Browsing by Author "Ogaji, S. O. T."
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Item Open Access Advanced gas-path fault diagnostics for stationary gas turbines(Cranfield University, 2003) Ogaji, S. O. T.; Singh, RitiThe reliabilities of the gas-path components (compressor, burners and turbines) of a gas turbine (GT) are usually high when compared with those of other GT systems such as fuel supply and control. However, in the event of forced outage, downtimes are normally high, giving a relatively low availability. The purpose of condition monitoring and fault diagnostics is to detect, isolate and assess (i.e. estimate quantitatively the magnitude of) the faults within a system, which in this case is the gas turbine. An effective technique would provide a significant improvement in economic performance, reduce operational and maintenance costs, increase availability and improve the level of safety achieved. However, conventional analytical techniques such as gas-path analysis and its variants are limited in their applications to engine diagnostics due to several reasons that include their inability to:- operate effectively in the presence of noisy measurements; distinguish effectively sensor bias from component faults; preserve the nonlinearity in the gas-turbine parameter relationships; and the requirement for more sensors for achieving accurate diagnostics. The novelty of this research stems from its objective of overcoming most of these limitations and much more. In this thesis, we present the approach adopted in developing a diagnostic framework for the detection of faults in the gas-path of a gas turbine. The framework involves a large-scale integration of artificial neural networks (ANNs) designed and trained to detect, isolate and assess the faults in the gas-path components of the engine. Input to the diagnostic framework are engine measurements such as spool speeds, pressures, temperatures and fuel flow while outputs are either levels of changes in sensor(s) for the case of sensor fault(s) or the level of changes in efficiencies and flow capacities for the case of faulty components. The diagnostic framework has the capacity to assess both multiple component and multiple sensor faults over a range of operating points. In the case of component faults, the diagnostic system provides changes in efficiencies and flow capacities from which interpretations can be sought for the nature of the physical problem. The implication of this is that the diagnostic system covers a wide range of problems - both likely and unlikely-. The technique has been applied to several developed test cases, which are not only thermodynamically similar to operational engines, but also covers a range of engine configurations and operating conditions. The results obtained from the developed approach has been compared against those obtained from linear and nonlinear (recursive linear) gas-path analysis, as well as from the use of fuzzy logic. Analysis of the results demonstrates the promise of ANN applied to engine gas-path fault diagnostic activities. Finally, the limitations of this research and direction for future work are presented.Item Open Access Bio-remediation of a sludge containing hydrocarbons(Elsevier, 2007) Ayotamuno, M. J.; Okparanma, R. N.; Nweneka, E. K.; Ogaji, S. O. T.; Probert, S. D.Bio-augmentation has been used as a bio-remediation option for hydrocarbon-contaminated, oily-sludge restoration. This sludge was obtained from the Bonny-Terminal Improvement Project (BTIP) for Bonny Island, near Port Harcourt, Nigeria. Its total hydrocarbon-content (THC) was 69,372 mg/kg of sludge. Three treatment reactors (X, Y and Z) and one control reactor (A) were charged with 1500 g of oily sludge and 250 g of agricultural soil (i.e. an oily sludge to soil ratio of 6:1), the mixture homogenized and allowed to settle for seven days before various CFUs were added to reactors X, Y and Z. Reactor A did not receive any bio-preparation. The agricultural soil served both as a nutrient and a microbe carrier. With regularly scheduled mixing and watering, the THC reduction in the oily sludge varied between 40.7% and 53.2% within two weeks as well as between 63.7% and 84.5% within six weeks of applying the bio-remediation. The CFU counts of the added bio-preparation varied between 1.2 × 1212 and 3.0 × 1012 CFU/g of sludge and decreased to 7.0 × 1011 CFU/g of sludge by the end of the sixth week. The pH of the degrading sludge fluctuated between 6.5 and 7.8 during the same period. When compared with the performance of the indigenous microbes in the control sample, the added bio-preparation evidently increased the THC reduction rate in the oily sludge.Item Open Access Bioremediation of a crude-oil polluted agricultural-soil at Port Harcourt, Nigeria.(Elsevier, 2006-11) Ayotamuno, M. J.; Kogbara, R. B.; Ogaji, S. O. T.; Probert, S. D.A combination of treatments, consisting of the application of fertilizers and oxygen exposure, was evaluated in situ during a period of six weeks. Conditions of a major spill were simulated by sprinkling crude-oil on experimental cells containing agricultural soil. The remedial treatments were then applied and the soil characteristics analyzed after set periods. Soil physicochemical parameters, such as moisture content, pH value, electrical conductivity as well as organic-carbon and total-nitrogen contents, showed distinct variations with time. The total heterotrophic-bacteria (THB) count in all the treatment cells increased with time. The control cell, O (which was not treated) indicated no signs of remediation within the study period. The hydrocarbon losses (50–95%) experienced in the five other treatment-cells revealed the effectiveness in degrading the hydrocarbon contaminant. The results of this study indicate that the application of increased concentrations of nutrients (by the application of fertilizers) lead to greater rates of biodegradation of petroleum-polluted agricultural soils.Item Open Access Development and implementation of preventive-maintenance practices in Nigerian industries.(Elsevier, 2006-10) Eti, Mark C.; Ogaji, S. O. T.; Probert, S. D.A methodology for the development of PM using the modern approaches of FMEA, root-cause analysis, and fault-tree analysis is presented. Applying PM leads to a cost reduction in maintenance and less overall energy expenditure. Implementation of PM is preferable to the present reactive maintenance procedures (still prevalent in Nigeria.Item Open Access Farm mechanization leading to more effective energy-utilizations for cassava and yam cultivations in Rivers State, Nigeria(Elsevier Science B.V., Amsterdam., 2006-12-01T00:00:00Z) Nkakini, S. O.; Ayotamuno, M. J.; Ogaji, S. O. T.; Probert, S. D.Surveys have been conducted, under the auspices of the Ministry of Agriculture and Agricultural Development Projects (ADPs), in the 23 local-government areas of the Rivers State, Nigeria. A structured questionnaire, personal visits to farms and interactions with information repositories were used. The quantities of energy consumed by tractors used in activities associated with the growing of cassava and yam crops in those areas were compared with traditional operations, using just manual labour. Within the period of 1986–2004, the total energy utilizations in the production of these crops, in the 23 local government areas, were 2738.87 and 33.5 MJ for tractor-power and traditional-manual operations, respectively. The tractorization intensity (TI) dropped from 0.352 hp/ha in 1986 to 0.345 hp/ha in 2004. This result was below the presently advocated 0.5 hp/ha for agricultural operations in order to increase crop production. This study identified the causes of this shortfall and recommended, at least for the short- term future, that farm industrialization of all sectors should be subsidizeItem Open Access Gas-turbine diagnostics using artificial neural-networks for a high bypass ratio military turbofan engine(Elsevier Science B.V., Amsterdam., 2004-08-01T00:00:00Z) Joly, R. B.; Ogaji, S. O. T.; Singh, R.; Probert, S. D.The Tristar aircraft, operated by the Royal Air Force, fly many thousands of hours per year in the transport and air-to-air refuelling roles. A large amount of engine data is recorded for each of the Rolls-Royce RB211-524B4 engines: it is used to aid the maintenance process. Data are also generated during test-bed engine ground-runs after repair and overhaul. In order to use recorded engine data more effectively, this paper assesses the feasibility of a pro-active engine diagnostic-tool using artificial neural networks (ANNs). Engine-health monitoring is described and the theory behind an ANN is described. An engine diagnostic structure is proposed using several ANNs. The top level distinguishes between single-component faults (SCFs) and double-component faults (DCFs). The middle-level class includes components, or component pairs, which are faulty. The bottom level estimates the values of the engine-independent parameters, for each engine component, based on a set of engine data using dependent parameters. The DCF results presented in this paper illustrate the potential for ANNs as diagnostic tools. However, there are also a number of features of ANN applications that are user-defined: ANN designs; the number of training epochs used; the training function employed; the method of performance assessment; and the degree of deterioration for each engine-component's performance parameter.Item Open Access Impact of corporate culture on plant maintenance in the Nigerian electric-power industry(Elsevier, 2006-04) Eti, Mark C.; Ogaji, S. O. T.; Probert, S. D.Comparisons have been made of modern maintenance-practices, i.e. in the more developed economies, with what occurs in Nigeria. Significant differences arise due to variations in corporate culture, pertinent learning opportunities and effectiveness of strategic planning. The managerial implications of these divergences are discussed. A systematic, total productive-maintenance (TPM) approach needs to be adopted to allow corporate changes to be implemented at a rate commensurate with each organization's evolving culture. This paper advocates that maintenance should be managed better, in each organization, so as to cultivate a sense of ownership in the operators. Also autonomous maintenance-teams, consisting of operators, engineers and managers, should be set up with the aims of improving personnel competence and equipment performance.Item Open Access Implementing total productive maintenance in Nigerian manufacturing industries(Elsevier, 2004-12) Eti, Mark C.; Ogaji, S. O. T.; Probert, S. D.Remarkable improvements have occurred recently in the maintenance management of physical assets and productive systems, so that less wastages of energy and resources occur. The requirement for optimal preventive maintenance using, for instance, justin-time (JIT) and total quality-management (TQM) techniques has given rise to whathas been called the total productive-maintenance (TPM) approach. This study explores the ways in which Nigerian manufacturing industries can implement TPM as a strategy and culture for improving its performance and suggests self-auditing and bench-marking as desirable prerequisites before TPM implementation.Item Open Access Local involvement in harnessing crude oil and natural gas in Nigeria(Elsevier, 2006-11) Nwosu, H. U.; Nwachukwu, I. N.; Ogaji, S. O. T.; Probert, S. D.Abstract Vast financial investments have been made in the upstream crude-oil and natural-gas (CONG) sector in Nigeria, but have not resulted in significant benefits for most Nigerians. The associated major activities, e.g., exploration, drilling, production, well intervention and service provision remain primarily controlled and managed by foreign multi-national companies. Only minor contracts have been awarded to local contractors. Several factors, ranging from locally inadequate finance being available, corrupt local operators, lack of technical expertise and the conflicting attitudes of multi-national operators and local contractors have contributed to this. Yet, numerous opportunities are increasingly available for indigenous entrepreneurs and local contractors. To achieve good public relations, sustainability and better economic performances, a wiser balance between globalisation and localisation is needed! This study considers the impedances to achieving greater indigenous inputs to the CONG sector, with recommendations proffered with respect to what could be done to alleviate them.Item Open Access Petrochemical industry in Nigeria: a performance appraisal(Elsevier, 2004-09) Eti, Mark C.; Ogaji, S. O. T.; Probert, S. D.For any country, having a large indigenous petrochemical-producing industry tends to lead to raised prosperity, improved average standard-of-living for the population and the introduction of associated modern-technology locally. However, such benefits in Nigeria have as yet not been forthcoming to significant extents. This project reviews what needs to be done in the industry to achieve these desired improvements.Item Open Access Petroleum contaminated ground-water: Remediation using activated carbon.(Elsevier, 2006-11) Ayotamuno, M. J.; Kogbara, R. B.; Ogaji, S. O. T.; Probert, S. D.Ground-water contamination resulting from the leakage of crude oil and refined petroleum products during extraction and processing operations is a serious and a growing environmental problem in Nigeria. Consequently, a study of the use of activated carbon (AC) in the clean up was undertaken with the aim of reducing the water contamination to a more acceptable level. In the experiments described, crude-oil contamination of ground water was simulated under laboratory conditions using ground-water samples collected from existing hand-dug wells at Eagle Island, Port Harcourt, Nigeria. Different masses of the absorbent (i.e., activated carbon) were then added to the samples of ground water. The so treated water samples were left to equilibrate for 7 days, after which the total petroleum hydrocarbon (TPH) contents of the samples were measured. Adsorption isotherms were derived for the two forms of activated carbon used, namely granular activated-carbon (GAC) and powdered activated-carbon (PAC). Results of the TPH analyses showed that activated carbon is an excellent means for the stripping-off of the contaminant: there were decreases in contaminant concentration from an initial concentration of 9304.70 mg/l to average final concentrations of 361.00 and 12.37 mg/l, that is, 96% and 99.9% resulting from the same amounts of GAC and PAC applications respectively. The results of this study revealed that the powdered form of AC would be very effective in the remediation of petroleum-hydrocarbon contaminated ground water and its use is therefore recommended.Item Open Access Prolonging the lives of buried crude-oil and natural-gas pipelines by cathodic protection(Elsevier, 2007-09) Lilly, M. T.; Ihekwoaba, S. C.; Ogaji, S. O. T.; Probert, S. D.In Nigeria, a major problem is the corrosion of the external surfaces of such pipelines, which are not usually adequately safeguarded during construction. A cathodic protection system should be applied to the pipeline before this period.Item Open Access Reducing the cost of preventive maintenance (PM) through adopting a proactive reliability-focused culture.(Elsevier, 2006-11) Eti, Mark C.; Ogaji, S. O. T.; Probert, S. D.The economic and political realities of the 1990s forced managers to reverse long-standing organizational cultures in order to reduce costs and energy expenditures in their organisations. For instance, these can be achieved, with respect to maintenance, by replacing a reactive repair-focused attitude by a proactive reliability-focused culture. Thereby far less (i) human effort is expended and (ii) energy would be wasted, both of which lead to increased profitability.Item Open Access Reliability of the Afam electric power generating station, Nigeria(Elsevier, 2004-03) Eti, Mark C.; Ogaji, S. O. T.; Probert, S. D.Today’s economic climate requires that each industry aim at achieving maximum production capability while minimizing capital investment e.g. in the maintenance function. This means finding ways to maximize equipment reliability and up-time and extend plant and equipment life through cost effective maintenance. This paper surveys the performance of gas turbine plants in Afam Thermal Power Station. The findings show that the impact of lost generation (through non-availability) exceeded within a few years, the initial purchase price of the power plants and associated equipments.Item Open Access Strategic maintenance-management in Nigerian industries(Elsevier, 2006-03) Eti, Mark C.; Ogaji, S. O. T.; Probert, S. D.A developing society needs to adapt to change and foster creativity. In the pursuit of continual improvement (e.g., reducing fossil-fuel consumption and waste, better service performance, greater availability and improved reliability), implementing wise maintenance-schedules is essential for contemporary organisations. Several studies of a wide range of Nigerian industries indicate that indigenous low availability and low productivity are endemic. The resulting closure of some of these industries has triggered off a realisation of the strategic challenges in maintenance management. In addition, the increasingly-competitive business environment in Nigeria has raised the strategic importance of maintenance functions, especially in organisations with significant investments in physical assets. Five strategic aspects of maintenance management have been identified, namely: maintenance methodology; support processes; organisation and work structuring; comparable culture; and general management policy. Three factors that permeate these dimensions are wise leadership, excellent communications and an understanding of the human factors involved.Item Open Access TERA- A Tool for Aero-engine Modelling and Management(2007-06) Ogaji, S. O. T.; Pilidis, Pericles; Hales, RichardOne of the distinguishing features of the civil aero-engine market is its high competitiveness. The costs and risks associated with new projects are such that the difference between two apparently equally attractive options could result in success from one and a threat to the survival of the company from the other. To conceive and assess engines with minimum global warming impact and lowest cost of ownership in a variety of emission legislation scenarios, emissions taxation policies, fiscal and Air Traffic Management environments, a Techno-economic and Environmental Risk Assessment (TERA) model is needed. TERA incorporates multi-disciplinary modules for modelling gas turbine and aircraft performance, estimation of engine weight, noise and emissions as well as environment impact and operating economics. The TERA software is integrated with a commercial optimiser and provides a means for cycle studies. It is to be expected that new legislative and fiscal constraints on air travel will demand an extension to the customary range of asset management parameters. In such a business environment there is potential for TERA to develop into a useful tool for aircraft and engine asset management. This paper presents a description of this tool as well as gives some results from scenario studies.