Gas compressor station failure in Texas

Distinct from the Mississippi case — gas distribution line where a failed check valve caused the pressurizing turbine to run in reverse. Cup-cone tensile fractures and Charpy bars from this case are passed around the class. Some steels tested were so brittle they snapped without deformation; others so tough they exceeded the 300 ft-lb capacity of the test machine.

Actually, this is a different pressure vessel — another gas distribution line where the turbine that pressurizes the whole system ran in reverse because of a check valve that failed. So I got my problems in Louisiana and Mississippi and Texas mixed up. This is a neck-down piece of steel from one of those. These are the ends of the cup-cone fracture. You have a 45° shear — this is what we call plane stress. Dr. Belmir has talked about plane stress. This region in here is plane strain. This is the cup. [Tom shows another sample.] This is the cup-cone failure from another specimen. It started out as a circle, and when it necked down it's no longer a circle, it's an ellipse. There was texture in this piece of steel. How do I know? Because it has an R value — it's not one. ε₃ and ε₂ are different. There's a much bigger ε₃ value than ε₂, or vice versa. From the shape of that ellipse I could get the R value pulling on it. This one is probably cut out of one-inch-thick piece of steel.