Fully automatic inspection systems for large underground concrete pipes partially filled with wastewater

The Emschergenossenschaft based in Germany is currently planning the Emscher sewer system, arguably the largest residential water management project in Europe in years to come. In 2002, the Emschergenossenschaft engaged the Fraunhofer Institute for Factory Operation and Automation (IFF) in Magdeburg, Germany, as the general contractor to develop automatic inspection and cleaning systems to meet the requirements imposed by legal guidelines. The systems must operate continuously in a sewer line that has diameters ranging from 1400 to 2800mm and is partially filled, 25% at minimum, all the time. To construct the Emscher sewer system, the Emschergenossenschaft favors a one-pipe line in long sections. A walk-through or inspection by personnel would be impossible in these sections. The Fraunhofer Institute IFF has developed prototypes of all systems for motion through the sewer and all sensor systems, thus achieving a new quality of inspection under these difficult conditions . This article describes significant project results and important components of inspection such as the inspection systems, pipe axis measurement, system positioning and sensor systems for damage detection. Fundamental for the development of the inspection systems are the detail of the inspection that far surpasses the video inspection common today and the capability to take comparative measurements throughout the sewer system's period of operation in order to track the development of damage.