Inspection of prestressing windings in concrete pressure pipe

A new method capable of inspecting the prestressing windings in concrete embedded-cylinder pressure pipe for breaks is described and results from field tests presented. The method exploits aspects of the remote field eddy current (RFEC) through-wall transmission technique, used for conducting tubulars and an additional transformer coupling effect. Laboratory tests have been conducted in 400 and 600 mm pipe and field tests in 1.2 and 2.4 m concrete embedded cylinder pressure pipes. Signal logs are analyzed using the standard RFEC voltage plane polar plot. Detection of even single breaks in the prestressing winding has been demonstrated. The relatively small tool can access large diameter pipes through standard 500 mm manhole. Scanning speeds of 35 m/min have been used.