IBR Codes and Dished Ends

An approximation for the diameter of a blank for a hemispherical head is:

BD = (pi)(OD - t/2)/2

where:

BD = blank diameter

OD = outside diameter of head

t = thickness before forming

OR ..........

For OD/t > 30 : BD ≈ 1.6(OD)

For 18 < OD/t < 30 : BD ≈ 1.65(OD)

For 10 < OD/t < 18 : BD ≈ 1.7(OD)

If you need great accuracy you should talk to your head fabricator as they will have the numbers for there exact fabrication techniques.

is there any reference regarding this

The first one is from some old spreadsheets I downloaded from http://www.pveng.com/ which don't seem to be available anymore.

The second one is from Plant Design and Economics for Chemical Engineers - 5th ed

pl give dished end weight calulation formula.

weight can be calculated as

Wt= ODxODx Tkx7.85x0.785 (for MS material)

Wt= OD xODx Tkx8x0.785 (FOR SS materail)

where OD is outside dia and Tk is thickness of material

Try searching for pressure vessel dished end suppliers. I haven't looked recently, but have found supplier information in the past in table format in which the specific details of formed heads are listed.

These are normally listed by diameter and plate gauge and the ones that I have located in the past show the blank diameter for each specific head configuration as well as such things as volume. You can probably find one that closely approximates your finished head radius and plate thickness to determine your needs. A hemi-head is the same whether to IBR, ASME, or any other standard.

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For calculating accurate BD the formula is as follows

Bd= OD+OD/41+(2/3)Kr+2SF.

where OD= outside dia

Kr= knuckle radius(between 6-18.5%)

SF= straight face