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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