Ultrasonic Detection of Stress Corrosion Cracks in Pipe Samples Using Guided Waves

Stress corrosion cracking (SCC) is a serious problem in gas pipelines. The detection of such cracks are difficult with currently available in-line inspection technologies. Recent work demonstrated the crack detection potential of using guided waves and gas-coupled broad band ultrasound by experimental detection of machined crack-like defects based on Halfwave's ART Scan® tool [1]. The present study experimentally investigated the detection of real SCC, with crack depths of up to 4.3 mm, on a real pipe, with a nominal wall thickness of 12.7mm, using broadband (0.3-1.3 MHz) transducers in a pitch-catch set-up. Acoustic signals were received by eight transducers, surrounding the transmitter, at cylindrical scan locations, and different processing parameters were extracted. 2D parameter scans displayed the crack and pitting corrosion areas. The summed power parameter resulted in signal differences of up to 8 dB for the crack area as compared to the surrounding area. In conclusion, the detection of real SCC by using an ART Scan® based set-up was successfully demonstrated on a real pipe section in water.