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Fuel Tank Testing

briancku said:
I rewatched vans webinar posted on the eaa site, Rian Johnson said the tanks were leaked checked at the factory using professional leak detection equipment same as would be used by a certified aircraft manufacturer...seems like that should be better than anything I could do.
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I agree but they also say to test. If you discover a leak they are not responsible.
 
briancku said:
I rewatched vans webinar posted on the eaa site, Rian Johnson said the tanks were leaked checked at the factory using professional leak detection equipment same as would be used by a certified aircraft manufacturer...seems like that should be better than anything I could do.
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Trust but verify
 
You definitely don't want to deal with a leaky tank after it's been installed and painted. Ask me how I know. 😬🤣
 
How does the factory leak test the tanks without the fuel fittings and access plates installed and sealed with fuel tank sealant?
 
dbhill916 said:
How does the factory leak test the tanks without the fuel fittings and access plates installed and sealed with fuel tank sealant?
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That is an excellent question, wondering the same, since I should get my QB wings and tanks in less than 2 months!
 
rocketman1988 said:
Yep, that's where I am at; nothing other than gas is going in the tanks.

Years ago, we tried to get the water out of a boat fuel tank after a freak T-Storm basically sunk it. We could never get all of the water out of the tank and had countless water in the fuel issues after it happened...yes, we removed the aluminum tank from the boat.
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Did you ever figure out if you have a leak?

I'm unfortunately building my own tanks. One has been finished for a few weeks. I sloshed the tank with 3 gallons of Avgas. Let it sit but the fuel was only on the bottom of the tank. I didn't have the access panels covered so couldn't do much tank tilting.

I did the balloon test. I found leaks around the Shrader fitting and balloon. I fixed those but the balloon won't hold pressure for more than 4 minutes. I soaked the entire tank with soapy water and can't find a leak. Van's says it's good to go according to the KAI but I'm leery.

The only thing that I can think of for sure is to fill the tank all the way with avgas and wait for a blue stain to show....

I'm going to try the manometer test but like what Rocketman says, How will you find the leak if it doesn't hold the pressure?
 
bigmikeh24 said:
Did you ever figure out if you have a leak?

I'm unfortunately building my own tanks. One has been finished for a few weeks. I sloshed the tank with 3 gallons of Avgas. Let it sit but the fuel was only on the bottom of the tank. I didn't have the access panels covered so couldn't do much tank tilting.

I did the balloon test. I found leaks around the Shrader fitting and balloon. I fixed those but the balloon won't hold pressure for more than 4 minutes. I soaked the entire tank with soapy water and can't find a leak. Van's says it's good to go according to the KAI but I'm leery.

The only thing that I can think of for sure is to fill the tank all the way with avgas and wait for a blue stain to show....

I'm going to try the manometer test but like what Rocketman says, How will you find the leak if it doesn't hold the pressure?
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If you did not seal the access panels, all the air will leak through them (i.e. losing balloon pressure in 4 minutes). Did you spray soapy water on the panels after you pressurized the tank?

The balloon does nothing for determining a leak. It may deflate but you don’t have a leak. It also may stay inflated but you have a leak. It tells you nothing.
 
RVbySDI said:
If you did not seal the access panels, all the air will leak through them (i.e. losing balloon pressure in 4 minutes). Did you spray soapy water on the panels after you pressurized the tank?

The balloon does nothing for determining a leak. It may deflate but you don’t have a leak. It also may stay inflated but you have a leak. It tells you nothing.
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I ended up filling them with fuel (they each held 29 gal) Made sure the wing was supported well with multiple cradles and supports under the spars. No leaks after a few days. Filling with fuel is still not 100%. Some of the rivets on the top of the tank are not submerged in fuel. At least I know all the seams and the fuel senders don't leak....
 
GaryK said:
I ended up filling them with fuel (they each held 29 gal) Made sure the wing was supported well with multiple cradles and supports under the spars. No leaks after a few days. Filling with fuel is still not 100%. Some of the rivets on the top of the tank are not submerged in fuel. At least I know all the seams and the fuel senders don't leak....
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So as an update to the story, I purchased another 0-3 psi gauge and related fittings so that I could check both tanks at once.

I pressurized them both to 0.8 psi and noted the time. I checked them every few hours and took readings. The leak down rate was about 0.01 psi per hour in the beginning, tapering off towards the end. I monitored them for 90 hours. At that point, the gauges read nearly zero but when I removed the caps, there was still a bit of pressure left in the tanks.

Next, I put about 22 gallons of 100LL in each tank. I supported the tank on sawhorses so that I could see underneath. I checked the tanks with a bright light every few hours for leaks. The fuel was in the tanks for 30 hours and I noted no leaks, seeps, or stains.

I am about as certain as I can be at this point that they don’t leak so they are now part of the wings and riveted in place.

Honestly, I think they should have used a welded aluminum tank that sat inside the wing. Those tanks are easily sourced and definitively pressure/leak checked after manufacture…and it isn’t a complex shape.
 
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