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View Poll Results: Plug tank vent line?
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Plugging the tank vent line, yes or no?

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Old 10-13-2017, 03:27 PM
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AEROSHELDON
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Question Plugging the tank vent line, yes or no?

Seeking some advice.... do you all plug your vent lines or leave them open for storage/transport?
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Old 10-13-2017, 03:41 PM
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jetflyr
 
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Originally Posted by AEROSHELDON View Post
Seeking some advice.... do you all plug your vent lines or leave them open for storage/transport?
Since I transport inside my car, and store inside my house, I plug them.
I make sure the plug is removed prior to filling by always attaching my taxi tank first.

Greg
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Old 10-13-2017, 03:43 PM
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Originally Posted by jetflyr View Post
Since I transport inside my car, and store inside my house, I plug them.
I make sure the plug is removed prior to filling by always attaching my taxi tank first.

Greg
Thank you. There seems to be a lot of pressure on the system when I plug them is why I am asking, lots of air either escapes or gets sucked in and it seems that might be unhealthy for the system.
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Old 10-13-2017, 03:45 PM
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I don't think it a critical thing. If you don't like it... then don't plug it. I personally plug mine, because I don't want to smell it in the workshop.
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Old 10-13-2017, 03:48 PM
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Originally Posted by AEROSHELDON View Post
Thank you. There seems to be a lot of pressure on the system when I plug them is why I am asking, lots of air either escapes or gets sucked in and it seems that might be unhealthy for the system.
The only time I have seen pressure changes has been going over Raton Pass heading to/from low level. If I take it to the field and it is blowing a gale, but we all sit and BS for awhile, the heat of being in a car in the sun at 7000' will create pressure (more in my gasoline container though). - I then just vent the system before I drive home
If you are getting a lot of air in the system, I'd check the system! it should be tight when sealed.

Greg
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Old 10-13-2017, 06:42 PM
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Originally Posted by jetflyr View Post
The only time I have seen pressure changes has been going over Raton Pass heading to/from low level. If I take it to the field and it is blowing a gale, but we all sit and BS for awhile, the heat of being in a car in the sun at 7000' will create pressure (more in my gasoline container though). - I then just vent the system before I drive home
If you are getting a lot of air in the system, I'd check the system! it should be tight when sealed.

Greg
Thanks... It's tight! The release is when I un-plug it. Temp changes are the biggest culprit. I will just do as you do and occasionally unplug it when I know that is happening.
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Old 10-13-2017, 06:47 PM
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Originally Posted by AEROSHELDON View Post
Thanks... It's tight! The release is when I un-plug it. Temp changes are the biggest culprit. I will just do as you do and occasionally unplug it when I know that is happening.
Just don't do it either in the car, or the house!
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Old 10-13-2017, 08:10 PM
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I plugged my vents for part of a season and it was a disaster. Air temperature swings will change the pressure in the tanks from positive to negative and you will develop leaks in your fuel tanks. My UAT even unscrewed it's own cap and started leaking. My airplanes were in a non temperature controlled environmentand were always defueled at the end of flying. My Kevlar tanks developed cracks and I had never had a fuel leak before in ten years of flying jets.

After I stopped plugging my fuel system , all problems vanished.
The air expands and contracts with temperature and will flex your tanks til they crack.

I only plug now to transport or flip the model over for repairs.
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Old 10-14-2017, 04:32 AM
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In the Sprint, I do not plug the vent during the flying season. However it does get plugged over the winter to keep moisture from creeping into the fuel system.

On the Flash when it had a wing tank, it was plugged because the wing goes into the wing bag and the vent is in the wing. The outlet to the tank was also plugged. never noticed air pressure to be a problem.

Now that the flash has saddle tanks, they are plugged for transport cause I do not want the fuel smell in the RV or plane trailer. Also, during the rainy season and winter both vents are/will be plugged. Again that is to keep out moisture.

It seems to me that subjecting the plane to so much heat variation that it backs off the UAT cap is unlikely. I know that we see some extreme temp changes here and that has never happened to me nor have I ever notice air pressure gushing out of a vent when I took a plug off ??? I have noticed that the UAT can contract when the fuel is sucked out of it by the fuel pump when using undersized fuel system components. Undersized fuel system components may have possibly led to a loose UAT cap for me. However, once I went to 3/16" fuel system components throughout, including the two vents, all clunks, all fittings and all lines, etc. the UAT does not contract and the UAT's cap has not loosened. Of course, my UAT's cap could have been loose from the get go.
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Old 10-14-2017, 12:01 PM
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I used to plug them until I got cracks in a fuel cell. They said it was from pressure that builds up in your hot car - over time. Now I plug a tube in and put it down into a 4 oz. plastic bottle. It has a pinhole in the top to let air come in and out. Works in both directions. It also catches what might spill. On smaller single fuel cell jets it can also serve as the overflow tank when filling.

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Old 10-14-2017, 05:26 PM
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Default plugging the vick

I usually don't plug the vent when in storage, but I just got one of the plugs that screw in and close the vent in an airplane. When working on the fuel system I pressure tested my tank, rinsed it out with a little denatured alcohol, then rinsed it again with a little diesel fuel a couple of times (I guess I did not get all the fuel out on that second rinse). Well I put the fuel tank in and connected the vent, connected the pickup to the uat, and then put all the lines on the uat. I plugged the vent but not the fill line from the uat. The pressure that built up in the tank had enough pressure to push the fuel up the pickup and into the uat (about an ounce). So if there is enough pressure to do that I will not be closing my vent for long periods of time. I will close them from the field to home, but I will either remove the vent plug or open the vent line on the uat so that pressure can escape.

patrick

Last edited by sirrom; 10-14-2017 at 07:33 PM.
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Old 10-14-2017, 11:49 PM
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Jets plugged, EDFs unplugged :-)
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Old 10-15-2017, 07:29 AM
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Originally Posted by Henke Torphammar View Post
Jets plugged, EDFs unplugged :-)
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Old 10-15-2017, 09:12 AM
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Interesting subject... I'm wondering if there is some sort if breather you can plug in for longer storage. To keep the moisture out and pressure equalized..
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Old 10-15-2017, 05:30 PM
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I promise you if you plug the vent, some time you will burst a tank.. don't know when, but it will happen..

If you want, hook up your overflow tank to it. that works even when you travel.

I dont plug mine.. I did burst a tank.. I learned.
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Old 10-15-2017, 10:24 PM
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I have been using a system best described as the ultimate fuel trap on the vents. Basically the opposite of a UAT...
It has an anti siphon valve to let air in but not out. So no pressure drops are possible that ruin your tanks.
Combined with a refuel return to the bowser when refueling it makes for a no spill system.
Andre
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Old 10-20-2017, 06:23 AM
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Thanks everyone, this is a ton of great info!
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Old 10-20-2017, 07:11 AM
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Support Jetflyer. Chic
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Old 10-20-2017, 11:51 AM
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Originally Posted by redtail View Post
Support Jetflyer. Chic
I'm sorry, but I don't know what that means....
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Old 10-20-2017, 12:04 PM
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I have a Kevlar tank in my jet, I always plug the line. I have never noticed any air entering or leaving when I pull the plug even with a +40F temp change. I store the jet in the basement so I want no fumes. I bought my jet used 11 years ago and this is still the same tank with no cracks or other issues related to pressure differences. I did one time have an issue after filling the take at home while doing some maintenance and then going to the field i did not have to fill it so I forgot to remove the plug. Started fine, took off fine but the available power was steadily dropping as I flew. It was about 2 or 3 minutes into the flight that it hit me so I killed the turbine and made a dead stick landing. There was a huge rush of air when I pulled the plug but no damage to the tank or other components. I find it hard to believe that just a small temp change could create enough pressure or vacuum to damage anything.
My tank is rectangular and is not a tight fit into the air frame. I can see where a round tank or one that is a tight fit will create more pressure change with the temp change. round will hold shape better against both pressure and vacuum, rectangular will allow the sides to bulge a bit to relieve some of the pressure change.
Now if the tank was full with little to no air and you had a big temp change then I could see the hydraulic pressure doing some damage.

Anyone have a little pressure gauge to do an actual measurement of the pressure change with temperature?
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Old 10-20-2017, 12:26 PM
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I can tell you, those U shaped tanks don't handle pressure too well. Of course the two I've cracked have both been during fueling, not a result of having the system sealed during storage.
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Old 10-20-2017, 12:36 PM
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AEROSHELDON - Guess I should have been more straight forward. What I mean is just like Jetflyr, I too transport my jet inside the car and store inside the workshop - so, I plug the vents. Almost blew up a tank once while filling it at the field before I realized I had not unplugged the tank. Chic
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Old 10-20-2017, 03:41 PM
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Got it, thanks !
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