What it finds

  • Surface damage such as cracks, corrosion, wear, dents, erosion and burn marks.
  • Weld problems such as undercut, poor profile, spatter, arc strikes and surface porosity.
  • Fit and condition: misalignment, missing fasteners, wrong parts, leaks and foreign objects.

How it works

Direct visual testing means looking at the surface with the unaided eye or with mirrors and magnifiers, at a close distance with enough light. Weld gauges, rulers and calipers turn what is seen into a measurement.

Remote visual testing reaches places that a person cannot. Borescopes, fiberscopes, video probes, crawlers and drones take the view inside engines, pipes, tanks and vessels, often with a recording.

The procedure sets what to look at, the lighting and viewing conditions, and what is acceptable. Inspectors need sharp near vision, which schemes check regularly, and enough knowledge of the product to recognize what they are seeing.

Where it is used

Everywhere. VT comes before and after welding, on aircraft walk-arounds and engine borescope checks, in pressure equipment and tank inspections, and on bridges and structures. Other methods depend on it too, because reading a PT or MT mark is a visual task. See our guides to aircraft maintenance, construction and welding inspection.

Limits

  • Surface only. It cannot tell you what is happening inside the material.
  • Tight cracks can escape the eye, which is why PT, MT or ET often follow up.
  • Access and light. Poor access, glare, dirt and coatings all hide things.
  • Human factors. Fatigue, distraction and repetitive work affect results, so good programs manage them.
  • Remote views can distort size and shape, so measurements need calibrated tools.

Who is allowed to do this work is set by a certification scheme. See How to Become an NDT Level I, II or III.

Frequently asked questions

Is visual inspection really NDT?

Yes. It does not damage the part, and when done under a written procedure with trained people it is a recognized method. SNT-TC-1A lists it alongside the others.

Is a borescope inspection visual testing?

Yes. It is remote visual testing, used when the area cannot be seen directly.

Is a CWI the same as a VT Level II?

No. A Certified Welding Inspector credential from the American Welding Society covers welding inspection more broadly. An NDT VT certification comes from an employer or scheme, and contracts say which is needed.

How NDT LLC can help

Our team of Level IIIs helps with VT procedures and qualification programs, and we take on field NDT and inspection work. Contact us.

This article is general information for a business audience, not engineering, legal or regulatory advice. Always work to the current edition of the codes, standards, regulations and manufacturer data that apply to your equipment and contracts.

NDT LLC is an independent consulting firm. It is not affiliated with, endorsed by or sponsored by ASNT, ASME, the American Welding Society (AWS), ASTM International, or any other organization named in this article; names are used only to identify the organizations and documents referred to.