What Is Radiographic Testing?
Radiographic Testing (RT) is a volumetric NDT method that uses penetrating radiation — X-rays
or gamma rays — to image the internal structure of a component. Radiation passes through the
material and is captured on a recording medium — film, a computed radiography (CR) imaging
plate, or a direct digital detector array (DDA) — producing a two-dimensional image that reveals
variations in material density corresponding to internal discontinuities, voids, inclusions, or
thickness changes.
Key radiation sources used in industrial RT include:
- X-ray tubes — for lower-penetration applications, controlled energy output, and
applications requiring high image quality
- Iridium-192 (Ir-192) — the most widely used gamma source for field RT of steel pipe and
pressure vessel welds in the 10–100mm thickness range
- Selenium-75 (Se-75) — preferred for thinner-wall stainless steel and lower-density
materials where Ir-192 produces excessive contrast variation
- Cobalt-60 (Co-60) — for thick-section steel inspection where high-energy penetration is
required