Visual testing (VT)

VOGT Ultrasonics is your partner for visual inspections by experienced and highly trained inspectors.

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State of the art

How powerful is the visual inspection (VT)?

This test method is limited to the detection of defects on the surface of the component.

Cracks, Impurities, Burr formation, Burn-in notches, Color changes, Surface roughness, Misbonding, Incomplete or faulty assembly

Defects must be detectable by eye or by an aid such as a camera or magnifying glass (armed eye).

The component to be inspected must be accessible, if necessary with the aid of a camera.

At your side

VOGT Ultrasonics visual inspection at your site

The requirements for visual inspections are numerous. VOGT Ultrasonics also uses various aids for visual inspection depending on the requirements.

Incoming goods inspection

In all industries, visual inspection is used for the evaluation of delivered goods during incoming goods inspection. Here, primarily the intactness, defects and qualities of the surfaces as well as the geometric shapes are tested.

In this application, VOGT Ultrasonics provides on-site support at the customer’s location to visually inspect delivered raw materials, preliminary products, components or even assemblies up to finished objects.

This starts with the accompanying documentation and continues with the design and finish of the components (defects, coloring, etc.) and includes dimensional checks, roughness tests and position checks.

New construction of a facility

VOGT Ultrasonics regularly inspects larger complex or permanently installed components on site. The visual inspection of piping and welded joints as well as the evaluation of corrosion are part of our core competencies in visual testing. Before the first operation, many inspections with unarmed or even armed eye are necessary. Here, VOGT Ultrasonics is happy to assist you so that flawed welds and other imperfections can be detected and reworked before initial operation. VOGT Ultrasonics supports you so that your facility can start production on schedule.

Inspection of installed facilities

The regular inspections are mandatory for planning a cost-efficient maintenance. VOGT Ultrasonics is your partner when it comes to inspecting weld seams, steel beams, rivets, bolted joints and much more for damaged areas. Visual inspection is the fastest way to evaluate the condition of a facility. VOGT Ultrasonics creates detailed reports, which are used to efficiently apply further inspection procedures. Thereby we have possibilities of visual inspection with various tools.

With so-called camera pigs even the inspection of complex pipe systems is possible.

An inspection provides certainty and enables planning. Spare parts for maintenance can be ordered in advance and the maintenance itself can be carried out in a more structured and thus time-saving manner. This reduces downtime due to maintenance and preventive repairs and optimizes facility availability.

visually inspected

Visual inspection in the VOGT test center

The quality of a visual inspection depends on many influencing factors on site. These include: Light, camera systems, optical aids, cleanliness, quietness and much more. The VOGT test center offers an ideal environment for the inspection of components and small parts. Here it is possible to carry out a comprehensive and cost-effective visual inspection under the best conditions. Especially for small parts, such an inspection can account for a large part of the production costs. Therefore, our test center is designed to perform serial inspections quickly and reliably, thus keeping inspection costs in limits.

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Error detection

What is a visual inspection?

Visual inspection (VT) is the oldest and most basic method of inspection. It involves checking a component for defects with the eye (unarmed eye) or with the aid of equipment (armed eye). Often, no instruments are required except the eye of a trained inspector.

Visual inspection can be used for internal and external surface inspection of a wide range of components, assemblies and equipment, including automotive components and assemblies, such as connecting rods, cylinders, plastic fixtures as well as aerospace seat rails, turbine disks, blades and vanes, and even storage tanks, pressure vessels and piping from the chemical and petrochemical industries.

Visual inspection is generally simple and less technologically advanced than other methods. Nevertheless, it has some advantages over high-tech methods. For example, it is much less expensive compared to other methods. This is due to the fact that it usually does not require any equipment. It is also one of the most reliable methods. A well-trained inspector can detect a comprehensive range of indications of damage.


Pro & Contra

Advantages of visual inspection

he advantages of this method of nondestructive testing include:

  • It is the most cost-effective nondestructive testing.
  • Allows detection and elimination of possible defects before starting or after completion of the welding.
  • It enables the identification of major defects and generally indicates possible areas where defects may occur that need to be controlled by other non-destructive testing.
  • A well-performed visual inspection can provide conclusions for process optimization and thus increase productivity in the long term.

Limitations and disadvantages of this testing method include:

  • It depends heavily on the experience of the inspector and his expertise.
  • It is limited to the detection of surface defects.
  • The areas to be inspected must be accessible to the inspector.

How efficient is a visual inspection?

A study on visual inspection of small integrated circuits showed that the duration of eye fixations of trained inspectors was about 200 ms. Whereby inspectors who perform visual inspections on a daily basis inspected the fastest and most reliably. Thus, it can be clearly concluded that practice and routine are an important part of performing high-quality and cost-effective inspections. For visual inspection, the false positive rate was 2% and the false negative rate was 23%.

How does a visual testing work?

There are two methods: Direct and indirect visual testing.

In direct inspection, the inspector looks at and assesses the component directly with his eye, if necessary with the aid of a magnifying glass, a microscope, a light source, a visual scope or a mirror.  Profile gauges are also an aid to visual inspection, if necessary.

In indirect inspection, the component is viewed using visual aids, e.g. flexible and rigid industrial endoscopes, fiberscopes with cameras, camera systems and even crawler devices.  Digital images or videos are often created, which are then digitally processed, measured, evaluated, stored and made globally available.

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The regulations

Which standards are relevant for visual inspection?

    • DIN EN 1330-10 Terminology/terms
    • DIN EN 13018 General principles of inspection methods
    • DIN EN 13927 Equipment
    • DIN EN 1370 Casting – Evaluation of surface condition
    • DIN EN 12454
    • ISO 17635 Non-destructive testing of welded joints
    • ISO 17637 Visual inspection of fusion welded joints
    • ISO 5817 Evaluation of defects of irregularities
    • ISO 6520-1 Classification of geometrical irregularities on metals

Standards and specifications for visual testing exist in extremely wide range for very different sectors and industries. The standards listed here are strongly limited to technology and the metal industry.

A little theory

Comparison of direct and indirect visual testing

Direct visual testing

n direct visual testing, the component to be tested is checked by an inspector. Testing, analysis and evaluation are performed by one person. Direct visual testing can be carried out with aids such as magnifying glasses, endoscopes, etc.

Advantages of direct visual testing
  • Non-destructive testing with simple technical equipment
  • Mobile testing
  • Ideal for sampling
  • No comparable test results, as there is no proper documentation
  • Dependent on the experience / judgment of a person 

Indirect visual testing

For an indirect visual inspection, the area to be inspected is captured by a camera and displayed on a monitor. The inspection image can be processed in further steps. For example, the image can be enlarged, digitally enhanced and details can be visually highlighted for analysis purposes. The image can be saved for documentation purposes. By displaying it on a screen, several people can evaluate. Comparisons with previous inspections by comparing the images or videos can thus be easily and reliably realized. In this way, even the smallest changes can be detected.

The trend is moving to indirect visual testing, as the use of camera technology offers more possibilities and leads to a more efficient interruption of the production process. Indirect visual inspection is performed, for example, with the help of videoscopes or stationary camera recordings. In industries with high quality requirements, inspection solutions are used that provide high-resolution images.

Advantages of indirect visual testing
  • Digitization enables image optimization for better defect evaluation
  • Reliable 100 % inspections
  • Defects can be documented
  • Improved analysis becomes possible
  • Via image or video comparison, an inspection can be evaluated efficiently and in detail with previous results
  • Traceability of documented defects for process optimization
  • Higher costs of acquisition than for direct visual testing
  • More space required than for direct visual testing
this is how

How is a visual testing effectively performed?

According to the British Institute of Non-Destructive Testing (BINDT), many defects are on the surface and can be detected by careful direct visual testing. In some cases, quality assurance inspectors may come to inconsistent visual inspection results because they either do not fully understand the defect specifications or do not have references for comparison.

Because it is one of the simplest and most cost-effective quality assurance methods, visual testing procedures vary by industry. In general, there are 5 simple steps to effectively perform visual inspections:

Critical to the quality of the visual inspection are the viewing conditions and lighting. Best possible contrast must be achieved to detect defects. The color spectrum of the component and the defect as well as the light conditions also have an impact. The viewing angle on the surface to be inspected is also essential for good results. 

The procedure

Clear definition of defect criteria

Key stakeholders, such as quality engineers, production personnel and customers, should reach consensus on defect specifications. Clearly defined defect criteria enable inspectors to make accurate pass/fail decisions. Defects are documented with sample photos and technical descriptions for daily visual inspection in production.

Step #1

Standardization of inspection performance

Identify how consistent the decisions made by inspectors are with the established defect criteria to standardize visual inspection performance across the organization. Occasionally, inspectors misinterpret the standard when visual displays of the defects are not available to them during visual inspection.

Step #2

Analysis of visual defects

If the decisions made by inspectors on the same product are inconsistent across different visual inspections, the most important visual defects must be analyzed. By frequency and number of defects, evaluate the cost of quality to determine which defect type has the greatest impact on daily operations. Quality managers must also consider cost, time to repair, and importance to the customer to create and implement effective action plans.

Step #3

Communication of actions for improvement

After resolving issues with specific visual detected defects, inspection performance is re-evaluated to confirm consistency between inspector decisions and established standards. The results are communicated objectively to all safety and quality personnel to ensure a continuous improvement process.

Step #4

Use mobile-enabled checklist

Most often, checklists are used for visual testing. If inspectors can access defect criteria anytime, anywhere, and if video and photo evidence of visual defects is captured, the accuracy of pass/fail decisions can be radically improved.

Step #5

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The future of visual testing

Indirect visual testing enables comprehensive documentation of a visual testing. It thus allows inspections to be re-evaluated at the desk, edited or even evaluated by several people.

Indirect visual inspection makes it possible to use camera technology and robotics to inspect areas that were previously inaccessible. The inner walls of complex piping systems can be inspected via crawlers. In addition, wind turbine blades can be inspected by a drone without incurring extensive costs for a crane.

if there are still questions


Visual testing is one of the oldest and most proven non-destructive testing methods for evaluating the condition of a facility or component as part of the production and overall maintenance process.

The task of a visual testing is to detect defects and flaws in materials as well as dimensional inaccuracies of components and materials within the scope of quality assurance.

Surface quality deviations, cracks, impurities, burr forming and penetration notches in welds, color changes, surface roughness, corrosion and erosion, incomplete or faulty assembly, geometric deviations.

We stand for quality
Certifications & Accreditations

Certified quality management for the industry

Certified quality management for the aviation industry

for the inspection of turbine disks (MTU)

for the ultrasonic testing of turbine disks in our testing center in Burgwedel (Hanover, Germany)


We are an accredited testing laboratory

for systematic and effective work safety

We can provide you with qualified testing personnel within the framework of temporary employment.

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