Correct 2nd moment of inertia calculation for a stiffening ring of rect. C/S

[plantprowler]

I'm reading an example from Coulson's Chem. Eng. Series on Design (by Sinnot) and one calculation there about a stiffening ring to reinforce a vacuum column against buckling that confuses me.

I post the example below. He seems to confuse the terms "breadth" vs "depth" in his formula & I'm trying to confirm whether the right 2nd moment of Inertia for the physical case he's describing (a ring 75 mm wide in the radial direction and 10 mm thk in the axial) is 10 x 75³ or 75 x 10³

Any thoughts?

 

[JStephen]

The formula for I is correct. It's misleading because he calls the thickness "depth" in the text and calls the radial dimension "depth" in the formulas. He should have used different terminology to avoid that confusion.

 

[plantprowler]

@JStephen

Thanks! Just wanted to confirm that it's just terminological confusion and that he's not using the wrong moment.