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The longest tunnel in the world

A project of the century is currently under construction in the Alps: The Brenner Base Tunnel, which links the Austrian city of Innsbruck with the South Tyrolean fortress of Franzensfeste. When completed in 2026, it will be the longest tunnel in the world.

The 55 km long route runs flat under the mountain Brenner. Adding to the already existing railway bypass around Innsbruck, into which the new tunnel merges, the tube impresses with a total length of 64 km. At 250 km/h, fast trains will race on a straight stretch under the Alps. The journey time between Innsbruck and Franzensfeste is shortened from 80 to 25 minutes.

In the tunnel of superlatives, huge tunnel boring machines are used, whose drill heads have a diameter of up to ten meters. The huge tunneling machines are cooled with water. In addition, the generated dust is bound by water. As a result, large quantities of poluted water are produced in the mountain, which are then prepped to be returned to nature. Regarding the water quality, strict requirements have to be fulfilled, therefore complex water treatment systems are used.
In order to transport the waste water between the treatment stages, pumping systems are needed that automatically adapt their pumping capacity to the local conditions. The inflow to the individual control stages, such as the control of the pH, must be done as continuously as possible and without large water surges. Only then the respective control process can be operated efficiently. At the same time, it must be ensured that the maximum possible water supply into the storage tanks can also be pumped out.

At this point, in autumn 2016, NOLTA, being an expert in machine and pump connection systems, entered the stage. Peter Schütz, Project Manager Tunneling International at STRABAG: „At the Brenner Base Tunnel, there is a water protection facility on the portal of the Sillschlucht access tunnel. It prepares all mountain and industrial waters accumulating at this point. Some of the treated water is used again as service or cooling water for the boring heads and other construction equipment. All water is pumped and as a result, the amount of water that is supplied to the water protection facility varies greatly. The operation of the system is significantly affected.“

„The task for NOLTA was to coordinate the motor protection, float switch and pump control so that the water flows evenly through the seepage basins - regardless of how much water is being pumped in from the construction site. In addition, the device needed to be portable so that it could be used with flexibility. For the concept and a prototype, the NOLTA developers had three weeks - an ambitious time frame, but in the end a viable and above all, economically feasable solution was found. The trick is that the control of the pumps is programmed in a way that only one frequency converter is necessary to ensure a steady flow. The process of cleaning the water is highly efficient and helps to complete the construction of the century in the Alps.