Re: NNG-Tacoma turbine explodes

I imagine it is much like a plant here where I live that was built in 1919. The Pelton wheel is pretty good sized in diameter, maybe around 5'. It is driven by the force of water comming out of the nozzle at 450psi. The plant is a 14 pole generator, so I think that works out to about 513 RPM. The original wheel sanded out some years back for lack of maintenance and cleaning on the forbay. The original wheel was replaced by a near identical used wheel with slighty differnet diameter. This made it less efficient because the nozzle was not at the correct hight with the new wheel. They could never get back up full output of 1350KW. A few years back they rebuilt the plant more extensively using a wheel that was fabricated out of weldments. It ran at full tilt for a while but started throwing pieces of metal. Even at what seems like a slow RPM the FPM on the periphery of someting this large is quite a bit and so the stress from centifugal force is apparently very significant. Fortunately the local power company saw fit to get this wheel reinforced and repaired. Another similar plant went to pieces in the neighboring town many years back due to a siezed bearing. It was a horizontal Francis turbine, but I guess it trew metal parts all over the power house. It was never rebuilt. Hopefully todays high demand for power will make it feasible to rebuild such a landmark as the Tacoma plant.