Question for all engineers out there. I am kind of in a quandary at work and need a little help locating a valve for a fuel tank. I am doing a test on an aircraft fuel tank to measure the oxygen concentration. The approach to take the sample is to insert a 1/4" od, 1/8" id ss tube into the tank and, via a vacuum pump, suck (insert joke here) a sample to the oxygen analyzers. The problem is that as the fuel level rises during the test, the tips of the probes are going to be immersed in fuel. This means we are going to suck JP-8 into the analyzers (not good) unless we put a mechanical float valve on the tip of the probe to eliminate getting fuel into the analyzers. Seems like a good solution.

Problem...
I cannot Find any Float valves suitable for my application. If anyone knows where I can find an extremely compact float valve that can be fully immersed in jet fuel, attached to a 1/4" tube by way of a swage-lock compression fitting, and can seal well enough to hold a -10psi vacuum, I would be eternally in your debt. For ever and ever and ever and ever and ever.

Peace out.

 

I'll tell you what, I ask around the garage and see if we have anything like what you are looking for. Maybe I can get a part number for you. Sounds similar to some of the testing that goes on around here. Not my area actually, I work with emissions.

I'll get back to ya'...

 

Big time thanks...

 

are you doing it just for the test or for a production type thing. If its just for the test use a toilet float valve that is used to turn off the water in your toilet bowl....

If thats to weird for ya just use the same principal and make a float type valve. some round stock aluminum/brass, a little leathe work, an O-ring and a float on the end of a stick.

<img src="http://boards.rennlist.com/upload/floatthing.jpg" alt=" - " />

some duck tape might help also...

I dont think I was of much help but check here for one... <a href="http://www.mcmastercarr.com" target="_blank">www.mcmastercarr.com</a>

 

"are you doing it just for the test or for a production type thing. If its just for the test use a toilet float valve that is used to turn off the water in your toilet bowl....
If thats to weird for ya just use the same principal and make a float type valve. some round stock aluminum/brass, a little leathe work, an O-ring and a float on the end of a stick. """

It's just for the test but the valve is going into the tank through a 3" hole and needs to be small. Also, it needs to be of a slightly higher quality than a toilet bowl valve. It's going into the wing of an operational C-5. What you showed in your drawing is what I was actually looking for, except with a ball type valve instead of a plunger. Regardless, I might have to have the shop make something up like you said.

"some duck tape might help also... """"

Now I think we are onto something... <img border="0" title="" alt="[Wink]" src="wink.gif" />

 

why not just put a trap in line between the tank and the analyzer? The trap would collect any fuel that was sucked into the line before it reaches the analyzer.

 

The test is 6 hours long. That is alot of fuel to trap. Besides, we want to keep any fuel out of the system. Thanks for the input. You all are cool.

 

Do you have an access panel/hole to get in the fuel tank situated by the place you wish to put the valve? If so, you could use something similar to the Brass Float valve, 3/8" NPT male by 3/8" NPT male. If you have an access hole, you could use an bulkhead fitting to get through the tank, use a x-over to tubing on the bottom fitting to make a reverse J that would be up to the top of the fuel tank.(1/4" female available)

McMaster Carr catalog page 300 item A, brass float valve, swl 125psi, 180° temp.

<img src="http://boards.rennlist.com/upload/fuelO2.jpg" alt=" - " />

 

insert a 1/4" od, 1/8" id ss tube into the tank

Maybe I am missing something here but why not make a mounting device on the outside of the access port that holds the metal SS tube so that it is pointed towards the top of the tank? The oxygen will be at a higher concentration at the top since the fuel vapors are heavier.

BTW: Did they ever fix the wing cracking problem on the C5?

 

Did you solve this?

 

Sorry, I have been offline all weekend. Yup, I got it solved. I found a ball valve that actuates with-in 1/4 of a turn. I am going to have the shop weld a float and extended lever onto the valve lever. It's compact. Seals well. And is fuel solluble. Thanxs for helping me get my noodle cookin... <img border="0" alt="[thumbsup]" title="" src="graemlins/bigok.gif" />

<img border="0" alt="[byebye]" title="" src="graemlins/wave.gif" />