NDE methodologies for characterisation of defects, stresses and microstructures in pressure vessels and pipes

Abstract

Assessment of integrity of pressure vessels and pipes is becoming increasingly important for both economic and safety reasons. Presence of harmful defects, tensile residual stresses and unacceptable microstructures may affect the integrity of any component and therefore assessment of defects, residual stresses and microstructures is essential. Many non-destructive testing techniques are employed for high sensitive detection and complete characterisation of defects, evaluation of residual stresses and assessment of microstructures. In this paper, the experience of the authors on high sensitive detection of defects by ultrasonic testing using advanced signal analysis and pattern recognition methodologies in the case of austenitic stainless steel and thin walled Zircaloy-2 weldments; residual stresses measurements and evaluation of adequacy of post-weld heat treatment of simulated tube to tube sheet weld joints of the steam generators of the prototype fast breeder reactor and evaluation of ASME repair welding procedures from the residual stress point of view in the case of 9Cr-1Mo steel; and assessment of microstructural degradation in 9Cr-1Mo steel, creep damage in 0.5Cr-0.5Mo-0.25V steel and detection of marteniste in AISI 304 type stainless steel is discussed. The miniature disc bend testing technology for evaluation of mechanical properties of components, particularly for obtaining individual properties of weld, HAZ and parent metal is also discussed. The development of expert systems for giving advice on optimum procedures for non-destructive testing and evaluation is also discussed.