The #8 boiler at the Ames power plant stands nine stories tall.  Inside this boiler, powdered coal is blown in through four burners, one in each corner. The coal has been ground to a fineness of flour and burns instantly when it reaches the inside of the massive boiler. The burning coal converges in the center of the boiler and produces a fire ball reaching a temperature of 2,000 degrees.

The inside walls of the boiler are made of heavy steel pipes about 2 ½ inches in diameter. Water, under very high pressure, flows through these pipes and turns to steam. This steam drives the steam turbine and produces electricity. Heavy electric use for air conditioning in the summer provides a real challenge to produce enough electricity for everyone. All of the equipment is running at full load and the equipment stress is high in the summer heat.

On this particular day in June of 1995, it was hot and the electric demand was high.  I was operating the #8 boiler and it was fully loaded.  It was suggested that we could increase the boiler pressure and that would allow the turbine to produce a little more electricity. While it is true that a pressure increase would allow for a slight increase of electric production, I felt that the unit was already running at its maximum limits. I did not raise the pressure.

Shortly after the shift change, I went home to enjoy my own air conditioner.  All of a sudden the lights dimmed and I heard unusual sounds in the direction of the power plant. Six of the water wall tubes had split open. This tube failure filled the boiler with huge amounts of steam, put the fire out and made a positive pressure inside the boiler. This steam was then forced out of the boiler and filled the power plant building its self.

All six tubes had ruptured within a couple of seconds of each other.  It is very unusual to have adjacent or multiple tubes fail.  Tube failure is not too common, and it is usually a single tube and does not make this massive release of steam.

This was the only time that I have seen this happen to so many tubes. This very large release of steam into the boiler caused much more damage than a single tube failure would have caused.