Flat plate machined concave
Flat plate machined concave
(OP)
If I have a flat plate blanking off the end of a vessel and machined it so the inside surface is concave to pressure and the outside remains flat, do I still need to use the Sec VIII rules governing flat plates to determine minimum wall thickness or can I now use other rules, such as those for sphereically dished covers for example? In other words, would the stresses change from bending to tension by changing the shape of one surface? I do not have access to FEA so I cannot determine easily what the result of this action would be.





RE: Flat plate machined concave
If this is a flanged attachment do not forget the requirements of Appendix 2.
RE: Flat plate machined concave
You're basically creating a "hub" on the skirt of the head, and both menbrane & bending stress are tending to peel across any laminations.
RE: Flat plate machined concave
zakk (Mechanical)you may want to deep water U.T., This can be a bad problem.
Also, for FEA use FE/PIPE - Finite Element Analysis for Piping / Vessels
Paulin Research Group
11211 Richmond Avenue
Suite 109,
Houston, Texas 77082.
Phone: 281-920-9775, FAX:281-920-9739
http://www.paulin.com
E-Mail: tony@paulin.com
Leonard
www.thill.biz
RE: Flat plate machined concave
RE: Flat plate machined concave
What I am inquiring is by concaving the pressure side only of a forged flat plate do the stresses go from bending towards membrane, hence I could use thinner material to cap the vessel.
RE: Flat plate machined concave
In your case: imagine cutting away from your head on the flat side some material in order to get a constant thickness head of, say, spherical shape. By doing this you also must fulfill the requirements at the attachment (knuckle radius, skirt length, butt weld and examinations of this weld, and so on).
If the included head satisfies code requirements then you are OK.
In all other cases you would need a detailed approach as figured out by other posters, but I guess this wouldn't be worth the cost of a flat head.
prex
http://www.xcalcs.com
Online tools for structural design
RE: Flat plate machined concave
Of course the material checking such as chemical, mechanical, soundness and so on shall be carefully be cosidered.