Bob
Thanks for that suggestion. I did some searching, and think I've found
the answer. It seems winter fuels use more butane, which has a vapor
pressure of 30 psi at 20C (twice atmospheric). That is quite a bit of
pressure! So the butane boiling off must be contributing to the
pressurization of my tank.
At first I suspected ethanol, but its vapor pressure is only 1psi.
On Wed, Jan 1, 2014 at 5:54 PM, Robert Borger <rlborger@mac.com> wrote:
>
> Andrew,
>
> Gasoline, MoGas, Petrol, is a very complex mixture of hydrocarbons (primarily
C4-C12) with quite a number of chemical additives to provide stability,
cleaning,
anti-knock, etc. You might want to read the Wikipedia page on Gasoline for
details. You will probably find your answer there.
>
> Best regards,
> Robert Borger
> President, Geowhiziks & Doodlebugging, Inc.
> AAPG Certified Petroleum Geophysicist #101
> 3705 Lynchburg Dr.
> Corinth, TX 76208-5331
> Cel: 817-992-1117
> rlborger@mac.com
>
> On Jan 1, 2014, at 4:29 PM, Andrew Sarangan <asarangan@gmail.com> wrote:
>
>
> I was filling my tank with gas (regular E10 mogas) to check it prior
> to bonding it into the module, and noticed something strange that I
> could not explain. I have the outlets sealed off. I poured 10 gallons
> in and closed off the inlet and the vent hole with rubber caps. After
> 5 minutes, when I open one of the caps, I can hear a pop, and a puff
> of gasoline vapor. I close it off, wait another 5 minutes, and it does
> the same thing. I put a tiny hole on the rubber cap to prevent
> pressurization, but I am dumbfounded by this observation. Surely, the
> vapor pressure of gasoline cannot be higher than atmospheric pressure?
> Both the filled jerry cans and the tank have been in the same location
> for a couple of weeks, so they should be at the same temperature. What
> could be causing this?
>
>
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