23 Visual Examination (VT)
Visual examination (VT) is the most common form of nondestructive examination (NDE), and also the cheapest. Welders are the first visual testers on any welding they perform; inspecting your own work for visible flaws is an essential habit to build. VT can involve the use of tools such as gauges, flashlights, picks, tape measures, or magnifying glasses.
The inspector performing VT should check to see if all welds comply with drawing requirements for size, length, and location. All craters should be filled to the full cross section of the weld. Fillet welds are typically checked for size and surface contour with fillet weld gauges. Groove welds should be filled to the full cross section of the joint or as specified. Face and root reinforcement should not exceed the acceptance criteria of the applicable code or standard.
Types of Gauges Used for VT
A Cam Type gauge is a multi-use gauge that can be used to measure many different things. It is adjustable. Cam Type gauges must be precision machined and therefore can be expensive.
A depth gauge is another multi-use gauge that can be used for butt joints and fillet welds. It is typically precision machined from stainless steel. Depth gauges include many different gauge styles.
A HI-LO gauge is a single purpose welding gauge. It is also typically precision machined from stainless steel. The tiny wire on a HI-LO gauge is fragile and can break easily.
A fillet weld gauge is another single purpose gauge. It comes in very specific dimensions to check fillet sizes. Fillet weld gauges come in adjustable and non-adjustable styles.