[PSUBS-MAILIST] port ring

Sat Apr 9 03:50:33 EDT 2016

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 psi
> Rick
>
> 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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