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

Jay,

Thanks for pointing that out...it's an important note. However, you can plug the data from the charts into the "hull Calculator" spread sheet located at

http://www.psubs.org/designguide/ABS_Hull_Calculation__Rev_12_17_2004.xls to get an idea of how different materials will react to external pressure.

Jon

-----Original Message-----
From: owner-personal_submersibles@psubs.org [mailto:owner-personal_submersibles@psubs.org]On Behalf Of Jay K. Jeffries
Sent: Sunday, January 28, 2007 7:00 PM
To: personal_submersibles@psubs.org
Subject: RE: [PSUBS-MAILIST] Steel Pipe Hull

Jon,

Please note these charts are for design of vessels that will experience an internal pressure not an external pressure like a submersible. Other modes of failure such as buckling predominate in submarine hull design so these tables are not applicable for a PSUBS (other than the VBT or compressed air tanks).

R/J²

Respectfully,

Jay K. Jeffries

Andros Is., Bahamas

It is the mark of an educated mind to be able to entertain a thought without accepting it.
- Aristotle