Visual Testing

Definition of Visual Inspection

Visual inspection is a form of Non-Destructive Testing defined as the monitoring of specific parameters by visual and optical assessments of test objects and surfaces using the visible portion of the electromagnetic spectrum.

Inspection may be by the use of the eye alone or can be enhanced using optical systems such as magnifiers and microscopes. A variety of equipment is available to the visual inspector including mirrors and gauges, which can be used for profile assessment, borescopes and endoscopes, which are used on parts with limited access, and video and computer enhancement systems.

Conditions for Visual Inspection

Visual inspection must take place in a clean, comfortable environment with adequate lighting. There should be reasonable access to the parts to be inspected and attention should be paid to safety, working position and atmospheric conditions. The test piece should be clean and free from protective coatings. Any equipment to be used should be checked for accuracy and its operation understood by the inspector. The procedures to be followed should be documented, all relevant specifications should be to hand, and results of any observations should be clearly presented.

The human eye is one of mankind’s most fascinating tools. It has greater precision and accuracy than many of the most sophisticated cameras. It has unique focusing capabilities and has the ability to work in conjunction with the human brain so that it can be trained to find specific details or characteristics in a part or test piece.

It has the ability to differentiate and distinguish between colours, hues, size, shape, brightness, contrast and texture. The potential of this valuable tool, however, is most often overlooked.

To examine parts, many companies employ or specify tests that are very expensive to perform and require expensive and elaborate equipment. The results of these tests are often evaluated visually, however, in many cases, a simple visual examination would serve the purpose in a very satisfactory manner.