Quote:
Originally Posted by VINMAN
no shear coupling?
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Nopers. A shear coupling lets go under extreme torque loads, like when something siezes all the sudden-like or the gererator gets loaded when not in sync with the grid.
In this case the load was exteremly low but the speed was a tad too high.
The gererator tripped off-line, which basically eliminated the load.
The governor valves were stuck with scale and did not move. The trip valve was also stuck and did not close. The turbine went from normal running speed to reeaaaaaalllllly fast in a couple of seconds.
Imagine running your car at full throttle in 5th gear and pushing in the clutch without lifting.
Then imagine you didn't have valves that would float and limit the rpm. Then imagine you didn't have an intake or exhaust system that would limit rpm. Instead you had an engine capable of accelllerating to rpm levels more than fast enough to make the engine go boom. That can be as low as 10,000 rpm for giant turbines or as fast at 150,000 rpm for smaller turbines.
Checking their overspeed trip valve and governor once in a while might have been a good idea.
Biggest steam turbine I ever overhauled was rated at 1,500,000 horsepower. Took quite a while and I couldn't do it all by myself.
See that red-oxide colored thingamajig in the picture? that's it.
The rotor was made in 5 different sections, the largest sections weighed 175 tons each.
Here's a nuther picture of it. This one shows units 2 and 3.
Fer perspective, the deck where the turbine sits and the rails where those 225 ton bridge cranes sit on are about 60 feet up in the air IIRC.
It's kinda hard to find a close up picture, I guess they're just shy
