Flying rotor in the Danube power plant Wallsee-Mitterkirchen

12/19/2019Aschach, Wallsee-Mitterkirchen

VERBUND will refurbish all six machine sets at the Danube power plant Wallsee-Mitterkirchen by 2025. The rotor and turbine 1 were already serviced in 2017; machine six followed this year. It rotor was taken to the Danube power plant Aschach for a general overhaul by ship in the middle of September 2019. The rotor weighing 218 tonnes returned by ship on 18 December 2019 and was reinstalled with millimetre precision. In the interim, turbine 6 underwent a service.

Main machine 6 at the VERBUND hydropower plant Wallsee-Mitterkirchen has been supplying electrical energy since February 1968, i.e. for almost 52 years. Which means the turbines – the heart of electricity generation – have to be serviced, just like you would a car. The eleven-metre diameter rotor weighing 218 tonnes was spectacularly unloaded from the VERBUND boat and reinstalled.

Complete vital service for turbine 6

The rotor and turbine 1 of the VERBUND power plant Wallsee-Mitterkirchen had already been refurbished in 2017. Since the end of August 2019, VERBUND has been carrying out a major service on main machine 6, which will probably continue until March 2020. 
In addition to the standard maintenance tasks – such as identifying and eliminating wear and damage to the corrosion protection – parts were renewed, in particular on critical system components, and leaks in the pipework system were sealed.

VERBUND additionally converted the water circuit of the cooling system for the waste head produced by the generator and transformer as well as by the bearing points of the turbine from an open to a closed cooling circuit. Last of all, critical parts on the main transformer were replaced and components of the automation for the renewed system parts were modernised.

Fifty tears and not a bit tired

“For the first time after 50 years in operation, the main generator and its switchgear also underwent a general overhaul,” says Kurt Schauer, operating engineer at the Danube power plant Wallsee-Mitterkirchen. “Another new aspect of this service is that after more than 50 years in operation the internal adjustment mechanism (lever mechanism) in the turbine impeller was thoroughly inspected and subjected to maintenance that involved replacing the main sealing elements.”

The turbine oil was also replaced for the first time after more than 50 years. “That’s the liquid medium that transfers forces and ensures sufficient lubrication,” informs Schauer, satisfied that the constant care of the turbine oil had such an extremely positive effect on the 50-year period of use. Schauer is pleased with the service work and the quality of the machine, and is convinced that it will continue to work diligently and without any problem on generating electricity from hydropower for the next 50 years.

The flying rotor

The arrival of the rotor for turbine 6 was spectacular. After an almost seven-hour night-time trip on the Danube from the VERBUND power plant Aschach to the Wallsee-Mitterkirchen power plant, the 218-tonne rotor was unloaded by two gantry cranes of the Danube power plant. The “flying” rotor swung high in the air and was lifted into the belly of the power plant with great finesse. The installation involved precision work and required maximum concentration by the employees of VERBUND and Andritz. 

Tonnes of equipment transported by boat

The completely refurbished rotor of turbine 6 underwent a general overhaul at the Danube power plant Aschach. After 13 weeks, a VERBUND boat brought the rotor back to its original place of use. The general overhaul of the rotor included the replacement of 92 poles, cleaning and rust removal, mechanical crack inspections, replacement of the bolts as well as the installation of two new fan impellers. The eleven-metre ring weighing 218 tonnes is now freshly renovated and will in future be able to devote itself entirely to the generation of electricity from hydropower.

More efficiency, less maintenance

The goal of the complete overall is not only to extend the service life but also to renew the turbine, generator incl. switchgear, transformer and the cooling system of the machine set. VERBUND’s Matthias Neckam, who headed up the rotor refurbishment, says, “All these measures should result in less maintenance effort in the future. Thanks to the latest state of technology, the machine set will also run more efficiently.”

In total, all six of the power plant’s machine sets should be replaced in the coming years. The gain in efficiency will then amount to a total of 12 million kilowatt hours, equivalent to the annual consumption of 3,500 households.

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Florian Seidl Florian Seidl

Media Spokesperson for Generation

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