Fuel Selector Valve - Gascolator.

[FFTravism]

What torque value should we be using for the drain valves?
Also what torque should the union between the fuel selector and the gascolator be?
I see people talking about torqueing them down but never mentioning what value.
Thanks

[alaskabearhawk]

FWIW, I didn’t torque any of my fittings. For the gascolator drain I put on a thin coating of Teflon paste on the threads and tightened it snug. For any AN fittings I put on just a very light touch of oil on the threads. I used a wrench to hold the fitting body while using another wrench to snug the B nut onto the fitting. There is no pressure in those areas. Sorry I can’t define “snug” as it’s a feel that is hard to describe. I just tighten until the the wrench doesn’t turn anymore with light to moderate pressure.

[AKKen07]

My friend and A&P/advisor recommends using the German technique: you torque them till they are “Gūtentite.”

[FFTravism]

That is what I was thinking..
Thanks

[Bcone1381]

I'll expand a bit on Pauls Excellant advice.

Bottom Line. I now tighten flare fittings by measuring "Flats past Finger Tight" using the chart below.

I've gone down this rabbit hole. I've re-made several lines and experimented in the shop and discovered....
1) Do not trust a chart that shows torque values for AN fittings -
2) Tubing material may be demand different torque values - different torque values for 3003 soft aluminum, hard 5052, 6061, and steel - charts will not show this.
3) 60 in lbs of torque deforms/squishes flat soft tubing flare ends.
4) Some charts show 110 in lbs +/-10 for example, some even more and will freeze up the nut so it wont turn freely.
4) Tube Strength is compromised when AN fittings are overtorqued.


I encourage experimentation. Google "AN fitting torque chart" and try it yourself. Look for the diameter of the flare to enlarge by measuring with a caliper or micrometer. I found that the sleeve will also mushroom out. This was experienced with -04 size (1/4") using both Race Car Phenix Fittings and authentic AN fittings from an aircraft hardware supplier.

However, on a chart by Aeroquip, their alternative method that they say is "EXCELLANT " says tighten a certain number of flats past finger tight. I'll attach the chart below.

Screen Shot 2023-02-13 at 5.32.49 PM.png

[Battson]

For any AN fittings I put on just a very light touch of oil on the threads. I used a wrench to hold the fitting body while using another wrench to snug the B nut onto the fitting. There is no pressure in those areas. Sorry I can’t define “snug” as it’s a feel that is hard to describe. I just tighten until the the wrench doesn’t turn anymore with light to moderate pressure.

Well....
I had a bad experience with not tightening up flared-tube AN fittings really firmly. They almost all leaked fairly badly, this did irreparable damage to my paint job in some locations. I ended up getting some help from a friend who knew how to do it correctly.

Edit to add - I would suggest seeking professional advice. I certainly cannot provide it, but I can say it isn't hard to get it wrong.

[alaskabearhawk]

Great advice as always Battson. I hired an A&P to show me and teach me how to do a number of things and this is one of them. He showed me the proper tool to use when flaring a tube end, how to do it, what is bad, what is good. He then showed me how to properly install the fittings and tighten the connections, so I'm confident that it is done properly. Trying to describe the process in a forum post is a challenge for sure.

[spinningwrench]

The torque chart in AC43.13 is for hard 5052 flared aluminum tubing. Which is way too much for soft 3003 tubing. The EAA video series has an entire presentation on proper torquing of flare fittings. I have found the quality of the flare makes a big difference. I spent a fair amount of time polishing up the end of the tubing before flaring so there are no scratches or stress risers. Lubricate the tubing end with a drop of oil before flaring and flare enough so it just reaches the perimeter of the B nut when done but not anymore. After flaring examine the interior of the flare with a magnifying glass you want to see a perfectly formed cone with no cracks.

[FFTravism]

Since this turned in to an fittings when flaring what type of oil should you use? Travis

[Collin Campbell]

I like to use EZ Turn Fuel Thread Lubricant on all the B nut threads. just on the threads... not on the mating surfaces. Just a little dab will do the trick. Keeps the threads from galling and makes them turn "easier"... Also good for the fuel cap threads...not the "O"rings.

[FFTravism]

Sorry what type of oil on the flaring tool?

[Battson]

I didn't use any... but it may depend on the type of tool. Plus I am not an expert.

[spinningwrench]

Any light petroleum oil, wipe it off when done. You are just preventing galling of the aluminum.

[Dpearson]

I use a Rolo-Flair tool. It has a depth stop which makes it easy to get the finished diameter of the cone correct every time. A couple of drops of 3in1 oil on the cone before each flair.
I haven’t tested the system yet, though!

[Bcone1381]

"Have I flared it enough or too much?"

Some sources I found that might help. On the chart for 1/4" tubing you see a .340" - .360" dimension. That gets checked with my caliper.

In application...I use a Parker Rolo-Flair tool. It forces a threaded mandrel (cleaned and lubricated with my favorite lube.) into the tube via a threaded rod which I turn by hand. I turn the handle three turns, progressing 1/2 turn at a time. Thats about right for 1/4" tube...maybe a bit on the smaller side of the chart. 3/8" tube might need more turns. Go Experiment. The wider the flare the more the tubing is stressed and likely to crack. You'll see the text validated Spinning Wrenches excellant practice of polishing the tubing prior to flaring to remove stress risers.

Lastly: I don't measure every flare any more. You'll do a few and just know if its right after a few. The chart below might help you get real data to help judge and evaluate your skillset.

Screen Shot 2023-02-14 at 10.24.32 AM.png



Screen Shot 2023-02-14 at 10.49.00 AM.png

[FFTravism]

Wow some great information thank you