Maximizing Probability of Detection in Long-Range UT Guided Waves Inspections with Innerspec's Coupling and Transmission Balancing (CTB) Technique

One of the greatest challenges in Long-Range Ultrasonic Testing (LRUT) inspection with guided waves has always been the application of the transducer ring on the pipeline.

• Piezoelectric rings are notoriously difficult to install, and verifying that all transducers are properly coupled is nearly impossible. Even a single poorly coupled transducer can create imbalances, causing the transmitted wave to rotate along the pipe and leaving dead or weak zones that escape inspection.
• Magnetostrictive strip rings are easier to install, but poor surface conditions can still lead to weak or uneven coupling.

Coupling and transmission imbalances significantly reduce the Probability of Detection (PoD). To address this, Innerspec has developed the Coupling and Transmission Balancing (CTB) technique—a patent-pending innovation designed to eliminate these imbalances entirely.

How the Coupling and Transmission Balancing Technique Works

The CTB technique works by firing shots at different angles. A proprietary algorithm then combines these into a composite A-scan, correcting imbalances and ensuring uniform inspection coverage regardless of transducer or coupling imperfections.

This procedure is designed to streamline the process by guiding the user through collecting multiple snapshots, verifying coupling quality, and applying an automated balancing algorithm. The software uses a "CTB" button to perform the balancing algorithm via a step-by-step approach. You can continue to load scans—which will be displayed in overlay mode—and then compile them into a single A-scan at the end. For detailed step-by-step instructions, please refer to the VOLTA 2 User Guide.

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CTB is proprietary to Innerspec and available exclusively in VOLTA 2. The technique ensures proper wave balance when using the LRUT axisymmetric ribbon and is available for both LRUT LITE and LRUT FOCUS software applications. With CTB, inspectors can finally achieve unmatched reliability and consistency in guided wave inspections.