NDT


Radiographic Testing (RT): Complete Guide (X-Ray & Gamma Ray)

⭐ Radiographic Testing (RT): Complete Guide (X-Ray & Gamma Ray)

Radiographic Testing (RT) is a powerful Non-Destructive Testing (NDT) method used to detect internal defects in welds, castings, and components using X-rays or Gamma rays.

RT is widely used in oil & gas, pressure vessels, pipelines, power plants, shipyards, aerospace, and heavy fabrication industries.

⭐ What is Radiographic Testing?

Radiographic Testing works on the principle of radiation absorption.
When radiation passes through a material:

  • Thicker or denser areas absorb more radiation

  • Defective areas absorb less radiation

  • The variation appears as dark or light areas on film or digital image

This makes internal defects clearly visible.

⭐ Types of Radiographic Testing

🔹 1. X-Ray Radiography

  • Uses X-ray tubes

  • Requires electrical power

  • High image quality

  • Used in labs, fabrication shops

🔹 2. Gamma Ray Radiography

  • Uses radioactive isotopes

  • Portable

  • Widely used on site

Common Isotopes Used

IsotopeTypical Use
Ir-192Welding inspection
Co-60Thick materials
Se-75Thin sections

⭐ RT Techniques

1. Film Radiography

  • Traditional method

  • Uses radiographic film

  • Chemical processing required

2. Computed Radiography (CRT)

  • Uses imaging plates

  • Digital image

  • Faster processing

3. Digital Radiography (DRT)

  • Real-time digital image

  • No film

  • Faster & cleaner

⭐ RT Equipment

✔ X-ray machine / Gamma camera
✔ Radiation source
✔ Radiographic film / imaging plate / detector
✔ Lead screens
✔ IQI / Penetrameter
✔ Film viewer / software
✔ Dosimeter
✔ Warning signs & barriers

⭐ RT Procedure (Step-by-Step)

1. Surface Preparation

Remove dirt, paint, spatter.

2. Selection of Technique

SWSI / DWDI / Panoramic / Elliptical.

3. Placement of Film / Detector

Ensure proper alignment.

4. Exposure Calculation

Based on material thickness, source, distance.

5. Radiation Exposure

Follow safety rules strictly.

6. Film Processing / Image Capture

Develop film or view digital image.

7. Interpretation & Evaluation

Compare with acceptance criteria.

8. Reporting

Record results, defects, location.

⭐ Radiation Safety (VERY IMPORTANT)

✔ Follow ALARA principle
✔ Use dosimeters
✔ Maintain controlled area
✔ Proper warning signs
✔ Qualified RSO supervision
✔ Safe storage of source

Radiation safety is mandatory by law.

⭐ Advantages of Radiographic Testing

✔ Detects internal volumetric defects
✔ Permanent record available
✔ High accuracy
✔ Accepted by all major codes
✔ Suitable for complex welds

⭐ Limitations of RT

❌ Radiation hazard
❌ Costly compared to UT
❌ Access required both sides
❌ Not ideal for planar defects
❌ Requires trained personnel

⭐ RT Codes & Standards

  • ASME Section V

  • ASME Section VIII

  • AWS D1.1

  • ISO 17636

  • API 1104

  • EN Standards

⭐ Common Welding Defects Detected by RT

DefectAppearance
PorosityDark round spots
Slag InclusionElongated dark lines
Lack of FusionLinear dark indication
Lack of PenetrationCentral dark line
CracksThin sharp dark lines

⭐ Industries Using RT

  • Oil & Gas

  • Power Plants

  • Petrochemical

  • Shipbuilding

  • Aerospace

  • Structural Fabrication

⭐ Best Tool for RT Inspectors

For RT exposure calculation, defect reference, safety & quizzes:

✔ RT calculators
✔ Exposure charts
✔ Defect gallery
✔ Procedures
✔ Radiation safety
✔ AI assistant

👉 Download NDT App

⭐ Conclusion

Radiographic Testing is one of the most trusted NDT methods for detecting internal defects.
With proper safety, technique, and interpretation, RT ensures structural integrity and compliance.