tsufang@CI
Posts: 39
Joined: Mon Feb 18, 2002 8:38 pm

How Moisture Gets Into Fuel Tank?

Mon Feb 10, 2003 5:43 pm

how many possibilities that moisture get into fuel tank
i think maybe ...refueling hose ,water mixed in fuel ......
anyone could help me?thanks!
 
Ralgha
Posts: 1589
Joined: Tue Nov 09, 1999 6:20 pm

RE: How Moisture Gets Into Fuel Tank?

Mon Feb 10, 2003 6:01 pm

The most common causes of water in the fuel tank are leaky fuel caps during rain and condensation inside the tank.

Fuel tanks are vented to prevent a vacuum from forming as the fuel is used, so when warmer, wetter air cools inside the fuel tank, the water condenses out of it.

 Big thumbs up
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ybacpa
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RE: How Moisture Gets Into Fuel Tank?

Mon Feb 10, 2003 10:37 pm

The answer depends heavily on what type of fuel tank you are referring to- I know nothing about aviation tanks, but, thanks to a very brief stint as a mechanic (VERY BRIEF) in college I might be able to help you, if you are referring to a car.

Condensation in car tanks comes from four possible sources.
1. The most likely- a leaking gas cap.

2. Water in the fuel itself (also common).

3. Leaks in the fuel system itself (not too common). Most cars pump fuel in a loop to prevent it from becoming stagnant, so a leak anywhere in the system could allow water to be returned to the tank.

4. Water condensing on the inside of the tank. Most cars' tanks have a slight vaccuum, to reduce the likelyhood of a leak, however, the fuel used is generally replaced by air from the outside (and usually through the filler cap). Depending on the weather, if a large amount of space is filled with unusually moist air, then the temperature drops, condensation will form. Granted, the amount of condensation on a tank of up to about 20 Gallons is generally negligible.
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broke
Posts: 1299
Joined: Wed Apr 24, 2002 8:04 pm

RE: How Moisture Gets Into Fuel Tank?

Mon Feb 10, 2003 11:17 pm

All aircraft fuel tanks are vented to the atmosphere for two reasons; first, if the tank was not vented you would not be able to get fuel out of the tank (just take a straw, put one end in a fluid [your choice] plug the top of the straw with you finger and lift the straw out of the fluid and nothing will come out until you take your finger off the top end, fuel tanks work the same way); two, when you are fueling the tank you could pressurize the tank if it were not vented and inflate the tank this has happened when the volumetric shut-off system did not open back up, inflated wings are very bad things  Wow! !! I've seen pictures of a F-28 that this happened to.

This flow of air into and out of the tank via the vent system also allows for moisture to enter the tank. Surprisingly, a large quantity of water will accumulate in the tank over time, if not drained.
 
fritzi
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RE: How Moisture Gets Into Fuel Tank?

Tue Feb 11, 2003 12:22 am

 
bsergonomics
Posts: 458
Joined: Thu Jan 31, 2002 5:07 am

RE: How Moisture Gets Into Fuel Tank?

Tue Feb 11, 2003 3:18 am

Also, if you happen to be flying an SR-71, air can get in through the gaps in the wings...  Big thumbs up
The definition of a 'Pessimist': an Optimist with experience...
 
fritzi
Posts: 2598
Joined: Sat Jun 30, 2001 2:34 am

RE: How Moisture Gets Into Fuel Tank?

Tue Feb 11, 2003 6:01 am

Bsergonomics,

I better look out for that the next time I rent one then.  Smile/happy/getting dizzy
 
Racers22
Posts: 109
Joined: Wed Jul 04, 2001 6:03 am

RE: How Moisture Gets Into Fuel Tank?

Tue Feb 11, 2003 6:06 am

When I worked on the line crew at the airport down the street from my house we constantly had to do quick turns on airplanes when it was pooring down rain outside. That is definitely a good way to get plenty of water into your fuel tank!
 
A/c train
Posts: 674
Joined: Sun Jun 10, 2001 7:57 am

RE: How Moisture Gets Into Fuel Tank?

Wed Feb 12, 2003 5:39 am

The consequences of lack of maintenance and lack of fuel additives is a Form of Corrosion known as Micro-biological corrosion, this is a micro-organism that grows in the moisture traps and it feeds on the tank linings, this type of corrosion it has to be said occurs predominantly in Aluminium integral fuel tanks, the organisms feeding on the tank lining then expose the structure to electrolytic attack and the Galvanic Cell sets up. The organisms are known as 'Cladasporium Resonae,' I think that's how you spell it?, it shows up as a Brown sludge floating in the fuel.
This type of corrosion is also seen around Toilets and Galley areas, with all that undigested and 'Digested' food spillage.
The fungi also feed on the icing inhibitor additive and live on the o2.
Hope that was of interest to the guys who didn't know any of the above !
regards
a/c
 
tsufang@CI
Posts: 39
Joined: Mon Feb 18, 2002 8:38 pm

RE: How Moisture Gets Into Fuel Tank?

Thu Feb 13, 2003 5:22 pm

thanks for your help!
 
saintsman
Posts: 2037
Joined: Fri Mar 15, 2002 12:34 am

RE: How Moisture Gets Into Fuel Tank?

Thu Feb 13, 2003 9:48 pm

With regard to the corrosion mentioned by A/c Train.

A couple of years ago my company had to carry out repairs on 4 BAE RJ-100s that had returned from lease in Columbia because of the effects of 'Gladis'.
All the wing components and pipes were replaced, most of the front and rear spars and several of the wing skin panels where the corrosion could not be blended out. Some of the corrosion had almost eaten through the skin.

All in all a pretty expensive exercise for a bit of fungus.
 
FDXmech
Posts: 3219
Joined: Sun Mar 19, 2000 9:48 pm

RE: How Moisture Gets Into Fuel Tank?

Fri Feb 14, 2003 3:34 am

As A/c train brought up the subject of fuel tank microbial growth, Airbus had an interesting solution to this on their A300-B4 model.

While working the B4's at Continental during the 1980's, I learned Airbus used radioactive pellets suspended in the fuel tanks which would slowly desolve and prevent or combat microbial growth. As I remember the maintenance manual warned against entry into the tanks without suitable protection.

I'm trying to find my old study guides to refresh my memory on this technique.
You're only as good as your last departure.
 
LMP737
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Joined: Wed May 08, 2002 4:06 pm

RE: How Moisture Gets Into Fuel Tank?

Fri Feb 14, 2003 8:10 am

When I started working for AA we were still flying DC-10's on the LAX-HNL run. It was not uncommon to pull a gallon or two of H2O out of the wing tanks.
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