DUVHA

not for publication – background info.

Duvha coal-fired power station unreported accident 

• A well-informed, close observer of this photographed turbine-explosion at the 3600MW fossil-fuel power station in Mpumalanga on February 10 2011 writes:“They were doing a test of the turbine overspeed protection system, and in short, the protection did not kick in. Conventional wisdom tells me that there should be a better way to test a protection system than to try and destroy the turbine and see if it feels like protecting itself, but that’s basically what they did. “…

“The turbine has a governor valve which controls the amount of steam coming into the turbine In order to keep it running at the right speed (3000 rpm for our grid frequency) and then it has a main isolation valve to shut the steam off completely. The protections systems (of which there are 3 independent systems, and a dude with his finger on the emergency button) are supposed to close this main isolation valve in a fraction of a second when the turbine overspeeds.

TESTS OF 3000 RPM TO 4500 RMP OVERSPEED, all three systems failed - yet the guy who was supposed to push the manual-trip button wasn’t even at his post…

“So they get ready for the test, they dump a helluva lot of steam onto the turbine, speed starts going crazy, it went from 3000 RPM to 4500 RMP in ten seconds (they are generally only designed for 10 to 15% overspeed, all three protection systems should have kicked in by the time you get to 110%). Anyway, I don’t know why, but all three systems failed, and the dude with his finger on the manual trip button wasn’t at his post. So the result was a big bang, some fire and a lot of steam going where it shouldn’t go.”

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DUVHA has a shared turbine hall… all six units neatly placed in one long line without missile shields in between…

“Scary thing is Duvha has a shared turbine hall. (picture below). All six units are placed in one long straight stripe, with no missile shield between them. And if you look at the third last pic you can see how big that shaft is, if that landed on another turbine it would have destroyed that too. They are very lucky they didn’t lose the entire station.” So anyway, what gets reported in the news? “Unforeseen maintenance” at one of the units at Duvha requires it to remain shut down for 18 months.” …  understatement of the century in my book. “

BELOW IS THE OFFICIAL SA GOVERNMENT VERSION OF EVENTS:

• ‘Repairs to Eskom’s Duvha Power Station to Take Time”
  February 11, 2011 - Eskom has warned that a unit which burst into flames this week at Eskom’s Duvha Power Station during a routine test will take extensive time to repair. Eskom spokeswoman Hilary Joffe said Unit 4 of Eskom’s Duvha Power Station was “damaged last night in the course of a routine test. No one was injured but the unit is expected to take extensive time to repair,” she said. Joffe said the other five units of the 3,600 MW Duvha power station were running normally and the national grid remains in ‘green’ status, meaning that Eskom is generating enough power to satisfy the demand in the national grid. The incident happened when the 600 MW units at Duvha had been taken off load to perform a required turbine test.“This is a statutory test that is carried out in every power station. In the execution of the test, the protection of the unit failed, causing severe mechanical damage and starting a fire, which was brought rapidly under control by the power station’s fire team,” said Joffe. Eskom have since launched a “technical review “ of the incident. Eskom’s divisional executive for power-generation, Thava Govender, said: “The technical review is aimed at finding the cause of the unit failure, so that we may take appropriate action to prevent similar incidents in future.” Source: Nthambeleni Gabara at BUA News agency.
  http://www.netnewspublisher.com/repairs-to-eskoms-duvha-power-station-to-take-time/