Portable UT Units Set to Transform Welding Workflow
Newly developed portable Ultrasonic Testing (UT) units could drastically alter welding workflow by allowing weld inspection as often as after each pass. Normal weld inspection at depth, called “Volumetric Testing,” normally requires X-ray or ultrasonic test setups. Both normally require specialized equipment be brought to the site and the area be cleared and/or the weld be cooled before inspection can begin. With today’s sensor technology, the weld need not be as cool and lowered energy levels make the UT technology portable. The result is almost immediate testing of weld passes before a defect is covered and repairs are expensive.
“Even good welders introduce defects,” says Scott Witkowski, President, Maverick Testing Labs in Houston, TX (http://www.mavlabs.co/). “Normal defect rates can be as high as 5% but with training and experience, it can drop to less than 2%.” Maverick specializes in qualifying welders for specific weld processes and working environments by asking them to weld under simulated task conditions and extensively testing the welds.
After welder qualification, the only way to monitor welder performance is inspect the weld made in the shop or field. A variety of techniques are available for such “non-destructive testing” or NDT but most can check for defects at or close to the surface. Despite their relative lower cost, surface or near surface techniques lack the in-depth results that volumetric testing can give. Except for visual inspection, most techniques require specialized training for good results.
Enter shearwave UT with the new Electro Magnetic Acoustic Transducer (EMAT). Ulrasonic Testing transmits a sound into the weld which is disrupted or reflected by the defect. Piezoelectric UT uses a couplant liquid or get help transmit the sound into the part. EMAT, in contrast, generates the sound in the part inspected instead of the transducer. It is a dry technology that can operate at high temperatures, 200°C or up to 650°C with cooling.
Figure 1 EMAT Eliminates couplant by inducing wave in material.
Because the technology can tolerate higher temperatures, is handheld and needs no special setup, it can be used by trained welders to inspect welds as soon after a layer is added to the weld. Innerspec Technologies Inc. demonstrated the new technology at the API Inspection Summit 2013.
Figure 2 EMAT UT sensor shows Standard Signal.
Figure 3EMAT UT sensor shows Attenuated Signal
Using this technology, welders and their helpers can quickly determine if their welds contain defects and correct them before adding to the weld. This could make 100% volumetric testing of welds economically feasible on many project with higher reliability and increasing welder skill through immediate feedback.
For more information, consult http://www.innerspec.com/