sealing fuel fitting threads

[gwoloshyn]

Im working on a new fuel system install and I have a few barb fittings that I need to seal. Is it safe to use a 3M scotchweld gasket maker adhesive to seal the threads? The tube says it is gas and oil resistant.

 

[gm280]

Re: sealing fuel fitting threads

Im working on a new fuel system install and I have a few barb fittings that I need to seal. Is it safe to use a 3M scotchweld gasket maker adhesive to seal the threads? The tube says it is gas and oil resistant.

Well that is a wide open question bound to stir the interest of folks. First of all, are any of your new threaded fittings tapered fittings? If so then nothing is needed. If not, you could use Teflon tape and move on. But that is just my opinion. I?m sure others will have their suggestions as well. Again there is no one way best type of answer... I tend to stay clear of adhesive type sealants just in case I have to one day take it apart...

 

[gwoloshyn]

Re: sealing fuel fitting threads

Yes all of my fittings are tapered, I think. They got tighter as I threaded them in so Im guessing they are.

So tapered fittings are guaranteed not to leak without anything sealing the threads?

 

[Grub54891]

Re: sealing fuel fitting threads

They shouldnt leak in theroy,you can use a sealant if you prefer,do not put it all the way to the butt end of the threads,it cuold get to the carbs.Do not use teflon tape at all either.If ya have a flare fitting,no sealer required,it flared fittings leak they need to be replaced.
Grub

 

[Silvertip]

Re: sealing fuel fitting threads

If NPT fittings were designed NOT to leak all the plumbing in your house that uses these fittings would not need pipe dope but they do by code in most areas. Any sealant you use that is gas and oil resistant would be a good bit of insurance since most of the fittings today come from gosh awful manufacturers in some offshore plant where quality control is very questionable.

 

[robert graham]

Re: sealing fuel fitting threads

I'd use that white teflon pipe thread dope/sealant...no teflon tape, as it can come apart like tiny "threads" of teflon, totally inert and capable of plugging any part of your fuel system.

 

[gwoloshyn]

Re: sealing fuel fitting threads

If NPT fittings were designed NOT to leak all the plumbing in your house that uses these fittings would not need pipe dope but they do by code in most areas. Any sealant you use that is gas and oil resistant would be a good bit of insurance since most of the fittings today come from gosh awful manufacturers in some offshore plant where quality control is very questionable.

The fittings I'm using are genuine Evinrude parts, so using those combined with a little 3M 847 I think I'll be in good shape!

 

[JoLin]

Re: sealing fuel fitting threads

I'd use that white teflon pipe thread dope/sealant...no teflon tape, as it can come apart like tiny "threads" of teflon, totally inert and capable of plugging any part of your fuel system.

What happens to dope if it enters the fuel system?

Not saying you're wrong, but I've never used anything BUT teflon tape on water and fuel fittings. Like everything else, there'a right and wrong way to use it. It needs to be placed carefully so that none of the tape extends past the threads, and only 2-3 turns of tape around the threads. If that doesn't seal it, there's a problem with the fitting.

 

[roscoe]

Re: sealing fuel fitting threads

What happens to dope if it enters the fuel system?

Not saying you're wrong, but I've never used anything BUT teflon tape on water and fuel fittings. Like everything else, there'a right and wrong way to use it. It needs to be placed carefully so that none of the tape extends past the threads, and only 2-3 turns of tape around the threads. If that doesn't seal it, there's a problem with the fitting.

And use the yellow tape for gasoline.

 

[Texasmark]

Re: sealing fuel fitting threads

Yes all of my fittings are tapered, I think. They got tighter as I threaded them in so Im guessing they are.

So tapered fittings are guaranteed not to leak without anything sealing the threads?

Pipe threads require a sealant. Reason is that the threads are not a perfect match, rather a close approximation. I just setup a new propane smoker and the directions said to use thread sealant.

I use TT on a lot of things, but when I am working with fuel, of any type, I use the paste with the dauber to apply. It states it's compatibility right on the container. Any hardware store has it. Service manuals for tractors say to not use TT on hydraulic fittings (they operate around 2500 psig). They instruct you to use the paste as the TT can get into the valving and get hung up causing leaking. I guarantee you that if you don't want a hyd fitting to leak you'd better seal it.

Mark

 

[Home Cookin']

Re: sealing fuel fitting threads

I was told not to use teflon tape b/c gas dissolves it and it gets into the system; use blue pipe dope in the tube instead.

 

[roscoe]

Re: sealing fuel fitting threads

Different teflon tapes are made for different applications.

•Water (Regular White)
•Steam (Premium Pink)
•Air, compressed (Premium Grade)
•Alcohols (Premium Grade)
•Fatty Acids (Premium Grade)
•Kerosene (UL Yellow Gas)
•Natural Gas (UL Yellow Gas)
•Nitrogen (UL Yellow Gas)
•Acids, dilute (Premium Grade)
•Ammonia, liquid (Premium Grade)
•Cutting Oils (Premium Grade)
•Soap, Liquid (Premium Grade)
•Ethylene glycol (Premium Grade)
•Gasohol (UL Yellow Gas)
•LPG (Premium Oxygen)


White Standard Grade PTFE Thread Sealing Tapes - Seal Tape

 

[seahorse5]

Re: sealing fuel fitting threads

The reason not to use pipe tape is the problem with tiny threads contaminating the fuel system WHEN YOU REMOVE THE TAPE-THREADED FITTING, not when it is first installed.

 

[gm280]

Re: sealing fuel fitting threads

As I originally stated, this subject would stir up the folks. I see so many different opinions and knew it would get them too. I have used teflon tape (in different colors for different applications) for years and have never had any problems. And contrary to what other s state, I'll continue using TT too... It has worked for me quite well without one issue...ever...JMHO!

 

[Texasmark]

Re: sealing fuel fitting threads

I was told not to use teflon tape b/c gas dissolves it and it gets into the system

I think I read that too. However, the paste I use that is suitable for all kinds of pressures and fuels has some in it to help lubricate the threads when tightening. This paste is off white in color.

Mark

 

[Lightning1]

Re: sealing fuel fitting threads

I have always used Permatex #2 non-hardening

 

[Outsider]

Re: sealing fuel fitting threads

So tapered fittings are guaranteed not to leak without anything sealing the threads?

Nothing is guaranteed to NOT leak, but tapered threads are designed to be leak resistant. Install 'em, if they leak take remedial action. If they don't leak, they ain't broke ... :joyous:

 

[dingbat]

Re: sealing fuel fitting threads

Common American National Standard Pipe Taper Threads

• NPT - National Pipe Thread Taper
• NPTF - Dryseal American National Standard Taper Pipe Thread (ANSI B1.20.3)

NPT threads may be referred to as MPT ('Male Pipe Thread'), MNPT, or NPT(M) for male (external) threads, and FPT ('Female Pipe Thread'), FNPT, or NPT(F) for female (internal) threads. Note that FPT and MPT are not authorized designations per the ANSI standard.
For NPT threads a sealant compound or Teflon tape must be used for a leak-free seal. For NPTF no sealant is needed for a sealing


The taper on NPT threads allows them to form a seal when torqued as the flanks of the threads compress against each other, as opposed to parallel/straight thread fittings or compression fittings in which the threads merely hold the pieces together and do not provide the seal. As the thread body is tapered a larger diameter keeps compressing into a smaller diameter and finally forms a seal. This means that NPT fittings should be lubricated using a lubricating material like lubricating paste or tape. The use of tape also helps to limit corrosion on the threads, which otherwise can make future disassembly nearly impossible.

A semi-compatible variant called National Pipe Taper Fuel (NPTF), also called Dryseal American National Standard Taper Pipe Thread, defined by ANSI B1.20.3, is designed to provide a more leak-free seal without the use of teflon tape or other sealant compound. NPTF threads are the same basic shape but with crest and root heights adjusted for an interference fit, eliminating the spiral leakage path.

 

[JoLin]

Re: sealing fuel fitting threads

The reason not to use pipe tape is the problem with tiny threads contaminating the fuel system WHEN YOU REMOVE THE TAPE-THREADED FITTING, not when it is first installed.

I understand the concern. I'm sure that could happen to somebody who doesn't know enough to clean the fittings before putting things back together. But I always knew that.

As amply demonstrated, it's a debatable topic.