Secure protection against flooding with RACO electric actuators

Adjustment of the flap gates of the new distributor weir in Döbeln

Four high-performance electric actuators by RACO are part of the new flood protection system in the town of Döbeln in Saxony that was commissioned on 04.08.2016. They have the important task of adjusting the weir gates on the new Schlossberg weir at the Freiberger Mulde. They are very powerful and can safely control the water flow to protect the town from flooding, even when the water level is very high like in 2002. The complex construction project in Döbeln, which was started at the beginning of 2009, involved a large number of specialists. Logistical expertise and punctuality were very important when installing the gates, and RACO proved itself to be a very competent supplier and project partner here.

Flooding disaster was the starting point for optimisation efforts

The floods of August 2002 hit Döbeln hard. The town, which is located on an island surrounded by water from the Freiberger Mulde, recorded water levels of up to 3.5 m above the normal level. Around 310 hectares were flooded, and the water destroyed numerous buildings, systems and roads. The damage totalled approximately 60 million euros. In the ensuing years, the dam authority of Saxony started a project to improve the flood protection. Intensive surveys were conducted followed by a simulation of an emergency involving a two-dimensional hydraulic model of the planning area. This confirmed that the current weir system, which is just 6 metres wide, would not be able to withstand flooding of this scale, and a decision was made to demolish it and redesign the protection system.

Large lifting forces and mechatronic fine tuning

Large RACO heavy duty electric actuators with lifting forces of up to 805 kN are used to direct the water masses in an emergency. The sturdy actuators have a very high level of corrosion protection on the hydraulic steel parts and other protection components that guarantee a long product lifecycle in these special conditions. The actuators are highly efficient and require little energy. A holding brake locks the actuators securely into their respective position and also offers protection in the event of a power failure. Adjustments can also be made with the hand wheel, if necessary. The even alignment of the weir gates, which are each 20 metres long and weigh 20 tons, requires special and precise mechatronic coordination. There are two electric actuators each working synchronously to move a weir gate. This allows the RACO absolute encoder EPS-CAN to provide feedback about the respective position. The process is controlled via a visualisation system that is located together with the emergency generator in the flood protected engineering room close by.

Logistical challenge for the project partners

The delivery and installation of the huge weir gates required special logistical planning and good cooperation by all the specialists involved in the project. All work was planned precisely before the first gate was delivered on a low-bed truck on 30th June 2015. On the same morning, a 400 ton crane was brought into position and secured. The crane was used to lift the gate, which had been secured with four wire cables, into the opening in the concrete body. Employees of the company RACO were then on hand to mount the electric actuators that keep the gate in place and also move it. The process was repeated on 15th March 2016 when the second weir gate was delivered and installed. By this time, all parties were familiar with the routine: Körting Ingenieure GmbH was contracted to oversee the general planning, Stahlwasserbau Beeskow GmbH was contracted to deliver the weir gates and RACO-Elektro-Maschinen GmbH supplied the lifting actuators and electric motors.

Well equipped for emergencies

The new weir in Döbeln was commissioned on 04.08.2016. The team ensured that all seals were mounted and all detailed work had been completed. This project will now be followed by the construction of new roads and bridges in the town and surrounding areas. A total of 7.5 kilometres of walls and dams have been planned for the town of Döbeln. It is also planned to build two flood control reservoirs in Oberbobritzsch and Mulda on the upper reaches of the Freiberger Mulde in the Erzgebirge region for effective flood control in Döbeln and other places. According to the construction plans, the work should be completed by 2022/2023.