Visual Testing

It is the oldest nondestructive testing methods. Visual testing is the observation of a test object, either directly with the eyes or indirectly using optical instruments, by an inspector to evaluate the presence of surface anomalies and the object`s conformance to specification. Visual testing should be the first nondestructive testing method applied to an item. The test procedure is to clean the surface, provide adequate illumination and observe. A prereqisite necessary for compotent visual testing of an item is knowledge of the manufacturing processes by whichit was made, its service history, potential failure modes and related industry experience.

Visual testing is used to define different type of surface discontiniuties. If no access to test region remote controled equipments like borescopes are used.

Many people think that visual testing is required after completion of work. However visual controls before welding and welding process time will diminish the defect rates and provides easy final control.
Basic controls after welding are

Welding profile
Welding dimensions
Welding defects.

Basic purpose of these controls is to be sure the quality. Therefore visual testing is necessary.

Advantages

Fast and Reliable
Provide information to other nondestructive testing method
Provide remote inspection
Economic