Re: [PSUBS-MAILIST] Steel Pipe Hull

I have these calculations in Mathcad if it could be of any help. if
you can use Mathcad I can send it to you. The values are metric by the
way.

On 1/29/07, djackson99@aol.com <djackson99@aol.com> wrote:
>
> Jon
>
> Your right about the stiffeners, but there must be other problems. Now I
> get 8 psi :) What are you using for "Center to center spacing of
> stiffeners"? When I change it the outcome changes, and that does not make
> any sense. Your calculation can not be right either; 57 psi for a 1/4"
> think 10 inch pipe? No Way! I get 57 psi out of a garden hose and I've used
> 10" steel pipes for temporary colverts and had concrete trucks drive over
> them. There is just no way they would not perform to anything less than
> 1500 feet.
>
> You can download my sheet from here:
> http://www.submarineboat.com/sub/BOB2_Hull_Calculation.xls
> to have a look if needed.
>
> I really do appreciate this exercise I hope the outcome is a simpler and
> more full proof approach.
>
> --Doug J
>
> -----Original Message-----
> From: jon@psubs.org
> To: personal_submersibles@psubs.org
> Sent: Mon, 29 Jan 2007 12:15 AM
> Subject: RE: [PSUBS-MAILIST] Steel Pipe Hull
>
>
> Doug,
>
> I get 57psi, 111 feet, for crush depth by external pressure on 10" pipe per
> the chart specs you referenced. Did you remember to remove the stiffener
> information in the spread sheet? By default, the spreadsheet employs 1.25
> inch stiffener web and 1.5 inch stiffener flange. To compare a common pipe
> you'd have to remove the stiffener info. The spreasheet won't accept "0",
> so change the stiffener info to ".0001" or some ridiculously small number
> like that. Then you'll see the difference between internal and external
> pressure on the pipe.
>
> Jon
>
> -----Original Message-----
> From: owner-personal_submersibles@psubs.org
> [mailto:owner-personal_submersibles@psubs.org]On Behalf Of
> djackson99@aol.com
> Sent: Monday, January 29, 2007 12:58 AM
> To: personal_submersibles@psubs.org
> Subject: Re: [PSUBS-MAILIST] Steel Pipe Hull
>
> Thanks for your help, Jay and Jon:
>
> Yes this is the right kind of chart, I just want it to have one more column
> which would be the working PSI if the PSI force was external, aka
> submarine.
>
> Look at:
> http://www.pveng.com/Charts/Pipe%201.03%2020ksi.pdf a 10"
> steel Schedule 20, .25 wall it shows Max PSI (I think E=1 means no safety
> margin, right?) of 827. And when if I am using the Hull Calculation sheet
> right I get 940 PSI for a 10 inch steel hull with a .25 plate thickness.
> But if I switch the Young's Modulus of Elasticity to 20,000,000 to match the
> steel pipe it drops to 845 PSI.
>
> So the PSI of the 10" steel pipe seems to be the same regardless of the load
> being internal or external. So, if that is true, would it hold true for
> larger diameter pipe? How about aluminum pipe or PVC or UPVC pipe?
>
> Looking forward to your comments, and thanks again for your assistance.
> --Doug J
>
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-- Vennlig hilsen
Øystein Skarholm

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