Dish End

Dear all,

I was used I/Dx0.904 (for crown radius) and I/Dx0.173 (for knuckle radius) to draw 2:1Elliptical Head, Some times i used O/D for calculating the Crown and Knuckle Radius (after drawn the Dished end O/D i offset the thickness towards inside of the vessel, for I/D), Sometimes i used I/D for calculating the Crown and knuckle Radius (After drawn the dished End I/D i offset the thickness towards outside of the vessel, for O/D) , I know The D/4 Formula also.
Recently i found there is difference in Dish height when I using I/D and O/D, now i confused which is correct,
please advise me to draw the dished end in correct way and clear the confusion.

Thanks gentleman.

As I understand the issue, elliptical end manufactures apply there own standard for tangents at the end of elliptical heads. So between two different manufactures for the same size head there "could" be a height different.
My question to you (as a piping designer) why would you care? In the capacity as a vessel designer I could see your interest, but not as a piping designer. A piping designer may be asked to generate a nozzle orientation drawing and generally locate the size, orientation, & projection on the nozzles, but this is a "wish list" to the vessel manufacture. He generates the drawing that is fabricated too. So worrying about the height of the elliptical ends is fruitless. I use the D/4 plus 2" formula myself, and wait for the vendor drawing to see what I get. ...My $0.02, good luck!