What non-destructive testing (NDT) methods are used in welding?

Non-destructive testing (NDT) methods allow checking weld quality without destroying the part. The most common methods:

1. Visual inspection (VT)

• The first step of any inspection. Checks: weld appearance, porosity, visible cracks, arc strikes, craters, undercut, overlap
• The inspector must be certified CGSB Level 1 or 2

2. Radiography (RT) — X-ray or Gamma

• Radiographic image of the weld revealing internal defects: slag inclusions, lack of fusion, internal porosity, cracks
• Standard: CSA W59 (acceptance criteria) or ASME Section V (method)
• Cost: no published price — it depends on the laboratory, the number of films and travel

3. Ultrasonics (UT)

• High-frequency sound waves that detect planar defects (cracks, lack of fusion) that radiography may miss
• Requires a CGSB Level 2 certified operator
• Faster and cheaper than radiography — with no price published by the platform

4. Dye penetrant (PT) and Magnetic particle (MT)

• Dye penetrant: For detecting surface cracks on any non-porous material
• Magnetic particle: For magnetic materials (steel). Magnetic particles reveal surface and subsurface defects