Teflon tape a no no?

[3RRL]

I have used both tape and paste and found I am as dumb with either one. Some good, some leaky ones. But I have had especially good luck with gas (yellow) teflon tape. It is a much thicker tape and seals with excellence. Just be sure you use your head when applying either ... taking care NOT to get any into the hydraulic system. Clean hydraulic fittings are a must.

 

[Wayne County Hose]

Now, after I let this thread go for a while, I'll tell you this. For my own stuff, I use just a tiny bit of lubricating oil. I only use a sealing agent on customers units. Why? they think that if you didn't put something on it, it will leak. Think about this, do you honestly think a little tape is going to hold back 2500 psi? NPT makes it's seal by mashing the metal of the 2 fittings together, this is what makes the seal. Tape or paste doesn't help. Call me crazy, you aren't the first. Don't believe me, try it. The only thing tape or paste does over a dry fitting is lubes the threads to make the fittings turn easier to engage more threads. A little oil does the same. Ever look at a male NPT fitting after tape was applied, assembled, then taken apart? Where is the tape? In the voids of the threads. The voids is not where the sealing takes place.

Try something if teflon tape is such a good high pressure sealer. Put some teflon tape on the sealing surface of any other fitting. Try using it in place of an o-ring on a fitting. Mash it in there as tight as you can, it will leak. I repeat, teflon tape will absolutely not hold back 2500 psi. Teflon tape was developed for use in low pressure water lines and propane/natural gas applications, all well under 100 psi.

The only sealing agent that will help NPT is something that you assemble with no oil flow allowed until it can cure. Otherwise, you're fooling yourself. I know that some "engineer" may tell me all kinds of reasons why I'm wrong. But this is a person that spends too much time with his head in a book and probably doesn't own a wrench.

 

[SPYDERLK]

Now, after I let this thread go for a while, I'll tell you this. For my own stuff, I use just a tiny bit of lubricating oil. I only use a sealing agent on customers units. Why? they think that if you didn't put something on it, it will leak. Think about this, do you honestly think a little tape is going to hold back 2500 psi? NPT makes it's seal by mashing the metal of the 2 fittings together, this is what makes the seal. Tape or paste doesn't help. Call me crazy, you aren't the first. Don't believe me, try it. The only thing tape or paste does over a dry fitting is lubes the threads to make the fittings turn easier to engage more threads. A little oil does the same. Ever look at a male NPT fitting after tape was applied, assembled, then taken apart? Where is the tape? In the voids of the threads. The voids is not where the sealing takes place.

Try something if teflon tape is such a good high pressure sealer. Put some teflon tape on the sealing surface of any other fitting. Try using it in place of an o-ring on a fitting. Mash it in there as tight as you can, it will leak. I repeat, teflon tape will absolutely not hold back 2500 psi. Teflon tape was developed for use in low pressure water lines and propane/natural gas applications, all well under 100 psi.

The only sealing agent that will help NPT is something that you assemble with no oil flow allowed until it can cure. Otherwise, you're fooling yourself. I know that some "engineer" may tell me all kinds of reasons why I'm wrong. But this is a person that spends too much time with his head in a book and probably doesn't own a wrench.

Ill try to limit it to a few:
1. Dont compare teflon tape to a gland. They work differently. An oring is elastic and moves in response to system pressure forcing it into whatever gap exists on the lo pressure side. The more pressure the more it is pressed into the gap - a living seal capable of tremendous pressure if the gap is small. Movement of the sealed parts is relatively unimportant.
2. Teflon is a non elastic gap filler. It is ideal for a tight fitting totally immobile joint such as is made with NPT. The teflon is squeezed down to near zero thickness in the majority of the thread, flowing under assembly forces to fill all imperfections and voids in the threads. It will make the difference between a fitting that remains totally dry and one that dust will stick to. It will seal to very high pressure, but only when very thin and over a broad expanse in an immobile joint. If the distance thru the sealed expanse is too short the teflon will slowly flow out of the joint under high system pressures.
3. Using teflon tape in joints for which it is not suited reflects less on the tape than on the understanding of the user.
4. Books and wrenches are not exclusive.

larry

 

[Wayne County Hose]

I think that I have a pretty good idea how fittings make their seal. The point I was trying to make is that teflon is a lubricant, not a sealer. It simply helps the threads engage further which is what makes the seal, not the tape.

I have also made many a NPT connection with just a little oil, nothing else on the threads. I've never had a sealing issue and I've never had to overtorque to obtain a leak free connection.

I'm not saying that I am right and anyone else is wrong. If it doesn't leak and there's no problems, then whatever you did is right.

This is just simply my opinion based on experience.

 

[bjcsc]

But I have had especially good luck with gas (yellow) teflon tape. It is a much thicker tape and seals with excellence. Just be sure you use your head when applying either

Agreed. I tried the paste and just like JerryG, 2 out of 3 leaked. The yellow gas line tape is all I use now and I think it works great...

 

[QRTRHRS]

I think that I have a pretty good idea how fittings make their seal. The point I was trying to make is that teflon is a lubricant, not a sealer. It simply helps the threads engage further which is what makes the seal, not the tape.

I have also made many a NPT connection with just a little oil, nothing else on the threads. I've never had a sealing issue and I've never had to overtorque to obtain a leak free connection.

I'm not saying that I am right and anyone else is wrong. If it doesn't leak and there's no problems, then whatever you did is right.

This is just simply my opinion based on experience.

I agee with Wayne County Hose. Teflon tape is a thread lubricant.

I used a couple of wraps on my hydraulic threads but then if I make repairs, I take my time cleaning the threads of shredded teflon.

The only time that I use paste is on the female side of water pipe and then I still use teflon on the male end.

 

[Leejohn]

NPT doesn't need a sealer. The main reason NPT leak is because it is tapped to deep. And 2nd the metal taring as it is tighten down. So I guess anything you use might keep the metal from taring, but if tapped to deep you need a filler.

 

[woodlandfarms]

So this is why the local hose shop said first time connection do not put anything on, but if I remove and re-attach then put some teflon tape on the threads?...

 

[Leejohn]

That sure is a good reason to use something. Just a note a don't like the tape thing, there sure are a lot of better stuff around.

 

[swampvol]

At about 20 hrs I had a leak on the fel. Instead of taking it to the dealer I just re-taped it myself. I no I didn't start a thread back, as a matter of fact I'm sure I started at the tip.

I changed the fluid at the 50hr mark and now I'm at 80 and am wondering if I should back the fitting out and tape it the right way. Easy to do, but with my luck I'll end up cross threading the fitting.

So, if the tape was to get into the system wouldn't it have done it by now, or should I re-tape it???