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Re: [PSUBS-MAILIST] Hull Penetration and Reinforcement
Frank,
Thanks for that. The headers were confusing because I trimmed back the
table a bit from a previous version. I've redone the column headings so
they should make more sense now.
Column E is the area of the finished opening, divided by two. The
standards say that for vessels under external pressure only, the
reinforcement can be 50% of the area of the opening. So if the finished
opening is 24 inches and the hull thickness is 1/2 inch, then the total
cross-sectional area of the opening is 24 x .5 = 12. However, since we
only have to replace 50% of that when building a submarine (as opposed
to a steam engine boiler) the value becomes 6.
Column D is the diameter of the "finished" opening, of the nozzle (the
red section in the diagram). It is different (and smaller) than the
hole you have to cut out of the hull to insert the nozzle (length of red
and green sections in the diagram). For example, if you want a conning
tower with a 24 inch opening and the required thickness is two inches,
then you are going to have to cut a 28 inch hole in the hull. However,
once you insert the conning tower with full penetration welds you've now
replaced four inches of metal leaving a 24 inch hole in the hull. So
the standards refer to it as the "finished opening" since there is only
one diameter to a circular hole or opening. However you could also
refer to it as the ID of the nozzle or penetrator since the nozzle has
thickness.
You've raised another good point that I forgot to mention in previous
mail which is that these results are for cylinders, not formed heads of
any kind including flat heads. Formed heads have their own formulas
which I haven't looked into yet, and probably won't get to until after
the convention.
Jon
ShellyDalg@aol.com wrote:
In a message dated 4/28/2010 7:18:32 A.M. Pacific Daylight Time,
jonw@psubs.org writes:
http://www.psubs.org/design/pvho
Hi Jon. Couple questions please........
_#1 _ What is column "E" representing. "area of nozzle cross
section" @ 6 inches.
_#2_ Is column "D" Diameter of nozzle ID or OD ?
I am considering a "fix" for my hull design (at a later date) and at
this point have planned on removing the main window assembly
completely and replacing the _3/8 inch thick window ring and 2 inch
wide X 1 inch thick window base ring_ with a _1.5 inch thick window
ring and a 2.5 inch wide X 2 inch thick window base ring_ for the
plexi disk to sit on.
I'll get a professional FEA analysis done on the design before I "chop
out" the old one but I am trying to understand what the different
values are.
I may have to replace the hatch ring assembly and two smaller window
rings too but for now am concentrating on the main window as the basis
for learning how the rules are applied.
I know this doesn't really apply to my design because I'm installing
all this stuff into the formed heads rather than a stiffened cylinder.
Thanks, Frank D.
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