Quest For Innovation At The Trenchless Technology Center

November 2012, Vol. 67, No. 11
Figure 3. FutureScan module in deployment

With visual inspection no longer reliable as the means of identifying the location of lateral services behind the newly installed liner, several indirect measurement technologies have been developed, including the use of eddy currents, thermal imaging, magnets placed in the lateral prior to relining and a pipe locator sonde. However, these methods can suffer from significant disadvantages depending on the method specifics including inaccuracy, incompatibility with some material types (e.g., thermoplastics), size limitations (e.g., cannot fit into a six-inch host pipe) and low productivity (up to six hours to locate a single lateral) or the need to place/retrieve an object in the lateral.

To avoid current problems, the TTC has developed a microwave-based, near-field sensor to pin-point the location of the lateral regardless of the material compositions of the main and the service line. The solution has used off-the-shelf components embedded into a custom-designed electronic board. This exciting technology, which is capable of entering a five-inch diameter pipe and locating a lateral in about two minutes regardless of the composition of the main and lateral pipe material, is expected to reduce the risk, and therefore the cost, associated with the rehabilitation of small-diameter pressure pipes. The prototype lateral locator is currently undergoing bench scale testing and in-pipe deployment is expected in the first quarter of 2013.

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Figure 1: Sensor positioned inside a cast iron pipe (8-inch diameter) lined with a 0.25-inch thick CIPP liner

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Figure 2: Surface plot of the signal from sensor: the circle represents the actual location of the lateral; green contours on the plot show the area which was discriminated by the sensor; blue color is the background

‘See through wall’ imaging technology

The impetus for this research has come from the needs in a wide range of commercial sectors for improved methods of “seeing” behind visually opaque objects. This is of special significance in the inspection of buried pipes where utility owners would like to understand the bedding conditions outside a pipe or the presence of soil voids without having to excavate from the surface down to the pipe level. In a now commercialized innovation, the TTC worked with Cues to develop a rapid deployment in-pipe radar system named ‘FutureScan’, which is incorporated with an advanced CCTV system and can scan for voids outside a sewer pipe without interfering with the speed and efficiency of the CCTV inspection.