Development of EMAT and piezoelectric transducers for high temperature ultrasonic thickness measurements

Improving reliability of components operating at high temperature, such as pipelines, boilers and reactors, within a range of industries is of importance in the asset management process. This thesis concerns the development and testing of ultrasound transducers for use at elevated temperatures, up to 500 _C, without the use of active cooling. Ultrasound thickness measurement applications employing these high temperature transducers includes both portable-type non-destructive testing (NDT) inspections and permanent condition monitoring, primarily towards detection of corrosion and erosion. The development and optimisation of an electromagnetic acoustic transducer (EMAT) design which generates and detects bulk radially polarised shear waves utilising a high temperature permanent magnet and a ceramic encapsulated spiral coil is discussed. This design was optimised for use on magnetite coated mild steel samples; it was shown that the magnetostriction mechanism tends to dominate, depending upon sample properties, producing large signals even at elevated temperatures. High temperature laboratory trials (up to 500 oC) demonstrated the non-linear change in signal amplitude with increasing temperature on magnetite coated mild steel samples, attributed to the complex non-linear relationship between magnetostrictive strains and applied external magnetic field. The EMAT provided good signal amplitude, even at relatively large sample-EMAT lift-off (up to 8.0 mm), demonstrating the applicability of this EMAT for high temperature scanning inspections. A longterm industrial field trial on a high temperature pipeline (≈ 350 oC) in a refinery exhibited the suitability of this design for high temperature continuous monitoring applications. A piezoelectric transducer with a novel compression-type design was optimised for application at high temperature, with the use of a waveguide, high temperature piezoelectric element and high temperature backing material; the optimisation of these components is discussed. This transducer design incorporates compression applied via a central bolt, to achieve acoustic coupling between the components, avoiding the use of adhesive layers, to generate bulk longitudinal waves. With the application of a bismuth titanate piezoelectric element, the transducer was able to generate signals on stainless steel whilst withstanding high temperatures (up to 500 oC) continuously without cooling

Technology 2000, volume 1

The purpose of the conference was to increase awareness of existing NASA developed technologies that are available for immediate use in the development of new products and processes, and to lay the groundwork for the effective utilization of emerging technologies. There were sessions on the following: Computer technology and software engineering; Human factors engineering and life sciences; Information and data management; Material sciences; Manufacturing and fabrication technology; Power, energy, and control systems; Robotics; Sensors and measurement technology; Artificial intelligence; Environmental technology; Optics and communications; and Superconductivity

Nuclear Power - Control, Reliability and Human Factors

Advances in reactor designs, materials and human-machine interfaces guarantee safety and reliability of emerging reactor technologies, eliminating possibilities for high-consequence human errors as those which have occurred in the past. New instrumentation and control technologies based in digital systems, novel sensors and measurement approaches facilitate safety, reliability and economic competitiveness of nuclear power options. Autonomous operation scenarios are becoming increasingly popular to consider for small modular systems. This book belongs to a series of books on nuclear power published by InTech. It consists of four major sections and contains twenty-one chapters on topics from key subject areas pertinent to instrumentation and control, operation reliability, system aging and human-machine interfaces. The book targets a broad potential readership group - students, researchers and specialists in the field - who are interested in learning about nuclear power