Criteria to optimize Skirt-Tapered transition accord, to UW-13 2

[JASR76]

Hi all!!

A tapered transition or skirt is the crown plate that separates the head (ellipsoidal, hemispherical..) of a cilindrical vessel from the shell (as you already know)

My question is , does anybody knows (based on an article or publication) how to calculate the optimal heigth of this piece of plate (there is not fillet in my design, we are talking about FIG UW-13 (d) )

Thank you very much to all

JASR76

 

[SnTMan]

Not sure exactly what your question is, but:

If you are talkng about the "straight flange" or skirt on a formed head, that will probably depend on the manufacturers tooling. 2" is a common length for the SF on a 2:1 head of moderate thickness. A spherical head may have none.

If the "taper" is between plates of different thickness, see Fig UW-13.1 (l) thru (o) and UW-13(b)(3).

Regards,

Mike

 

[jte]

JASR76-

As SnTMan pointed out, a 2" straight flange ("skirt" as used in VIII-1) is probably the most common for 2:1 SE heads. Second most common length is 1.5". For replacement heads I've ordered them with SF's as long as 4" so that the original circ seam is completely cut out and the weld for the replacement head is to an area of the shell which has not been previously welded. As far as "optimal" length, I would leave that to the fabricator / head spinner to determine. See UW-13 for VIII Div. 1 requirements. I learned something today. That's part of the fun of eng-tips. I can't say I ever knew that there was a Code mandated minimum SF length If there is a difference in thicknesses between the SF and shell, be sure to add a 3:1 taper if necessary [UW-9]. Also be sure that the SF is thick enough - you have to run a separate calc to determine this, not just the head thickness calc [UG-33(l)].

jt

 

[JASR76]

SNTman & Jte,

First of all , thank you very much.


You were rigth, i was talking about the "straight flange" or skirt on a formed head with a "taper" between plates of SAME thickness. I know typical lengths are about 1.5" or 2" but I heard once that there is an optimal length related to buckling and so on.

You can check something related in this web:

http://www.aiaa.org/content.cfm?pageid=406&gTable=japaperimportPre97&gID=27603

"Design guides for tapered transition sections for pressure vessels"

DINGWELL, I. W. (ARTHUR D. LITTLE, INC., CAMBRIDGE, MASS.)
JOURNAL OF SPACECRAFT AND ROCKETS 1964
0022-4650 vol.1 no.1 (115-116)


I think the best option is to leave that to the fabricator / head spinner to determine, but I would like to know if someone knows which is the optimal number and how to calculate and its basis.

I hope you can understand now my question about theoretical basis of design

thank you very much again

JASR