Date:         Tue, 4 Feb 2003 11:07:32 -0500
Reply-To:     David Beierl <dbeierl@ATTGLOBAL.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         David Beierl <dbeierl@ATTGLOBAL.NET>
Subject:      Re: Calculations or formulae for LPG tank
Comments: To: Richard Stevens <resteven@BTINTERNET.COM>
In-Reply-To:  <!~!UENERkVCMDkAAQACAAAAAAAAAAAAAAAAABgAAAAAAAAAdw5OdeebBk6
              92Ym40/4b/sKAAAAQAAAAy2F62IQdlkix6frr+Wf8zAEAAAAA@btinternet.com>
Content-Type: text/plain; charset="us-ascii"; format=flowed

At 10:34 AM 2/4/2003, Richard Stevens wrote:
>Hi.
>  I have just recently converted the engine of theTintent on run on LPG and
>have fitted the largest tank I could find that would be able to provide a
>decent mpg but I would like to determine the volume of the cylinder as I do
>not believe the plate stamped with the tanks details is correct,

Um...what leads you to doubt the certification plate?  If by chance you
think it's about 20% less than it should be, remember that 20% of the "W.C"
(water capacity) of the tank is reserved headspace for safety.  Also, if
the certification is in pounds of LP, the density of LPG is just over half
of water.

>  the problem
>is that my math is not that hot and whilst I'm OK with the volume of a
>cylinder I am at a loss to calculate the volume plus the domed ends ( if
>they were two halves of a sphere it would be no problem but they are not ).
>Can any of you mathematicians out there please help with a formula??

You can get a good approximation -- really really really good if you are
willing to do the work -- by taking diameter measurements of the dome at
known intervals, and calculating the volume of each as though it were a
cylindrical ring of that diameter; then adding the volumes together.  The
thinner you make the rings, the more accurate the answer.  Don't forget to
allow for the wall thickness, likely significant in an ASME tank.

You can also fill the tank with water, measure it, take 80% of that as the
LP capacity.

Or submerge it in water, yell "EUREKA," measure the displaced water, allow
for tank thickness x surface area, then subtract 20% from that...

david


--
David Beierl - Providence RI USA -- http://pws.prserv.net/synergy/Vanagon/
'84 Westy "Dutiful Passage"
'85 GL "Poor Relation"