Fuel Fittings - Thread Sealant

Rob58

Rob58

Pre-takeoff checklist
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Rob
When replacing fittings in the side and end of my fuel pump, what's the correct sealant to use on the threads? Thanks for your help!
 
A question this vague can't really be answered. What kind of threads? Straight or pipe makes a difference. Is there supposed to be some kind of sealant or maybe just an o-ring?

I'd consult the appropriate manual and see if it will provide some guidance on what to use before taking an answer off a web board like this.
 
I'm resurrecting this post as I am replacing more fittings in my fuel system (also a few hydraulic fittings). I am not convinced that Fuel Lube is the best for sealing up threads. I say this because of the consistency of this material compared to other thread sealants that I have used in non-aviation applications. I believe that there are other materials made by Loctite and Permatex... maybe other companies. I have nothing against Fuel Lube; I am just looking for some additional feedback. Regarding the questions mentioned by the previous post:

1. The fittings that I am attempting to seal would generally be types AN-816 or AN823. Unless I am mistaken these are tapered pipe threads on one end and AN straight threads on the other end. It is the taper pipe end I am applying sealant to. I would never apply a sealing to the end that has the tapered seating surface.

2. There are no manuals available on my aircraft to offer any assistance. If there were, I would make the assumption that information from 65 years ago might not be fully up to date anyway.

Again, I am just hoping for some feedback on what alternate sealants might be available and any comments - good or bad - on their performance. Thanks!
 
How many owners here believe the OEM will give advice on after market products?
 
My RV-7 assembly manual says, "Two sealants popular for use on aircraft are Tite-seal and Permatex #2. Teflon based pipe dopes and sealants, and some of the anaerobic thread sealants are also used by some builders with success. Do not use Fuel Lube. It is not a sealant. "

I have used Permatex #2 and #3. So far I have not died in a fiery crash. That said, I don't like them all that much either.
 
DaleB said:
I have used Permatex #2 and #3. So far I have not died in a fiery crash.
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I'm pretty sure you are mistaken about not having died yet.

I tried a number of things to get my fuel senders to not leak around the mounting screws that were just drilled / tapped through an aluminum ring welded to the top of the tank. Permetex didn't cut it. The Loctite 567 was an instant fix.
 
Capt. Geoffrey Thorpe said:
I'm pretty sure you are mistaken about not having died yet.
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You could be right. I am feeling a bit run down this week.
Capt. Geoffrey Thorpe said:
I tried a number of things to get my fuel senders to not leak around the mounting screws that were just drilled / tapped through an aluminum ring welded to the top of the tank. Permetex didn't cut it. The Loctite 567 was an instant fix.
Click to expand...
That is why God gave us Proseal. :)
 
Rob58 said:
I'm resurrecting this post as I am replacing more fittings in my fuel system (also a few hydraulic fittings). I am not convinced that Fuel Lube is the best for sealing up threads. I say this because of the consistency of this material compared to other thread sealants that I have used in non-aviation applications.
Click to expand...

I and many others have used FuelLube (now EZ Turn) for fuel line threads for a long time. It was originally made and MIL-spec'd for the tapered-plug type fuel shutoff valves. Fuel doesn't touch it. It's also a good anti-seize and doesn't harden, making subsequent removal easy. I've never had a pipe thread leak with it. Fuel systems typically use very low pressures anyway.

Too much sealant of any sort is worse than none. See this: https://www.google.com/url?sa=t&rct...a05o0146.pdf&usg=AOvVaw1Td7OAO1g2rNL9TZpnDTiu
 
Makes great gasket paste too.
 
Yep, pipe threads were designed to seal themselves. Fuel lube (ez-turn) gets to the torque better.
Continental advises #2 permatex with 00 silk thread for case halves FWIW.
 
EZ-turn for me, it may not technically be a sealant but fuel doesn’t dilute or desolve it and can’t get past it.
 
Permatex #3. The ooey gooey black tar looking stuff.
 
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You should be more specific. With AN aircraft fittings we are talking about NPT threads. They are not designed to seal themselves. Look at a print for the thread forms, the root and crest of the threads are machined within a tolerance that can leave a spiral path up the thread, hence the need for a thread sealant. There are thread profiles that are designed for an interference fit at the root and crest that make a "dry seal" but you won't find them on AN fittings (made to proper specs). Therefore, with NPT threads you need some sort of thread sealant. Before modern sealants, horse hair was used very successfully. Depending on the pressures and liquid it is sealing, pretty much any grease/lube/liquid gasket will work. Now days, be have application specific products companys have spent millions of dollars designing, why not take advantage of that? That's why I use and recommend Loctite 567. Its all we use at my shop for thousands of NPT fittings a year and have never had a leak in the 20 years we have been using it. The PTFE in is an incredible lubricant, especially on stainless steel fittings to the point we use it as a general purpose anti seize on all stainless on stainless fasteners and galling is a thing of the past.
Dan Johnson said:
Yep, pipe threads were designed to seal themselves. Fuel lube (ez-turn) gets to the torque better.
Continental advises #2 permatex with 00 silk thread for case halves FWIW.
Click to expand...
 
I use fuel lube on all NPT fuel fittings. The threads are what seals, the lube just makes sure it sees the proper tq to do the job.
 
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Tom-D said:
Stand by for problems when that stuff comes loose and gets in the fuel strainers.
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Like anything else in aviation, if you’re not competent to do it right you shouldn’t do it at all.
 
Well there ya go, way too many people think they are competent.
 
I have a can of real fuel lube, probably older than me. The uncovered portions of the can has the really sticky stuff. Great for holding stainless hardware to your screwdriver.
 
Grum.Man said:
I use fuel lube on all NPT fuel fittings. The threads are what seals, the lube just makes sure it sees the proper tq to do the job.
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I use it on almost all pipe thread fittings as well.
 
G-force said:
You should be more specific. With AN aircraft fittings we are talking about NPT threads. They are not designed to seal themselves. Look at a print for the thread forms, the root and crest of the threads are machined within a tolerance that can leave a spiral path up the thread, hence the need for a thread sealant. There are thread profiles that are designed for an interference fit at the root and crest that make a "dry seal" but you won't find them on AN fittings (made to proper specs). Therefore, with NPT threads you need some sort of thread sealant. Before modern sealants, horse hair was used very successfully. Depending on the pressures and liquid it is sealing, pretty much any grease/lube/liquid gasket will work. Now days, be have application specific products companys have spent millions of dollars designing, why not take advantage of that? That's why I use and recommend Loctite 567. Its all we use at my shop for thousands of NPT fittings a year and have never had a leak in the 20 years we have been using it. The PTFE in is an incredible lubricant, especially on stainless steel fittings to the point we use it as a general purpose anti seize on all stainless on stainless fasteners and galling is a thing of the past.
Click to expand...

NPT is supposed to be self-sealing, but with gasoline anything's possible. If you install a JPI or EI fuel flow system, you must install the NPT fittings in the flow transducer with no sealant of any sort, according to the instructions. I do that, and it doesn't leak. Any escaped sealant would stop that tiny wheel in the transducer.

I've used the 567. It's good stuff and works well. But you must be careful that you use only a tiny bit; after all, the gaps that need sealing are microscopic. Too much is liable to go where it's not wanted. 567 also has a habit of hardening with age (years), locking that fitting in there real tight and risking damaging the whole affair when you have to dismantle it.

Permatex Form-A-Gasket will harden, even the non-hardening variety if it gets hot enough. I have had an awful time disassembling aluminum fittings sealed with it without breaking or bending things. Isopropyl alcohol dissolves it.

It took me 20 years to figure out what would dissolve Fuel Lube. Acetone, it was. Nothing else I tried would clean it up.
 
JAWS said:
I have a can of real fuel lube, probably older than me. The uncovered portions of the can has the really sticky stuff. Great for holding stainless hardware to your screwdriver.
Click to expand...

I probably used more of it for that than I ever did for lubing gaskets. It will also hold a nut on the flat blade of a long screwdriver so you can reach it in and hold it against a stud, and turn the nut with another long screwdriver pushing on the hex corners.

I found that some gaskets would slide right out (extrude) with Fuel Lube once the pressure came on them, fuel sender gaskets in particular. Then they'd leak anyway. Fuel Lube seals the sender screw threads much better than the silly little washers and gaskets that the OEM used.
 
With fuel and hydraulic fittings that aren't flare? I generally want them to be permanent. I see no benefit in having the fittings come apart easily. Fittings that are made to come apart don't require sealants.

And all the references to the sealant allowing torque? What about when you install tees and elbows? Those are turned to position, not torque. The sealant is critical.
 
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If you only need a little bit of "Fuel Lube," and want to fix your scraggy engine primer, and save money as well, buy this kit......for $5.95. I've used the included "Fuel Lube" for years.
http://www.aircraftspruce.com/catal...6HXy8W9PnOI9CIAoSzb_H1Mp3QQkNEpcaAgkuEALw_wcB
05-03637.jpg
 
I have an AirFlow Perfomance fuel injection system on my O360 / RV-7A. That company recommends Loctite 565 for fuel fittings. Just a little on two threads.
 
G-force said:
You should be more specific. With AN aircraft fittings we are talking about NPT threads. They are not designed to seal themselves. Look at a print for the thread forms, the root and crest of the threads are machined within a tolerance that can leave a spiral path up the thread, hence the need for a thread sealant. There are thread profiles that are designed for an interference fit at the root and crest that make a "dry seal" but you won't find them on AN fittings (made to proper specs). Therefore, with NPT threads you need some sort of thread sealant. Before modern sealants, horse hair was used very successfully. Depending on the pressures and liquid it is sealing, pretty much any grease/lube/liquid gasket will work. Now days, be have application specific products companys have spent millions of dollars designing, why not take advantage of that? That's why I use and recommend Loctite 567. Its all we use at my shop for thousands of NPT fittings a year and have never had a leak in the 20 years we have been using it. The PTFE in is an incredible lubricant, especially on stainless steel fittings to the point we use it as a general purpose anti seize on all stainless on stainless fasteners and galling is a thing of the past.
Click to expand...
Not to beat a dead horse but,
NPT is not specific to AN fittings:
National Pipe Thread Taper (NPT) is a U.S. standard for tapered threads used on threaded pipes and fittings. In contrast to straight threads that are found on a bolt, a taper thread will pull tight and therefore make a fluid-tight seal.

https://ipfs.io/ipfs/QmXoypizjW3WknFiJnKLwHCnL72vedxjQkDDP1mXWo6uco/wiki/National_pipe_thread.html
 
kgruber said:
If you only need a little bit of "Fuel Lube," and want to fix your scraggy engine primer, and save money as well, buy this kit......for $5.95. I've used the included "Fuel Lube" for years.
http://www.aircraftspruce.com/catal...6HXy8W9PnOI9CIAoSzb_H1Mp3QQkNEpcaAgkuEALw_wcB
05-03637.jpg
Click to expand...

Do not confuse "Fuel Lube" with EZ-Turn.
http://www.aircraftspruce.com/catal...MIpM_plIGE3AIVD45-Ch0vCA5eEAQYAyABEgLDwPD_BwE

http://www.aircraftspruce.com/catalog/cspages/ezturnlube.php?clickkey=5414
 
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Tom-D said:
Do not confuse "Fuel Lube" with EZ-Turn.
http://www.aircraftspruce.com/catal...MIpM_plIGE3AIVD45-Ch0vCA5eEAQYAyABEgLDwPD_BwE

http://www.aircraftspruce.com/catalog/cspages/ezturnlube.php?clickkey=5414
Click to expand...

Fuel Lube is now nown as EZ Turn. Same stuff. It's a heavy, sticky grease. Seal Lube, on the other hand, is a thick liquid, looking like runny honey but thicker. Same purposes, but it's not Fuel Lube or EZ Turn.

https://www.aviall.com/aviallstorefront/Chemicals-&-Consumables/Lubricants/FUELUBE-MIL-G-6032-TYPE-1-1LB,/p/EZTURN1LB=33
 
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Dan Thomas said:
Fuel Lube is now nown as EZ Turn. Same stuff. It's a heavy, sticky grease. Seal Lube, on the other hand, is a thick liquid, looking like runny honey but thicker. Same purposes, but it's not Fuel Lube or EZ Turn.

https://www.aviall.com/aviallstorefront/Chemicals-&-Consumables/Lubricants/FUELUBE-MIL-G-6032-TYPE-1-1LB,/p/EZTURN1LB=33
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Just because Avial says they are doesn't make it so. Aircraft Spruce doesn't think they are. But neither are final authority.
Fuel lube is also sold as Parker "O" ring lubrication.
 
the two side by side. EZ turn & Parker "O" ring lube
 

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Tom-D said:
Just because Avial says they are doesn't make it so. Aircraft Spruce doesn't think they are. But neither are final authority.
Fuel lube is also sold as Parker "O" ring lubrication.
Click to expand...
Fuel Lube and EZ-Turn both meet the same MIL spec, G-6032. In fact, see if you can find genuine Fuel Lube anywhere anymore. I can't.

Fuel Lube is a polyester grease with propylene carbonate in it. Parker O-ring lube is a barium grease. Parker Super O-ring lube is a thick silicone fluid. All of them are totally different. And Seal Lube is another thing entirely: castor oil, zinc stearate, and paraffinic solvent.

https://www.google.com/url?sa=t&rct...antusage.pdf&usg=AOvVaw2zF4aMbZxX59TfPqZMZ376

https://p11.secure.hostingprod.com/@site.skygeek.com/ssl/MSDS/ezturn1lb.pdf

https://www.aircraftspruce.com/catalog/pdf/MSDSsealube.pdf
 
Dan Thomas said:
Fuel Lube and EZ-Turn both meet the same MIL spec, G-6032. In fact, see if you can find genuine Fuel Lube anywhere anymore. I can't.

Fuel Lube is a polyester grease with propylene carbonate in it. Parker O-ring lube is a barium grease. Parker Super O-ring lube is a thick silicone fluid. All of them are totally different. And Seal Lube is another thing entirely: castor oil, zinc stearate, and paraffinic solvent.

https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=3&ved=0ahUKEwjNu7Hr2IXcAhUoIDQIHeskBL0QFggzMAI&url=https://www.parker.com/literature/O-Ring%20Division%20Literature/Static%20Files/lubricantusage.pdf&usg=AOvVaw2zF4aMbZxX59TfPqZMZ376

https://p11.secure.hostingprod.com/@site.skygeek.com/ssl/MSDS/ezturn1lb.pdf

https://www.aircraftspruce.com/catalog/pdf/MSDSsealube.pdf
Click to expand...

Like I said to start, don't confuse the products
 
Lot's of great dialogue and certainly the experience of others was the feedback I was looking for. Thanks to everyone that replied!
 
If you use the wrong stuff, you die.
If you use too much of the correct stuff, you die too ;-)
 
I wonder how many guys who replied actually have built or installed an aircraft fuel system? I know a couple of the pro mechanics have and some of their replies have me scratching my head.
 
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