Visual Inspection (VT)

1. What is Visual Inspection (VT)?

Visual inspection (VT) is the oldest and most widely used non-destructive testing method. It is based on the examination of defects on the surface of materials by a trained eye or with auxiliary equipment (magnifying glass, endoscope, borescope, camera, etc.). This method, as old as human history, has become systematic in industrial quality control processes and is currently defined by various standards (e.g., EN ISO 17637, ASME BPVC, AWS D1.1). Visual inspection is divided into two categories:
• Direct visual inspection: The operator examines the object directly with the naked eye or with simple aids.
• Indirect visual inspection: The use of equipment such as cameras and borescopes in hard-to-reach areas.
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2. What are the advantages over other NDT methods?
Economical: Low equipment requirements; the naked eye, illumination, and a magnifying glass are generally sufficient.
Fast: It is applied much faster than other NDT methods, and results are achieved.
Provides a basic preliminary assessment: Provides a first impression of whether other methods are necessary.
Application flexibility: Widely used in all industries.
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3. What Defects Can Be Detected with This Method?
Visual inspection can only detect surface defects. The main detectable defects are:
Detectable Defects
Surface cracks: Fine superficial cracks in the weld area.
Porosity: Large surface porosities are particularly visible.
Slag, metal spatter: Deposits not removed after welding.
Incomplete fusion: Joint defects that are visually noticeable.
Undercuts: Grooves formed at the weld edge.
Geometrical Deformities: Weld irregularities, overflows, concavities, etc.
Corrosion, oxidation: Rust, surface deterioration.
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4. What is its Importance in Industry?
Visual inspection:
• It is considered the first step in every NDT process. It is generally mandatory for surface preparation and preliminary assessment before inspection.
• Visual inspection is stipulated in many standards, such as EN ISO 17637, ASME, and AWS.
• It is considered the first line of defense, particularly in welded fabrication, pressure vessels, pipelines, automotive, and aerospace industries.
• Inadequate visual inspection can lead to serious quality problems, even if other advanced NDT methods are used.
• Due to its cost-effectiveness, it is widely used in high-volume production.