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Go Back   SailNet Community > General Interest > General Discussion (sailing related) > Myth of Condensation in Fuel Tanks
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Thread: Myth of Condensation in Fuel Tanks Reply to Thread
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Topic Review (Newest First)
08-03-2009 02:22 PM
RichH
Quote:
Originally Posted by camaraderie View Post
Rich...he specifically states there was never ANY fuel in his tank.
Naaaaah, that didnt happen !!!!! In a desert with normal dewpoints at 30-40 deg. of less, it would take hundreds of years for a cupfull of water to accumulate in an EMPTY motorcycle tank (1-2ft. cu. ft). If there was thermally driven mass transfer (heat/cooling cycles of the tank), then the same mass transfer would equilibrate BACK to the atmosphere - net equilibrium =~0. The same reason that the WWII Saharan debris is still in the SAME condition as the day its was destroyed. --- very 'doubtful'.
:-)
08-03-2009 12:53 PM
wright1d So I'm still confused?

Why leave the tank filled in the winter if this is going to happen anyway? Sounds like the water settles to the bottom pushing the lighter fuel up?
08-03-2009 12:14 PM
camaraderie
Quote:
Originally Posted by RichH View Post
What you had is 'old' fuel that became saturated with water, the free water gravimetrically settled and crossed the liquid-liquid phase boundary in the bottom of the tank and started 'pumping'.
Rich...he specifically states there was never ANY fuel in his tank.
08-03-2009 12:00 PM
RichH
Quote:
Originally Posted by bobmcgov View Post
Good science has to explain the observed phenomena. I removed better than half a cup of water from a small, vented motorcycle tank that had never contained gasoline or oil, stored indoors, in a desert. Pls explain how it got there.
I did, its called partial vapor pressure equilibrium. What you had is 'old' fuel that became saturated with water, the free water gravimetrically settled and crossed the liquid-liquid phase boundary in the bottom of the tank and started 'pumping'.

Next time close the vent on your tank and see what happens. If you leave fuel in direct contact with atmospheric air it WILL become saturated with water - thats the whole point of my 'discertation'. Again, 'condensation' is the end stage symptom that the fuel HAS become saturated with water.
Either close the vent (on tanks that can withstand the pressures) upon long term non-usage, or 'enjoy' water saturation.
08-03-2009 09:55 AM
RichH
Quote:
Originally Posted by bobmcgov View Post

Good science has to explain the observed phenomena. I removed better than half a cup of water from a small, vented motorcycle tank that had never contained gasoline or oil, stored indoors, in a desert. Pls explain how it got there.
Please reread my post ... especially the part that states that when the FUEL becomes saturated with water, the symptom of the full saturation becomes the condensation effect. With dehydrated fuels (as normally delivered from a refinery) will not appreciably 'condensate' until the fuel becomes saturated with water.
08-01-2009 05:44 PM
badsanta I replaced all my deck fill O rings as they were all flat and cracked. Just in case.
08-01-2009 05:27 PM
pdqaltair
Which is why e-10 is not used in aircraft... of on the Hood River bar.

Quote:
Originally Posted by Guzzi View Post
Anyone ever had to drain the fuel tanks on an airplane of the water that condenses overnight?
They have drains in them just for that purpose. Evaporation of the fuel causes cooling. The sun warms the surface of the wing and you have cool inside/warm outside, voila! Condensation. Fill a glass with water and add ice. What happens? Condensation forms on the glass.

E-10 makes matters worse, alcohol is hydroscopic-it attracts water, making the condensation problem worse, as the water doesn't separate out as in pure gas. Water and alky mix, but don't burn well.

Ragtimedon-I was a guest aboard your beautiful Endeavor one afternoon when you and your wife gave us a tour.
I'm a friend of Tom, the guy down the dock with the Helms 27.
Might have a boat after next week...gotta find it first.

Jon
11111
08-01-2009 02:55 PM
Capnblu Well said Rich.
08-01-2009 02:45 PM
Guzzi Anyone ever had to drain the fuel tanks on an airplane of the water that condenses overnight?
They have drains in them just for that purpose. Evaporation of the fuel causes cooling. The sun warms the surface of the wing and you have cool inside/warm outside, voila! Condensation. Fill a glass with water and add ice. What happens? Condensation forms on the glass.

E-10 makes matters worse, alcohol is hydroscopic-it attracts water, making the condensation problem worse, as the water doesn't separate out as in pure gas. Water and alky mix, but don't burn well.

Ragtimedon-I was a guest aboard your beautiful Endeavor one afternoon when you and your wife gave us a tour.
I'm a friend of Tom, the guy down the dock with the Helms 27.
Might have a boat after next week...gotta find it first.

Jon
08-01-2009 02:26 PM
pdqaltair
Is it all about temperature swings, and airplanes see the greatest swings of all.

E-10 exaggerates this, and the following link explains:

http://www.epa.gov/otaq/regs/fuels/rfg/waterphs.pdf

True condensation, without fuel - common sense tells us this is rare (tanks do not fill). Water accumulation due to saturation followed by temperature swing - common, though not as common as leaking filler caps.

I am a chemical engineer working around refineries, and the effect is real.
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