Complete vital service for turbine 6The 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 rotorThe 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 boatThe 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 maintenanceThe 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.