UPDATE: The Duvha turbine incident occurred in 2011 and has gone viral over the last few days as angry South African are facing the possibility of a national black-out.
A turbine at the Duhva power station exploded, in a failed attempt to test a safety feature.
Duvha Power Station in Mpumalanga, South Africa, is a coal-fired power plant operated by Eskom. The 300 metres (980 ft) tall chimneys at Duvha are the second and third tallest structures in Africa
Sweeping the bullshit as well as the taxpayer’s money under the carpet!!
Not really intended for the public, BUT, amazing how pics like these can get out even after Eskom put a blanket of secrecy around the whole incident. Eskom like hiding stuff like this?
So I found out what happened at Duhva power station and the busted turbine.
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 over speeds.
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% over speed, 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.
Scary thing is Duvha has a shared turbine hall. All six units are placed in one long straight stripe, with no missile shield between them. And if you look at the third 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. But you shut off the containment ventilation system at Koeberg for one hour and a radiation alarm goes off, then it’s a front page news national crisis. I give up.
Article content & images By Cobus Viljoen
Other Sources:
RidgeTimes 6 Dec 2014
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