[PSUBS-MAILIST] port ring

[hank pronk via Personal_Submersibles]

Hi Steve,I assumed just that, if the hatch was a perfect match to the sphere with a perfect fit it would not require a reinforcement.  I can say that Gamma has a very small reinforcement for the hatch.  The hatch is 18 inches in dia  with a 1 by 1 inch ring that acts as both the land and reinforcement.  But the hatch land rests on a spherical surface.   It seems to me that an opening in a cylinder requires a significant reinforcement but spheres seem to need less.  Just an observation because I have no clue.Hank 

    On Friday, April 8, 2016 7:34 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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