Theses and dissertations (Engineering and Built Environment)

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An investigation into the development of a portable, ultrasonic, density measuring instrument
(1987) Hulse, Nigel Douglas; Stewart, A. B.
In the gold mining industry, one of the significant physical properties of the mineral slurry is its density and it is important to be able to measure this parameter in most processes. There are many techniques for determining the density of fluids, but because of the hostile, abrasive nature of mineral slurry, very few of these are suitable, This dissertation describes the deveiopment, construction and testing of a portable, ultrasonic, density measuring instrument. The instrument uses an ultrasonic transducer as the primary measuring element, and system operation is based on the fact that the driving impedance of the transducer varies with changes in the physical properties, and hence the characteristic impedance, of the surrounding medium into which the ultrasonic energy is being transferred. The technique may a-Lao be used to measure the relative concentrations of two liquids in a mixture or emulsion, provided that the characteristic impedances of the liquids are sufficiently dissimilar. The electronic circuitry is fairly straightforward, consisting essentially of an oscillator, driving circuit for the transducer and a voltage monitor to provide a d.c. voltage proportional to the impedance of the transducer, and hence to the density of the surrounding medium. Most of the research has been concentrated on the probe design, as the type of transducer, the type and thickness of facing material and the method of construction all contribute to the sensitivity of the instrument. A design of probe assembly has been developed that may be used for both slurry density measurement and the measurement of the ratio of aqueous to organic liquids in emulsion.
The design of digital signal processing electronics for a steel wire ropetesting instrument
(1989) Nair, Dhavan; Scott, R. W.
This thesis describes the design work undertaken at the Anglo American Electronics Laboratory to implement an electronic instrumentation system to evaluate the condition of steel wire ropes.
The development of a hand-held direction finder
(1990) Atkinson, John Kevin; Shearer, M. S.
This dissertation is primarily concerned with the design in development and performance of a hand-held radio direction finder
A study to assess the energy savings potential in the ocean going trawler 'Roxana Bank'
(1990) Fiddler, David Michael; Gowans, B.; Calder, P.
Increasing fuel prices have forced marine engineers and diesel engine manufacturers to look at methods of. reducing fuel consumption without a loss in output power. Engineers are always Investigating the following points: (1) decreasing the specific fuel consumption (2) enabling engines to use worse fuels ... (3) extending part load capability (4) using as much waste heat as possible. The sources of heat loss are investigated and the design of an efficient heat recovery system has been evaluated for Ideal temperature and heat conditions. after taking lnto consideration the various methods of heat recovery that are possible on the fishing trawler MFV Roxana Bank. Sources of heat loss identified by engine manufacturers are found primarily in engine cooling water and exhaust systems. These methods are investigated and extra heat transfer systems have become apparent. The use of exhaust gas boilers in diesel engine installations has become widespread as there is always a demand for heating services regardless of vessel type. The predominant form of heat transfer on the Roxana Bank is by forced convection and fluids must always remain in a turbulent state when passing through heat exchange apparatus. The introduction to heat exchangers shows that a high degree of turbulence in both primary and secondary fluids will the overall heat transfer coefficient and also reduce fouling. The design parameters of the heat recovery systems discussed as suitable for the Roxana Bank require the existing cooling water system to be scrapped and a fresh water system with one central cooler to be designed with a high temperature and a low temperature circuit together with a variable speed pump arrangement. should be fitted with such central cooling systems for a number of reasons. The central cooler system Is discussed In detail and it is shown that existing ships and/or new buildings The heat recovery system requires a certain degree of automation to prevent undercooling of the main engine systems and to maintain set Inlet and outlet temperatures to makers specifications. After attending the Roxana Bank on the 09/10 November 1989, the monitored operati~g parameters show a marked deviation to the Ideal temperatures, particularly In the cylinder cooling water circuit ... temperatures. The adverse effects these deviations have on the heat recovery and combined engine load fluctuations found on the Roxana Bank show that steady state heat recovery Is difficult to achieve on this particular type of vessel. Through calculation it Is shown that the envisaged steam turbine alternator is not practical due to the combination of low feed water inlet temperatures to the boiler and insufficient driving steam. The consequence of the reduction in electrical load on the power take off alternators have on the exhaust gas mass flow rates due to reduced engine load are also discussed. A brief mention is also made of organic fluid and thermal oil systems as a form heat recovery and possibilities for efficient heat transfer using these systems. ii Recommendations are made to Irvin and Johnson with regards to a centralised cooling system and the benefits that can be realised with regard to more efficient heat exchanger operations, but that heat recovery on the Roxana Bank from the proposed sources is not a viable proposition.
Preaging techniques as a means of stabilising thermoelectric drift in nickel-chromium/nickel-aluminium thermocouples for use in an aluminium heat treating furnace
(1991) Hart, Roderick William Wenham; Smuts, D. J.
This dissertation is primarily concerned with investigating and improving the degree of accuracy and precision that may be achieved from temperat~re measurements made utilising nickel-chromium/nickel-aluminium (Type K) thermocouples. The practice of heat treating extruded aluminium section creates specific metallurgical properties within section. Development of specialised aluminium alloys has necessitated the use of treatment temperatures,- close to the limit beyond which the alloy experiences undesirable, permanent, metallurgical change. This situation has demanded urgent attention to, in quality assurance terms, the, 'fitness for purpose', of primary temperature sensors. The most established of these sensors, the Type thermocouple, has known problems relating to calibration stability and drift. The substantial amount of furnace control instrumentation and cabling dedicated to measurement from Type K sensors precludes the simple conversion to an alternate sensor type. The more practical option of applying calibration correction factors to existing measuring systems is only feasible if sensor stability characteristics permit measurement traceability to' be established within required uncertainty limits.
Factors affecting brinelling and its detection in cylindrical roller element bearings
(1992) Smith, Brian Holman; Rae, G. J.; Coertze, Dirk J.
Brinelling exists ID two fonns, namely true brinelling and false brinelling. Bearing damage due to false brinelling is a common problem and is known to occur on powerstations in Eskom.An example of false brinelling has recently been identified on the ejector pump motors at I.ethabo Pow'er station. True brinelling does not pose a problemto Eskom,and has therefore not been included in this study False brinelling is a special form of fretting and is found to occur in stationary roller element bearings subject to vibration. The vibration creates load fluctuations and varying degrees of relative motion within the bearings. As a result, small depressions or flutes are fonned in the race (Plate 1.1) which eventually lead to increased operational vibration and premature bearing failures. Previous studies do not makeany reference to factors affecting false brinelling in horizontally mounted bearings. The need for a better understanding of false brinelling has increased with the cold storage and partial cold storage of under utilized powerstations. This investigation approachesthe problemof false brinelling froma new angle. Horizontally mountedbearings have been used for testing as opposed to vertically mountedbearings used by other researchers. The effects of static bearing load, impedance,vibration amplitude and direction on false brinelling have been investigated. The study has shown that bearing impedanceand load do not have a significant influence on the rate of bearing damage,while vibration
Stress evaluation of a monolithic refractory concrete rotary calciner lining for Tioxide Southern Africa
(1993) Ilbury, M. W.; Stone, Nigel A.; Coertze, Dirk J.
The construction, development and evaluation of a portable ferro- precipitator
(1994) Sunjka, Ivan; Coertze, Dirk J.; Rawlins, Mark
This dissertation is concerned with the construction of the locally developed Ferro-precipitator which can be utilised outside a laboratory environment. The American developed Ferrograph machine, besides being expensive (R42 000 + GST in 1984), can only be used inside a dust free, temperature controlled room. As lubricants in machinery moving parts play an important role in their performance and durability many methods of evaluating the health of machines have been devised, but none by themselves can give a complete picture of what is happening inside the machine. Various methods of oil analysis have been studied in this dissertation for comparison and/or complementary purposes, so as to establish the role of the Ferro-precipitator in the context mentioned. Spectrometric, Debris and Radio Tracer methods are based on quantitative aspects of wear particle analysis, whereas the Magnetic Plug method shows visibly large wear particles in the very high wear pattern range. A further aspect to consider is the fact that the Spectrometric analysis method, which is the most common and comprehensive method available in South Africa, is laboratory orientated. This means that an oil sample has to be taken from a machine and then sent to a laboatory for analysis. Besides being time consuming from the time the samples are taken to the time when the results are known, the Spectrometric analysis method is also very expensive. The Ferro-precipitator that has been developed, is sensitive to particle size and to the rate at which these particles are generated. This is due to the phenomenon that a varying magnetic field strength will attract different size ferrous particles accordingly. This concept was validated by manufacturing ferrous particles of various sizes, firstly by grinding and secondly by sieving. These particles, in both cases, were passed through the Ferro-precipitator in a medium of oil, and graphs of density versus distance along the slide were plotted. The graphs showed distinct variations between particle sizes. The manufactured particles were also statistically evaluated by establishing the correlation between the machined and/or the sieved particles to the optically measured particles. The sensitivity of the Ferro-precipitator was further demonstrated by comparing results obtained from an engine test carried out under controlled conditions using the Spectrometric method. If developed further, the Ferro-precipitator .could, be used in the field, which would eliminate the time lost due to samples being sent ot a laboratory. Also the cost of the machine would be a fraction of the price of the Ferrograph and/or the Spectrometer. An in-depth study of particle morphology can be carried out on the wear particles deposited on the slide, with the aid of a Scanning Electron microscope using its X-Ray attachment. The potential for such a study was demonstrated on the engine test performed for this dissertation.
Controlling the feedrate of material from a vibratory pipe conveyor using an electro-magnetic vibrator and load cell system
(1994) Janse van Vuuren, Gary Peter; Eitelberg, E.
This work presents a novel way of controlling the feed rate of raw material from a vibratory pipe feeder system. The system consists of a hopper, feeder pipe, electromechanical vibrator and a loadcell which measures the mass of the complete system. Raw material is gravity fed onto the vibrating pipe whose amplitude of vibration controls the amount of material fed.
Development of an interface monitor to operate over a data transmission line
(1994) Crankshaw, Brett Robert; Bajic, Vladimir B.; Galbraith, Bruce G.
One of the telecommunication facilities provided by Telkom S.A. is connection to the National and International X.25 data network. This network follows the international data protocol standard based upon the CCITT Recommendation X.25. The network allows data calls to be made from the X.25 user in very much the same fashion as a caller on the Public Switched Telephone Network (PSTN), in that the caller must specify the number of the called user on the network in order to be connected. It is in this environment, specifically in the testing and maintaining of these data circuits, that this study is based.
An investigation into exterior illumination of buildings
(1995) Wimbush, J. C.; Martins, M.
"The nature of light is only describable by enumerating its properties and founding them on the simplest possible principles. As these principles transcend our ordinary experiences, they must be cast in a purely logical, that is to say, mathematical form. But that is never enough, for, though logic tells us what deductions must be right, it does not tell us what will be interesting, and so gives no guidance as to the direction the theory will take. In choosing this direction, much help is derived from analogies and models which are often loose and incomplete but without which no proper understanding of the subject can be acquired. We shall, therefore, describe, largely by means of analogies, the behaviour of light and this is the 'real' nature of light. "
Cost effective electrical reticulation of the rural areas in Transkei at the district of Lady Frere (Nkolonga)
(1995) Booi, Bongani Mpumelelo; Khumalo, J.
The purpose of this study is to investigate the most cost effective way of electrifying rural areas in the Transkei concentrating in the district of Lady Frere. One Administrative Area (A.A) was used for research. Questionnaires were send to people of this area where a like rat format was followed. For the purpose of this study, 20 families were randomly selected for investigation.
Hierarchical identification of large-scale system models
(1997) Jankovic, Boris R.; Bajic, Vladimir B.
In this study we propose a new concept and methodology of hierarchical identification. The need for such a methodology comes from the fact that identification of large-scale systems (LSSs) by one-shot approach may be numerically very complex. The analysis of LSSs is, in general, not approached by the one-shot methodologies normally associated with non-LSSs. The proposed method of hierarchical identification can be therefore viewed as an extension of LSS methodologies to system identification. LSS methodology aims at breaking up the initial, complex problem into a set of smaller size subproblems.
An investigation into the feasibility of the use of an electrostatic technique for the measurement of mass flow rate of pneumatically conveyed solids
(1997) Hole, Evan D.; Bajic, Vladimir B.
This report details the findings of work carried out over the course of 1994 and 1995 to determine if it is feasible to use an electrostatic technique for the measurement of mass flow rate of pneumatically conveyed solids. This includes results from tests done on a flow rig and at various power stations.
Design of a non-linear analog PID controller
(1997) Govender, Poobalan; Bajic, Vladimir B.
In this study we propose an analogue nonlinear PID controller with antiwindup and dead-time compensation to optimise the control of loops experiencing degradation in the control performance as a result of dead-time and saturation nonlinearity. Loops containing a significant dead-time are notoriously difficult to control. The proposed controller optimises the control of loops experiencing the negative effects of saturation and dead-time.
An analysis of the factors influencing the relationship between soil properties and optimum moisture content and the formulation of an abbreviated test method of determinig maximum dry density
(1997) Allinsin, Anthony James; Coetzee, J.
The strength and durability of any soil structure is dependent on the quality of the compaction of the soil. This quality is measured by employing a standard compaction test, which provides a standard with which density may be compared, called the maximum dry density, and the moisture content of the soil at which this is achieved, called the optimum moisture content. As a matter of routine during quality control, the particle size distribution, plasticity index and liquid limit of the soil are determined at the same time as its maximum dry density and optimum moisture content.
Optimization approach to the frequency design of compensators for nonlinear systems with dead time
(1998) Stavrou, Marios; Bajic, Vladimir B.
Designing compensators in the frequency domain is a complicated problem even for linear systems that have dead time. The situation is far more difficult if the system is also nonlinear. This study introduces a new method for the design of compensators for time-invariant, nonlinear systems that have dead time. The method is based on an optimization approach and utilizes large signal linearization methodology.
Towards a more effective and efficient public transport system : a case study
(1998) Allopi, Dhiren; Sarkar, Ashoke Kumar
The Government of South Africa has recognised transport as one of its five main priority areas for socia-economic development. One of the Governments strategic objectives, as reflected in the white paper on National Transport Policy, is to promote the use of public transport with the goal of achieving a ratio of 80:20 between public transport and private car usage, as a long term vision. This is no easy task and in order to achieve this goal, an in depth analysis of the current transport situation is required. The structure and land-use patterns of most of the South African cities have forced the residents to be predominantly dependent on private transport, resulting in high car ownerships. Over the years, this has caused the traffic on the major links connecting the suburban areas leading to the city centres to be very high and some of them have already approached forced flow conditions during morning and evening peak periods
An investigation into the quality of supply voltage dip-proofing
(1998) Lange, Lyle George; Crow, A.
With the ever increasing electrical demand on an electrical system, the quality of the supply will be tested more and more. And it is with this deteriorating quality that the topic of voltage dips and depressions has become a contentious issue amounts the industrial sector and supply authorities, hence the means to combat this issue in recent years.
An investigation into concrete pole damage to the Inwabi Plateau distribution line
(1998) Turner, Stephen; Kurz, M.
The use of pre-stressed concrete poles for the Inwabi Plateau rural distribution line has presented unforseen problems for the Durban Electricity Service Unit, such as poor line performance and structural damage to the poles. The effects are thought to be due to lightning. This dissertation deals with an investigation into the cause of the damage as well as recommendations regarding the repair and prevention of future damage. To achieve this, an evaluation of the line Basic Insulation Level (B.I.L.) together with a review of the existing literature on the effects of lightning to overhead lines was used in order to establish what the specific damage mechanisms are. Field and laboratory tests were also undertaken as part of the investigation. Based on the results obtained, the overhead line was modified in terms of it's B.I.L. A preliminary evaluation of the modifications was done, with recommendations regarding further work to be done in the future.