Best fuel line thread sealant?

[Steeveedee]

I'm not aware of a conical washer that is made for inverted flare fittings. The only ones I've ever used were for spacecraft fuel systems, where single flares were used. That use comes from aircraft use. I think that they (single Vs double flares) have a different flare angle, but I'm willing to be educated about that. The thing with copper is that it is malleable enough that it would conform to the slightly different flare angle. I would like to point out that if you use a copper conical washer, it is one-use only. Don't try and save money, for what they cost. Of course, at 7 PSI they'll probably seal again, But a spacecraft fuel system typically runs about 600 PSI. Aircraft hydraulic systems run much higher, and those washers just get tossed after removal.

[special-K]

I've clamped neoprene on straight cut fuel line with no leaking or blowing off issues. I'd be more concerned about the tube cutting the hose if not straight in line off of the union. As mentioned above, we are only talking approx 7#.

[Willie Makeit]

Teflon tape is NOT a sealer. It's purpose is to lubricate the threads in order to torque to proper specs without galling and to achieve a mechanical seal with the threads.

[davepl]

Originally Posted by Willie Makeit

Teflon tape is NOT a sealer. It's purpose is to lubricate the threads in order to torque to proper specs without galling and to achieve a mechanical seal with the threads.

"Thread seal tape (also known as PTFE tape or plumber's tape) is a polytetrafluoroethylene (PTFE) film tape commonly used in plumbing for sealing pipe threads."

You might be correct about how YOU use use, but it's still properly called PTFE Thread Seal Tape. I've been calling myself a plumber for over 40 years and selling sealants longer than that!

The tape is intended to seal in SPECIFIC applications, though in reality most applications people try to use it on here wind up being a flare or compression seal that the threads have no role in doing anything except clamping anyway.

So you're right that people here shouldn't call it thread seal the way they use it, but it still is called that, and particularly in LPNG, it's meant to seal in some cases.

[Willie Makeit]

Originally Posted by davepl

"Thread seal tape (also known as PTFE tape or plumber's tape) is a polytetrafluoroethylene (PTFE) film tape commonly used in plumbing for sealing pipe threads."

You might be correct about how YOU use use, but it's still properly called PTFE Thread Seal Tape. I've been calling myself a plumber for over 40 years and selling sealants longer than that!

The tape is intended to seal in SPECIFIC applications, though in reality most applications people try to use it on here wind up being a flare or compression seal that the threads have no role in doing anything except clamping anyway.

So you're right that people here shouldn't call it thread seal the way they use it, but it still is called that, and particularly in LPNG, it's meant to seal in some cases.

regardless of what you call yourself, Teflon tape is NOT a sealant. I'm not a plumber & not gonna get into a pecker measuring contest with you, but I do work for NASA and know a lil' bit about sealing pneumatic and hydraulic systems, specifically on flight hardware.

[special-K]

Originally Posted by Willie Makeit

Teflon tape is NOT a sealer. It's purpose is to lubricate the threads in order to torque to proper specs without galling and to acheive a mechanical SEAL with the threads.

Alright, I sure don't want to hop in this or see it continue on. But in the quote above it sure looks like a contradiction. Ok, so it's a component used in creating a seal. Is the tape a seal? No. Are the treads a seal? No. But Teflon tape used on threads creates a seal. The fact is it doesn't hurt to use it in this case, even if it's belts & suspenders. What is really needed is a correct fuel line.

[Sheepdip]

Originally Posted by Willie Makeit

Teflon tape is NOT a sealer. It's purpose is to lubricate the threads in order to torque to proper specs without galling and to achieve a mechanical seal with the threads.

^^^^^^^^^^^This is 100% correct^^^^^^^^^^^^^^^^

[davepl]

Give me an RO number you order it under at NASA. What's it called, Willie? Sealant.

[Willie Makeit]

Originally Posted by davepl

Give me an RO number you order it under at NASA. What's it called, Willie? Sealant.

NASA doesn't use RO numbers, sorry. But I can tell you that I just did a quick search and out of about 60-65 line item descriptions for TEFLON TAPE or PTFE, the word SEAL or SEALANT was not in any of them.

[davepl]

If you won't be specific I can't help you. There is a ptfe film tape used as a thread lubricant, but it's different from the thread sealing tape pictured here.

As for the stuff in this thread, https://en.wikipedia.org/wiki/Thread_seal_tape

[Willie Makeit]

Originally Posted by davepl

If you won't be specific I can't help you. There is a ptfe film tape used as a thread lubricant, but it's different from the thread sealing tape pictured here.

As for the stuff in this thread, https://en.wikipedia.org/wiki/Thread_seal_tape

I don't recall asking for any help. PTFE tape, regardless of name its sold under, is NOT a proper sealant for mechanically sealing threads.

[davepl]

Originally Posted by Willie Makeit

I don't recall asking for any help. PTFE tape, regardless of name its sold under, is NOT a proper sealant for mechanically sealing threads.

Wait, which kind isn't for thread sealing? The thread sealing kind or the film kind? Because there are two different types. See I was going to be all pedantic and helpful and give you an out whereby you're probably thinking of ptfe friction reduction film tape, but you doubled down, so... oh wait, I already did. But you're still a solid red X in the wrong column today.

I'll just leave this exerpt from 3M Part Number 48, their teflon thread sealant tape, which explains how it should be used. Reader can decide if what you're saying jives with the manufacturer:

"Scotch® Thread Sealant and Lubricant 48 is a white unfused plastic film made of polytetrafluoroethylene (PTFE). This fluorocarbon resin film tape designed to provide a leak-resistance seal when used as a pipe thread sealant."

I can guess the next steps, so I'll leave them to the reader as an exercise and take my leave... I don't personally use any of the stuff in fuel applications, for what its worth. Maybe on bushings and other tapered-thread stuff. Can't think of anywhere its under pressure through, in stock form I think it's all taper or clamp.

[Willie Makeit]

ok bud. you win, you got the last word.

[GRX]

Teflon tape does serve to lubricate threads. But not made for sealing? That is a new one. It is designed and used for that very purpose millions of times every day. Grades depending on application. Red for larger joints. Yellow for fuels, Green for sealing oxygen systems, and so on.

[davepl]

There are several types, as you note. It's quite possible that Willie is using a style intended only to prevent galling, and that has nothing to do with sealing. That's why I asked for the RO or part number early on to look it up instead of guessing.

I think the best answer is "it does both" but there are only certain applications where it's is appropriate as a sealant.

95% of the people using it on the threads have no idea that the seal is from a 45 or 37 degree tapered flange and not the threads anyway! Other than where your pipe nipple screws into the intake manifold for your heater hose... not many places.

[geezer#99]

Good info Dave!
Far too many people believe that if it has threads it needs sealer.
And the same people use a whole tube of silicone sealant where a thin bead is all you need.

[Mike_The_Grad]

In case this is still up for discussion. Try "lapping" the inverted flare portion of that brass fitting or any flare type of joint. How I usually go about it when I am either bending a premade length of steel tubing with tube nuts already installed, or creating a new inverted flare on a piece of steel tubing is: first use a tubing cutter. Take a rat tail file or round chainsaw file and ream the i.d. of the tubing. Then take a fine cut flat file and put a slight chamfer or bevel on the o.d of the tubing.(really only necessary for double flaring of lines.) Then put a thin smearing of high pressure wheel bearing grease on the conical flaring die.(also in tube bending channel if making a bend, it allows smooth operation of the bender and flaring die.) Onve the flare is made wipe with a rag, grab a piece of 1500 or 2000 grit paper and use your finger tip to work the flare smooth,wipe again and your done. On double flares I put a little water on the sand paper to help cut the seam joint down a little faster. But same result. Oh, and now I ALWAYS put those store bought premade pieces into my flaring block and "seat" the flaring die to ensure the flare is concentric. Meaning just enough pressure to ensure it's even. Or another suggestion if it's possible, is to make the flare nut joint up by hand then rotate the tubing into the joint, once you cant turn it anymore back it and the nut off a 1/4 turn then the tube a 1/4 turn beyond that and retighten by hand. I do this a couple of times at different spots on the tube. In my opinion, ever since I began doing these simple quick things, i have yet to have a leak. It's also important to use 2 wrenches when tightening a flare joint and as long as the wrenches are the correct size, dont be afraid to put some torque into it. If you start rounding the nut off, then you dont have the right wrench or the tube nut is cheap.