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f14rio · Posted: Wed Sep 10, 2008 2:02 pm Post subject: Fule Tank Vent Lines

After reading one of the recent RVators @ Van's website I got a little concerned over my vent lines. My concern is that when I leak tested my tanks I recall that it took a little bit of pressure build up from the air pump before the balloon would inflate. When the air finally did start to rush in ... it was just that... it rushed in and filled the balloon quickly with very little pump action on the air pump. This scenario held true in both tanks...

I didn't think much of it then but now I am worried. Should I be concerned with the way this worked out or should I consider putting in new vent lines?

The article I am referring to in case you are wondering is something about a clogged vent line and then the fuel pump sucking so much (without venting) that it collapses the ribs!

Page 12: http://doc.vansaircraft.com/RVator/2008/3-2008-RVator.pdf[/url]
_________________
Larry Enyeart
RV-7 N907LJ
Status-Fuselage
Website: http://www.rv7x.com

bullojm1 · Posted: Wed Sep 10, 2008 3:05 pm Post subject:

Larry-

I don't know what caused your "instant inflate" phenomenon, but I doubt you need to worry about your vent lines. Unless your fuel lines are severely bent/pinched, they should work just fine.

In preparation for first flight, one test that can be performed on the airplane is to use the electric fuel pump to empty a gas tank to test fuel flow, venting, etc..

Finally, not a whole lot of air goes through the vent lines at a high rate. Assuming 9 Gallons per Hour (gph) fuel consumption rate, you will be sucking in 0.58 cubic inches of air per second. It doesn't sound like all that much volume of air going through the vent tube.
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Mike Bullock
http://www.rvplane.com
RV-7 | Superior IO-360 | Whirlwind 200RV
Garmin 430W | GRT Dual Sport EFIS
Status: Firewall Forward / Wiring

weezbad · Posted: Wed Sep 10, 2008 7:12 pm Post subject:

larry like mike said it is doubtfull your lines could be pinched that bad.

i know what you are talking about with the wait on the inflation of the balloon. if you blow one up the old fashion way you will see it takes a great deal of effort to get it started then all goes well after the initial stretch..remember you have to fill the tank with enough air for the pressure to begin building ...try blowing up the balloon a couple of times or stretching it. it will change the rate that it inflates as the material is stretched.. inspect the line visually then the simply blow through them you should be good to go....

as far as can suck the tank down ,,,that much is true...cadillac had a bulletin on fuel tanks getting colapsed on long trips due to the consumption of fuel and the tank not venting enough..... it can happen.

good luck.
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william....don't let it beat you down, you are stronger than you think.

f14rio · Posted: Thu Sep 11, 2008 8:28 am Post subject:

Hehe I just noticed how I spelled fuel in the subject line... I are good at english skills Smile

Anyway... thanks for the information guys. I like the idea of hooking up an electric fuel pump for a trial run.
_________________
Larry Enyeart
RV-7 N907LJ
Status-Fuselage
Website: http://www.rv7x.com

cnpeters · Posted: Thu Sep 11, 2008 9:51 am Post subject:

Larry - when I pumped up my tanks with a bike pump, same thing. It is a factor of pressurizing a large vessel - if the tank was a gallon, it would have occurred more quickly to reach the minimum pressure to inflate the balloon.
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Carl Peters
RV-9A
N92RV (reserved)
Fuselage
http://www.mykitlog.com/cnpeters/