[PSUBS-MAILIST] New submarine

[Alan James]

Scott,
just did a quick Google & these people make 1.5" segmented hemispheres 6ft in diameter.
http://www.cmforming.com/tankheads-and-accessories.htm

http://www.cmforming.com/pdfs/hemispherical-asme-code-type.pdf

You may have to compromise depth to line up with what's available if there is a stock item
somewhere.
Alan




________________________________
 From: swaters <swaters at waters-ks.com>
To: Personal Submersibles General Discussion <personal_submersibles at psubs.org> 
Sent: Thursday, April 10, 2014 3:37 PM
Subject: Re: [PSUBS-MAILIST] New submarine
 


Jon, 
I haven't thought as far as that yet. Mostly still seeing if this project is even feasable still.
Thanks,
Scott Waters




Sent from my U.S. Cellular© Smartphone
Jon Wallace <jonw at psubs.org> wrote:


As far as I'm aware, ABS doesn't deal with crush depth only
      maximum working pressure which incorporates usage factors (n), in
      this case of n=.67.  If n=1 could be considered "crush depth",
      then the calculator shows crush occurring at 2287 psi with 1.5
      inch thick hemisphere and max working depth of 1532 psi with a
      usage factor of n=.67 which is right in the parameters that he is
      looking for.  The problem with using n=1 as an indicator of crush
      depth, I believe, is that there's no way to guarantee it's an
      accurate representation of when the hull will fail because actual
      fabrication variables resulting in less than ideal geometric
      structures can lower the calculated result.  When using ABS/ASME
      we should always be solving for max working pressure, not crush
      depth.

So your observation is correct, and solving for a working depth of
      ~3000 feet results in a much thinner hemisphere.  I didn't know
      what Scott was using for a safety factor so just plugged the
      numbers to get 2578 psi from the ABS calculator, but that
      obviously is over-built for what Scott's intended use is.  Using a
      thickness of 1.25 inches, ABS is showing max working pressure of
      1268 psi or 2849 feet, just slightly less than his 3000 foot
      requirement.

Jon


On 4/9/2014 10:08 PM, Alan James wrote:

I'm a bit confused Jon,
>Scott was asking for the thickness for a crush depth of  5709 feet (2543 psi).
>You are saying 2.5 for a maximum working pressure of 2578 psi. The working pressure
>I thought was the design depth or maximum operating depth.
>Alan
>

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