than simple fractionation products.

Jan 1, 1999

By Dagbert M, Belisle J. M

Several packages for the estimation of porphyry type deposits exist and produce acceptable results. Recently, however, the need for really trying to obtain maximum information from drill holes has prompted the generation of geostatistical solutions to the problem of reserve calculation. It will be shown that an understanding of a few key points is necessary in order for these solutions (variogram analysis and kriging) to he really ptimal. The most important new fact to be ecognized in open pit ore reserve estimation is that block models do not give an accurate rediction of ore tonnage when a cut-off is pplied but often yield an overestimation of p to 25%. When checked against extensive roduction records, geostatistical methods provide a practical solution to this problem. t now seems that the model used here gives he best possible results. Inasmuch as all arge deposits present very similar geostatis- ical characteristics only a few days of work re necessary to produce a complete inventory f these. The techniques used will be demon- trated using examples from five deposits and pecial emphasis will be given to the accurate rediction of tonnages of ore and waste using he new "transfer function" technique of G.

Jan 1, 1977

By Chugh Y. P

A simplified, three-dimensional, time-dependent, mechanistic model of the overburden-coal seam-floor interaction has been developed and validated at two Illinois coal mines. The model based on the thin plate theory can involve any complex layout of mine workings, time-dependent sequence of extraction and, rheological properties of immediate floor strata. The model output data consist of spatially distributed surface subsidence and its slope and curvature, as well as load acting on pillars in one or more panels. A comparison of calculated and monitored surface subsidence or in- mine convergence measurements has proven the model's effectiveness for surface subsidence and load transfer Prediction.

Jan 1, 1992

By T E. Hayward, D H. English, S J. Smith

Gold mineralisation at Bendigo is exclusively associated with quartz reefs, commonly found within or near anticlinal fold hinges. The gold is typically coarse grained (0.5 mm to 5 mm), free milling and displays a complex, nuggetty distribution within the veins. This ore is highly amenable to gravity recovery processes. As the Bendigo operation is not permitted to treat whole ore by a cyanide leach/CIL circuit, the flow sheet is more complex than conventional gold recovery circuits. Primary gold recovery is from a gravity circuit closing the grinding circuit to a bulk gravity concentrate and from a flotation circuit treating cyclone overflow to a bulk float concentrate. The plant capacity is relatively low by current gold industry standards at 600 000 tpa. Re-establishing gold production at Bendigo has presented several challenging, and sometimes competing, issues in process design and operation. The mine, process plant, associated services and infrastructure are at Kangaroo Flat, a low density, semi-rural zone in the southern urbanisation of the Bendigo metropolitan area. One of the main processing challenges during the design was the competing comminution requirement to avoid over-grinding, which would flatten or smear the characteristic nugget gold and hinder effective gravity gold recovery, whilst also providing sufficiently well liberated particles that would respond well to flotation. Important, non-metallurgical challenges were to minimise impacts on the local community from noise, dust, air emissions, visual impact, water egress and off-site traffic.

Jan 1, 2007

THE choice of a pumping plant for the drainage of a mine is a matter of such importance that it is obvious that in a short paper it is impossible to go fully into the reasons governing the adoption of any particular type. The author, therefore, proposes to briefly discuss the methods.in vogue, and, as far as possible, to point out the advantages and disadvantages of the numerous systems. The probiem is of extreme importance to the mining engineer, and it appears that in the past sufficient thought has not been given to this branch, as shown by the numerous failures which are encountered.When water is met with in large quantities, the development of the mine depends upon the pumping plant to such a great extent that the most careful consideration should be given before deciding on any particular scheme for drainage. The pumpingplant in a mine should be looked. upon in the light of an insurance policy, and should be treated as such, care being taken that the premium is as low as possibl~, and to ensure this it is necessary that the most efficient plant be secured. Local conditions play such an important part ill the design of a plant that no hard and fast rules can be laid down. When the amount of water to be handled is small, and there is no possibility of any increase...

Jan 1, 1912

In this paper, a subtle, but important, difference has been drawn between responsibility and mandate. Responsibility has a connotation of financial involvement assigned to an organ- isation as a result of some action it takes, the ramifications of which can be ascribed directly to the organisation. In contrast mandate relates to the power and authority to act. The paper outlines the role of poli- ticians as community decision-makers and the need for Government policy to be flexible in an advanced industrial society so that decision- making options are kept open for as long as necessary. Further, broad community objectives need to be understood and defined so that plans and policies can be consistent. Co-ordination through communication at all levels, especially at the public administration interfaces and with the private sector,is essential for effective resource allocation and efficient implementation. The paper discusses several aspects of the infrastructure responsibility question and some considerations which might be viewed as important by the community decision-makers in considering what responsibility the "community" should accept in providing infrastructure.

Jan 1, 1974

By R Soong

The Wharekirauponga (WKP) epithermal gold-silver deposit is located about 10 km north of Waihi in the Hauraki Goldfield east of Auckland. WKP is notable for its sheeted to stockwork quartz veins hosted in rhyolitic rocks, that have attracted exploration interest as a low grade, bulk tonnage exploration target. Exploration between 1978 and 1993 included 23 diamond drill holes totalling 5505 m. The mineralisation occurs in a rhyolite dome complex (Miocene), consisting of flow-banded rhyolite and rhyolitic pyroclastic rocks, with minor andesite. Fifty four drill core samples were collected from six exploration drill holes and analysed by semiquantitative XRD techniques. Hydrothermal alteration of the rhyolitic and andesitic rocks has developed secondary mineral assemblages of quartz, adularia, albite, chlorite, illite, sericite, interlayered illite-smectite, carbonate, halloysite and pyrite. The main zone of mineralisation is characterised by quartzadularia alteration, which grades oiItward to quartz-clay (illite, local halloysite and/or interlayered illite-smectite) alteration. Propylitic alteration is present at the southern end of the drilled area of the prospect. Depth-related changes in mineralogy include a decrease in illite and appearance and increase in quantity of chlorite with increasing depth, and the localisation of halloysite and interlayered illite-smectite in the shallow parts of some drill holes.

Jan 1, 2001

By Sans H

The geostatistical Discrete Gaussian (DG) model is demonstrated to be capable of providing an effective means of implementing change of support for Enterprise-style mineralisation and thus providing reliable global recoverable resource estimates. At Enterprise, sample grade distribution proves to be highly positively skewed, therefore significant deskewing of the histogram and reduction of variance occurs when going from sample to block support. The DG model was experimentally tested in'the Southern Primary Zone (SPZ) at Enterprise, where high anisotropy ratios and pronounced short range structures are observed in variograms. The experimental test was run for a change of support for which the variance reduction was. approximately 60 per cent. This reduction is similar to that predicted by Krige's Relationship ('the volume-variance relationship') for the practical situation of a change of support from 5 m vertical blasthole samples to 3 m x 8 m x 5 m selective mining unit (SMU) blocks. The DG model was found to correctly predict the grade tonnage relationships for a wide range of cut off grades. The experimental test indicated that, given a representative histogram and variogram, the DG change of support provides a computationally efficient and practical means of reliably assessing global mineable resources at the early stages of a mining project. Further, it allows a range of selectivity strategies to be meaningfully and comparatively considered prior to mining.

Jan 1, 1995

By D Caley

During the response to the Moura No 4 disaster, use was made of the New South Wales Mines Rescue Service’s ‘Mineshield’ inertisation equipment. The equipment had to be transported from Newcastle, approximately 1400 kms, and the liquid nitrogen a similar distance. The time taken, and therefore availability of the liquid nitrogen, became a significant problem. Operational issues were also experienced during use. Typically the liquid nitrogen is converted to a gas (vaporised) before being injected into the mine. However, as the propane gas tanker used for the vapourising unit was delayed, an attempt was made to inject the liquid nitrogen directly down uncased boreholes. This proved unsuccessful.Following the Moura No 4 disaster and the Moura No 2 disaster, recommendations were made relating to having inertisation capacity for the Queensland coal mining industry. Today the Queensland industry has multiple options available for inertisation, including the high-volume GAG and smaller volume units such as boilers and membrane separation units. Although it ultimately aided re-entry into Moura No 4, most likely due to the issues associated with supply to Central Queensland, liquid nitrogen has not found favour within the Queensland industry as an inertisation tool.Coregas has commissioned an air separation plant in Mackay, improving the availability of liquid nitrogen to Central Queensland. Based on the availability of this nitrogen, recent sealing operations at Kestrel have trialled using liquid nitrogen and associated vapourising units. This paper details the practical application and findings of using liquid nitrogen during routine longwall panel sealing.CITATION:Caley, D, 2017. Using liquid nitrogen for the inertisation of goafs, in Proceedings Australian Mine Vent Conference 2017, pp 35–40 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 28, 2017

By J Ortiz

In almost all copper mining companies, mine planning is done considering different time frames, leading to long-term (life-of-mine) (LOM), medium-term (first three years) and short-term (first year, monthly, weekly, and up to daily plans). Shorter term plans are usually associated with more abundant information, hence models with lower uncertainty. However, they capture more of the variability found on the geological attributes. In long-term models, usually estimation methods tend to hide this variability, providing smoothed interpretations.Medium and long-term plans consider average values for the parameters and optimisation techniques are applied aimed at maximising the economic profit. Short-term plans, on the other hand, are made to comply with the medium-term promises, maximising the use of the available resources (equipment and processing capacities) and dealing with the variability not characterised in the previous planning stages. This generates an important gap between the short-term and the medium and long-term plans. A case study was made using an important oxide copper mine, where the variability found in the short-term plan has a large impact in the productive process, thus reducing the daily ore grade variability is an important goal. In this paper, this planning issue is addressed by creating medium-term mine plans using mixed integer programming which are compared using the output of a simulation of the daily extraction that is aimed at satisfying the daily constraints of the processing plant, the availability of mining equipment and the variability of ore grade. The result shows the expected gap between these mine planning processes, which suggests correcting some of the parameters used in future medium and long-term plans.

Sep 26, 2011

The centrifugal elevator invented and patented by the writer is designed for the purpose of conveying the tailings of a gold dredge to such a distance that it shall not impede the dredging opperations. Formerly this was usually accomplished by means of a belt of buckets travelling round a ladder set at an angle of about 30 degrees to the horizontal, but this meant heavy wear and tear on the travelling buckets and the tumblers actuating them. The centrifugal elevator throws the tailings through the air to the required height and distance and it is manifest that during their flight from the elevator to the heap there is absolutely no wear and tear, only the attraction of gravity and the resistance of the air has to be overcome. All then there is left to he considered is how to throw the stuff with the minimun of prower and wear on the elevator.The elevator consists of a cam-shaped steel casting with a disc of mild steel plate on either side: These side plates project a few inches beyond the tips of the beaters, in order to prevent odd stones from straying in an undesired direction; they serve also to prevent extra large stones from reaching the beaters, for they slide off the rims into the water.

Jan 1, 1904

Bakelite is fairly widely known as a suitable material for the mounting of ore specimens, concentrates and tailings for microscopical study, but has not as yet had extensive application. It is the most suitable mount for specimens which are to be held in the mechanical holder of a polishing machine, based on that described by J. W. Vanderbilt*, which is installed in the Geological Department of the Melbourne University.Bakelite products are prepared by subjecting bakelite powder to a temperature of about 1600 C. under a pressure of approximately two tons per square inch for a period of four minutes. The shape and size of the products are governed by the use of suitably constructed dies. When the concentrate or tailing is mixed with the bakelite powder, a briquette is produced which can be polished so that the opaque minerals in the sample can be examined microscopically in the same way as in a piece of solid ore. A simple machine for the construction of these briquettes has been described by Head and Slavin. It consists of a small four-pillar press in which the pressure is supplied by...

Jan 1, 1933

A calibration of the Frantz isodynamic magnetic separator relates the current in the electromagnet and the transverse slope of the chute to the specific susceptibility at which separation is being effected. In addition to providing a rapid measure of the specific susceptibility of minerals and composite grains, the calibration provides a guide to operation of the Frantz isodynamic separator for mineral separation, and to the nature of composite grains. The most sensitive magnetic separation is obtained by using the highest practicable current and transverse slope, and the lowest practicable longitudinal slope.INTRODUCTIONProbably all minerals have a magnetic susceptibility measurable by sensitive techniques. However, magnetic separation between minerals which have low but different specific susceptibilities, and which for many purposes are considered essentially non-magnetic, has only become practicable with the development of the Frantz isodynamic separator.The construction and principle of this highly sensitive separator has been described by S. G. Frantz as an appendix to a description by 'Gaudin and Spedden (1943) of its application to the separation of sulphides constituting mill products.Various publications (e.g. Hess, 1949, Hutton, 1952) refer to its use in separating the mineral constituents of rocks, ores, and unconsolidated sands.As used in this study the Frantz isodynamic separator consists of a vibrating chute mounted centrally between the pole pieces of an electromagnet (Fig. 1). This unit may be inclined in any direction by the universal mounting, and the electromagnet current is continuously adjustable from 0 to 1·5 amperes.

Jan 1, 1957

By R Simcock

Why Rehabilitate? Legislative Requirement Land rehabilitation is a condition of resource consents for mining. Clause 17 (1) of the Resource Management Act 1991 (duty to avoid, remedy, or mitigate adverse effects) provides the legislative basis for local authorities to impose resource consent conditions requiring land to be rehabilitated to approved uses during and after mining.

Jan 1, 1997

By D N. B Skinner, R L. Brathwaite, M S. Rattenbury

The Institute of Geological and Nuclear Sciences is undertaking a mineral resource assessment study of the Coromandel region, due for completion in July 2000. A key part of the study is the assembly of a geographic information system (GIS), a computerised tool for layering, analysing and presenting spatial information. The GIS is being assembled with ArcInfo/ArcView software and to date includes layers for a digital terrain model, an aeromagnetic map (open file mining company data), a geological map (from the QMAP project), areas of hydrothermal alteration, locations of mineral deposits (GERM database), stream sediment geochemical analyses (REGCHEM database), and a lineament map derived from satellite remote sensing data.

Jan 1, 1999

By B L. Dickson, E, M F. Lee, P A. Mikula

Computational techniques are needed to assist in the analysis and interpretation of the increasing amounts of geoscientific and mining related data and information that are routinely gathered at mine sites. New interpretation methods are needed to provide an integrated approach so as to establish relationships (cause and effect) or to be predictive about possible outcomes based on acquired data. Traditional multivariate statistical methods are often confused by variable relationships that are non-linear, data distributions that are non-normal, and by the data themselves that may contain missing values, text and both continuous and discontinuous numeric values. Modern data mining methods are available to understand the relationships within and between diverse data sets, and identify relationships or trends associated with processes, measurements and mine design parameters in mines. The self-organizing map (SOM) is a data mining approach with the advantage that all input data samples are represented as vectors in a data-space defined by the observations (variables). The SOM procedure is an exploratory analysis tool that highlights patterns and relationships. Results are internally derived, in an unsupervised fashion based on measures of vector similarity. Our SOM outputs are highly visual, which assists in understanding and illustrating the dataÆs structure and internal relationships. Two studies are presented. The first uses SOM to investigate the relationships between a range of measured and derived rock property parameters and their observed behaviours during mining. Our aim was to determine whether a SOM analysis would allow a better understanding of observed and predicted rock behaviours from their rock properties. The SOM analysis showed that there were indeed relationships between æbrittleÆ, æsugaryÆ, æslabbyÆ and æsqueezingÆ rock behaviours and a number of the input parameters. The computed SOM æstructureÆ was then used to assess the likely behaviour of unknown samples by assigning them into behavioural fields based on their measured and derived geotechnical responses. The second study was aimed at assessing whether a SOM analysis of microseismic data at the Kalgoorlie Consolidated Gold MineÆs (KCGM) Mt Charlotte mine can contribute towards understanding and potentially forecasting/minimising seismicity at the mine-design stage. The database comprised 40 sample æclustersÆ of microseismic parameters from the MS-RAP software package, which were derived from 2500 individual seismic events. The SOM analysis showed that some of the initial mining conditions are related to the seismic parameters. In each of the studies, the SOM procedures assisted in understanding the data and provided new insights. Because of its æordered vector quantisationÆ foundation, the SOM procedure is a substantial improvement over traditional statistical methods in three main areas:its ability to analyse data from disparate sources, including different data types; its ability to analyse sparse data sets with missing values; and its ability to analyse and visualise non-linear relationships within a data set.

Jan 1, 2006

By Ryan A, Dennis R, Dekker D, Ellis W, Sowerby B

An automated facility for non-destructive elemental analysis of mine samples has been developed and tested at Mount Isa in association with the CSIRO. The analysis is based on the prompt and delayed measurement of gamma radiation emitted by the sample during and after separate fast and thermal neutron irradiation. No sub-sampling or sample preparation is required and the analyser is operated by one person that would otherwise be splitting drill core in preparation for conventional analysis. The analyser has been calibrated to measure the following (precision in parenthesis): Ag (14 ppm), Pb (0.5 wt%), Zn (0.5 wt%), Cu (0.04 wt%), Fe (0.7 wt%), S (1.1 wt%), SiO2 (0.8 wt%), A1203 (0.07 wt%), Mn (0.05 wt%), specific gravity (0.02 g cmt). Crushed or whole drill core samples that range in size between 0.5 m and 1.8 m of equivalent BQ size drill core can be analysed at a rate of six samples per hour. If required, drill core samples can be re-packed in their original configuration for storage following analysis. Standard samples are measured every day to ensure operational stability. The analyser is controlled by a personal computer which prints the results and stores them along with the raw data on the computer hard disk. This paper reports the performance of the analyser during 1992 for routine analysis of drill core from the lead ore bodies of both Mount Isa and Hilton mines.

Jan 1, 1993

By J D. Tolley

The shift towards clean energy technologies is having a significant impact on the mining industry, with the demand for minerals such as copper, nickel, cobalt, lithium, manganese, and graphite increasing exponentially. To meet the goals of the Paris Agreement, mineral requirements for clean energy technologies would need to quadruple by 2040, and to achieve net-zero globally by 2050, mineral inputs in 2040 would need to be six times more than today. The most significant driver of mineral demand is electric vehicles (EVs) and battery storage, with lithium seeing the fastest growth, and copper demand doubling over the same period due to the expansion of electricity networks globally. The demand for these minerals is expected to rise significantly as investments in clean energy technologies continue to grow in the future. As the world moves towards a decarbonised economy, the minerals industry is under increasing pressure to reduce its environmental and social impacts and meet the increased demand for minerals. Mining companies are facing additional challenges due to the depletion of near-surface mineral deposits globally, with more mines transitioning from open pits to underground. The transition to underground mining requires the right strategy to economically access deeper mineable inventories and to keep up with future clean energy technology demands to achieve net-zero globally by 2050. One key way to achieve this is through decarbonisation using ‘green’ mining technologies such as replacing current primary diesel mining fleets with battery electric vehicles (BEVs). However, these measures through electrification overlook the bigger opportunity to maximise the socio-economic returns from the mine while also reducing the overall carbon footprint. Corporate cut-off grade policy is one of the most significant influencers on the total environmental and social impacts of the mining industry. The purpose of a corporate cut-off grade policy is to implement strategies aligned with achieving all the mining companies’ corporate goals, with decarbonisation targets becoming a primary driver for mining companies. Table 1 shows the evolution of cut-off theory with the increasing number of dimensions and driving inputs per iteration.

Aug 2, 2023

By Y Xie, D Willingham

Predictive maintenance (also known as ‘condition/health monitoring’) refers to the intelligent monitoring of equipment to avoid future failures. In contrast to conventional preventive maintenance, the maintenance schedule is not determined by a prescribed timeline; instead, it is determined by analytic algorithms, such as machine learning, using data collected from equipment sensors and/or via simulation.Predictive maintenance offers the following benefits for operators and equipment manufacturers:- reduces equipment downtime by identifying issues before failure, thereby enabling convenient scheduling of equipment service and extending equipment lifetime- determines the root cause of the failure, enabling appropriate service to be performed without utilising resources to determine a diagnosis- avoids the unnecessary costs of maintenance and unexpected failures- improves safety and product quality.Algorithms and data are critical to predictive maintenance success. Sensor data is first preprocessed using advanced statistical and signal processing techniques; it is then combined with predictive modelling techniques, such as machine learning, to estimate equipment health.Once tested, predictive maintenance algorithms may be used in an operational setting within an IT environment, such as a server or cloud. Alternatively, algorithms may be implemented in an embedded system directly on the equipment, allowing for faster response times and significantly reducing the amount of data sent over the network.CITATION:Willingham, D and Xie, Y, 2017. Predictive maintenance modelling for bearing-based equipment, in Proceedings Iron Ore 2017, pp 627–630 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 24, 2017

Fine Gravity Separation in the Reflux Classifier, Exploiting a High Shear Rate, Laminar Flow Mechanism The Reflux Classifier is used in the gravity separation of particles over a broad range of particle sizes. The device consists of a fluidised bed zone, with a system of parallel inclined channels above. The inclined channels provide a significant hydraulic advantage over conventional fluidised beds via the so-called Boycott Effect (Boycott, 1920). This paper describes a new advance in fine gravity separation based on the high shear rate and laminar flow profile that arises when closely spaced inclined channels are deployed. As reported recently (Galvin et al, 2009a), a powerful density based separation mechanism develops from this arrangement, suppressing the effects of particle size. In this paper we focus on two areas, firstly the application of the separator in the laboratory for batch fractionation of particles of varying size and density to determine the grade recovery curve and hence the liberation, and secondly the step change in separation performance achieved on a continuous steady state basis when closely spaced inclined channels are used. The variation in the separation density with particle size decreases significantly, and the Ecarte Probable Error (Ep) remains at low levels over a broad size range.

Sep 13, 2010