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Re: [PSUBS-MAILIST] Re: Propane tank
The industry standard is to use the Minimum Yield strength for the
material according to the standards (SA-516-Gr70, has a 70,000 psi minimum
Yield strength and the material will most often be10% higher) and then a
"Fudge factor" called "corrosion allowance" onto after all the calculations
are done. That is, calculate the strength based on 0.5/16" WT (0.312") and
then specify 0.375" (3/8") material for construction. The corrosion
allowance then being 1/16" (0.062"). The corrosion allowance varies
depending on where the pressure vessel is used, pressure rating, risk
factors, etc. I have no idea what the corrosion allowance for submarines
would be. I guess it would probably depend on use (military, tourist),
saltwater vs fresh, etc.
Unless the propane tank saw elevated temperatures I wouldn't think that
the Carbon from the propane would migrate into the tank material, but
dents, or cracks (esp Stress Corrosion Cracks) will have a dramatic effect
on the strength of the vessel.
Empirical testing as suggested would make me the most comfortable were I
the one inside.
Hope this may help some.
Jay.
Thanks,
J. Barlow CET
Sr. Mechanical Designer
BJ Pipeline Inspection
Ph (403) 531-5412
Fax (403) 236-8740
Cell (403) 807-2195
Ian Roxborough
<irox@ix.netcom.com> To: personal_submersibles@psubs.org
Sent by: cc:
owner-personal_submersibles Subject: Re: [PSUBS-MAILIST] Re: Propane tank
@psubs.org
04/09/2002 01:43 PM
Please respond to
personal_submersibles
Sorry, I didn't mean to undermine your calculation, I was
just implying that without examining the pressure-vessel
nobody on this list can accurately predict the crush
depth, we don't even know the diameter (althought your
40inich guess would seem like a good guess).
I'd be interest in how you where accounting for rust
and weakness in your calculation.
Thanks,
Ian.
On Wed, 4 Sep 2002 11:51:57 +0900
"Problah" <problah@zonenet.net> wrote:
> Wow, thanks for the support fellas, but I did do a calculation accounting
for
> rust and a higher flexibility (weakness). The absorption was a good note
> thoe, I'll give you that, I just figured for crush depth, not for diving
in.
>
> Support your local zonenet
>
>
> ---------- Original Message -----------
> From: Ian Roxborough <irox@ix.netcom.com>
> To: personal_submersibles@psubs.org
> Sent: Wed, 4 Sep 2002 11:13:40 -0700
> Subject: [PSUBS-MAILIST] Re: Propane tank
>
> > Hi Mike,
> >
> > if you don't have access to resources to make a 1-ATM
> > submarine, have you consider making an ambient sub
> > instead.
> >
> > I'm not saying that ambient subs are easier to build
> > than 1-ATM subs, but it does remove the issue of finding
> > a safe pressure vessel to use. After learning more
> > about ambient subs at the psubs conference I think they
> > look like a LOT of fun.
> >
> > You don't mention a lot about the propane tank you want
> > to use, any estimation of crush depth that people have
> > give on this list will be working with the assumption
> > that the propane tank is new and in perfect condition.
> > I'm sure you are aware that any small (invisible) cracks
> > or dents could drastically reduce the usable strength
> > of the propane tank. If it is a used propane tank, then
> > you'll have to deal with the propane that has been absorbed
> > by the metal.
> >
> > Ian.
> >
> > On Mon, 2 Sep 2002 22:39:23 -0500
> > majerus@iowatelecom.net wrote:
> >
> > > To anyone that might know,
> > > I have a 500 gallon propane tank with a .312 thousands
thickness
> and was wondering if that might be able to stand pressure of 75 feet or
so, I
> know that some are not keen on using one but I really want to build a sub
but
> do not have some of the resources that some might have. Also, I was
wondering
> how to make a depth gauge.
> > > Thank you, Mike
> > >
> > >
> >
> > --
> > The moon ate the sun on Monday and it was an awsome sight to see.
> ------- End of Original Message -------
>
--
The moon ate the sun on Monday and it was an awsome sight to see.