In this paper, research and developmental efforts that demonstrate high sensitivity detection and characterization of defects and assessment of microstructural degradation, residual stresses and fatigue damage in materials using different non-destructive evaluation (NDE) techniques, have been discussed. Applications of eddy current techniques for quantitative defect characterization and for generalized applications, and remote field eddy current technique for inspection of steam generator and heat exchanger tubes have been discussed. Advanced ultrasonic methods such as time of flight diffraction, synthetic aperture focusing technique, phased array and signal processing for detection, characterization and imaging of defects have been discussed. Applications of ultrasonics and magnetic Barkhausen emission techniques for characterization of microstructures and residual stresses have been discussed. Applications of acoustic emission and infrared thermography techniques for weld quality evaluation of critical nuclear components as part of intelligent processing of materials (IPM) work have been discussed. Application of acoustic emission technique for integrity assessment of pressurized components has been discussed. Development of a software called assets and infrastructure management system (AIMS), for storing and retrieving information for various materials, components and systems, has also been highlighted. The techniques and applications discussed are result of systematic and innovative R&D efforts in the multidisciplinary areas of physics, materials, instrumentation, sensors and softwares for providing solutions to various challenging problems.
Pressure retaining components are fabricated to meet stringent design specifications with respect to fabrication quality and in-service performance. Important pressure retaining components are pressure vessels, pipelines, storage tanks, boiler drums, boiler tubing, headers, superheaters, reheaters, economizers, etc. These components are subjected to complex service environment such as exposure to elevated temperature, hostile media and loading. The adverse synergy of manufacturing realities and service environment (normal and off-normal) leads to degradation in mechanical properties of materials like strength, fracture toughness, etc. due to microstructural changes, corrosion, creep and fatigue damage. The successful performance of these components during entire life requires comprehensive implementation of a dedicated programme for stringent quality control during fabrication and condition assessment through on-line and periodic in-service inspection (ISI), coupled with mechanistic assessments and structural analysis. The condition assessment and life prediction approaches enable uninterrupted safe operation, avoidance of unplanned shutdowns and taking decision on repair, upgradation, modernization and replacement of necessary components for extension of the life of plants beyond their design lives. A key role is played through meticulous planning and incorporation of non-destructive evaluation (NDE) techniques which aim at detection and characterization of defects and evaluation of residual stresses, corrosion, microstructural degradations and dimensional changes that occur in components during their service life, due to exposure to high temperature, pressure, static and dynamic loads, hostile environment, etc.
Advanced NDE sensors, techniques, procedures and softwares are applied to meet stringent quality and in-service performance requirements of materials and components. Research in this field has been undertaken to gain in-depth understanding of interaction of probing medium with material through multidisciplinary bench mark experiments, and innovative analysis for characterization of defects and microstructural degradation of materials with high sensitivity and reliability.
In this paper, a few of the research and developments that demonstrate the usefulness of synergy between systematic and innovative approaches and sound knowledge in the multidisciplinary areas of physics, materials, instrumentation, sensors and softwares in providing effective solution to challenging problems, are given. The specific topics discussed include advanced eddy current impedance imaging for defect evaluation, remote field eddy current systems for inspection of steam generator and heat exchanger tubes, ultrasonic and magnetic Barkhausen analyses for characterization of microstructures and residual stresses, and intelligent welding for obtaining reliable quality components and systems. After discussing these emerging developments, a few activities of significance towards quality control and in-service performance assessment of pressure retaining equipment are also highlighted.
Research and developmental efforts that demonstrate high sensitivity detection and characterization of defects and assessment of microstructural degradation, residual stresses and fatigue damage in various materials using different NDE techniques have been discussed. Applications of eddy current intelligent imaging for quantitative defect characterization and remote field eddy current testing for in-service inspection of ferromagnetic tubes of steam generators have also been discussed. Application of ultrasonics and magnetic Barkhausen emission techniques for assessment of microstructural evaluation, deformation and fatigue damage in ferritic steels and austenitic stainless steels has been presented. Application of on-line infrared thermography technique for quality evaluation of welding process has been highlighted. Application of acoustic emission technique for integrity assessment of pressurized components has also been discussed. Advanced ultrasonic methods such as ultrasonic time of flight diffraction (TOFD), ultrasonic synthetic aperture focusing technique (SAFT), phased array and signal processing for detection, characterization and imaging of defects are also highlighted. Development of a software called assets and infrastructure management system (AIMS) for storing and retrieving information including design specifications, material composition and properties, fabrication history, quality assurance, pre-service inspection and in-service inspection data for various materials, components and systems used in a plant, has also been highlighted. The techniques and applications discussed in this paper are the result of systematic and innovative research and development efforts in the multidisciplinary areas of physics, materials, instrumentation, sensors and softwares for providing solutions to various challenging problems and/or those found promising in laboratory studies. It should be the endeavour of the NDE community and the industry to translate these unique developments in to practical applications on a wider scale.
