Industrial X-ray vs. Gamma Radiography: Key Differences

Both are used for NDT, but which one is right for you?

Victoria Russman
Victoria Russman

What are the differences between industrial x-ray radiography and industrial gamma radiography?

Industrial x-ray radiography and industrial gamma radiography are both used to inspect materials. However, they differ in the way that examination is performed, as well as how the data is collected and interpreted.

Industrial X-ray Radiography

Industrial x-ray radiography uses a beam of electrons to irradiate a target, producing x-rays which are then incident upon the the material being inspected.

  • The beam passes through a collimator which controls the size of the beam and its direction. Think of it like a lens and the way that it controls light.
  • The x-ray beam then passes through the sample material leaving an image on a detector screen or film that is placed on the opposite side of the source.
  • This detector screen converts x-rays into visible light, recording the image to be examined.

Overall, the x-ray radiography technique is more accurate than gamma radiography and is typically used to detect internal flaws on critical manufactured parts or assemblies.

Industrial x-ray radiography diagram

Industrial x-ray computed tomography (or industrial 3D imaging) is a lab-based x-ray inspection technique in which data is collected and digitized. Specialized computer software is used to interpret the data and interrogate the specimen by providing both cross-sectional and 3D volume images. There are various viewing options with ct scanning like slicing, rotating, or colorization to get the user the exact detail or area of interest they need. Industrial ct scanning is useful for in-situ characterization and measurements of assemblies where there might be difficult to access geometries. The operator can also identify voids or porosity, measure wall thickness, detect flaws, conduct failure analysis, or analyze materials.

Computed tomography 3D image showing porosity

Industrial Gamma Radiography

Industrial gamma radiography works similarly but uses radioactive isotopes (naturally decaying atoms) instead of electrons as its source of radiation.

  • The x-ray radiography source is housed inside equipment and needs electricity to operate. Whereas, the gamma source comes from a small pellet of material housed inside a titanium capsule and does not require electricity to operate.
  • Typically, mobile gamma radiography uses either cobalt-60 or iridium-192 sources as most other radioactive isotopes have been found unsuitable.
  • The gamma source material produces energetic photons, is cheaper than x-ray, and is smaller and more portable. This makes it suitable for on-site NDT, but it should also be noted the exposure times are much longer.

The mobile gamma technique is often used for inspection of metal castings, poured concrete, or welded joints on large critical structural equipment.

Typical industrial pipes that might use gamma radiography for inspection

Nel PreTech applies industrial x-ray computed tomography to bring you the best in quality assurance for your manufactured parts. We use the foremost in x-ray inspection equipment including the Zeiss 800 (130kV) and Zeiss 1500 (225kV) ct machines.

Contact us today for a free, no-obligation quote!

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