Detecting Wire Breaks from the Outside of PCCP

When the electromagnetic condition assessment technology known as Remote Field Transformer Coupling (RFTC) was developed for prestressed concrete cylinder pipe (PCCP) water mains, one of the main design considerations was that it works from the inside of the pipe, as most pipelines are buried. Recently, it was discovered that the technology worked from the outside of the pipe as well. While internal electromagnetic inspections are still more practical for standard condition assessment projects, external scanning has several useful applications. External scanning is clearly an asset for un-buried pipe, as it eliminates the need to dewater, and it is strategically useful in rehabilitation work for pipes that have been identified as distressed with conventional internal scanning. Scanning an excavated pipe and reviewing the data for locations of break regions, will confirm that the right pipe was located prior to executing rehabilitation. Scanning an excavated pipe can also provide more detailed information on wire break regions of pipes that are difficult to analyze, as the signal is clearer because it does not need to penetrate the steel cylinder. This information can help determine if rehabilitation is actually required. This paper presents the design, capabilities and applications of external electromagnetic inspections, including case study where an exposed pipeline was successfully inspected.