1,720,989 research outputs found
Evaluating the impact of auxiliary fan practices on localised subsurface ventilation
Get PDFMines are continually expanding in size and depth, leading to an increased reliance on localised subsurface ventilation systems. The use of underground auxiliary fans is a favoured method to increase and control airflow in working areas. However, the effectiveness of auxiliary fans in this regard is not clear. This paper evaluated the performance of these underground fan systems in four different South African deep-level gold mines. A total auxiliary fan system efficiency of 5% was found across six systems, with the average fan efficiency of 33 fans at 38%. The results showed that these fans deviate significantly from their design operating points. Therefore, there are significant shortcomings in current underground fan practices. Our detailed investigations led to the conclusion that the assemblage of underground auxiliary fan systems results in significant energy inefficiencies. Therefore, maintaining good underground fan practice such as optimal fan selection, ducting design and maintenance is crucial for the efficacy of a mine ventilation networ
Implementing a DIKW model on a deep mine cooling system
Get PDFThe South African mining industry has been experiencing increasing economic pressure. Deep mines also suffer from very hot workplaces, which leads to safety risks. These factors place stress on managers to reach their production targets while providing safe workplace conditions. The data information knowledge wisdom (DIKW) model, also known as the wisdom hierarchy, was implemented on a deep mine cooling system. This study aims to show that a simple model such as the DIKW model can assist managers in improving their deep mine cooling system’s performance. The study found that the DIKW approach is a suitable approach for use on mine cooling systems to facilitate operational improvements. Applying the DIKW approach to a case study on a mine cooling system created substantial awareness and facilitated a cooling duty improvement of 55% which relates to an increase of 5.3 MW of refrigeration. The results of this study indicate that the DIKW approach may be a suitable approach to optimise management on deep mines using their existing infrastructure. Keywords: DIKW, Cooling system, Mining, Reportin
Assessment model for annual worker radiation dose calculation for the 400MWth PBMR plant
Get PDFPhD (Nuclear Engineering), North-West University, Potchefstroom Campus, 2014Increasing demands on energy supplies have renewed interest in high temperature gas-cooled reactors such as the Pebble Bed Modular Reactor. However, public pressure due to nuclear power plant accidents, such as at Chernobyl, has highlighted radiation safety as a primary concern. In the radiation safety assessment and the safety planning of a nuclear facility, worker dose assessments play an important role. For water-cooled nuclear power plants, these assessments are based on operational experience gained and data collected during the design and operation of existing reactor designs.
Most of the research on high temperature gas-cooled reactors was stopped as far back as the 1980s. Information on safety assessments for these reactors is therefore outdated. This forces a new approach, as the 400 MWth Pebble Bed Modular Reactor is a first-of-a-kind development with design parameters set higher than previous designs. Most worker dose assessments are retrospective studies, based on historical or existing information captured in dose and maintenance records.
With the innovative Pebble Bed Modular Reactor, a new integrated dose assessment and integrated dose assessment model were developed, as operational experience and dose measurements are absent. These were developed within the processes and procedures defined for the nuclear industry. It is recognised that when operating experience or radiation monitoring data is not available, dose estimation requires extensive research, compilation of theoretical scenarios and innovative models. A new simplified dosimetric formula was developed based on the exposure determinants that will contribute to the representative worker’s dose. This formula makes it possible for the conceptual exposure scenarios to be quantified in order to arrive at an annual worker’s dose. Sensitivity analyses of the key input parameters were conducted to assess their impact on the results. This formula aims to calculate a conservative estimate of the upper limit of annual worker doses received on the plant.
Implementing the integrated assessment model provided the design team with new quantitative and qualitative information. Quantifying the annual worker dose brought an improved understanding of the level of radiation hazard present on the plant. It provided a method to carry out comparative assessments for various combinations of alternative design and maintenance concepts. This is especially important during system optimisation evaluations. It also established a quantitative benchmark for comparison of design improvements.
The results of this study were biased towards upper limit values, due to a lack of safety analysis results for normal operating conditions. Most of the available safety design analyses focused on abnormal plant conditions and accident scenarios during early design phases. It is recognised that as a design matures, more information regarding normal operating plant conditions becomes available. This requires regular updating of the assessment model to ensure that the selected missions are representative of actual exposure scenarios expected.
This integrated assessment and integrated assessment model proved to be a useful engineering tool. It provided the engineers with feedback on the adequacy of the integration of safety considerations early in the design process. The results of the worker dose assessment and the insights gained from the assessment also allow for easier compilation and changes of safety programmes and procedures for the operating plant.
Die toenemende vraag na energie het tot hernude internasionale belangstelling in die ontwerp van hoë temperatuur gasverkoelde reaktors gelei. Die Korrelbed Modulȇre Reaktor Kragsentrale is ’n voorbeeld van hierdie tipe reaktors. Stralingsveiligheid in die ontwerp van kernkragaanlegte is van primȇre belang. Dit is kernkragongelukke soos die van Chernobyl in 1986 wat tot openbare kritiek van kernkrag gelei het. In die analise van stralingsveiligheid en die veiligheidsbeplanning van ‘n kernaanleg, speel werkerdosisontledings ’n belangrike rol. Vir waterverkoelde kernkragaanlegte is werkerdosisontledings gebaseer op operasionele ervaring en empiriese data wat versamel word tydens die ontwerp en bedryf van bestaande kernaanlegte.
Navorsing op hoë temperatuur gasverkoelde reaktors is reeds so lank terug as die 1980’s gestop. Die bestaande inligting oor stralingsveiligheidaspekte van hierdie tipe reaktors is om hierdie rede verouderd. ’n Nuwe benadering word vereis in die ontwerp van die 400 MWth Korrelbed Modulȇre Reaktor Kragsentrale, wat ’n ‘eerste-van-’n-soort-ontwikkeling’ is. Die ontwerpparameters van hierdie aanleg is hoër as die van vorige ontwerpe.
Die meerderheid van beskikbare werkerdosisontledings is terugblikkende studies, gebaseer op historiese inligting van dosis- en onderhoudsrekords. Die ontwerp van die innoverende 400 MWth Korrelbed Modulȇre Reaktor verg dat ’n dosisontledingsmetode gevind word, wat in die afwesigheid van operasionele ervaring en dosismetings uitgevoer kan word.
Die doel van hierdie studie is om ’n nuwe geïntegreerde dosisontledingsmetode te ontwikkel om werkerdosisontledings uit te voer tydens die ontwerp van ‘eerste-van-’n-soort’ ontwikkelings, veral waar operasionele ervaring en empiriese data afwesig is. Hierdie is binne die prosesse en prosedures van die kernindustrie ontwikkel. Dit word erken dat dosisramings uitgebreide navorsing, opstel van teoretiese scenario’s en nuwe modelle vereis wanneer operasionele ondervinding en data oor stralingsregulering afwesig is.
‘n Nuwe prosedure, gebaseer op die blootstellingsdeterminante van die dosis van ’n verteenwoordigende werker, is ontwikkel. ’n Vereenvoudigde formule maak dit moontlik om die konseptuele blootstellingscenario’s te kwantifiseer. Hierdie scenario’s is verteenwoordigend van onderhoud en inspeksies op die aanleg wat ’n virtuele werker jaarliks uitvoer.
Sensitiwiteitsanalises is gedoen om die invloed van die belangrikste invoerparameters op die resultate te evalueer. Hierdie vereenvoudigde metodologie poog om ’n konserwatiewe beraming van die boonste limiete van die jaarlikse werkerdosis te bereken.
Implimentering van die metodologie verskaf nuwe kwantitatiewe en kwalitatiewe inligting oor die stralingsvlakke op die aanleg. Die geïntegreerde model maak dit moontlik om vergelykende studies van verskillende kombinasies van alternatiewe ontwerpe en onderhoudskonsepte uit te voer. Dit is veral belangrik tydens sisteemoptimiseringsevalusies. Dit verskaf ook ‘n kwantitatiewe basislynkriterium vir vergelyking van ontwerpverbeterings.
Die resultate van hierdie studie neig na die boonste verwagte limiet waardes van jaarlikse werkerdosisse, weens ’n gebrek aan beskikbare veiligheidsanaliseresultate vir normale operasionele toestande. Die veiligheidsanalise fokus op abnormale toestande en ongelukscenarios in die vroeë ontwerpfases van ’n aanleg. Soos meer detail tydens die ontwerpproses verkrygbaar word, moet hierdie evalueringsmodel hersien raak. Dit is om te verseker dat die geselekteerde missies verteenwoordigend van realistiese normale blootstellingscenario’s is.
Die geïntegreerde model kan as ’n nuttige ingenieurshulpmiddel gebruik word. Vroeg in die ontwerpproses, verskaf dit ’n terugvoermeganisme aan ingenieurs oor die geskiktheid van die integrasie van veiligheidsvereistes. Die resultate van die werkerdosisontleding, en die insigte verkry uit die ontleding, vergemaklik identifisering van voorstelle en veranderinge vir die radiologiese veiligheidsprogram en -prosedures vir die operasionele aanleg.Doctora
Novel method of improving squirrel cage induction motor performance by using mixed conductivity fabricated rotors (MCFR)
Get PDFThesis (Ph.D. (Electrical Engineering))--North-West University, Potchefstroom Campus, 2007.The ideal squirrel cage motor should have a varying rotor resistance; large at standstill, and decreasing as the speed rises. Overseas - designed high impedance rotors try to fulfil these conditions - mostly used are double cage rotors and die cast aluminium rotors. However, in the South African coal-mining industry these rotors recorded high rate failures with heavy financial losses. As a result, the need for an alternative rotor type that was able to comply with basic conditions ignored before appeared on the market: • Higher reliability with extended life expectancy • Lower total ownership costs • Easy re-manufacturing with components available on the market • Specific performance stability at competitive price. Over the years, only two principles were tacitly accepted in designing squirrel cage rotors: 1. For a single cage rotor, in a circumferential direction around the rotor the squirrel cage bars are placed in the same cylindrical shell, with the same shape and same conductivity. 2. For a double cage rotor, the same rule as above applies; however, in the radial direction, the bars have different shapes and typically different conductivities. The Invention is based on a new principle, i.e. "in a circumferential direction around the squirrel cage rotor, squirrel cage bars may have different conductivities and same shapes, or different conductivities and different shapes”. Mixed Conductivity Fabricated Rotors (MCFR) are designed and manufactured based on this
new principle, and are able to withstand the harsh South African mining conditions.
Since patented, the invention has been materialised in a set of special rotors powering continuous miners of a reputable coal-mining house, which was spending about R5 million annually on replacing specific imported die cast aluminium rotors only. Fully complying with the above-mentioned basic conditions, the patent offers a large variety of technical and economical advantages, increasing mining processes efficiency beyond expectations.
The thesis describes the MCFR's design adaptability by altering the rotor design to meet the demands of a specific engineering application as a base line of drives design.
The patent is part of the new South African trend of increasing processes efficiency. It offers large possibilities of designing dedicated motors with a positive impact on the South African economy. Some socio-economical advantages are worthy of considerable study: • Being locally manufactured, the MCFR may reduce the country's economical dependence. • Requiring no special expertise, the MCFR can be produced in any quantity and size without excessive investment. • The MCFR offers an alternative option (product interchangeability) on the market as well as sound competition (with export potential). • The patent ensures business sustainability conditions which diffuse financial constraints on motor manufacturers and end-users during the re-capitalisation process (very loaded in South African economic and industrial environment).Doctora
Energy efficiency opportunities in mine compressed air systems
Get PDFThesis (M.Ing. (Mechanical Engineering))--North-West University, Potchefstroom Campus, 2010.Demand Side Management (DSM) is one of the most viable and sustainable short term methods to address the shortfall in electricity generation in South Africa. This is because DSM projects can be implemented relatively quickly and inexpensively when compared with alternative generation options. This specifically applies to the mining industry. South African mines presently consume 15% of Eskom-generated electricity. Mine compressed air systems are some of the biggest users, consuming approximately 21% of mine electricity consumption. Electricity savings on compressed air systems are therefore important. With this study, various Energy Efficiency methods on compressed air systems were
investigated. These methods include variable speed drives on compressor motors, temperature control of compressor discharge, minimising pressure drops in the air distribution systems, eliminating compressed air leaks, and optimising compressor selection and control. The most efficient strategies were identified, taking into account factors such as financial viability, sustainability, and ease of implementation. The best strategies were found to be the
optimised control and selection of compressors, minimising compressed air leaks, and the optimal control of system pressure. These strategies were implemented and tested on large
compressed air systems in gold and platinum mines. Savings of between 10% and 35% on the maximum demand of the systems were achieved. In present monetary terms this translates to as much as R108 million savings for the mines per year at the end of 2009 tariffs. If total mine compressed air electricity consumption can reduce by 30%, it will result in nearly a 1% reduction in total Eskom demand. This shows that mine
compressed air savings can make a significant contribution to the drive for Energy Efficiency in South Africa.Master
Reducing energy consumption on RSA mines through optimised compressor control
Get PDFThesis (M.Ing. (Electrical Engineering))--North-West University, Potchefstroom Campus, 2010South Africa experienced a severe shortfall in electricity supply during 2008. Eskom, the national electricity supplier, implemented several strategies to alleviate the situation. The Power Conservation Programme set the mining sector a mandatory target to reduce its annual power consumption by 10%. The quickest way to achieve these savings is by optimising the largest power consumers on the mines. Compressed air is one of these, constituting approximately 40% of total
electricity consumption on platinum mines.
Several methods to reduce power consumption on compressed air systems were investigated. The investigation revealed that centrifugal air compressors on the
mines are typically manually operated at a fixed delivery output. Attempts to reduce electricity consumption by reducing air demand will therefore not necessarily lead to savings. A control system that will enable the compressor to automatically match the supply with system demand is required. An optimised control strategy was then developed and implemented on three compressed air systems. Measurements demonstrated savings between 13% and 49%. With the Eskom tariffs proposed for 2010, this implies a total saving of R 46 million per year for these three case studies. This will achieve, and may even exceed, the mandatory reduction in electricity consumption of the mines. These results demonstrate that one of the quickest ways to reduce energy consumption on South African mines is by implementing optimised compressor controls.Master
An energy efficient mass transportation model for Gauteng
Get PDFThesis (MIng (Mechanical Engineering))--North-West University, Potchefstroom Campus, 2012.Public transportation in South Africa is characterized by little or no consideration for energy efficiency and use of cleaner fuels. In the case of transport planning in South African cities, no assessment of the economic or environment impact of limited or highly priced electricity or conventional liquid fuels has been included in the decision-making process. Recent examples of the Gautrain and the Bus Rapid Transit programmes (both in Gauteng) reinforce this weakness in current planning methodologies. This study has focused on the need to introduce energy efficiency and greenhouse gas consideration in mass transport decision-making in Gauteng. The intention of the study was to produce a strategic modelling tool that would be a high-level product for politicians to use. At the same time, the tool should feature more advanced capabilities such as optimisation algorithms to satisfy specific objective functions, such as time, cost, energy or global warming potential. In this way, sensitivity studies based on different orderings of these objective functions could be undertaken using this model. The model's performance was tested using two different scenarios. In the least time scenario, which is practically the base case, the order of optimisation was time first, then cost, then energy and then global warming. The constraint on objective functions was relaxed by 10% after each optimization to get to the final result, which is then understood to be the least global warming impact for a particular plan that was initially optimized for time. In the least global warming scenario, the order of optimisation was changed, with first global warming, then energy, then time and then cost optimised. The resultant plan is the lowest cost plan that could be developed if global warming was the most important consideration. The results obtained for both scenarios are discussed and compared to each other where practical. Where possible model verification and validation have been undertaken and where it has not been possible, the approach to be taken in a follow up study will serve to provide such validation. The model has been shown to be an effective high-level strategic decision-making tool. It is a tool that should be used by politicians and transport planners alike to ensure energy efficiency and greenhouse gas reduction are factored into future transport options considered.Master
Energy efficiency through variable speed drive control on a cascading mine cooling system
No full textAn ever-expanding global industry focuses on energy supply and use. Cost-effective electrical energy production and reduced consumption pave the way for this expansion. Eskom's demand-side management (DSM) initiative provides the opportunity to reduce electricity consumption with cost-effective implementations for their respective clients. South African gold mines extend their operations to up to 4000 m below the surface to remain profitable. Deep-level mining therefore requires large and energy-intensive cooling installations to provide safe working conditions. This paper investigates the improved energy efficiency and control of a South African gold mine's cascade cooling plant. Variable speed drives (VSDs) were installed on the chiller evaporator and condenser water pumps to provide variable flow control of the water through the chillers. This results in reduced motor electricity usage and improves chiller efficiencies. The results indicate that effective control and utilisation of energy efficient technology can produce substantial electricity cost savings. This indicates the potential for reducing energy inefficiencies and operating costs on technologically outdated machineryhttp://www.ieee.org/conferences_events/conferences/xplore_conference_proceedings.htm
Modernising underground compressed air DSM projects to reduce operating costs
No full textCompressed air is an energy intensive utility that is frequently used in the deep level mining industry. Most compressed air networks are designed to ensure ample compressed air supply to consumers. This has created the foundation for existing compressed air energy saving projects on deep level mines. Over the past decade, electricity costs in South Africa increased drastically. As a result, the need to further improve and optimise existing Demand Side Management (DSM) projects with modern technology and expertise has become more feasible. This study therefore provides and evaluates a solution to reduce the electricity consumption and operating costs of a compressed air system on a deep level mine. This was achieved by modernising and improving an existing underground compressed air DSM project. It was found that the improvements realised significant additional electrical energy savings. This resulted in ample cost savings to justify the implementation of the improvementshttp://www.ieee.org/conferences_events/conferences/xplore_conference_proceedings.htm
An integrated energy efficiency strategy for deep mine ventilation and refrigeration
No full textMine-cooling and ventilation energy cost saving projects are implemented ad hoc and scattered throughout the system. Therefore, an overhead view and strategy is needed to help realise the total savings available on the entire mine-cooling and ventilation system. An overview and foundation is given of all the systems forming part of the mine ventilation and cooling system as well as the available energy and cost saving projects on each system. Every project on each system was then evaluated against their yearly monetary saving, potential risks and other factors. From this the optimal combination of projects was determined from the interaction between the projects and systems. Using the optimal combination and three important indicators, an implementation sequence was then developed. The resultant sequence ensures that all savings throughout the entire mine-cooling and ventilation system is attained. Implementing this sequenced combination of cooperative projects on a typical mine resulted in substantial annual savings. This was due to substantial reductions in the ventilation and cooling electricity billhttp://www.ieee.org/conferences_events/conferences/xplore_conference_proceedings.htm
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