The five Kaplan turbines of the Jochenstein run-of-river power plant have been in operation since the 1950s. They are serviced every nine years. This year it is the turn of turbine 5. But before that, important preparations have to be taken to make the machine accessible.
Heavy labour under water
In the middle of October, the divers of the VERBUND subsidiary Lestin spent a whole week removing sand, gravel and wood from in front of the inlet screen, 18 metres down on the bottom of the Danube. This time, a particularly large amount of sediment lay in the lower area of the inlet screen; even a four metre-long log had to be lifted out by the gantry crane. The work is not without its issues – it’s very dangerous under water and involves dirty work that requires a sensitive touch. Details on the work of the divers at the Danube power plant Jochenstein on our blog With the VERBUND diver under water and on the diving video Diver at VERBUND (German only).
“No inspection without divers,” says inspection master Albert Weishäupl of the Danube power plant Jochenstein. “The bed in front of the inlet screen needs to be cleaned so that we can optimally place the dam beam, which weighs several tonnes. A clean bed means the dam beam can create an optimal seal. The turbine can then be drained and the inspection works commenced.”
Vital treatment for the Kaplan turbine
Now in the autumn, the turbines together with the generator and rotor are checked for their function and for “traces of use”. That means the impellers, the control equipment, electrohydraulic plant components and the generator in the powerhouse have to be inspected and refurbished by the power plant employees.
“Additionally during this inspection, we will also replace the right-hand inlet screen, which has protected turbine 5 against coarse sediment, logs and stones since 1956. The left-hand side was replaced during the inspection in 2012,” says Weishäupl. A giant undertaking, given that this inlet screen is 18 metres tall and 12 metres wide. The screen is divided into upper and lower screen fields. The individual fields are 1.20 metres wide, 9 metres tall and supported on and bolted to 3 cross-members (fish beams). The screen is lifted out and inserted again with the aid of a gantry crane.
The comprehensive servicing work should be completed and the turbine returned to its actual task again before Christmas. The revision of the south shipping lock chamber will follow starting in January 2020.
The role of hydropower in a sustainable energy system
Electricity from hydropower has may functions in the energy system. Border power plant group manager Karl Maresch: “The run-of-river power plants on the border between Bavaria and Austria are in operation 24 hours a day and supply electricity to the Bavarian and Austrian grids. The border power plants generate a quarter of the electricity requirement of Upper Austria. Hydropower is CO2-neutral, protects resources, reduces dependency on imported fossil fuels and thus makes a key contribution to climate protection.”