[PSUBS-MAILIST] port ring

Sat Apr 9 17:28:44 EDT 2016

Rick,if you go with the scuba 1st stage regulator for O2, check with your dive store as to what brands of regulators they can clean. My store recommended only a couple of models. Alan

      From: Rick Patton via Personal_Submersibles <personal_submersibles at psubs.org>
 To: Personal Submersibles General Discussion <personal_submersibles at psubs.org> 
 Sent: Sunday, April 10, 2016 7:10 AM
 Subject: Re: [PSUBS-MAILIST] port ring

Thanks SteveI am trying to keep any high pressure gas outside of the sub including O2 but cant find an O2 regulator yet that can be exposed to salt water unlike the scuba regulaters so I figured I'd have the reg attached to the sked 80 nipple just inside the sub to knock it down to LP and then to the flow meter.Rick
On Fri, Apr 8, 2016 at 9:50 PM, Stephen Fordyce via Personal_Submersibles <personal_submersibles at psubs.org> wrote:

Hi Rick,Yep, SCH80 1/2" pipe is good to about 500bar/7500PSI per my favourite pressure rating chart:http://prochem.cloudsites.net.au/wp-content/uploads/2013/09/Prochem-Piping-Products-1-Pipe-and-Tube.pdf
Hi Hank,I suspect the buckling failure mode and/or standards overriding practicalities (or just inability to achieve close enough to perfect fit) will mean that reinforcement is necessary - really interested to hear what Sean has to say on it.
Cheers,Steve

On Sat, Apr 9, 2016 at 2:56 PM, Rick Patton via Personal_Submersibles <personal_submersibles at psubs.org> wrote:

Does anyone know how much pressure a stainless steel schedule 80,  1/2" ID nipple is rated for 3" long? Can it take 3,000 psiRick
On Fri, Apr 8, 2016 at 4:39 PM, Stephen Fordyce via Personal_Submersibles <personal_submersibles at psubs.org> wrote:

Hi Rick,You're correct there - the reinforcing can be in the form of thickening the small piece of pipe ("nozzle") that is welded on, rather than thickening the shell.  Although it's not very practical for large holes.  There are also limits on how far away the reinforcing can be before it doesn't count.
Actually, for small holes, there probably isn't a requirement to reinforce.  I'm not so familiar with ASME, but in the Australian Standard for pressure vessels (which is very similar to ASME), you don't have to reinforce a hole unless it's bigger than 90mm.
Cheers,Steve
On Sat, Apr 9, 2016 at 12:21 PM, Rick Patton via Personal_Submersibles <personal_submersibles at psubs.org> wrote:

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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