Some additional information.
1) Vessels under external pressure only need 50% of the reinforcement as
a vessel under internal pressure.
2) Reinforcement pads are no longer acceptable under current standards.
All reinforcement must be integral to the hull and/or penetration nozzle.
3) The maximum size hole for a vessel with diameter up to 60 inches, is
20 inches. So what do you do if you want a 24 inch ID conning tower?
ABS says to submit plans for specific approval. ASME says that 2/3 of
the reinforcement has to be within the "limits of reinforcement" which
is the lessor of 2.5x hull thickness or 2.5x nozzle thickness. Since
manned submersibles must have ALL reinforcement integral to the hull or
nozzle, a 24 inch ID conning tower already complies with the 2/3 rule
assuming you have followed all other requirements as well.
4) I forgot to provide the link in my previous mail for the white paper
proposing an alternate method of calculating reinforcement. One of the
arguments presented by the author was that the current rules are so
conservative they result in a material thickness that poses a structural
threat to the pressure vessel due to the weight of the finished nozzle
alone. I noticed that this paper was written in 2000 and although I
have not seen the 2010 version of ASME BPVC rules, I know that in BPVC
2007 ASME had not adopted this papers argument. Of course, I'm not sure
it was even submitted to ASME for approval. It's very interesting
reading since the authors proposal is based upon FEA and field tests of
prototype vessels that he shows match FEA results.
http://www.codeware.com/support/papers/bildy.pdf
Jon
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