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ASNT VT Level III study materials
ASNT VT Level III study resources

ASNT VT Level III: Visual Testing Techniques and Procedures

ASNT VT Level III · Work through your exam, one topic at a time.

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Visual Testing Techniques and Procedures

Planning the Inspection

A visual testing procedure must define how, where, and when to look. The Level III must ensure the procedure is technically sound and compliant with standards.

Key concepts:

  • Inspection stages: VT can be performed before, during, and after manufacturing (in-process, final, in-service). Each stage has different access and lighting challenges.
  • Surface preparation: The surface must be clean and free of contaminants that could mask discontinuities. Sometimes lighting techniques (e.g., grazing light) enhance surface detail.
  • Viewing angles: The angle between the eye and the surface affects detection. For surface-breaking discontinuities, viewing at an angle (not perpendicular) can improve contrast.
  • Direct vs. remote viewing: Remote viewing (borescopes, cameras) may be necessary but can reduce reliability; the procedure must address resolution and lighting.
  • Documentation: Records must include equipment used, lighting conditions, and results. Sketches or photographs help.
  • Personnel qualification: The examiner must be qualified to the applicable standard (e.g., ASNT SNT-TC-1A, NAS-410, CP-189).

Traps in questions:

  • Assuming that a procedure written for one code is acceptable for another; always follow the specified standard.
  • Forgetting that surface preparation can introduce discontinuities (e.g., grinding marks).
  • Overlooking the need to inspect at multiple stages (e.g., after machining).
  • Misunderstanding that remote visual inspection may require higher qualification or different techniques.

Rule of thumb: For critical inspections, use a written procedure that specifies minimum illumination, viewing distance, angle, and equipment. A common rule is to view the surface at an angle of 30° to 45° to the surface to enhance contrast of surface irregularities.

Worked example: A procedure requires inspection of a weld for surface porosity. The inspector uses a flashlight at 500 lux. The procedure specifies 1000 lux. The inspection is nonconforming. The inspector should obtain a brighter light or reschedule.