PipING inspection using a smart flexible phased array

The inspection of piping in nuclear power plants is mainly performed in contact with ultrasonic wedge transducers. Some areas of circuit pipes have variable geometries (variable radius of curvature, irregular surface conditions) which may limit the efficiency and even the accessibility for wedge transducers. A prototype of smart flexible probe was developed with the support of EDF in order to improve such inspections. The phased array is flexible so as to fit the variable surface. A profilometer, embedded in the transducer, measures the local surface distortion allowing the computation, in realtime, of optimized delay laws and compensate the surface aberration. Those delay laws are transferred to the real-time UT acquisition system, which applies them to the piezoelectric elements. This self-adaptive process preserves, during the scanning, the features of the focused beam (orientation and focal depth) in the specimen. This paper presents results obtained with the prototype on realistic pipes configurations. The inspected configurations were also simulated with the CIVA Software. The good agreement between experimental and simulated results validates the acoustical behavior of the probe and confirms the accurate control of the beam focusing during the tests. (orig.)