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Fast Fully-Focussed Ultrasonic Inspection of Girth Welds

Structural integrity inspection of pipeline girth welds is crucial to maintain the continuous flow of resources from the production site to the user. Ultrasonic testing plays a vital role in managing the integrity of millions of miles of pipeline across the globe. Using post-processing algorithms to interpret ultrasonic data can help simplify the inspection process.  These algorithms can be used to view the data in ways not considered before, improving the way in which flaws can be detected and sized, while also increasing the variety of flaw types that can be found.

Phased array ultrasonic testing (PAUT) and conventional ultrasonic testing (UT) have been used for the inspection of pipeline girth welds for decades. However, recent developments in computer hardware allow for real time inspection capability using total focussing method (TFM) based algorithms, such as full matrix capture (FMC), plane wave imaging (PWI) and virtual source aperture (VSA). These algorithms process the ultrasonic data to synthesise a PA focal spot at every pixel in an image, giving a fully focussed, easily interpreted image.

Objectives

  • Develop an inspection technique that can deliver fully focussed imagery of a girth weld using the advanced UT imaging techniques FMC, VSA or PWI
  • Maximise the angular coverage of the area of interest and improve the variety of flaws that can be detected by using the half skip, full skip and self tandem imaging views, including views where mode conversion occurs during propagation
  • Add the ability to use multiple probes at any given time, with the ability for these to communicate with one another, further increasing the angular coverage
  • Achieve real-time inspection speeds
Full matrix capture inspection of a pipeline girth weld sample using TWI’s Crystal testing software. Half skip, full skip and self-tandem modes considered, along with a pitch catch channel.
Full matrix capture inspection of a pipeline girth weld sample using TWI’s Crystal testing software. Half skip, full skip and self-tandem modes considered, along with a pitch catch channel.
Image depicting the half skip and full skip views (top), the self-tandem views (middle), and the pitch catch half skip and full skip channels (bottom).
Image depicting the half skip and full skip views (top), the self-tandem views (middle), and the pitch catch half skip and full skip channels (bottom).

Solution

TWI Crystal was developed for advanced TFM based ultrasonic imaging. The advantage of TFM based imaging is that the image is fully focussed and that many different imaging views can be considered. Each view is specifically designed for a certain type of flaw, in a certain part of the weld and at a certain orientation. The imaging views that Crystal is capable of providing includes the half skip, full skip and self-tandem. The software allows two transducers to be used at a given time, allowing the weld to be scrutinised from each side. A pitch catch channel can be used, where the probes communicate with each other.

Conclusion

TWI Crystal combines TFM based UT techniques with high-power Graphics Processing Units (GPU) to give the most advanced method of UT testing available in real time. The software allows for a coordinated inspection with two transducers, each displaying a half skip, full skip and self-tandem channels, along with a half skip and full skip pitch-catch channel. These imaging views can be combined into a single image by using known reflectors for calibration. Each view was designed to highlight a specific flaw type and orientation. By combining the imaging views, the Crystal software gives the user the highest probability of detecting and sizing a wide variety of flaws that can occur within a girth weld.

Full Matrix Capture inspection of a pipeline girth weld sample using TWI’s Crystal testing software. Half skip, full skip and self-tandem modes considered, along with a pitch catch channel.
Full Matrix Capture inspection of a pipeline girth weld sample using TWI’s Crystal testing software. Half skip, full skip and self-tandem modes considered, along with a pitch catch channel.
Avatar Ewan Hoyle Project Leader, Technology

Ewan joined TWI in 2016 as an NSIRC PhD student and the topic of his PhD was ‘Advanced Virtual Source Aperture Ultrasonic Imaging for Non Destructive Testing’. Following completion of his PhD in 2019, Ewan began working for TWI as a software developer and he is also responsible for the commercial activities for the software section of TWI Wales.

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