Visual Testing (VT) in Belgium
Visual testing is the most fundamental and widely used NDT method. It constitutes the essential first step of any industrial inspection process, enabling the rapid detection of surface defects, dimensional anomalies and visible deterioration.
What is Visual Testing?
Visual testing (VT) is the oldest and most fundamental non-destructive testing method in industrial inspection. It consists of the systematic and methodical examination of a component, weld or structure using the human eye, optionally assisted by optical instruments. Although it may appear straightforward, visual testing requires thorough training, precise knowledge of acceptance criteria and a high degree of methodological rigour.
This method enables the detection of a wide range of surface defects such as cracks, surface-breaking porosity, undercut, arc strikes, misalignment, distortion, corrosion and mechanical damage. In welding, visual testing is essential before, during and after the completion of welded joints to ensure compliance with the specifications and applicable standards.
At LCNDTEST, our certified inspectors carry out visual inspections in accordance with the most stringent requirements, whether in fabrication workshops or on industrial sites throughout Belgium. Visual testing is systematically recommended as a prerequisite to any other NDT method, as it effectively guides further investigations and optimises overall inspection costs.
Inspection Methodology
Visual testing is divided into two main categories: direct visual testing and indirect visual testing. Direct visual testing is performed when the inspector has direct access to the surface under examination, typically at a distance of less than 600 mm and at an observation angle of at least 30 degrees. The inspector uses tools such as calibrated magnifying lenses, weld gauges (Cambridge gauges, Hi-Lo gauges), thickness gauges, rulers and lux meters to ensure adequate lighting (minimum 350 lux, ideally 500 lux or more).
Indirect visual testing is employed when the area to be inspected is not directly accessible. It utilises advanced optical instruments such as rigid or flexible endoscopes, videoscopes, inspection cameras and fibre optic systems. These devices enable the inspection of the interior of piping, vessels, boilers and other enclosed equipment without the need for costly dismantling.
Each inspection is documented with a detailed report including photographs, annotated sketches and an assessment of the defects identified against the applicable acceptance criteria (quality levels B, C or D according to EN ISO 5817 for steel welds, for example).
Industrial Applications
- Inspection of welds before, during and after welding (verification of preparations, intermediate passes and final appearance)
- Inspection of mechanical components, metallic structures and bolted assemblies
- Surface condition assessment and detection of corrosion, erosion and pitting
- Inspection of piping, pressure equipment and pressure vessels in accordance with the PED
- Inspection of coatings, surface treatments and pre-painting surface preparation
- Fabrication surveillance in workshops and erection monitoring on site
Advantages of Visual Testing
- Non-invasive method that is rapid to implement and requires no chemical products
- Applicable to all types of materials (steels, alloys, plastics, composites, concrete)
- Essential first step and indispensable prerequisite for any other non-destructive testing method
- Cost-effective inspection with high added value, reducing overall inspection expenditure
- Immediate results with photographic documentation readily available for assessment
Reference Standards
EN ISO 17637 • EN 13018 • EN ISO 5817 • EN ISO 6520-1 • EN ISO 10042
Frequently asked questions
Visual testing is the most fundamental NDT method, involving the systematic examination of components, welds and structures using the human eye, optionally aided by optical instruments such as magnifying lenses, endoscopes and cameras. It enables the detection of surface defects including cracks, porosity, corrosion and dimensional anomalies. At LCNDTEST, our certified inspectors carry out visual inspections in accordance with EN ISO 17637 across Belgium.
Visual testing is required before, during and after welding operations, as part of fabrication surveillance, during periodic maintenance inspections and for regulatory compliance on pressure equipment. It is systematically recommended as a prerequisite to any other NDT method such as penetrant testing or ultrasonic testing, as it effectively guides further investigations and helps optimise overall inspection costs.
Yes, visual testing is mandatory under most fabrication codes and standards, including EN 1090 for structural steelwork, EN 13445 and EN 13480 for pressure equipment, and the PED (Pressure Equipment Directive 2014/68/EU). It is considered the essential first step of any quality control programme for welded joints, and 100% visual inspection is typically required before any further non-destructive testing is performed.