Pipe Penetrating Radar inspection of large diameter underground pipes

Pipe Penetrating Radar (PPR) is the underground, in-pipe application of GPR, a non-destructive testing method that can detect defects and cavities within and outside mainline diameter (>18 in / 450mm) non-ferrous (concrete, PVC, HDPE, vitrified clay, etc.) underground pipes [1, 2]. The method uses two or more high frequency GPR antennae carried by a robot into underground pipes. The radar data are transmitted to the surface and are recorded together with the output from CCTV (and optionally sonar and laser). Proprietary software analyzes the data and pinpoints defects or cavities within and outside the pipe. Thus the testing can identify existing pipe and pipe bedding symptoms that can be addressed to prevent catastrophic failure due to sinkhole development and can provide useful information about the remaining service life of the pipe. This paper describes the Vancouver, WA, USA project where PPR was used to inspect two main line diameter (21 - 36 inch) pipes and was successful in quantitatively determine the amount of H2S corrosion in these critical interceptors.