Non-destructive testing (NDT) examines materials, components, and welds without causing damage, enabling quality verification while preserving equipment for service. NDT is essential for pressure vessel fabrication, structural inspection, and quality assurance across industries.

Primary NDT methods include radiographic testing (RT) using X-rays or gamma rays to detect internal weld defects, ultrasonic testing (UT) using sound waves for volumetric examination, magnetic particle testing (MT) revealing surface and near-surface cracks in ferromagnetic materials, liquid penetrant testing (PT) highlighting surface-breaking discontinuities, and visual testing (VT) as the foundation of all inspection.

For ASME pressure vessel fabrication, NDT requirements depend on construction code, service category, and joint efficiency factors. Full radiographic examination, spot radiography, or ultrasonic examination may be specified. Acceptance criteria from code sections define allowable indications.

Advanced NDT techniques include phased array ultrasonics providing detailed imaging, time-of-flight diffraction detecting crack-like defects, computed radiography enabling digital image processing, and automated ultrasonic testing for consistent examination. These methods improve detection reliability and productivity.