Detecting weld defects

Tube and pipe fabricators have been improving quality and reducing scrap with non-destructive testing (NDT) for many years using traditional methods – eddy current testing (ECT) and ultrasonic testing (UT). As powerful as these traditional NDT methods are in testing formed and welded tubes and pipes for defects and discontinuities, they do present several challenges such as complexity in setup, sensitivity to external conditions, and requiring multiple probes to obtain reliable data. ECT and UT methods are unable to detect or classify certain weld defects that are critical to the integrity and quality of tubes and pipes.

A solution to the shortcomings of traditional NDT methods is the introduction of laser-based non-destructive inspection (NDI) of the weld bead on formed and welded tube and pipes. With advancements in machine vision technology, laser-based NDI can be used to find specific weld defects related to the surface profile of a weld, resulting in improved quality assurance and process control.

The WI-2200/3000 by Xiris Automation Inc. is an NDI system that uses laser triangulation and a camera offset to the axis of the laser plane to measure variations in the surface of a weld bead. The system makes several measurements that can be used to monitor and enhance the productivity of tube mills. These measurements are based on the differences between the actual laser profile line seen by the camera, and the ideal mathematical profile which is determined by the tube diameter.

By knowing the position of the actual laser profile, the ideal profile, and the size of the pixels in the image, the WI-2200/3000 Weld Inspection System can calculate various profile defects that are often missed by ECT and UT methods.

Various weld profile defect measurements

Mismatch

The mismatch defect measurement compares the two edges on either side of the weld to see if there is uneven joining of the two edges of the tube material as they come together at the weld point. Mismatch could be a result of incorrect forming setup, edge break issues, or twisting of the strip feed into the rollers. This defect may result in significant thinning of one side of the tube wall after ‘scarfing’ or grinding the weld area, compromising the tube quality …

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Read the article online at: https://www.worldpipelines.com/special-reports/13122022/detecting-weld-defects/