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Fuel line sealant

Phil

Phil

Well Known Member
Post Oshkosh and I'm putting in my fuel system finally.......

Last night, a buddy (A&P many years removed) of mine was at the house and he asked what I was going to seal my NPT fittings with. I said, Permatex #2.

You would have thought he bit into a lemon. He said I was crazy for using it and that I should use something else designed for aviation fuel systems. He said that "what ever you use, should be able to be dissolved in the fuel and combusted".

That sounds 100% counter intuitve to me. Why in the world would I want something sealing my fuel system if it dissovles in the fuel. Especially when you consider that it's dissolving so fast the process is completed before it reaches an injector.

Am I just wayyy off base?

Phil
 
AN fuel fittings

Phil, I've heard of folks doing differnt things to their AN fuel fittings. My favorites are nothing (dry threads) and fuel (easy) lube.
Regards
 
AN fittings will certainly be dry, but his comment involved all the NPT (tapered) fittings.

Phil
 
I've been using Permatex #2 on aircraft for over 35 years.
And on automotive NPT fittings before that. It works great for any NPT fittings where petroleum based products are involved.
BTW, just a little dab on the second thread is all that's needed.
 
Phil said:
Post Oshkosh and I'm putting in my fuel system finally.......

Last night, a buddy (A&P many years removed) of mine was at the house and he asked what I was going to seal my NPT fittings with.
Click to expand...

Pipe threads don't really need sealant to do their job. What they need is to be lubricated so they can be assembled in a manner that the threads perform the seal that they were designed to do.

Try this test, take a male and female pipe thread fitting and thread them together dry. Finish off with a torque wrench to a given torque. Mark the parts with a scribe. Now remove the fitting and lubricate the threads with oil, grease, pipe dope, or PTFE. Now re-assemble the parts and re-torque and notice that the scribe marks have passed way before you reach the same torque setting.
 
I recommend Permatex® Thread Sealant with PTFE. I see no need to use "tape" at all.:mad:


And that would be at a min......2 points for Mel.
 
gasman said:
Pipe threads don't really need sealant to do their job. What they need is to be lubricated so they can be assembled in a manner that the threads perform the seal that they were designed to do.
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I do have a different opinion on that one. Being in the HVAC business for over nearly 40 years, running natural gas lines is part of our job. After completion, we run a pressure check, which needs to hold until the inspector checks it. To get a good seal, we use the pipe thread sealant. To get even a better one, we wrap the joint with teflon tape & then with pipe sealant. By doing this, the lines pressure will stay pumped up for weeks, and even months. With pipe dope only, it rarely does. Of course, in aircraft use, teflon tape can cause problems if shreads get in the wrong places, so usually, it's not used. Just taking a joint apart with teflon tape will allow shreads to remain in the female fitting.

On my airplane, I used Rectorseal #5 yellow. The gray works well too. Even though this is one of the better sealers I buy from my suppliers, it's available at Home Depot too.

L.Adamson -- RV6A
 
L.Adamson said:
I do have a different opinion on that one. Being in the HVAC business for over nearly 40 years, running natural gas lines is part of our job. After completion, we run a pressure check, which needs to hold until the inspector checks it. To get a good seal, we use the pipe thread sealant. To get even a better one, we wrap the joint with teflon tape & then with pipe sealant. By doing this, the lines pressure will stay pumped up for weeks, and even months. With pipe dope only, it rarely does. Of course, in aircraft use, teflon tape can cause problems if shreads get in the wrong places, so usually, it's not used. Just taking a joint apart with teflon tape will allow shreads to remain in the female fitting.

On my airplane, I used Rectorseal #5 yellow. The gray works well too. Even though this is one of the better sealers I buy from my suppliers, it's available at Home Depot too.

L.Adamson -- RV6A
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Gas and water pipe threads are the crudest of all pipe threads. I can understand you wanting to use the teflon tape. But, you are only testing at 50 pounds and working pressure is only 7" (less than 1/2 pound) wc max for nat gas. I am also in the gas business, and we need to have 4" sch. 80 threaded pipe hold 150 psi of liquid propane for ever, or the life of the installation. Nothing that you swab on the threads will seal without the threads fitting as designed.
 
I used Loctite Quickstix 561 PST. (push up tube) One of the few sealers I have found that holds back the "blue juce". Smells good too!:p
 
I use fuel lube from ACS or Permatex #2 from Auto Zone

I also do hvac and use yellow teflon tape/pipe dope on natural gas lines. Works great on the crude threads. The bottom of the vee in npt pipe threads does not mate up between the male and female parts so you need something to seal it otherwise you may get a spiraling leak in the little space at the bottom of the vee.
 
There is an opinion in the Sport aviation with the Dc3 on the cover. Joe Norris on page 99 explains why he uses sealant.
 
100LL Solubility of Permatex #2

There was an interesting article in the June 2016 Kitplanes magazine by Elliot Seguin analyzing aircraft related chemical hazards, and an interesting point relevant to this thread was the following:

"Unfortunately the Permatex in the joint had become significantly compromised sitting in fuel overnight. The sloshing was creating little jets of fuel, which squirted through the bolted flange, hitting me in the back of the ankle with noticeable force. It surprised me to find that Permatex #2 is gasoline soluble (cured or not, we tried several batches), and sitting in contact with the fuel overnight, the seal had become significantly compromised. It took me a lot of testing in two airplanes to believe that a product described as a fuel tank sealant was fuel soluble, so I pass that on now to save you the trouble."

The full article is well worth reading (as have been all of Elliot's articles) if you have the magazine or online access.

Cheers,

Tom.
 
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Don't get too excited yet . . .lets verify.

tgmillso said:
There was an interesting article in the June 2016 Kitplanes magazine by Elliot Seguin analyzing aircraft related chemical hazards, and an interesting point relevant to this thread was the following:

"Unfortunately the Permatex in the joint had become significantly compromised sitting in fuel overnight. The sloshing was creating little jets of fuel, which squirted through the bolted flange, hitting me in the back of the ankle with noticeable force. It surprised me to find that Permatex #2 is gasoline soluble (cured or not, we tried several batches), and sitting in contact with the fuel overnight, the seal had become significantly compromised. It took me a lot of testing in two airplanes to believe that a product described as a fuel tank sealant was fuel soluble, so I pass that on now to save you the trouble."

The full article is well worth reading (as have been all of Elliot's articles) if you have the magazine or online access.

Cheers,

Tom.
Click to expand...

I have used #3 for 40 years, and never found "soluble" in petroleum products - oil, gas, diesel fuel. You cannot get it off your fingers. But, it is soluble in alcohol. Things change, so worth checking.

He did say "tank sealant" , not gasket or joint sealer. It is certainly not an alternative to polysulfide sealants.

Edit - yes I said #3 - aviation gasket sealer. Not #2. But - the SDS shows little difference between the two. #2 is thicker.

REf: http://www.vansairforce.com/community/showthread.php?t=130852
 
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This is one of those confusing issues for which there seems to be a myriad of points of view.

One A&P I know says to use fuel lube and nothing else

Someone else said that will bot seal the thread channel

When I mentioned the idea of using Permatex #2 as a thread sealant, in another forum someone said it's not a thread sealant and you must use an official thread sealant.

When I watched the EAA video on installing NPT fittings they guy said "Use a thread sealant but didn't specify any particular brand nor indicate any characteristics one needs to look for in a thread sealant.

So I have Permatex #2, got Permatex High Performance Thread Sealant, I have fuel lube. ;)

I still don't know which is best.
 
The Superior Vantage assembly manual calls out Titeseal #2 (part number T2-01) for pipe threads.

I use it and it seems to have a viscosity that works well.
 
I wan't trying to rev anybody up, I just thought it was an interesting data point, and given that this is the experimental category, you are free to use what you like. I have used permatex #2, as it was all I could purchase locally. I used it on the fuel drain location on my tanks when I did the manometer test, so there actually wasn't any fuel involved, however I think I will order some ez-turn and use that in the future given that I now have time available in my build before I need to do any more work on the fuel system.
Tom.
 
tgmillso said:
I wan't trying to rev anybody up,
Tom.
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You didn't. I find this discussion extremely informative. I have to install a new fuel pressure sender and I MUST get this right:

The manifold block is near the top, left, of the firewall. I have these nightmares of not doing this job correctly and having fuel drip done onto the exhaust.
 
Fuel Lines and Tape Pipe Thread?

Sorry to bring up an old tread I am trying to better understand what is right and wrong. I was reading a review of another EAB and when looking at the pictures saw tape pipe thread sealant on the fittings for the fuel shut off. Is it okay to have this if it is this far back or should it be avoided?

image.jpg
 
Teflon tape

Teflon tape should never be used on an airplane. There are accidents attributed to pieces clogging fuel systems.
 
TFeeney said:
Is that teflon tape for sure, or maybe an over-eager installer with some sealant?
Click to expand...

I agree.
It looks like heavy use of a teflon type sealant rather than tape.

BTW, if that is a fuel valve used by the pilot in flight it aught to be labeled what its function is.....
 
Agreed

rvbuilder2002 said:
I agree.
It looks like heavy use of a teflon type sealant rather than tape.

BTW, if that is a fuel valve used by the pilot in flight it aught to be labeled what its function is.....
Click to expand...

+2 on this one. Rectorseal #5 is good stuff for this app - but like any other NPT sealant - use sparingly, and keep the sealant away from the first thread or two.

Best,
Mark
 
F1Boss said:
+2 on this one. Rectorseal #5 is good stuff for this app - but like any other NPT sealant - use sparingly, and keep the sealant away from the first thread or two.

Best,
Mark
Click to expand...

Thank you for the explanation. I am continuing to learn!
 
Fuel sealent

1422 or 8802, every Douglas, Boeing, airbus, etc every one use's it because it works. jet fuel, avgas, 100ll, alcohol, prof, fuel sealent
 
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