Feature Laser Tool Offers Alternative for Precise Visual Weld Inspection Three-dimensional laser precision measurement technology is now available for hand-held visual weld inspection purposes Inspection Trends / Fall 2011 15 By Jeff Noruk, Blake Holmes, and Bob Bruss For many years, manual weld gauges have remained the go-to tool for every inspector performing nondestructive visual weld inspection. Examples of these type gauges are shown in Fig. 1. Simple in design, these gauges have done what they were intended to do: give simple feedback as to whether a weld meets the minimum weld quality standard requirements. However, these devices are limited to the types of joints and weld sizes they can measure, and various joints require different gauges and techniques. Many types of gauges are on the market today, with most doing only one specific task. In fact, one company even sells a fanny pack to carry all these gauges. Even with the correct gauge for an application, the inspector gets only a go/no-go result since most manual gauges do not give actual measurements. These gauges are also only useful for basic welds and joints so, for example, if a fillet weld has unequal leg sizes or an angle that is not 90 deg, additional calculations and equipment are required to accurately measure the weld. These subjective measurements are then typically recorded manually making the whole process quite time consuming and open to possible errors. Three-dimensional laser precision measurement technology has been around for decades, but due to equipment size, cost, and complexity has been mainly reserved for robotic and hard automation applications. With recent developments in computer component size, battery life, and wireless technologies, laser-based measurement tools have been developed for hand-held weld inspection purposes. With simple interfaces not unlike a currentgeneration smart phone (Fig. 2), these tools are easy to use, small in size for tight-area access (Fig. 3), and repeatable so that subjectivity is reduced, thus minimizing the possibility of error. A simple click of a trigger can yield many useful measurements such as leg sizes, convexity/concavity, and toe angles, as well as the detection of discontinuities such as undercut and porosity. Figure 4 offers a pictorial view of the possible measurements with a T fillet weld joint. This information can then be downloaded and saved into a database for reporting or to be maintained as a permanent record. If this sounds too good to be true, it’s not, it’s simply combining the technology that’s already available today into a wireless hand-held device. To help point out the advantages of the laser precision tool, the following scenario of measuring a skewed fillet (Fig. 5) is reviewed. Laser Tool vs. Fillet Gauge for a Skewed Fillet Weld Fillet Gauge 1. Choose correct fillet gauge for specific weld. 2. Consult AWS D1.1, Structural Welding Code — Steel, to get correct calculations for the skewed joint. 3. Determine the included angle of the fillet joint. 4. Consult the skewed fillet calculator. 5. Measure the leg sizes of the fillet. 6. Decide if the weld fits within the pass/fail criteria. 7. Manually record results. Fig. 1 — A variety of commercially available manual weld gauges. Fig. 2 — User interface screen.
Inspection Trends - October 2011 - Fall
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