Within the wastewater treatment plant, the wastewater first enters a screening plant with several filter stages and then a primary clarification basin, where the sludge settles before being extracted. In two secondary clarification basins, the continuously fed biological sludge is evenly distributed by a scraper and, after settling, removed from the basin via a pumping station. One of the two secondary clarifiers is rectangular and equipped with a longitudinal scraper that travels at a speed of 1m/min via a gear drive and continuously distributes the sludge in the 38-metre-long and 3.15-metre-deep basin – 24 hours a day, 365 days a year. The scraper, like the pumps below the water level, requires energy and control signals.
Since the energy supply system required for this will work outdoors, it must not only be insensitive to sun, frost and rain. Extraordinarily aggressive gases such as hydrogen sulphide are also produced during wastewater treatment and represent a major challenge. In addition, leaves and snow can interfere with the movement of the cables - precautions must be taken here. And at the same time, you have to be sure that the system runs trouble-free around the clock. This is because every unscheduled use of the on-call service incurs additional internal costs - this is registered precisely in the Aggerverband.
Originally, a cable drum was used for this task. For those responsible, this solution was not very satisfactory, because with every forward and backward movement, the cable performed a slight twisting movement, which contributed to the increased wear.
After searching for a suitable solution for the plant, the operator found what he was looking for in the energy supply product range from igus. With the LTB flizz system igus offers a weather-resistant energy supply system that can be modularly adapted to the respective conditions of use. But also in terms of price, the system is a good alternative, especially in comparison to festooning solutions. The tried and tested chain of the igus series E2, type 250.07.100.0 was used as the energy chain. This runs in a guide trough consisting of extruded guide profiles attached to a support frame. Since the trough is closed at the top, neither snow nor leaves can interfere with the movement of the filled energy chain in the guide trough. A total of 38 metres of the guide trough were installed on the secondary clarifier. The special chainflex cables used in it are approx. 20 metres long; in addition to the electrical cables for the three pumps and the traversing motor, the trough also houses 16 signal cables and a Profibus cable. The individual igus chainflex special cables of the series CF9, CF10, and CF 31 have a TPE outer jacket and can be used in a temperature range of -25° to +100° with a minimum bend radius of 5 x d.
With longitudinal scrapers of this design, a lateral offset of up to 150 mm must always be expected. To compensate for these transverse movements, igus developed a cost-effective floating moving end and installed it on the moving end arm of the scraper bridge.
The polymer components and the metal parts are permanently protected against corrosion.