Inspection method · VT
Visual testing (VT)
Most nonconformities are visible to a trained inspector with the right lighting, gauges and acceptance criteria. Visual testing comes first, always.
01How it works
Visual testing examines the surface of a component with the eye, aided where needed by magnifiers, mirrors, borescopes or cameras (remote visual testing). Adequate illumination, viewing angle and access are required, and the inspector's near vision is verified periodically.
For welds, VT according to ISO 17637 includes measurement of weld size, reinforcement, undercut, misalignment and other surface imperfections with weld gauges, and evaluation against the quality level specified, for example ISO 5817 level C.
02Typical industrial applications
- Welds before and after NDT
- Castings and forgings surface condition
- Machined surfaces and edges
- Coatings and finishes
- Assemblies and workmanship
- Internal surfaces with borescopes
03Benefits and what it detects
- Fast and inexpensive
- Detects most surface defects and workmanship issues
- Guides where other NDT is needed
- Can be applied at every stage
- Immediate results
04Limitations
- Only surface breaking and visible features
- Requires good access, cleaning and lighting
- Fine cracks may need PT or MT for confirmation
- Results depend on inspector competence
05Specifying and reviewing the method
Specify the acceptance standard and quality level, the stage of inspection (before or after heat treatment, before coating) and whether remote visual testing is permitted. For welds, reference ISO 17637 for the method and ISO 5817, ISO 10042 or the applicable code for acceptance.
Other references: ISO 17635 (general rules for NDT of welds)