A HIGH SENSITIVITY TRANSFORMER COUPLED SYSTEM FOR THE DETECTION AND IMAGING OF BREAKS IN PRESTRESSING TENDONS IN CONCRETE PIPES.

A system has been developed, described here, which can detect and image localised faults and breaks in the prestressing tendons of large bore concrete pipes, intended for the transport of water. The system exploits the principle of magnetic field transformer coupling, in which a low frequency time varying field is transmitted over the region being inspected. Perturbations in the amplitude and phase of the signal that arise from variations in the coupling conditions are detected by a receiving system and fed to instrumentation for processing, image reconstruction and interpretation. The system has been field trialled in 4 m diameter pipes in the Sahara desert. Results confirm that it is capable of detecting and imaging as few as two adjacent tendon breaks, in which the diameter of the tendon was 7 mm and the pitch was 20 mm. [ABSTRACT FROM AUTHOR]