Inspection of Welds with Corrosion Resistant Alloy (CRA) Cladding

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In order to extend the service life of oil, gas and petrochemical components prone to corrosion, the use of Corrosion Resistant Alloy (CRA) cladding and/or weld overlays are now common practice, and pipelines transporting hot and corrosive materials are no exception. When it comes to inspecting these clad pipelines, inspectors must —among other things— pay attention to the dissimilar girth welds, including weld root integrity as a failure here equates to carbon steel being exposed to sour fluids and potentially catastrophic consequences.

The Challenge

Ultrasonic inspection of CRA-clad girth welds is a challenge due to their anisotropic nature, their high attenuation factor and the interference with the protective layer, making typical shear wave examinations unsuitable.

The protective layer designed to extend the useful remaining life of pipelines presents a challenge during ultrasonic testing (UT) of cladded pipes with dissimilar girth welds. CRA welds interfere with the shear wave transmission because of velocity changes and grain structure, creating mode conversion and other adverse effects. Rather, inspection is performed using longitudinal waves, and is typically limited to half-skip mode (half-vee) – which requires removal of the cap for complete coverage of the weld root, volume and upper area.

CRA-clad dissimilar material welds (Photo credit: Absolute NDE)

The Solution

Low-frequency dual linear and dual matrix array (DLA and DMA) probes with large apertures controlled by a user-friendly and easy-to-setup Phased Array Ultrasonic Testing (PAUT) instrument capable of firing up to 64-element probes simultaneously.

To overcome transmission challenges through dissimilar materials, the use of linear and dual probes in Transmit-Receive Longitudinal (TRL) mode is recommended by the industry. These probes are known as dual linear and dual matrix arrays (DLA and DMA). In the TRL technique, sometimes called pitch-catch technique, the transmitter and receiver transducers are unique to each other so that collected signals originate only from the area where the two beams intersect. Using a separate pulser and receiver, the wedge size is reduced, and the probe can operate closer to the weld for increased sensitivity. This allows inspectors to determine whether there is Lack of Fusion (LOF) at the weld bevel, for example. Using the TRL technique with a large aperture and precise steering enables better Signal-to-Noise Ratio (SNR) and Probability of Detection (PoD) in thick CRA welds. In terms of equipment, this translates into 64+ parallel architecture systems driving probes with 64+ elements.

For example, the M2M Gekko® system, available in the 64:64PR and 64:128PR configurations come with a standard DMA/DLA interface for easy programming of the setup directly in the flaw detector. Operators can configure the entire inspection procedure directly from the unit using the embedded Capture™ software. The dual probes can be used with a set of optimized techniques per inspection requirements. Phased array sector scanning and Total Focusing Methods (TFM and variations) can all be programmed and adjusted in real-time by the user.

DMA Probe L-Wave, Iconel 625 - Single V, 50mm thick with 12.5mm stainless cladding

The proposed solution includes:

  • Gekko (or Panther™) units to operate with high channel count dual probes for high resolution sector scanning and TFM, plus automatic Time Corrected Gain (TCG);
  • Capture software with live configuration offered through the intuitive operating system;
  • 1-axis chain scanner for data encoding and defect positioning;
  • Linear, DLA and DMA probes and wedges kit.

Eddyfi Technologies has developed advanced PAUT instruments that enable inspectors to detect and characterize flaws found in CRA-clad pipes while reducing setup time and moving away from complicated setup and programming. Operators can collect the most comprehensive dataset with a user-friendly operating system that enables detailed reporting. Contact our team to learn more about the M2M Gekko phased array flaw detectors for your CRA weld inspections today.

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CRA with Iconel 625 weld and cladding (real defect)

Benefits

  • On-board setup of dual probes
  • Advanced ultrasonic techniques available in real-time
  • High-channel count phased array probes
  • Automatic TCG for dual probes
  • Compatible with all dual probe manufacturers

Thanks to advanced PAUT, reliable CRA weld inspection is not only feasible, it is optimized using intuitive software and configuration tools. With easy onboard setup of dual probes and natively implemented PAUT, TFM and hybrid methods on both Gekko and Panther instruments, operators can easily adjust ultrasound settings for the best data collection results powered by high channel count phased array probes. Finally, Eddyfi Technologies’ advanced PAUT flaw detectors are compatible with all dual probe manufacturers and typical scanners on the market.