What is Radiography Testing (RT)?
Radiography Testing (RT) is a non-destructive testing (NDT) method which uses either x-rays or gamma rays to examine the internal structure of manufactured components identifying any flaws or defects. In Radiography Testing the test-part is placed between the radiation source and film (or detector). The material density and thickness differences of the test-part will attenuate (i.e. reduce) the penetrating radiation through interaction processes involving scattering and/or absorption.
RT is commonly employed across industries such as aerospace, construction, oil and gas, and manufacturing to detect hidden flaws such as cracks, voids, inclusions, and other discontinuities that may compromise structural integrity.
The differences in absorption are then recorded on film(s) or through an electronic means. In industrial radiography there are several imaging methods available, techniques to display the final image, i.e. Film Radiography, Real Time Radiography (RTR), Computed Tomography (CT), Digital Radiography (DR), and Computed Radiography (CR).
Principles of RT
RT operates on the principle of differential absorption of radiation. X-rays or gamma rays penetrate the test object, and the variations in material thickness and density cause differences in the absorption of radiation. A radiographic film or digital detector captures these differences, producing an image that reveals internal structures and potential flaws.
The key steps in radiographic testing include:
> Source Selection: Choosing the appropriate radiation source (X-ray or gamma-ray) based on material type
and thickness.
> Exposure: Directing radiation through the component onto a detector.
> Imaging: Capturing the transmitted radiation to produce an image.
> Interpretation: Analyzing the radiographic image for indications of flaws.
Importance of Radiography Testing in NDT Testing
- Defect Detection:
- Identifies internal flaws such as porosity, inclusions, cracks, and incomplete weld penetration.
- Quality Assurance:
- Ensures components meet industry standards and regulatory compliance.
- Preventative Maintenance:
- Detects potential failure points before they lead to costly repairs or catastrophic failures.
- Safety Compliance:
- Critical in industries where failure can have severe consequences, such as nuclear power and aerospace.
- Process Improvement:
- Provides valuable feedback to improve welding and manufacturing processes.
Types of RT
There are two primary types of RT based on the radiation source used:
1. X-ray Radiography: It uses X-ray tubes to generate high-energy radiation. Suitable for thinner materials and finer details.
2. Gamma-ray Radiography: Uses radioactive isotopes such as Iridium-192 or Cobalt-60. Penetrates thicker materials and is more portable
for field applications.
How does it Work?
Radiographers project radiation through the material being inspected and capture the resulting image on a detector.
The process includes the following steps:
- Analysis: The captured image is analyzed to identify any anomalies or defects within the object.
- Setup: The object to be inspected is positioned between a radiation source and a detection medium (such as a film or digital detector).
- Radiation Exposure: X-rays or gamma rays are directed toward the object. The radiation passes through the material and interacts differently depending on the material’s density and thickness.
- Image Capture: The varying levels of radiation that pass through the object creates an image on the detection medium. Denser areas block more radiation and appear darker, while less dense areas appear lighter.
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