Radiographic Testing (RT)

1. What is Radiographic Testing (RT)?
Radiographic testing is a non-destructive testing method that uses ionizing radiation (X-ray or gamma ray) to detect discontinuities in the internal structure of materials or welded joints.
📸 Basic Principle:
• Irradiation is applied to the material using an X-ray tube (electric source) or a radioactive isotope (e.g., Ir-192, Co-60).
• The radiation passing through the material strikes a background film or digital detector (CR/DR systems).
• If a defect is present within the material (e.g., a void, slag, or crack), more radiation passes through that area.
• This difference is used to detect the defect as a contrast difference on the film or digital image.
🧪 Radiation Sources:
• X-ray devices (usually between 100-300 kV)
• Radioactive isotopes:
o Iridium-192 (Ir-192): medium-thickness pieces
o Cobalt-60 (Co-60): thick pieces
o Selenium-75 (Se-75): thinner pieces
🖼️ Imaging Methods:
• Conventional film (X-ray)
• Computed radiography (CR)
• Direct digital radiography (DR)
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✅ 2. What are the advantages over other NDT methods?
Volumetric flaw detection is very effective. It clearly shows volumetric flaws such as porosity, slag, and lack of penetration.
It provides a permanent record. Film or digital images can be archived and viewed.
Interpretation is visual. The operator can physically examine the flaw visually.
It is not dependent on part shape. : It can also be applied to parts with complex geometries.
The orientation of the defects is not important. : It can be detected regardless of the defect's direction.
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🛠️ 3. What Defects Can Be Detected with This Method?
Radiographic examination successfully detects defects that create volumetric and density differences. However, it has low sensitivity to fine surface cracks.

Gas voids (porosity): Small or large gas-induced voids.
Slag inclusions: Slag particles trapped within the weld.
Penetration deficiency: Insufficient fusion at the root.
Lack of fusion: Incomplete interlayer fusion.
Solidification cracks: Especially in cast parts.
Foreign material inclusions: Entrapment of non-metallic particles (tungsten, slag, metal particles, etc.).
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🏭 4. What is its industrial significance?
Radiographic testing is frequently preferred in industries requiring high quality and for safety-critical components. It is particularly indispensable for certification and customer-approved projects.
Sectors and Applications
Pressure Vessels and Pipes: Volumetric inspection of weld seams (e.g., boilers, pipelines, heat exchangers)
Petrochemical/Refinery: Tanks, valves, flange welds
Nuclear Energy: Reactor sections, high-risk joints
Aerospace: Critical castings, landing gear components
Casting: Detection of porosity and mold defects within castings
Defense and Shipyards: Military hardware, armor panels, submarine welds