Visual inspection of welds
A visual weld inspection (Visual Testing or VT) is a Non-Destructive Testing (NDT) procedure in which the quality and integrity of a weld seam are carefully assessed without damaging the material. It is the most widely used and efficient method for detecting surface imperfections.
The inspection is performed by a certified welding inspector and can be divided into three main phases:
Before welding: Checking the welding procedure specification (WPS), weld seam preparation, weld seam shape, fit, and cleanliness of the material.
During welding: Monitoring progress, such as the quality of the root layer, any intermediate cleaning, and the correct welding parameters.
After welding: Visual assessment of the final weld seam for dimensions, profile, and any external defects.
During the inspection, the welding inspector checks the weld joint for imperfections that could compromise structural integrity. Common defects include:
Cracks and pores, insufficient penetration, undercut, lack of fusion, overlap, spatter, craters, and unwanted deformations
Although the inspector starts with the naked eye, specific tools are often used to measure and assess accurately:
Weld gauges : For measuring the angle, thickness, and any deviations in the profile of the weld.
Magnifying glasses and mirrors: For better observation of small details or hard-to-reach places.
Good lighting: Essential for observing every detail and surface defect.
Standards
Visual inspections are often performed according to ISO 17637. A widely used assessment standard in Europe is ISO 5817, which defines the quality levels (e.g., B, C, and D) for imperfections in fusion welds.
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