Teflon thread tape on fuel lines

[skeptic36]

Hi all,

 

I am doing some work to the fuel system on my trike atm and I'm surprised to find teflon tape on all the threads. These are installed at the factory.

 

Should I use teflon or should I use Permatex Aviation Sealant, or something else?

 

Thanks

 

Regards Bill

 

 

[rgmwa]

Loctite 567 also works. I've read that there's nothing inherently wrong with Teflon tape provided it's installed correctly. However it's not recommended because it's too easy to shred bits into the fuel system.

 

rgmwa

 

 

[Nobody]

Hi all,I am doing some work to the fuel system on my trike atm and I'm surprised to find teflon tape on all the threads. These are installed at the factory.

Should I use teflon or should I use Permatex Aviation Sealant, or something else?

 

Thanks

 

Regards Bill

The flared part of the fitting should not have teflon or sealant. The tapered thread part should have a fuel sealant not tape. Do not use RTV.

A good discussion with pictures is here:

 

http://www.vansairforce.com/community/showthread.php?t=130852&highlight=teflon

 

AC43-13-1b says not to use teflon on the flared part of the fitting. (but is silent on the tapered part)

 

http://www.faa.gov/regulations_policies/advisory_circulars/index.cfm/go/document.information/documentid/99861

 

 

[facthunter]

Generally speaking teflon makes the part move too easily and it can get in the fuel. A tapered fitting (particularly an elbow) needs to NOT move in service. Nev

 

 

[aj_richo]

NPT threaded fittings require sealing, ain't no other way around it.

 

I haven't experienced any issues with Teflon paste

 

 

[facthunter]

I'm referring to the use of tape, frequently incorrectly used. Nev

 

 

[Guest ozzie]

Flared fitting, no. From what i have read. liquid thread lock (not sealant) may be used in high vibration areas.

 

I have always tried to avoid using anything that will find it's way into a fuel system.

 

 

[kgwilson]

Permatex is the best IMHO. It seals, is not affected by petroleum products but does not go hard like some others so removal is not an issue. High strength threadlock compounds can be a problem as they can be difficult to undo.

 

 

[M61A1]

Loctite 567 is good for tapered thread fittings.

 

If you feel the need to use thread tape on a flared coupling, stop working on machinery and get a desk job. If a flared coupling leaks at normal torques, it's damaged and should be replaced.

 

I have worked helis that specify a threadlocking liquid on the threaded parts of hydraulic unions, but not the mating faces.

 

 

[Guest ozzie]

Here is a little hint for removing fittings with thread lock. Just heat them up. I used a steam cleaner with a pointy nozzle so it would just heat the fitting where it was needed also safer when fuel is involved. Heat softens the compound.

 

 

[M61A1]

If you use the correct thread locker for your application, it shouldn't be too hard to undo, and it will actually prevent galling and corrosion.

 

 

[dutchroll]

It's fairly universally considered bad practice to use Teflon tape on threaded fuel fittings in aircraft (or even cars) and there are documented cases of tape shreds getting into fuel lines and carburettors. The Kitfox has an interesting service letter on fuel system fabrication which talks about the 25 fuel tanks sent out with Teflon tape incorrectly used on threaded fittings by the vendor.

 

I agree it's very surprising to see it come out of a factory like that and wonder how intentional it is.