Andair check valve

[akarmy]

Here's a picture of the new Andair one way check valve I installed in the fuel return line coming from the engine. Without this in place you can still get fuel flow forward even with the selector off since the return line back feeds from the gravity head pressure. It's easy to put this in place (got the tip from John M at the factory as they use them on the LSA models) the only downside is it's a bit pricy! but then what's not in this game.

[Paul Z]

That is how I did mine

[jiott]

I am wondering about this installation. I do believe that the little check ball in this valve is free floating (not spring loaded against its seat). Therefore it depends on gravity to seat itself reliably and prevent reverse flow. The way its mounted in the photo gravity will try to keep it OPEN and will possibly allow a small amount of reverse flow. I think it is better to mount it near the header tank where the hose slopes upward, keeping gravity working with you rather than against you.

[Dave S]

This might help some with the design and construction of the andair valve....

From their website at http://www.andair.co.uk/category/check-valves/

================================================== ==
"The Andair Check Valve is a complete closure valve. It allows fluid to pass in one direction whilst preventing it from flowing in the reverse direction. Arrows on the outside of the body indicate the flow direction. The valve is machined from L168 Aluminium and then anodised for greater protection. To connect to the valve a range of fittings are available.
Optionally a bleed can be fitted to the valve at no extra cost, here the internal shuttle has been drilled with two small holes. This allows for bleed back to occur. This particular valve is useful in the vent line of a fuel system where allowance for fuel expansion is necessary.
The internal shuttle and spring are extremely light giving a cracking pressure of between 0.4-0.7 PSI. Optionally, a cracking pressure of between 12-17 PSI (0.8 - 1.2 Bar), suitable for the Rotax 912iS is available (£8.00 extra)."
================================================== ====


Sincerely,

Dave S

[akarmy]

I do believe that the little check ball in this valve is free floating (not spring loaded against its seat). Therefore it depends on gravity to seat itself reliably and prevent reverse flow.

Good question. I have not seen any information from Andair as to how it works. Guess we could buy one (for $70) and cut it open!

The information they provide says 1psi or less pressure to stop the flow. I was going to zip tie it up horizontal before closing it up. It's sitting there just this way right now with the return line open about 12 inches in front of it while I do the hose replacement project and the flow is stopped just fine. Nothing dripping FWF, so I guess it works. With a 1psi close rate and 2-3 at least from the head pressure it should be fine.

[jiott]

That is interesting information Dave. When I installed mine I could shake it lightly and hear the ball shuttle rattling back and forth. If it has a spring, as the description says it does, it must be "extremely" light. If I was going to mount it "upside down" I think I would do a little bench test first.

[Dave S]

Jim,

Yeah, I think doing some testing as you suggest is a good point.......

last year I had a master solenoid deal where it took some digging and discussion on the list to fully understand how mounting the thing could affect it's operation.....turns out no information with the unit on orientation (that was buried in the engineering information not normally distributed) ; but, it does have have a "green side up" deal, like planting sod.....this valve may be like that too...

I am interested since I currently do not have the rotax bleed orifice, return line or this valve in my installation.....want to get it taken care of by the time we get back to hot weather.

When people are doing the return line, is it normally plumbed back to the header tank?

Sincerely,

Dave S
KF7 Trigear

[akarmy]

When people are doing the return line, is it normally plumbed back to the header tank?

Yes in my case it goes into the top of the header tank for the return.

[jiott]

Ditto for me too-to the top of the header tank.
This is what the instructions say to do when you buy the Kitfox optional return line kit.

[jiott]

I know some guys run the line into the top of their gascolator and I guess this works. However, one of the main purposes of the return line is to recirculate cool fuel from the tank back to the engine to help prevent vapor lock. Recirculating it only to the gascolator (usually mounted in the hot engine compartment) seems to partly defeat this purpose.