Re: [PSUBS-MAILIST] Pressure Hulls

[Ian Roxborough <irox@ix.netcom.com>]

Hi Dewey,

On Sun, 30 Jun 2002 21:20:44 -0700 (PDT)
Dewey Mason <drmason2001@yahoo.com> wrote:

> Hey All,
>    Today I found 3 stainless steel spheres about 9
> feet in diameter+/-. They are about 1" minimum
> thickness with a small increase near the inlet head.
> They are used, having been commercial CO2 tanks for a
> local gas producer. While I do realize the potential
> problems of using used stuff, I think the maintenance
> was good enough to consider it. Does anyone have a
> means to calculate the unreinforced crush depth on
> such a piece?

P = 2Ut/R
Where:
 U = min yield strength
 t = hull thinkness
 R = outside radius

Beware, I could have gotten this wrong...

I copy this out of  The American Bureau of Shipping's
"Rules for Building and classing: Underwater vehicles, systems
and hyberbaric facilities."  But I've seen it many other places
as well (so no worries on copyrights and such).

I'd recomend getting the above book, I've hardly started
it and it's proved very useful.

I'd also recommend check the crush depth several different
ways, such as using different equations and checking them
against a Finite Element Method.  I guess using a real high
safety factor since it's "used" would help too.

>  Hopefully the much smaller diameter will leave enough strength
> difference to put the crush depths very nearly the same. At least to
> where I can P-test the cabins at 75%, and run them at
> 50% of calculated crush, and P-test the mechanical
> compartment at 90%, running it at maybe 80% or so.

Do you have access to a pressure testing facility/chamber?

>    Maybe someone will think I am one of the ones
> needing banishment after this, but I hope to hear the
> thoughts and ideas of those who think I might can
> stay.

Let's save the banishment for people who post multilevel
marketing schemes and adverts not relating to submarines...

Ian.
-- 
The moon ate the sun on Monday and it was an awsome sight to see.