Radiography Testing (RT) in NDT – Complete Guide

What is RT?

Radiographic Testing (RT) is a Non-Destructive Testing (NDT) method that uses X-rays or Gamma rays to inspect the internal structure of materials.
It helps detect internal and surface defects like cracks, voids, porosity, inclusions, and lack of fusion in welds without damaging the component.

Principle of RT

RT works on the principle of differential absorption of radiation:

• X-rays or Gamma rays pass through the test material.

• Thicker or defective areas absorb more radiation.

• A detector (X-ray film or digital imaging system) captures the variation in radiation.

• This forms a radiographic image (like a medical X-ray), showing internal defects.

Sources of Radiation

1. X-ray Machines – For controlled lab/industrial use.

2. Gamma-ray Sources – Radioactive isotopes (Ir-192, Co-60, Se-75) for field use.

Techniques of RT

1. Film Radiography – Traditional method using radiographic films.

2. Computed Radiography (CR) – Digital imaging plates.

3. Digital Radiography (DR) – Real-time digital detectors.

4. Computed Tomography (CT) – 3D imaging with high resolution.

Step-by-Step Procedure

1. Preparation of Component – Clean and position the material.

2. Setup of Radiation Source – Place X-ray or Gamma source opposite to detector.

3. Exposure – Radiation passes through the material for a calculated time.

4. Film/Detector Processing – Develop film or capture digital image.

5. Interpretation – Inspect the radiograph for defects.

6. Evaluation & Reporting – Compare results with codes/standards.

Applications of RT

• Weld inspection (pipelines, boilers, pressure vessels).

• Aerospace (turbine blades, structural parts).

• Automotive (engine blocks, castings).

• Petrochemical and Oil & Gas industries.

• Foundries (detecting shrinkage cavities, inclusions in castings).

Advantages

• Detects surface and internal defects.

• Permanent record available (film/digital image).

• High accuracy and reliability.

• Can inspect thick materials.

Limitations

• Safety hazards due to radiation exposure.

• Requires trained, certified personnel.

• High equipment and operational costs.

• Access required to both sides of the component.

• Time-consuming compared to some other NDT methods.

Standards & Codes

• ASME Section V – NDT methods, including RT.

• ASTM E1032 – Radiographic examination.

• ISO 5579 – General principles of RT.

✅ Summary:
Radiographic Testing (RT) is a highly reliable NDT method that provides internal visibility of materials and welds, making it indispensable in industries where safety and quality are critical. Despite its high cost and radiation risks, it remains one of the most powerful inspection tools.