Visual testing (non-destructive testing) relies on the adequate illumination of the test surface and the technician’s visual competence. Visual testing requires training (for example, knowledge of product and process, anticipated service conditions and acceptance criteria), and visual testing deploys specialised range of NDT VT equipment. Defects found by other NDT methods are ultimately substantiated by visual inspection. VT can be classified as direct visual testing and remote visual testing.
The most common NDT methods, MT and PT, are scientific ways of enhancing the visual examination. The equipment needed is simple. For direct, you need a light source, various measurement devices or gauges and magnifying devices when appropriate. For remote viewing or internal inspection, equipment, such as a light-lens system or bore scope, allows remote surfaces to be examined. More sophisticated fibre-optic equipment allows the introduction of a device into very small access holes or channels. Most of these systems provide a permanent recording of the inspection. Cameras are indispensable for visual examination as a method of documentation.