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At the heart of Itaipu: U07 ‘beating’ again
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02/04/2009

It is 11:36 am, Thursday, April 2. Generating unit 07 is reconnected to the system. After 14 days in the hands of Maintenance ‘doctors’, the heart of Itaipu is ‘beating' again. Four minutes later, at 11:40, the unit reaches its maximum production of 710 MW and continues that way. Operation takes command. At 11:55 am, U07 is placed in operational mode by the Scada digital system. Beating hard and in full force, heart 07 begins to generate energy again, along with the other units. 

It is 11:36 am, Thursday, April 2. Generating unit 07 is reconnected to the system. After 14 days in the hands of Maintenance ‘doctors’, the heart of Itaipu is ‘beating' again. Four minutes later, at 11:40, the unit reaches its maximum production of 710 MW and continues that way. Operation takes command. At 11:55 am, U07 is placed in operational mode by the Scada digital system. Beating hard and in full force, heart 07 begins to generate energy again, along with the other units.

 

 

 

 

Operation reassuming control of the generating unit is a tricky job - like the program for delivering it to Maintenance. 

 

One by one, the areas finalize their parts of the job and release the machine’s components. The Maintenance surgeons have done their job. It is time to let the machine get back to work.

 

After the activities in the suction tube and the turbine wheel, the area is sealed once again - with the suction tube filled, the platform used in the fish rescue and wheel inspection was removed. A little above, in the spiral casing, the small platforms placed above the turbine ‘teeth’ are also taken out.  The two hatchways, for the suction tube and spiral casing, are sealed again and will remain that way.

 

The water rises up the heart, arriving at the spiral casing. Safe, the hatchways closed. With the pressure balanced, the two gigantic downstream stop-logs rise. While this happens, the radiators are replaced in the generators and the final inspections in that area are made. The red plugs are replaced and sealed. 

 

The Operations team goes into action and checks the work done on the velocity controllers. They drill the blade openings through the powerful arms of the servomechanisms. Open, close, open, close. Everything is in order. The team carries out the machine return simulation in the shutdown command room. It is 5:20 pm on April 1, and the OPUO.DT professionals are excited. The simulation did not find any faults. The machine is ready.

 

Upstream of the plant, the bridge and gateway team complete the tedious task of lifting the stop-log gates. There are seven segments divided in three parts - one valve and two sets of three segments. The whole set weighs 86 tons and is over 14 meters high. At this moment only the service gate is holding the reservoir water. 

 

The ‘blood’ then runs through the heart. The whole penstock is filled and pressure is equalized in the reservoir. The service gate is finally lifted, allowing the reservoir water to flow once again. The turbine’s mechanic spin is done step by step. The blades open and water enters the turbine wheel. Ten, twenty, thirty, forty percent of the speed until it reaches 100%. At 8:32 am on April 2, the wheel reaches its maximum spin. The heart stops, new tests are done, in order to continue production. The maintenance activities are finalized at 11:05 am. At 11:36, the machine is released. The heart begins to beat again.

 

Epilogue

 

U07 operating routine. The unit is now operating via Scada and monitored by the attentive eyes of the real time Operations team on shift.  With alarms and supervision devices in full operation, the Control Center Room staff can do their work: control and supervise production. But down below, on elevation 108, on the U07 cover, the Maintenance and Operations technicians are busy. Carrying their tools they move over to U04. It’s April 13, biennial maintenance in that unit. The work begins again…