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NPT fittings and Fuel Lube

snoopyflys

Well Known Member
Hi all,

Been skipping along with my FWF build installing my NPT fluid fittings using Fuel Lube ( a.k.a. EZ Turn) and recently discovered in a few postings and in Section 5 of my build manual to not use Fuel lube with NPT fittings :eek: :(

So, should I remove all of the NPT fittings and clean them using some sort of solvent or leave it be a see what leaks then address it? Not sure what will clean Fuel lube enough to allow Permatex #2 to do its job. Any words of wisdom would be appreciated for my dumb use of sealants.

Thanks
 
I'm not sure why the current thinking is to avoid Fuel Lube. I've never used anything else on NPT fittings and never had a leak or other issue with them. Yes, it would be a problem if someone sloppily got the stuff past the threads such that a glob could enter the hose/pipe bore, but that's a technique issue vs. a problem with the material.
 
fwiw
i put permatex #1 or 2 on a piece of metal and a week later cleaned it up with gasoline.i called permates and got an ''old timer'' there that confirmed neither #1 or #2 was truly gas proof. something about since laws prohibiting use of a compound extracted from trees.
i do know i have heard of a lot of guys using it.
another fwiw......a company that does gas pump installations and repairs for service stations uses ''gasoila'' on the pipe fittings.
i have always used #567 and never had a leak.
 
Truly discussed at length here on VAF. If you read section 5.27 of your drawings from Van’s, they list Permatex #2 and Tite-seal, but also suggest “others with success”. You can’t go wrong with Permatex #2, which I’ve used extensively in my work over many years, but also on airplanes.

And while some folks use Loctite 567, which a great sealant/locker, it is Loctites general thread sealant that will definitely do the job well, but was initially designed for stainless threads with a permanent installation in mind.

The specific Loctite for hydraulic lines, including oil, brakes and fuel, is 565. It will also minimize galling and I highly recommend it if you ever think you’ll pull those aluminum NPT fittings apart sometime in the life of the airplane.

Just to be clear, don’t use sealants on flared fittings - a couple of drops of light oil (think air tool oil) on those work well.

I personally only use EZ-Turn on applications where metal meets rubber, such as fuel drains in rubber bladders; that really is it’s target application.

To directly answer your question, I personally would go back through where you’ve used EZ-Turn on NPT fittings, remove clean (thoroughly with denatured alcohol) and install with Loctite 565. It’s also easier to do now than later when you find that hard to reach fitting leaking.
 
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Anecdotal Story

More than 45 years ago I discovered the wonder of Permatex Aviation #3 and it became my go-to sealant all those years for anything NPT. I used it for gasket and gasket-less (VW cases) with perfect success. Hundreds of dry engine overhauls and thousands of other applications attested to my golden find.

I continued with #3 on the RV7, but had two failures, both on 1/8" NPT. The sensor block and brakes. I think the special ROYCO fluid dissolved it on the brakes.

I have no technical explanation as to why #3 has failed, but for now, for the airplane, 567 is my standard.

#3 is dissolved by any alcohol, but not touched by anything petroleum. #2 is the same but more pasty.

EDIT: Interesting comment on the 565, Ron, I will check into that.
 
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I personally only use EZ-Turn on applications where metal meets rubber, such as fuel drains in rubber bladders; that really is it?s target application.

Can you cite an authoritative reference for this claim? I've been all through the tech data sheets over the years and don't recall a single specific reference to metal/rubber interfaces. At the same time, the product is advertised as being suitable for anti-seize, anti-galling, and threaded fastener (such as NPT fittings) applications.

There's absolutely nothing wrong with the stuff and I've found it to be ideal for use with NPT fittings.
 
I've used both EZ Turn and Tite Seal with no issues at all. Much ado about nothing. Any of them will work fine if you apply them correctly and thread the fitting in correctly.
 
....a company that does gas pump installations and repairs for service stations uses ''gasoila'' on the pipe fittings.
That's what everybody uses on black iron pipe for natural gas or propane. When I built my house, I used regular Teflon pipe dope and had several leaks. I redid those joints with Gasoila and no leaks. I wouldn't hesitate to use it on my airplane.
 
Can you cite an authoritative reference for this claim? I've been all through the tech data sheets over the years and don't recall a single specific reference to metal/rubber interfaces. At the same time, the product is advertised as being suitable for anti-seize, anti-galling, and threaded fastener (such as NPT fittings) applications.

There's absolutely nothing wrong with the stuff and I've found it to be ideal for use with NPT fittings.

It works very well easing metal drain valves into rubber bladders. I have experienced NPT fittings leaking from aluminum fuel tanks many years ago when I used it for tapered thread sealant and switched to Loctite. So I don’t know about “authoritative”; It’s just my 30+ years experience using the sealants.

I do note that alcohol does break EZ turn down, so using fuel with ethanol may be the cause of my personal experience where it leaked.

I would put EZ Turn under the Van’s reference category from section 5.27 of “you may find success with other sealants”. I prefer Loctite 565.
 
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