[PSUBS-MAILIST] port ring

[Rick Patton via Personal_Submersibles]

while were on the subject, I need some clarification on the "replace or add
what you took out of the pressure vessel skin theory" as when I wanted to
add a few extra view ports, I called the captian,Ketterage, and asked about
cutting extra holes in the hull and he said the same thing but then got to
wondering about that statement.
When you cut a hole in the hull and weld in a piece of solid round
stainless steel with a 1/2" hole in it for gas/wires, you still have a 1/2"
hole in the hull so that theory can only work if you take into
consideration the amount of ss rod that is also on the inside and outside
of the hull?
If that is the case, it doesn't seem correct to use a pipe with a 1/2" ID
schedule 40 but you extend it inside and outside until you equal the same
volume as you removed?
Rick

On Fri, Apr 8, 2016 at 3:34 PM, Stephen Fordyce via Personal_Submersibles <
personal_submersibles at psubs.org> wrote:

> 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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