[PSUBS-MAILIST] port ring

[Stephen Fordyce via Personal_Submersibles]

Hi Hank and Sean,
Given Hank is probably halfway through building this already and Sean might
be in the middle of other things I thought I might jump in - I think I can
help in general terms.  The rule off thumb is if you make a hole in a
pressure vessel, you're supposed to put this material back as reinforcing
around the hole to keep the same pressure rating.

So if you want to take advantage of the full 4" thickness (wow!!!) and
associated depth rating, then you would need to reinforce the hole - and it
would need to be a pretty serious reinforcement to replace that thickness
of material.

Alternatively, if you don't reinforce, then you lose some of your depth
rating, because some of the thickness is locally credited as
reinforcement.  This means an amount of thickness over the rest of
the shell away from the hole is basically dead weight, which may or may not
be a problem depending on whether this gets lowered or is free-floating.

To put it another way/thought experiment: if you could machine away all
the unnecessary material after you've machined the landing area and
hole, the result would look like a thinner shell with a reinforcement ring
welded around the hole.

Cheers,
Steve

PS: All that said, it seems theoretically possible that if you had a hole
with a spherical hatch and the right angles, and it all mated perfectly,
that with everything in compression it shouldn't matter there was a hole.
Probably this doesn't account for the buckling failure mode though.  This
is getting a bit out of my depth (if you'll pardon the pun!).

On Fri, Apr 8, 2016 at 11:22 AM, hank pronk via Personal_Submersibles <
personal_submersibles at psubs.org> wrote:

> Hi Sean,
> If a guy was to buy a 48inch id CNG sphere with a 4 inch shell thickness,
> would it be necessary to weld in a land ring and port seat.  Or could a guy
> or gal rough cut the necessary holes then put their  flange machine to work
> to machine seats in the shell.    It seems logical to me that could be done
> for the hatch because the load would be supported by the same steel in the
> hatch.  Or am I out to lunch?
> Hank
>
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