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Welder Red Seal · Question

A welding inspector is performing an NDT on a 20 mm thick butt weld in a pressure vessel. They need to ensure there are no internal flaws like lack of fusion or slag inclusions. Due to geometric constraints, radiographic testing is impractical. Which alternative NDT method would be most appropriate for detecting these subsurface discontinuities?

Ultrasonic Testing (UT) is an excellent method for detecting subsurface discontinuities such as lack of fusion, slag inclusions, and porosity in thick materials

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Question: A welding inspector is performing an NDT on a 20 mm thick butt weld in a pressure vessel. They need to ensure there are no internal flaws like lack of fusion or slag inclusions. Due to geometric constraints, radiographic testing is impractical. Which alternative NDT method would be most appropriate for detecting these subsurface discontinuities?

Answer options:

  • Visual Testing (VT)
  • Liquid Penetrant Testing (PT)
  • Magnetic Particle Testing (MT) ✅ Ultrasonic Testing (UT)

Correct answer: Ultrasonic Testing (UT)

Explanation: Ultrasonic Testing (UT) is an excellent method for detecting subsurface discontinuities such as lack of fusion, slag inclusions, and porosity in thick materials when radiographic testing is not feasible due to access or safety. Visual and Liquid Penetrant Testing are restricted to surface flaws, and Magnetic Particle Testing is for surface/near-surface flaws in ferromagnetic materials.

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