DonFromTX

DonFromTX

Well Known Member
I am in need of a check valve type fitting, this crude drawing I hope illustrates what I want. Ideally it would be with 1/8 NPT outlets. The flapper valve would have to be in the upper drawing until pressure is applied from the bottom leg of the T, at which time the flapper would seal off the right hand leg of the T. Anybody know of such a valve and where I could find one?
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I don't have a source for such a valve, but depending on how the flow operates in the pipes, you might be able to rig up a T with a couple of normal check valves.

Greg
 
It might help if I revealed what I am trying to accomplish. The straight thru flow symbolizes the fuel vent line. The bottom fitting will be pressurized fuel from an aux tank. I am of course trying to make the fuel flow into the tank (to the left in the photo) when pumping from the aux tank, but it would revert to a vent when the pumping stopped. Make sense?
Obviously I want a simple foolproof system, clogging up the vent is not an option.
 
DonFromTX said:
?... The straight thru flow symbolizes the fuel vent line. ... I am of course trying to make the fuel flow into the tank.....but it would revert to a vent when the pumping stopped. Make sense? ....
Click to expand...

So, you want to use the fuel tank vent line as a fill line from an aux fuel tank. Won't closing the main vent exit while you pump aux fuel into the main tank seriously pressurize the main tank, possibly beyond its safe limit? Displaced air needs to exit but you've blocked the exit, unless it works its way backwards through the fuel into the aux tank somehow.
 
Well you are correct of course, but my tank venting has not yet been totally worked out. This vent is for the "standpipe" of the system inside the aircraft and is therefore about the only way to add fuel while flying. The other four wing tanks have a vent system of their own, which I am not too thrilled about anyway, would like all five tanks to have a common vent. Currently they are vented thru a short pipe on the fuel filler caps, but I don't like that either. It is definitely still a work in progress.
WenEng said:
So, you want to use the fuel tank vent line as a fill line from an aux fuel tank. Won't closing the main vent exit while you pump aux fuel into the main tank seriously pressurize the main tank, possibly beyond its safe limit? Displaced air needs to exit but you've blocked the exit, unless it works its way backwards through the fuel into the aux tank somehow.
Click to expand...
 
Mcmaster has a variety of check valves with different ratings. A Tee or two with with the check valve should work for you in your design efforts

I made a tee in my vent line and put a check valve inside the cabin. It is arranged so that if the vent inlet freezes over, it will pull air from the cabin to equalize pressure in the tank. It is a 1 PSI check valve.

Larry
 
a single vent line for all five tanks is a very bad idea, one blockage and all tanks are rendered inop.
I would not try to use a vent line to fill a tank. to many things to go wrong. check valve hang up tank is inop or worse.

I you are trying to use an aux to fill another tank the best way is a dedicated line just for that. keep feed and vent lines separate.

bob burns
RV-4 N82RB
 
I THINK I recall that in certificated planes, all tank vent lines must share a common source, am I remembering wrong?
In this case, if I were to vent the four tanks to the RIGHT of the illustrated T, then the filling would not be restricted, since four tanks would all be vented while filling. Regardless, "clogging" this one vent while transferring fuel would have no effect on the other four vents. There seems to be little other option.
 
Don---take a look at the Raven inverted ball valve for oil systems and scale it way down. Seems to be what you have in mind, or similar.
Tom
 
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