Visual Testing is one of the most widely used nondestructive testing methods and is used in almost all industries to identify defects and discontinuities in part. For visual testing, good eyesight is required either natural or corrected. Defects or discontinuities are enhanced by mirrors, magnifiers, Borescope, and other various visual aids. Visual examination is performed usually at a distance of approximately 10 to 24. The light requirement for Visual testing Inspection is a minimum of 150 Lux and it increases as the seriousness of discontinuities increases. In general residential light, the requirement is of 200-250 lux for normal vision and minimum contrast of 3:1 for lighter objects and dark background. Advantages of Visual Testing- Visual testing is less expensive than other testing methods. It is very convenient to perform a visual inspection at a different place, hence it is a very portable method. After inspection results of inspection is immediate and this makes visual inspection as one of the fastest NDT inspection methods. Moderate skill is required for visual inspection. Workpiece or specimen can be inspected with less part preparation also. Disadvantages of Visual Testing- Only surface defects can be viewed by visual inspection. Micro or small defects are not visible to unaided eyes. Confusion occurs between relevant indication and non-relevant indications.
