Catastrophic situations often occur as a result of complacency. If, over time, warnings of abnormal conditions are ignored without any apparent consequence, those situations begin to slide into the realm of routine. Then, if the pattern of consistent oversight persists, stakeholders suddenly and unexpectedly find themselves in a crisis situation that endangers both life and property.
That is exactly what happened at the Sayano–Shushenskaya hydroelectric power station in Khakassia, Russia, on August 17, 2009. At 8:13 a.m. on that day, when Turbine 2 violently broke apart, 75 people were killed and 40 more injured, and millions of dollars in turbine equipment was damaged or destroyed as a result of a collapsed ceiling and flooding of the turbine hall and engine room.
Such a tragedy could easily have been avoided.
Russia’s largest hydro station, operated by RusHydro, a quasi-state-owned utility company, generated enough energy to power a city of 3.8 million people. The station, which was commissioned in 1978, was undergoing repairs and upgrades when the disaster occurred. The main hall was filled with workers focused on their specific tasks. One count had 52 workers on the main floor and another 63 down deep within the plant. Nine of the 10 turbines were operating at full capacity -- including Turbine 2, which had experienced a history of issues (see text box).
That particular turbine had been offline, but because of a sudden decrease in electricity production (due to a fire at the Bratsk power station, 500 miles to the northeast) the turbine was rushed back online. What happened less than a day after Turbine 2 was brought back into service led to a series of cascading failures that culminated in the deaths of 75 workers.
Consequences for making the wrong safety decision
As a result of previous vibration issues, Turbine 2 had been taken offline until August 16. That was the day when the fire at the remote Bratsk power plant prompted Sayano-Shushenskaya managers to bring the temperamental turbine back online.
Back in operation, Turbine 2 began to vibrate at four times the maximum limit. As the control system flagged a decrease in the turbine's output on the morning of August 17, the vibrations increased. The unit shuddered violently forcing additional stress on the fatigued metal pins that held it into place, and which, eventually, led to the turbine breaking apart.
Turbine 2, a 1,500-ton device located one floor below a room that housed a power generator, was catapulted 50 feet into the air upon rupture, piercing the roof above before it came crashing back down. The penstock water that had been spinning the turbine shot up out of the now-vacant shaft at a rate of 67,600 gallons per second. The power of the raging water tore down the metal joists over Turbines 1, 2 and 3; the entire roof above gave way and collapsed.
Water continued to pour into the hall, flooding its lower levels and eventually submerging other turbines. Since turbines 7 and 9 were flooded, but still operating at full speed, a series of short circuits blacked out the plant. This caused the plant's failure of the automatic safety system. As a result, the turbines and the intake gates on the penstocks at the top of the dam were not shut down and closed.
To better understand how some of the various mistakes that occurred over time should have been addressed and prevented, click here. To learn more about steps to take for ensuring better plant and control systems process safety click here.