Visual testing provides a means of detecting and examining a variety of surface discontinuities. It is also the most widely used method for detecting and examining for surface discontinuities associated with various structural failure mechanisms. Even when other nondestructive tests are performed, visual tests often provide a useful supplement. For example, when the eddy current testing of process tubing is performed, visual testing is often performed to verify and more closely examine the surface condition. This verification process can impact the evaluation process associated with other nondestructive test methods being used. The following discontinuities may be detected by a simple visual test: surface discontinuities, cracks, misalignment, warping, corrosion, wear and physical damage.

Applicable standard:

• Acceptance criteria standard.
• Structural welding: AWS D1.1
• Power piping welding: ASME B31.1
• Piping process welding: ASME B31.3
• ISO 5817: Welding - Fusion -welded joints in steel, nickel, titanium and their alloys (beam welding excluded) -Quality levels for imperfections.
• Others standard: AS, JIS, ASTM ….