Also known as conventional radiography, film radiography uses photographic film and a source of ionising radiation placed on either side of the part being inspected to show the internal detail of the part. The radiation is partly absorbed during transmission and differences in the amount of absorption are recorded on the film.

Industrial radiography requires X-rays or gamma (g) rays to reveal hidden flaws. The terms X-radiography and gamma radiography indicate the source of radiation in use. X-rays are generated electrically by means of a high voltage X-ray tube. Gamma rays are produced by the natural disintegration of nuclei in a radioactive isotope, Iridium 192 and Cobalt 60 being most commonly used. Radiation safety procedures must be followed when radiographic inspection is carried out.

What Will It Find?
Radiography is a well-established technique that is widely used to detect volumetric flaws in welds (e.g. voids or slag inclusions). It is typically used to verify weld quality during the fabrication of pressure vessels, pipelines, storage tanks and other engineering structures. It can be used on all metals, from light metals such as aluminium to dense metals such as copper. It cannot reliably detect tight planar, crack-like flaws in steel welds such as lack of fusion if they are misaligned relative to the radiation beam, because the volume is too small to produce a significant difference in radiation absorption properties. This is particularly so when the crack interface lies perpendicular to the radiation beam.