Browsing by Author "Lyne, Peter William Liversedge."

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An integrated sugarcane supply chain model : development and demonstration.
(2006) Stutterheim, Peter.; Bezuidenhout, Carel Nicolaas.; Lyne, Peter William Liversedge.
The South African sugar industry is a large industry which relies on expensive capital equipment to harvest, transport and process sugarcane. An average of 23 million tons of sugarcane are annually supplied to 14 mills from over 2 000 large-scale commercial growers and 48 000 small-scale growers. Supply chain stakeholders can benefit if operations are successfully streamlined. Computer-based mathematical models have been used in other industries to improve supply chains, especially in forestry, and are expected to play an increasingly important role in future planning and management. Management of sugar supply chains has historically focussed on generating competitive individual supply chain components. However, inter-component optimisation generally disregards many important intra-component interactions. Hence, efficiency improvements may be significantly limited. Integrated supply chain modelling provides a suitable approach for addressing this problem. The aim of this project was to develop and demonstrate, in concept, an integrated supply chain model for the sugar industry. Such a model could be used to address various integrated planning and management problems throughout the supply chain. A review of existing integrated agri-supply chain models was conducted followed by the development of CAPCONN, an integrated sugar supply chain model framework, that incorporate all steps from field to mill back end. CAPCONN estimates sugarcane quality, mill recovery, capacity utilisation and production costs. Bottlenecks are highlighted and the model could contribute towards capacity manipulation for efficiency improvements under different harvesting scenarios. CAPCONN was demonstrated by analysing a number of scenarios in a mechanisation case study at Komati Mill where sugarcane is currently burned and manually cut. A total of twelve scenarios were compared, including variations in cropping system and time of year. The model framework predicted that a decrease in sugarcane quality and sugar recovery would occur under mechanical harvesting scenarios. Estimated production costs were also higher, even though the transport fleet was significantly reduced. A manually cut green (unburned) harvesting scenario showed a further decrease in sugarcane quality and sugar recovery. Mechanical harvesting during wet weather caused a substantial reduction in supply chain capacity and an increase in production costs. CAPCONN output trends compared favourably with measured and observed data, though the magnitude of the trends should be viewed with caution, since the CAPCONN framework is only a prototype. This shows that it may be a suitable diagnostic framework for analysing and investigating the sugarcane supply chain as a single entity. With further development to a model, the CAPCONN model framework could be used as a strategic planning tool although, one drawback is that a relatively large number of technical inputs are required to run the model.
Automated processor for optimizing tractor operation.
(1991) Lyne, Peter William Liversedge.; Meiring, Pierre Andre.
The agricultural tractor is designed as a general purpose machine and consequently, does not perform all its tasks at maximum efficiency. Various methods of increasing the field performance of these vehicles have been studied. Traction is one of the main factors limiting the field performance of the modern tractor. The process of developing traction has therefore been investigated by many researchers and although this study has resulted in a better understanding of the mechanics, it has not to any great extent assisted the operator to optimize performance in the field. It was concluded that in order to solve the problem the operator required a control system to maintain the dynamic load and inflation pressure at optimum levels. Work was carried out to develop and evaluate such a system using the Single Wheel Traction Research Vehicle at the USDA's National Soil Dynamics Laboratory in Auburn, Alabama, USA. A computer management system was developed to control the dynamic load, net traction and inflation pressure of the test tyre. During a simulated field operation the system was programmed to cycle the tyre over its operating range of dynamic load and inflation pressure while monitoring tractive efficiency. A tractive efficiency response surface was computed for the particular condition and the surface searched for the dynamic load and inflation pressure levels which resulted in maximum tractive efficiency. The tyre was then controlled and operated at maximum tractive efficiency. Evaluation showed that within the operating range of the tyre, tractive efficiency varied considerably with dynamic load, inflation pressure, net traction and soil condition. The results indicated that a considerable advantage could be obtained by using such an arrangement on a tractor. The system would automatically maximize the tractive efficiency of the tractor under the particular field conditions and with the particular implement being used. Implements could be ballasted and the hitch system used to control the weight transfer to ensure maximum tractive efficiency. Systems such as these would result in a significant improvement in the field performance of the machine and a reduction in management time required to optimize the performance of the tractor implement combination.
The design and testing of soil pressure sensors for in-field agricultural and forestry traffic.
(2005) Eweg, Jonathan Lindsay.; Lyne, Peter William Liversedge.; Bezuidenhout, Carel Nicolaas.
River stage or flow rates are required for the design and evaluation of hydraulic structures. Most river reaches are ungauged and a methodology is needed to estimate the stages, or rates of flow, at specific locations in streams where no measurements are available. Flood routing techniques are utilised to estimate the stages, or rates of flow, in order to predict flood wave propagation along river reaches. Models can be developed for gauged catchments and their parameters related to physical characteristics such as slope, reach width, reach length so that the approach can be applied to ungauged catchments in the region. The objective of this study is to assess Muskingum-based methods for flow routing ill ungauged river reaches, both with and without lateral inflows. Using observed data, the model parameters were calibrated to assess performance of the Muskingum flood routing procedures and the Muskingum-Cunge method was then assessed using catchment derived parameters for use in ungauged river reaches. The Muskingum parameters were derived from empirically estimated variables and variables estimated from assumed river cross-sections within the selected river reaches used. Three sub-catchments in the Thukela catchment in KwaZulu-Natal, South Africa were selected for analyses, with river lengths of 4, 21 and 54 km. The slopes of the river reaches and reach lengths were derived from a digital elevation model. Manning roughness coefficients were estimated from field observations. Flow variables such as velocity, hydraulic radius, wetted perimeters, flow depth and top flow width were determined from empirical equations and cross-sections of the selected rivers. Lateral inflows to long river reaches were estimated from the Saint-Venant equation. Observed events were extracted for each sub-catchment to assess the Muskingum-Cunge parameter estimation method and Three-parameter Muskingum method. The extracted events were further analysed using empirically estimated flow variables. The performances of the methods were evaluated by comparing both graphically and statistically the simulated and observed hydrographs. Sensitivity analyses were undertaken using three selected events and a 50% variation in selected input variables was used to identify sensitive variablesThe performance of the calibrated Muskingum-Cunge flood routing method using observed hydrographs displayed acceptable results. Therefore, the Muskingum-Cunge flood routing method was applied in ungauged catchments, with variables estimated empirically. The results obtained shows that the computed outflow hydrographs generated using the Muskingum-Cunge method, with the empirically estimated variables and variables estimated from cross-sections of the selected rivers resulted in reasonably accurate computed outflow hydrographs with respect to peak discharge, timing of peak flow and volume. From this study, it is concluded that the Muskingum-Cunge method can be applied to route floods in ungauged catchments in the Thukela catchment and it is postulated that the method can be used to route floods in other ungauged rivers in South Africa.
Designing optimisation of a cane haulage vehicle.
(2008) Cowling, Simon L.; Bright, Glen.; Lyne, Peter William Liversedge.; Morozov, Evgeny.
The sugar industry transports in excess of 20 million tons of sugarcane per annum, equating to approximately 800 000 road consignments. This entails substantial expenditure on vehicle capital and operational costs. There exists substantial scope to redesign vehicle configurations to reduce the vehicles tare mass and optimise the process of cane transportation. These modifications could potentially save the industry approximately Rl36 million per annum, and in addition will increase a vehicles lifespan, performance and speed. This project is one aspect of a larger project organised by the South African Sugarcane Research Institute, with the general aim of optimising the entire sugarcane transportation system. Aspects of this particular project include literature research as well as field investigation into the various sugarcane transportation systems in South Africa and throughout the world. The design of a cane haulage vehicle will be analysed and optimised, using tools such as finite element analysis. The aims of this project include the investigation of the engineering design issues with respect to vehicle/trailer configurations, and the design of an optimised cane haulage vehicle which increases the efficiency of raw sugarcane transportation in South Africa.
The development and assessment of a direct energy calculator for use in sugarcane production.
(2014) Boote, Darran N.; Smithers, Jeffrey Colin.; Lyne, Peter William Liversedge.; Van Antwerpen, Rianto.
The rising cost of energy coupled with an increasing awareness of Greenhouse Gas (GHG) emissions has led to a concerted effort to reduce fossil fuel Energy Use (EU) in all sectors. Sugarcane production in South Africa is dependent on fossil fuel to provide a source of energy for production. To remain commercially and environmentally sustainable, measures need to be taken to reduce EU and increase EU efficiencies of on-farm operations. The first step toward realising this is to identify and quantify energy inputs. Following on from this, total GHG emissions, also known as carbon footprint, can be estimated. The primary objective of this research is to develop an energy calculator to estimate EU in sugarcane production in South Africa. The results generated by the calculator highlight areas of high energy intensity and low energy efficiencies at three different levels of detail. Based on these results, changes in management practices and technological improvements can be made to reduce EU and carbon footprint. Case studies were used to test the functionality of the calculator. Results from the case studies show that, in irrigated sugarcane production, the harvest and transport process together with irrigation account for a majority of the total on-farm EU. For one of the case studies, an estimated 20 % saving in the total on-farm EU was identified and can be achieved if appropriate technology is adopted in irrigation practices. Less significant energy savings were realised when in-field tractor operations were optimised for best tractor-implement matching. It is envisaged that the energy calculator will help farmers minimise on-farm EU and subsequently reduce input costs and carbon footprint. It will also provide a valuable tool for researchers to benchmark and profile EU in sugarcane production in South Africa. Research focussed on the sustainable production of sugar, from the agricultural to milling phase is of high priority at present. The quantification of on-farm EU in sugarcane production will form a critical component of such research.
The development and evaluation of a performance-based standards approach for regulating the use of heavy vehicles in South Africa.
(2013) Nordengen, Paul Anthony.; Lyne, Peter William Liversedge.; Bezuidenhout, Carel Nicolaas.
The regulation of the use of vehicles on the road network is aimed at ensuring acceptable safety and recovery of road maintenance costs, as well as minimising congestion, road wear, excessive noise and air pollution. The traditional approach of regulating heavy vehicles is prescriptive, i.e. enforcing regulations that primarily limit the mass and dimensions of these vehicles. This approach is generally favoured because such regulations are easy to understand and enforce. However, an underlying disadvantage is that the prescriptive approach does not always adequately safeguard the dynamic performance of heavy vehicles while travelling on the road. Principle-based and performance-based standards are primarily aimed at specifying desired outcomes, rather than how these outcomes should be achieved. Under a performance-based standards (PBS) approach, performance measures (such as low-speed swept path, rearward amplification, load transfer ratio and high-speed offtracking) are utilised to specify the performance required from vehicles. Although more complex to regulate, a PBS approach has a number of potential benefits such as: (a) improved vehicle safety, (b) improved productivity, (c) reduced infrastructure wear and emissions, (d) a more optimal use of the existing road network, and (e) the encouragement of innovation in vehicle design. The aim of this research was to apply, refine and demonstrate an alternative approach to the design and operation of heavy vehicles in South Africa with improved outcomes in terms of road transport productivity, vehicle safety performance, emissions, congestion and preservation of road infrastructure. The research included the development and implementation of a PBS demonstration project in South Africa and the monitoring and evaluation of PBS demonstration vehicles operating in the forestry industry in the provinces of KwaZulu-Natal and Mpumalanga. Evaluation focused on improvements in productivity (fuel efficiency and trip reduction) and load control with reference to initial results regarding road wear and safety performance. Results show a significant improvement in payload control and fuel efficiency of the PBS vehicles compared with the baseline vehicles. This also resulted in a reduction in CO2 emissions per ton.km. Road wear assessments of PBS and baseline vehicles showed that in some cases a reduction in road wear of up to 200% per ton of payload can be achieved through the use of PBS vehicles. Safety assessment results of four PBS vehicle designs showed various shortcomings of prescriptive baseline vehicles in terms of the performance standards.
Development of network theory approaches to analyse cause and effect relationships in complex integrated sugarcane supply and processing systems.
(2013) Sanjika, Thawani M.; Lyne, Peter William Liversedge.; Bezuidenhout, Carel Nicolaas.; Bodhanya, Shamim Ahmed.
Network theory has been widely and successfully used to model, analyse and visualise complex systems. This study aimed to develop approaches to analyse complex integrated sugarcane supply and processing systems. A literature review includes network theory, complex systems, the Theory of constraints, indicator analysis and root cause analysis. The cause-and-effect networks of four sugarcane milling areas in South Africa; viz. Eston, Felixton, Komati and Umfolozi were developed, where the factors that negatively affected the performance of the milling areas were represented by vertices, the relationships among the factors by arcs and the strength of these relationships by weights. Three network theory based analytical tools namely; (a) primary influence vertex analysis, (b) indicator vertex analysis and (c) root cause vertex analysis were developed to analyse the networks. The results from the analyses indicate variations in the numbers and strengths of primary influence factors, problem indicator factors and root causes of problems between the four milling areas. Rainfall, drought and high soil content in sugarcane were identified as the strongest primary influences in the respective milling areas. High crush rate variability, low cutter productivity, running behind allocation and increases in operating costs were identified as the strongest indicators of poor performance in the respective milling areas. Rainfall was found to be the most dominating root cause of poor performance in all the milling areas. Since the South African integrated sugarcane production and processing system is complex, it is likely that the unique approaches developed in this study can be used successfully to also analyse other relatively complex systems. It is recommended that these approaches be tested within other systems. The main contribution of this study is in the form of a relatively easy-to-use network theory based comprehensive systems analyses tool. This analytical approach has, to the author's knowledge, not been used in any agri-industrial application previously.
The effects of precipitation on the sugarcane supply chain of Sezela and Umzimkulu.
(2015) Dzapatsva, Precious.; Lyne, Peter William Liversedge.; Lagerwall, Gareth.
Abstract available in PDF file.
Estimating traffic induced sugarcane losses for various harvesting, loading and infield transport operations in South Africa.
(2016) Tweddle, Peter Brian.; Lyne, Peter William Liversedge.; Lagerwall, Gareth.
Infield traffic has been understood to cause adverse field conditions for crop growth. Literature containing traffic induced yield responses for sugarcane was reviewed and synthesised to better estimate the impact of infield traffic on sugarcane yields. Approximately 128 sugarcane yield responses to infield traffic treatments from local and international trials were collated and analysed. The impact of soil compaction effects on soil properties were not considered as there is a substantial body of knowledge on this topic. The results confirm that traffic on a sugarcane row is more detrimental than inter-row traffic. Soil water content at the time of infield traffic and infield traffic load intensity are further critical factors affecting soil compaction and sugarcane yield. Further aggregation of the data by soil textural groups was found to establish yield response trends useful for modelling of infield traffic scenarios, but were not statistically significant. Infield traffic paths of equipment movements were surveyed and mapped for a range of typical harvesting systems found commercially in the South African sugarcane industry. The maps were analysed to proportion the field area by row traffic, inter-row traffic and remaining non traffic areas for each machine component used infield. Yield losses based on vehicle traffic impacts were assigned to each corresponding component as determined from the results of the literature synthesis. The traffic induced yield loss was apportioned to the areas trafficked to determine a field based yield loss estimate for each of the harvesting and extraction systems and a corresponding economic impact reported. The ranking of system costs, reported off a mechanisation costing base, altered when the additional field traffic induced yield loss components were added, particularly when yield losses were compounded across multiple ratoons within a cropping cycle. Systems operating with low impact vehicles, of low traffic extent combined with controlled traffic practices resulted in the lowest yield losses on a field basis and also resulted in the lowest overall cost. Controlled traffic practices reduce the impact of heavy infield equipment on yields. The significance of this work is that the yield losses due to infield traffic can now be attributed to systems to allow for improved costing analyses and system comparisons to be conducted. It is proposed that this new contribution be incorporated into standard mechanisation costing methodologies to allow for such crop yield losses to be accounted for.
The evaluation of pressure distribution and bulk density models for infield agriculture and forestry traffic.
(2006) Marx, Barend Jan.; Bezuidenhout, Carel Nicolaas.; Lyne, Peter William Liversedge.
There is evidence that soil compaction, through the use of mechanised equipment, causes detrimental effects to soil quality and reduces long-term productivity of soils. For economic reasons, farmers need to purchase larger, heavier machinery in order to cultivate larger areas under crops, resulting in larger forces on the soil. The severity of soil compaction is governed by various soil and vehicle properties and normally causes an increase in the soil's bulk density and a decrease in the air filled porosity. These changes in soil properties have negative effects on crop production and environmental sustainability. The aim of this study was to investigate and develop a model based decision support system for soil compaction management and research. Soil compaction occurs during the transfer of stresses from the tyre interface into the soil. Numerically, it has been modelled using both mechanistic and empirical models, which attempt to simulate the stress propagation and also sometimes the consequent damage to the soil. The SOCOMO soil compaction model is described and this model computes the stress at a point in the soil for any given horizontal and vertical stress distribution at the soil / tyre interface. It has been successfully used in the Netherlands and in Sweden to map the impact on the soil. The SOCOMO model was tested and verified at a forestry site in Richmond, KwaZulu- Natal. Relationships to determine bulk density were also tested and verified. The SOCOMO model performs satisfactory (RMSE = 47.9 kPa), although it tends to overestimate the pressures within the soil. This could be as a result of the high organic carbon content in the particular soil. Models predicting bulk density also performed satisfactory (RMSE = 69.9 kg.m" ), but resultant densities in the soil are generally underestimated. Future research is needed to find better relationships to estimate changes in dry bulk density and to test the model on a wider range of soils. If the model performs satisfactory it could provide a useful tool to determine the impact of soil compaction on crop yield.
Evaluation of systems to harvest, process and transport sugarcane biomass.
(2015) Rees, Bryan.; Smithers, Jeffrey Colin.; Lyne, Peter William Liversedge.; Van Antwerpen, Rianto.
One of the problems facing the world today is the fact that fossil fuel reserves are declining and, as a result, petrol and diesel costs are increasing. For the past century, fossil fuels have been the primary fuel source for most countries around the world and this has had an impact on the environment. This has resulted in the South African government, in line with international trends, investigating alternative energy sources to supplement and meet an increasing demand for energy. Biomass (e.g. leaves of sugarcane, referred to as sugarcane residue) is receiving increasing attention, as it is a sustainable and environmentally-friendly source of renewable energy. In South Africa, the majority of the sugar industry manually harvests burnt sugarcane. Thus, innovative residue recovery systems need to be developed to accommodate the manual harvesting of green/unburnt sugarcane. In this document, sugarcane residue refers to green/wet and brown/dry leaves, tops and green leaves constitute green residue, brown leaves constitute dry residue, and bagasse is the pulp left after the juice has been extracted from the sugarcane stalks. The name ‘residue recovery route’ encompasses both green and dry residue as, although ideally dry residue is collected, some residue recovery routes collect green residue in addition to dry residue. The objectives of this study are: (i) to assess the potential energy available from dry sugarcane residue, taking into account the benefits of leaving a residue blanket in the field, and (ii) to investigate the harvesting systems, energy and costs required to recover the residue and deliver it to a mill for both new production and harvesting systems and systems currently used in South Africa, which range from manual harvesting to fully mechanised systems. Current residue recovery methods, as well as potential methods which are still under development, are reviewed in this document. A costing model has been adopted and further developed, with the objective of estimating the costs incurred by residue collection and transport. The different residue recovery routes, which were identified in the literature review, were incorporated into the model. These routes include different methods of harvesting, residue separation infield or at the mill, the method of residue collection, residue processing and the transportation of the residue. Processing to increase the bulk density of the sugarcane residue prior to transport has been considered in this study, as its low bulk density has been identified as a critical issue in other studies. By processing the residue, the energy density and bulk density of the residue can be increased, which, in turn, improves the transport efficiency. Problems encountered when modelling residue processing included estimating the capital cost requirements, as well as the maintenance and operating costs, for each processing plant. The model was applied to two case studies, in order to compare the costs for each individual residue recovery route. This enabled the lowest cost and appropriate residue recovery route to be identified for the case studies. The cost per unit energy was used to compare the cost of the residue recovery to the cost of coal at the mill, which is required to determine whether sugarcane residue is an economically-viable source of renewable energy. Based on the assumptions made for the lowest cost routes which were identified, it was found that the cost of the residue recovery i.e. the cost of the residue, was less than that of coal and, thus, these routes are potentially economically beneficial for the mill.
Issues pertaining to cane supply reliability and stockpiling at the Umfolozi sugar mill - model development and application.
(2011) Boote, Gordon L. N.; Bezuidenhout, Carel Nicolaas.; Lyne, Peter William Liversedge.
The co-owned Umfolozi Mill area has developed as an integrated supply chain. Cane supply reliability was identified as a potential area for productivity improvement at Umfolozi. It is important that the cane supply to a sugar mill arrives at a steady and reliable rate. A reliable cane supply ensures that the mill can operate at an optimum efficiency. Sugarcane supply reliability depends on how the mill area adapts to unforeseeable changes in the supply chain. An important aspect to this is the weather and how it affects the harvesting regimes. The sugarcane supply chain at Umfolozi is divided into two branches, road transport and tram transport. The trams account for 70 % of the cane delivered to the mill and the can is sourced from a climatically homogenous region. In the occurrence of a rainfall event of above 5 mm, infield harvesting cannot take place on the Umfolozi Flats; hence 70 % of the mill‟s supply is halted for one or more days. To address the problem, a stochastic model was created to simulate the effectiveness of an enlarged cane stockpile if it were maintained on the current tram sidings outside the mill and were crushed when wet weather prevented further harvesting. The stockpile was simulated on a first-in first-out principle and was able to supply the mill with enough cane to continue running for 24 hours. The model was then used to conduct a series of Monte Carlo simulations on which sensitivity analyses and economic feasibility assessments were carried out. Results show that the stockpile was effective in reducing the length of milling season and the number of no-cane stops. However, on further analysis into the implications of creating a stockpile it was found that 1% recoverable value (RV) was lost during the 24-hours that the cane is stored outside the mill. The loss in revenue as a result of the RV reduction had a negative impact on any savings created with the implementation of the stockpile. This result made apparent the negative impact of deterioration to the whole supply chain. Further research is required to determine more accurately the rate of deterioration, and therefore, quantify more accurately the losses that occur in the supply chain. A significant outcome of the study was the development of a mechanistic tool which drove decision making at Umfolozi Sugar Mill. It lead to the development of the modelling framework LOMZI, a simulations based framework which places more emphasis on environmental factors and risks.
Predicting emissions using an on-road vehicle performance simulator.
(2002) Govindasamy, Prabeshan.; Lyne, Peter William Liversedge.
South Africa is coming under increasing pressure to conform to the rest of the world in terms of emissions regulations. The pressure is caused by a number of factors: international organisations requiring local companies to adhere to environmental conservation policies, evidence from within South Africa that efforts are being made to reduce environmental pollution in line with other countries and keeping abreast of the latest technologies that have been incorporated into vehicles to reduce emissions. In light of these problems associated with emiSSions, a study was initiated by the Department of Transport and the School of Bioresources Engineering and Environmental Hydrology at the University of Natal to investigate and develop a method of predicting emissions from a diesel engine. The main objective of this research was to incorporate this model into SimTrans in order to estimate emissions generated from a vehicle while it is travelling along specific routes in South Africa. SimTrans is a mechanistically based model, developed at the School, that simulates a vehicle travelling along a route, requiring input for the road profile and vehicle and engine specifications. After a preliminary investigation it was decided to use a neural network to predict emissions, as it provides accurate results and is more suitable for a quantitative analysis which is what was required for this study. The emissions that were predicted were NOx (Nitric oxide-NO and Nitric dioxide-N02), CO (carbon monoxide), HC (unbumt hydrocarbons) and particulates. The neural netWork was trained on emissions data obtained from an ADE 447Ti engine. These neural networks were then integrated into the existing SimTrans. Apart from the neural network, an algorithm to consider the effect of ambient conditions on the output of the engine was also included in the model. A sensitivity analysis was carried out using the model to prioritise the factors affecting emissions. Finally using the data for the ADE 447Ti engine, a trip with a Mercedes Benz 2644S-24 was simulated using different scenarios over the routes from Durban to Johannesburg and Cape Town to Johannesburg in South Africa to quantify the emissions that were generated.
Simulation modelling of sugarcane harvest-to-crush delays.
(1998) Barnes, Andrew.; Meyer, E.; Hansen, Alan Christopher.; Lyne, Peter William Liversedge.
Long delays between harvesting and crushing of sugarcane lead to excessive deterioration in the quality of sugarcane. The aim of this project was to develop a computer based model of sugarcane harvesting and delivery systems that could be used to investigate methods of reducing harvest-to crush delays. A literature review was conducted and simulation modelling was chosen as the most appropriate modelling technique for the situation of sugarcane harvesting and delivery and the purposes of this project. The Arena modelling system was chosen as the simulation software with which to construct the model. A model was developed on the scale of a particular sugar mill and the area of farms supplying it with cane. The Sezela mill on the south coast of KwaZulu-Natal, South Africa was chosen as a case study on which to develop and test the model. The model integrated a harvesting and transport section which represented all the individual farms or combinations of farms in the area with a millyard section. After the model had been verified and validated, it was used to investigate the effect of a number of different scenarios of harvesting and delivery systems and schedules on harvest-to-crush delays in the Sezela mill area. The results of the experimental runs performed with the model indicated that the most significant decreases in harvest-to-crush delays could be brought about by matching harvesting, delivery and milling cycles as closely as possible. It was also evident that burn-to-cut delays where daily burning is not practised constitute a large proportion of overall harvest-to crush delays. The model proved to be useful in making comparisons between systems and in providing a holistic view of the problem of harvest-to-crush delays. Recommendations for future developments of the model include adding a mechanical harvesting component and making the model more easily applicable to other mill areas.
A study on reducing primary transport costs in the South African timber industry.
(2005) Lusso, Cary D.; Lyne, Peter William Liversedge.; Bezuidenhout, Carel Nicolaas.
Harvesting and transport accounts for up to 70% of the total production cost of roundwood in South Africa. This invokes an interest to improve harvesting systems through the introduction of improved equipment, road networks and more refined operating techniques. A literature review was conducted which investigated the various harvesting systems and equipment with a focus on ground based extraction, as it accounts for 96% of the timber being extracted annually in South Africa. A review of forest roads in South Africa was also conducted and it was concluded that at present there has been little focus on the upgrading and maintenance of forest road networks. It was concluded that the most significant reduction in transport costs would be achieved by reducing the distances travelled by expensive extended pnmary transport (R5.83 t-1.km-1) and by allowing less expensive secondary terminal transport (R0.4 t-1.km-1) to move further into the plantations. This could only be achieved by investing large amounts of capital into the upgrading of forest roads to a standard suitable to service secondary transport vehicles. A model was developed which was able to determine the tonnage of timber needed to flow over a particular road that will warrant the upgrading cost. The model was applied to two study areas, the first study yielded no results due to the already dense network of B- class roads, possibly excessive. The second study area identified three possible road upgrades to improve the existing transport system. A full costing of the existing and modified transport system was completed and a significant cost saving was shown, not accounting for the road upgrading cost. Capital budgets were used to account for more complex parameters, such as tax and discount rates, previously excluded from the simple model. These were used to determine the economic viability of the upgrades and to evaluate the suitability of the model. The model proved to be successful and confirmed that forest roads can be optimised accompanied by significant cost savings. The model is generic and simple allowing for easy application to a variety of situations and is also flexible to modifications.
The feasibility of automatic on-board weighing systems in the South African sugarcane transport industry.
(2009) Pletts, T. R.; Lyne, Peter William Liversedge.; Lagrange, Louis F.
Sugarcane hauliers in South Africa have high variations in vehicle payloads, which influence both transport economics and the legitimacy of their operations. Increasing economic pressure due to declining sugar prices and ever increasing fuel prices has invoked interest to improve vehicle utilisation and reduce costs, while complying with the local traffic legislation. On-board weighing technologies, such as on-board load cells, could assist operators to control their payloads more accurately and hence reduce the frequency of both over and under loaded consignments. In this study, an investigation is conducted to evaluate the feasibility of on-board weighing systems in the South African sugarcane transport industry. An overview of on-board weighing systems is presented. The overview gives insight into the technical composition of an on-board weighing system as well as presenting various benefits and drawbacks that are associated with an on-board weighing system. Earlier studies conducted on the use of on-board weighing systems are scrutinised and evaluated and it is concluded from these that vehicle utilisation could be improved, while concurrently reducing the overloading of vehicles. Field research was conducted to evaluate the accuracy and consistency of on-board weighing systems currently being utilised in the sugarcane transport industry as well as to determine the critical factors that influence the effectiveness of the system while assessing if overloading of vehicles was reduced when on-board weighing systems were employed. It was concluded that the systems evaluated were reasonably accurate with mean error being 0.4 tons. The consistency of the systems was good with 75% of all measurement being within 0.5 tons of each other. The critical factors determining the effectiveness of the on-board weighing systems were established as being management of the system as well as cane variety and quality. Overloading was reduced by 9% in one field evaluation and 5% in another. Further reduction can be realised through tighter management of the on-board weighing systems. An economic evaluation of an on-board weighing system was performed using the capital budget method. This method was used to determine the pay off period required to realise the investment into an on-board weighing system for scenarios where the payload is increased by 2, 3 and 4 tons and transport lead distance is 20, 40, 60, 80, and 100 km. The shortest pay off period occurred when the lead distance was 60 km and the time was 1, 2 and 3 years for payload increases of 2, 3 and 4 tons respectively. For lead distances of 40, 60 and 80 km the investment is worthwhile and considerable returns in investment can be realised, however, for the other lead distances the pay off period could be deemed to be too long. From the observation made during the field evaluation together with the literature studied, guidelines for the use of on-board weighing systems under various transport scenarios were formulated and are presented in chapter six.
Validation of a vehicle performance modelling system.
(2007) Herbert, Russell Lloyd.; Lyne, Peter William Liversedge.
Transport costs can account for a significant portion of the total production costs in an agricultural system. In order to ensure maximum efficiency of a transport operation, the transport manager is required to select a suitable vehicle and choose the best route. This is a complex process as vehicles should not be selected based solely on lowest capital cost, but with several variables taken into account. In order to determine an optimal haulage system and to aid the decision making process, a computer model called SimTrans has been developed. SimTrans simulates a haulage vehicle travelling on any given route under normal vehicle operating conditions. The model produces a set of simulated vehicle performance results and a summary of trip details. The vehicle input parameters and route details can be modified to enable the user to simulate different vehicle configurations on alternate routes. The SimTrans model was used in this research project as it provides a comprehensive output of simulated results. However, under certain conditions there is variance between actual and the simulated vehicle performance in SimTrans, particularly with the gear selection routines. The primary objective of this research was to refine, calibrate and validate the current SimTrans model. An initial investigation focused on diesel engine management systems for heavy-duty commercial vehicles and how these systems affect a vehicle's performance. This investigation was aimed at gaining an understanding of how performance data could be gathered directly from the onboard vehicle electronics of a haulage vehicle. A data logging system was developed to measure and record certain operating parameters of a haulage vehicle during operation. The system was installed on a Mercedes Benz 2637 and the vehicle was driven on two alternative routes between the Eston Sugar Mill and a loading zone near Mid-Illovo. The Mercedes Benz 2637 used for the vehicle tests was simulated in SimTrans using identical operating conditions of route and speed limits. By comparing the observed and simulated data sets, errors particularly with gear selection routines were identified. The SimTrans model was modified such that these errors were corrected and a new gear skipping routine was added. The modified SimTrans model was validated through a comparison of a new set of simulated results with the observed data. The modified model showed significant improvement in simulation accuracy over the previous version of SimTrans.