Immediately upstream from the port of Hamburg, between Finkenwerder and the Elbe island of Schweinesand, the Este flows into the Elbe. The Este flood barrage was built at the confluence. It is equipped with barrage gates and a bascule and allows motorised traffic to easily cross the river. It primarily serves as flood defence, in particular to prevent flooding of the nearby industrial area.
In order to fulfil this requirement, the facility was equipped with four mitre gates. Each gate is equipped with a hydraulic cylinder which can exert a force of 1,800 kN and can be closed within 4.5 minutes if necessary.
The four identical mitre gates are not solid, but instead consist of several
chambers. The lower chambers are watertight and provide buoyancy. This relieves the bearings. The upper chambers have inlets and outlets for the river water, in order to allow pressure compensation when opening and closing.
Mud deposits in the wing walls cause problems
Sediments are stirred up by flushing works and the natural tidal range. This mud-water mixture penetrates through the chambers. It calms in the wing walls and then settles out. The deposited mud became so hard that it had to be removed, by muscle power or by using a diver (depending on the degree of siltation). This additional effort was necessary to avoid subsequent damage as a result of the extra weight of the deposited mud. In order to avoid further deposits, agitators were first installed to provide improved flushing. However, it was not possible to make a sustained improvement to the cause of the problem by this means.
Submersible pumps solved the problem
A number of options were considered to solve the siltation problem. Eventually, it was decided to install pipes with nozzles in the lower two chambers. With the aid of submersible drainage pumps, installed outside of the wing walls, the water is pumped from the Este and thus into the pipes, where a spray pressure of approximately 1.5 bar is applied to the nozzles.
Because sediment backflushing only makes sense when the water is draining, that is when the chambers have drained, pump controls were necessary. The barrage has a control room, where a programmable logic controller (PLC) is installed. This can also control pump functioning with the aid of water level sensors. Backflushing allows the gates to be operated without impairing their function.
It was possible to remove the previously installed agitators. Using the flushing system the chamber corners, in particular, could be kept free of sediment. Bottom deposits are also permanently avoided using this method. The facility has been running without problems since August 2012. The flushing line does not require servicing. Impairment due to the weather or frost need not be feared.
Söndgerath submersible pumps are built to meet the highest demands
The SPT pumps used in the Este barrage are four PXFlow 2-100.04 Channel1. They are designed to meet the highest demands. Operating and servicing were considerably simplified by numerous functions. All PXFlow models are equipped with two moisture sensors connected in series. An increase in moisture around the terminals, the interior of the motor or in the oil chamber is recognised early by the moisture monitors. The pumps are equipped with heat sensors to protect the motors against overheating. The pump casing is high quality cast iron. The casing's smooth internal surfaces minimise turbulence and thus allow higher hydraulic efficiency. The impellers (single channel) consist of hard wearing cast iron. They are dynamically balanced and produced to high tolerances to reduce undesirable vibrations.
The four PXFlow pumps employed here are equipped with high-efficiency motors
(EFF1). Rotor shaft and ball bearing allow for uniform, smooth and vibration-free running. This results in a considerably extended motor service life. The shaft seal consists of a double mechanical face seal. If necessary, the replaceable seal cartridge can be replaced on-site, without the use of special tools. The pumps used in the Este barrage are precisely coordinated with the medium to be pumped and the necessary performance. The high freight river water can be pumped without any problems.
In the past mud deposits in the barrage gate chambers caused the operator considerable problems, leading to cost-intensive mitigation works as a consequence. In order to maintain shipping in the required manner and at the same time guarantee sustainable flood protection, a perfectly operating barrage is needed. Problems caused by the deposits can be permanently eradicated using the SPT pumps.
If the units require servicing, fast and easy inspection is possible thanks to the self-guiding coupling system. This was not possible in this way in the past. A diver was generally required if servicing was needed. Not only is the task at hand completely resolved with the adopted solution, but the energy costs are also substantially reduced by optimal pump design. As a consequence, additional costs for diver deployment and manual mud removal are no longer an issue.
Designation: PXFlow 2-100.04 Channel1
Impeller: single channel
Rated power: 6 kW
Configuration option: wet configuration
Task: Pumping river water with sediment freight
Motor: Class EFF1
Shaft seal: 'Fast Seal' double mechanical face seal