Large waste water pipes are a hazardous working environment for humans. Nevertheless such pipes must be inspected on a regular basis. Many of todaypsilas inspection systems for underground sewer pipes consist of a single TV-camera and are designed for pipes smaller than one meter in diameter. The most recent automatic inspection systems are equipped with advanced sensors that make it possible for an operator to perform this task from an outside position for larger pipes (diameter between 1.4 to 2.8 meters). The cable-guided damage surveying system, SEK, (see Fig. 1) was developed by the Fraunhofer IFF on behalf of the Emschergenossenschaft to be a versatile and easy-to-use tool to detect various kinds of damages above and below the water-line with high accuracy.

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. 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 2800 mm 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 above and below the water line 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 is the detail of the inspection, which goes far beyond the video inspection common today, and the ability to take comparative measurements throughout the sewer system's period of operation in order to track the development of damage.

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 2800 mm 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