Copyright Goodheart-Willcox Co., Inc. Chapter 18 Weld Inspection and Repair 267 • Optical comparator. Magnifi es, illuminates, and precisely measures weld discontinuities. • Magnifi cation lenses. Pocket-sized magnifi cation lenses. • Extension mirrors. Used for root pass inspection of pipe welds. • Fillet weld gauge. Measures the size of fi llet welds. • V-WAC gauge. Used for measuring height and depth. The gauge checks undercut depth, porosity comparison, amount of porosity per linear inch and crown height. • Automatic weld size gauge. Measures several aspects of a weld, including the height. • Bridge cam gauge. Used for measuring several aspects of welds, such as depth of undercut, depth of pitting, and fi llet weld throat size and leg length. Visual tests provide very important informa- tion about a weld’s general conformity to specifi ca- tions. The following weld features are measured and compared to specifi cations to ensure that the weld meets expectations: • Crown height • Crown profi le • Weld size • Weld length • Dimensional variation • Root side profi le • Root side penetration • Surface color (titanium welds) In addition, a visual test may reveal discontinui- ties in the weld. A discontinuity is any disruption in the consistency of a weld. A fl aw in the weld is a discontinuity that is small enough that it does not render the weld unacceptable. A defect is a disconti- nuity that is serious enough to make the weld unac- ceptable. The following common problems can be detected by visual tests: • Underfi ll • Undercut • Overlap • Surface cracks • Crater cracks • Surface porosity • Joint mismatch • Warpage Penetrant Test A penetrant test (PT) is a sensitive method of detecting and locating minute discontinuities that are open to the surface of the weld. A penetrating liquid (dye) is applied over the surface of the weld. The fl uid then enters the discontinuity. After a short period of time, the excess penetrant is removed from the surface. A developer is applied to the surface and allowed to dry. The penetrant in the discontinuity rises to the surface by capillary action, making the discontinuity easy to see. The penetrant test sequence is shown in Figure 18-4. Figure 18-2. Fillet weld size and crown gauge. (Mark Prosser) Figure 18-3. This adjustable fillet and crown gauge is being used to check the height of the weld bead. (Mark Prosser)