Live Inspection of Large Diameter PCCP Using a Free-Swimming Tool

Remote Field Transformer Coupling (RFTC) inspection has become the industry standard in condition assessment of Prestressed Concrete Cylinder Pipe (PCCP) since its commercial introduction in 1997. While the technique works for almost all types of PCCP, it is a huge challenge to actually conduct RFEC/TC inspections for many PCCP lines, especially since most of these can not be taken out of the service and fully dewatered. In 2007, a free-swimming tool was developed and successfully used in the field for small diameter PCCP (24" – 48"). It is capable of conducting RFTC inspection in a live PCCP line. This innovative tool can be launched into an in-service pipeline through a small hot-tap, travel along the pipeline with the water flow while collecting RFTC data and then be retrieved from another small hot-tap at the downstream end. Currently, this free-swimming tool is being scaled up for large diameter application (60" and larger). This paper will describe its technical capabilities and operational requirements for live inspection of large diameter PCCP. The field test results will also be presented.