12/24/2009
NEWS BRIEFS
Vibration-Induced Fastener Fatigue Blamed for Fatal Russian Dam Disaster
On August 17, 2009, the No. 2 turbine at the Sayano-Shushenskoye hydroelectric power station, in Khakassia, south central Russia, disintegrated, lifting the massive rotor, weighing over 900 tons, several meters, forcing off the turbine cover and allowing a torrent of water to engulf the turbine hall.
The turbine hall roof collapsed and nine out of ten turbines were damaged or destroyed and 75 people died, Fastener + Fixing Magazine reported.
In addition to the impact on power supplies, 40 tons of transformer oil spilled into the Yenisei River spreading 80 kilometers downstream.
A report by a Russian parliamentary commission, released on December 21, found that the failure was due to fatigue cracking in the 8 cm diameter bolts securing the turbine cover.
In September Izvestia published an article, based on unofficial information, suggesting the accident was caused by turbine vibration, apparently recognized as an increasing problem on turbine No 2 for several years.
An official report from the Federal Environmental, Technological and Atomic Supervisory Service (Rostekhnadzor) released in November, confirmed that vibration had led to fatigue damage in the turbine mountings and cover. At least six of 80 bolts securing the turbine cover are reported to have been missing nuts.
Of 49 bolts tested after the accident, 41 had fatigue cracks – on eight bolts the cracks were said to have exceeded 90% of the bolt cross section.
The parliamentary committee blamed poor maintenance as contributing to the failure of the bolts. Faults in the dam’s design and lack of adequate protective measures were also cited as exacerbating the accident. ©2009 GlobalFastenerNews.com and Fastener + Fixing Magazine
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