Dished End Formation Fomula

Search on-line for " formula for dish end blank dia".

There's a bazillion.

Er, surely it should come out the same diameter as the cylindrical part of the vessel?

??? I think he means the flat plate the dished end is rolled from, obviously greater dia than the finished vessel. Roughly the length measured over the top of the end to the weld line on either side, but not exact as there is some stretching. If I'm not mistaken there is no formula for the semi-circumference of an ellipse, but no doubt there are rules of thumb. For a torispherical end there probably is a formula but I haven't got time just now to work it out.

Yes codemaster, you are right.The OP need the formula to find the blank diameter to make the dished end after forming to match it with the diameter of rolled shell.Obviously the blank diameter will be more than the diameter of shell due to forming operation on dished end blank.A pressure vessel fabricator can answer it more precisely.Excel spread sheets are available for this purpose. Unfortunately, I don't have.

It may also depend on the forming method; e.g., spinning vs. drawing of various types.

Torisprical Dish end

(OD+OD)/23+2/3 KR+2SF+ Cutting Allowance

Ellipsoidal Dish end

24(0.9OD)/23+ 2 SF+ Cutting allowance.

OD = Outer Diameter

KR= Knuckle redius

SF= Straight face

I think there's something wrong with those formulas. They look odd and don't give sensible answers. Can you recheck, it would be useful to have formulas if they work!

As a check I did a calc for 2m head dia, 0.5m height (2:1), knuckle radius 0.2m for torispherical case.

For ellipsoidal, couldn't find a formula by integration (neither could Mathcad) but numerical integration gave 2.422m. Your formula gives 0.307m (both ignoring straight flange and cutting allowance)

For torispherical a bit of geometry came to 2.374m. Your formula gives 1.878m, closer but clearly wrong as < dia.

I don't guarantee my answers are right (somebody might check) but they look like the right sort of figures.