Albert LaFrance
Lifetime Supporting Member
I know we have some full-time instructors in this group, and I'm sure many of you teach informally on the job, so I was wondering if there's any interest in discussing cases of control-related mishaps which might offer valuable insights for students.
One of my favorites is the Taum Sauk disaster of 2005, in which the mountaintop reservoir of a pumped-storage hydroelectric plant in Missouri overflowed, undermining and finally collapsing part of the reservoir wall and releasing a torrent of water down the mountain.
It's an interesting case because so many things went wrong. In terms of control systems alone, there were multiple failures. The primary monitoring system for the water level was a pressure transducer at the bottom of the reservoir, enclosed in a plastic pipe which extended to the top of the wall. The pipe came loose and floated upward, so the sensor was no longer at the bottom of the reservoir and thus understated the water level.
The backup level sensor was a pair of conductivity probes, which ended up being higher than the overflow level of the reservoir due to uneven settlement of the wall foundation. And in addition, the PLC to which they were connected was (inexplicably) programmed to require both the HI and HI-HI probes to be actuated before shutting off the pumps!
One of my favorites is the Taum Sauk disaster of 2005, in which the mountaintop reservoir of a pumped-storage hydroelectric plant in Missouri overflowed, undermining and finally collapsing part of the reservoir wall and releasing a torrent of water down the mountain.
It's an interesting case because so many things went wrong. In terms of control systems alone, there were multiple failures. The primary monitoring system for the water level was a pressure transducer at the bottom of the reservoir, enclosed in a plastic pipe which extended to the top of the wall. The pipe came loose and floated upward, so the sensor was no longer at the bottom of the reservoir and thus understated the water level.
The backup level sensor was a pair of conductivity probes, which ended up being higher than the overflow level of the reservoir due to uneven settlement of the wall foundation. And in addition, the PLC to which they were connected was (inexplicably) programmed to require both the HI and HI-HI probes to be actuated before shutting off the pumps!