Optimized Inspection of Thin-Walled Pipe Welds Using Advanced Ultrasonic Techniques

Abstract

In this paper an effective way to optimize the inspection of welds in thin-walled pipe less than 6 mm (0.24 in.) thick using automated ultrasonic testing (AUT) is described. AUT offers a better solution than radiography for detecting and sizing of planar defects. However, cap width, weld shrinkage and defect sizing put constraints on the actual ultrasonic approach for inspection of pipes with wall thickness less than 6 mm (0.24 in.). The applications of high-frequency single/multiprobe techniques and phased-array technology for inspection of thin-walled pipe welds have been investigated in this paper. It has been demonstrated that combining an advanced ultrasonic phased-array technique with a novel approach for modeling and simulation of ultrasonic inspection have potentially significant advantages for enhanced detectability, better sizing and improved flaw characterization of randomly oriented planar fabrication imperfections in thin-walled pipe welds.

Effects of array transducer inconsistencies on total focusing method imaging performance

“…One array probe can replace a number of standard monolithic transducer inspections by firing the array elements in ranged sequences (often termed a delay law) to steer and focus the physical wavefront. In this way defects in the test structure can be directly detected from real-time images that include, for example, plane and focused B-scans [2,3]. Alternatively, the time-domain signals from every pair of transmitter-receiver elements can be captured in a process termed Full Matrix Capture.…”

Ultrasonic array imaging in nondestructive evaluation: total focusing method with using circular coherence factor

“…Figure 6 shows the image comparison by using different filters (1 -5 MHz) and different image algorithms. As shown, with using the filters with a low centre frequency (1 -2 MHz), the defect is visible in all images and CCF suppresses image noise, but the defect is invisible in all images when using the filters with a high centre frequency (3)(4)(5). Figure 7 shows the extracted SNR, r, as a function of central frequency of filter.…”

“…By firing the array elements in ranged sequences (often termed a delay law), one array probe can steer and focus the physical wavefront at any location of a test structure, and generate real-time images for inspecting the test structure, for example, plane and focused B-scans [2][3]. Some non-linear denoising procedures, such as phase coherence imaging (PCI) [4][5], can be further used to reduce electronic and uncorrelated material noise and improve the image quality.…”

Nondestructive Detection of Tilted Planar Flaws on Back Surfaces Using Ultrasonic Wave Interference

“…Inclined flaws such as stress corrosion cracks change the reflection efficiency, which is a basic parameter of the amplitude-based sizing approach, when adapting an ultrasonic pulse-echo method for nondestructive inspection (3) . The signal-to-noise ratio is the dominant factor in determining the detection limit of the ultrasonic pulse-echo method (4)(5)(6)(7)(8) . The signal available for measurement by the interference of waves attains a higher signal-to-noise ratio, because random noise does not show interference, and only the interference due to the existence of flaws is measured.…”