A Test Bed for the Development of Eddy Current Inspection Techniques for Non Ferrous Heat Exchangers

Turner, Michael Martyn (2006). A Test Bed for the Development of Eddy Current Inspection Techniques for Non Ferrous Heat Exchangers MPhil Thesis, School of Information Technology and Electrical Engineering, University of Queensland.

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Author Turner, Michael Martyn
Thesis Title A Test Bed for the Development of Eddy Current Inspection Techniques for Non Ferrous Heat Exchangers
School, Centre or Institute School of Information Technology and Electrical Engineering
Institution University of Queensland
Publication date 2006
Thesis type MPhil Thesis
Supervisor Dr Gordon Wyeth
Subjects 0906 Electrical and Electronic Engineering
Abstract/Summary This thesis describes the development and implementation of a test bed for the investigation of eddy current inspection techniques used in the examination of nonferrous heat exchangers found in thermal power stations. This thesis is the product of a research project funded by the Queensland electricity industry and is also the report of its progress. The pressures placed on the environment by the emission of green house gasses and the commercial pressure to decrease the cost of electricity generation has lead to a change in plant inspection philosophy. With the development of nuclear power generation the need for safe reliable operation led to the development of heat exchanger inspection techniques. These techniques placed a priority on guaranteed results with little emphasis on cost. The techniques developed were slow and labour intensive. They were therefor inappropriate for use in non-critical inspections. With the change in environmental policy a move was made within the Queensland electricity industry to develop a cheap effective method to inspect balance of plant heat exchangers in thermal power stations. The development of computer based analysis techniques highlighted basic deficiencies in the theory generally applied to eddy current testing of heat exchangers. This resulted in the commissioning of a project to investigate the process of heat exchanger inspection and develop a more efficient technique to carry out the task. This thesis is the report on the main stream research carried out for this project. The thesis reviews the current techniques available for the inspection of non-ferrous tubing. It covers main stream techniques, as well as specialised and experimental processes. The results of the review indicate that eddy current inspection is still the most appropriate method. A review of the research being undertaken into eddy current inspection was carried out. The review highlighted the pure physics approaches being taken and concluded that their complexity ruled them out for practical implementation. The parametric approaches showed much greater promise and a recommendation for the implementation of some findings was made. The review also highlighted the lack of data for further investigation and indicated the path for the continuation of the project. To enable investigation to be carried out a review of the current state of test instruments was carried out. This review indicated that commercial equipment was unsuitable for research purposes. A design for a modern test instrument was developed using the latest digital concepts and electronics. This equipment allowed data to be collected in its pure form with no black box electronics modifying the raw data. The equipment was prototyped and found to be successful. To enable the accurate collection of data an eddy current probe manipulator was designed. It allows the probe to be manipulated in such a manner as to ensure the probe position and velocity is know and is accurate. The development of an air bearing was carried out to ensure the minimum transmission of mechanical noise to the data being collected. The design of the manipulator was successful for use within the bounds of current standards but will require modification to exceed these standards. To enable the analysis of the electromagnetic effects on defect parameters a technique for the production of artificial defects was developed. Plain defects were designed and a series of defects manufactured. At this point, due to a change in the political climate, the funding for the project was removed. This prevented the implementation of the final stage of data collection and theory development. The thesis then indicated the steps required to bring the project to a fruitful conclusion and those for further development.

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Created: Fri, 21 Nov 2008, 14:57:23 EST