While Germany still faces many unsolved problems in terms of implementing the energy turnaround, they have moved significantly further on in South America. Especially the developing nation of Brazil is proving itself to be the role model when it comes to renewable energies. Around 75 percent of the electricity requirement is covered by hydroelectric power there.
Look behind the scenes
Brazil's special geographical features make it seem as if it was made for hydraulic power. No expense was spared either with the latest plants: for example the largest Kaplan turbines in the country so far are running at the new Estreito power station on the Rio Tocantins. Their rotor alone weighs 470 tonnes.
In addition to pumps, the systems developed for this also include filters, heat exchangers, instruments, control units and pipes and comprise two essential sub-areas: an injection unit and the actual lubrication oil circulation. The enormous weight of the turbines which rests on the bearings means that the lubricant has to be applied at very high pressure, above all when starting up and switching off, so as to be able to create any lubricating film at all between the rotating and static components. Gear pumps are used for this which can generate 100 to 250 bar. This means the moving components of the dry bearing can easily be raised and reliably lubricated.
Injection is stopped as soon as a stable film of oil is established. From this point onwards, the continuous supply of lubricant and the feedback to cooling and filtration are taken over by special screw pumps. These comprise two spindle-shaped rotors whose helical profiles are exactly attuned to one another and to the housing geometry. This means the screws intermesh as they rotate and sealed conveying chambers are formed in which the medium is conveyed from the inlet to the discharge side. The capacity is substantially determined by the incline of the spirals, the diameter of the spindles and the shape of the spindle profile. Due to the hydraulic thrust compensation of the pump, the axial forces here are close to zero even for high pressures. In addition, an integrated spring-loaded overflow valve protects the system against overload.