Last Wednesday (10th) morning, Itaipu technicians finished taking apart Generator 06 (U6). The last part removed was the 300 ton, 8.6 meters round and 4.5 meters tall turbine wheel. The set was hoisted by one of the plant’s traveling cranes, a sort of giant crane used in major operations. The turbine wheel contains the bottom wear ring that showed cracks and needs to be replaced. The problem was found during preventative maintenance work last September. One of the wheel’s 13 blades will also be undergoing repairs. A crack was found in it.

According to the Maintenance Superintendence (SM.DT), the ring replacement and the wheel repair are expected to be completed within 45 days. Before reassembly, all the generator’s parts will be reviewed. If all goes according to plan, U6 will be going back online in March 2012. The removal of the last U6 part was monitored up close by Jorge Samek and Gustavo Codas, the Brazilian and Paraguayan general directors, respectively, along with Cecílio Perez, Paraguay’s Public Works minister.

Samek pointed out that, in three decades of operation, this was the first time an Itaipu generator is completely taken apart. “Basically, this work has lent itself as a lab, an open university”, he said about how important the service has been for the new maintenance technicians. “Besides, as the machines have been operating for 30 years, it was about time to PET scan each and every generator”, added the Brazilian General Director, comparing the work performed by the maintenance personnel to the medical procedure that helps doctors see hard-to-reach organs. “This action will be very important for the maintenance of the next generators”.

First time ever

Marco Cesar Castella, deputy Maintenance superintendent, explained that the turbine wheel is one of the generator’s most important parts for turning the water’s kinetic energy into mechanical energy and then into electricity. “It is the wheel that drives the entire turning assembly, the axis, the rotor, that generates power”, he noted.

According to him, as the bottom wear ring is the last part in the assembly, the entire generator had to be taken apart – the first time ever the procedure has been carried out at the plant. “[The ring] needs to be replaced because it could cause much bigger losses in case it broke away”, he said.
“All this is a learning experience, a university for people working on it”, the superintendent emphasized. “Today, the maintenance team has been renewed by 65%, these are new people who have never seen this. And the other 35% will be leaving Itaipu in the next few years. Therefore, this experience is priceless for those who will be staying with us”.

Castella further highlighted that the entire U6 disassembly service is being performed by the plant’s own teams. In addition to the wheel and several other small parts, the axis, the top crosspiece, the top axis, the rotor, the bottom axis, the bottom crosspiece, two servomotors and the cover have been removed.