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

Isotope	Typical Use
Ir-192	Welding inspection
Co-60	Thick materials
Se-75	Thin 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

Defect	Appearance
Porosity	Dark round spots
Slag Inclusion	Elongated dark lines
Lack of Fusion	Linear dark indication
Lack of Penetration	Central dark line
Cracks	Thin 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.

Ultrasonic Testing (UT): Complete Guide (2025 Update)

Ultrasonic Testing (UT) is one of the most widely used Non-Destructive Testing (NDT) methods.

It uses high-frequency sound waves to detect internal defects, measure thickness, and evaluate the integrity of materials.

UT is essential in industries like Oil & Gas, Aerospace, Manufacturing, Railways, Pipelines, Power Plants, Shipyards, and more.

⭐ What is Ultrasonic Testing?

Ultrasonic Testing sends sound waves (usually 1–10 MHz) into a material.

If there is any flaw (crack, porosity, lack of fusion, inclusion), the sound wave reflects back and shows a signal on the screen.

UT detects:

✔ Internal cracks

✔ Lack of fusion

✔ Porosity

✔ Lamination

✔ Corrosion / thickness loss

✔ Welding defects

✔ Inclusion & foreign material

⭐ How UT Works (Simple Explanation)

A UT probe generates high-frequency sound
Sound enters the material through couplant
Hits the back wall or defect
Reflects back to the probe
Signal appears on the A-scan display
Inspector interprets the signal

UT = simple, accurate, and fast.

⭐ Types of Ultrasonic Testing (UT Methods)

🔹

1. Straight Beam (0° UT)

Used to detect:

Laminations
Thickness measurement
Internal vertical defects

🔹

2. Angle Beam (45°, 60°, 70°)

Used in weld joints to find:

Lack of fusion
Lack of penetration
Cracks
Slag inclusion

🔹

3. Phased Array Ultrasonic Testing (PAUT)

Advanced method, used to create real-time images of the weld.

Detects even small cracks & complex flaws.

🔹

4. TOFD (Time of Flight Diffraction)

Excellent for crack sizing and accurate depth measurement.

🔹

5. Immersion UT

Used in manufacturing & aerospace components.

High accuracy.

⭐ UT Equipment (Basic Components)

✔ UT Machine

✔ Straight/Angle Probes

✔ Calibration Block (V1/V2)

✔ Couplant (gel/oil)

✔ Cables

✔ Marker & Chalk

✔ A-scan Display

Proper calibration is mandatory before inspection.

⭐ UT Calibration – Step-by-Step

1. Select Calibration Block

V1 block (most common)
V2 block (for angle beam)

2. Set Calibration Parameters

Velocity
Range
Delay
Gain
Probe angle

3. Adjust Using Reference Reflectors

Side drilled holes
Radius
Notches
Back wall echo

4. Check DAC / TCG Curve

Ensures consistent sensitivity.

5. Verify before & after testing

To ensure accuracy.

⭐ UT Procedure (Step-by-Step)

1. Clean surface

Remove rust, paint, dirt.

2. Apply couplant

Helps sound travel into material.

3. Move probe slowly

Scan entire area with overlap.

4. Observe A-scan signals

Look for:

Peak echoes
Noises
Drop in back-wall echo
Consistent patterns

5. Mark defect location

Use marker & grid system.

6. Evaluate defect size

Using DAC, TCG, DGS charts.

7. Prepare report

With:

Location
Depth
Length
Type of indication

⭐ Advantages of Ultrasonic Testing

✔ High accuracy

✔ Detects internal defects

✔ Portable & fast

✔ Safe (no radiation)

✔ Depth of penetration high

✔ Useful for all metals

✔ Good for welds & castings

⭐ Limitations of UT

❌ Skilled inspector required

❌ Surface must be clean

❌ Difficult on rough/few geometries

❌ Couplant mandatory

❌ Interpretation varies per operator

⭐ NDT Codes & Standards for UT

ASME Section V
ASME B31.3 / B31.1
AWS D1.1
ISO 17640
EN Standards
API 650 / 653 / 1104

These define acceptance criteria, scanning, calibration, reporting.

⭐ Common UT Welding Defects

Defect	How UT Detects
Lack of Fusion	High reflection, near weld toe
Lack of Penetration	Back-wall loss, central indication
Slag Inclusion	Multiple clustered echoes
Crack	Sharp peak, angle reflection
Porosity	Scattered low-intensity signals

⭐ Applications of UT in Industries

Oil & Gas

Pipeline welds, tanks, offshore structures.

Power Plants

Boilers, heat exchangers, steam lines.

Railways

Axles, wheels, rails.

Construction

Structural steel, bridges.

Aerospace

Aircraft parts, composites.

⭐ Best UT Tool for Engineers (Use This App)

If you work in UT or preparing for Level 1/2:

✔ UT Calculators

✔ Angle Beam Tools

✔ Weld Defect Analysis

✔ Formulas

✔ Quizzes

✔ Procedures

✔ AI Assistant

👉 Download NDT App:

⭐ Conclusion

Ultrasonic Testing is one of the most important NDT methods for detecting internal defects.

With proper calibration, technique, and tools, UT provides highly accurate results for industrial inspection.