`Ethanol production centrifuge disc failures`

Forensic case — 3-ton duplex stainless steel disc cast in Pennsylvania, improperly heat-treated, fractured in service in France (near-miss) and China (fatality). 700 worldwide in service; critical flaw size < 2 mm at quarter-inch drilled holes 10 inches deep, raising the inspection problem. Used to demonstrate that flaw size, not material identity, governs catastrophic risk in a brittle-heat-treated condition.

This was one I had a few years ago. When they started making a lot of ethanol about 10 or 15 years ago to put into gasoline — you know, the 10% ethanol in gasoline, using most of our corn crop to do that. You can talk about the politics of whether that made any sense. To make the corn syrup, to make the ethanol, you have to crunch up all the corn stalks and corn, and then you end up having to separate the liquid from the solid. To do that they use a big centrifuge. The centrifuge is just a big spinning disc. It's about a three-ton disc of stainless steel, with some holes in it. As it spins, you put the silage inside, and it's a wet silage, and you're trying to get the corn sugar liquid out so you can turn it into ethanol to make a substitute for gasoline. It has holes in it, so you spin it around. About 4 feet in diameter, weighs 3 tons, cross-section about 10 by 15 inches. Spinning, as I remember, over a thousand RPM. One of these things let go in China. It had been made in Pennsylvania, cast in Pennsylvania out of a duplex stainless steel.