Thread sealants on NPT and others?

[Sodo]

I do as well but I never wrap the tape over the last 1/16" of the threads.

yep.....it's for tapered threads......just about "ONLY" for sealing tapered threads.
Pay attention to keep it out of servo valves, and understand that it causes trouble on the internets.

 

[jrsavoie]

I will defer to Parker on this, I know that they have done testing to determine the best way to seal fittings.

This is what they state for O-ring Boss. R4
Inspect components to ensure that male and female port threads and sealing surfaces are free of burrs, nicks, and scratches, or any foreign material.
2. If O-ring or seal is not pre-installed to fitting male port end, install proper size O-ring or seal, taking care not to damage it.
3. Lubricate O-ring with light coating of system fluid or a compatible lubricant to help the O-ring slide past the port entrance corner and avoid damaging it.
4. Screw fitting into port and tighten to proper torque from the appropriate table located on pages R5 - R6

Below is for JIC R26
Torque Method
With proper tube fl are alignment with the nose of the fitting, tighten the nut to appropriate torque value in Table R23. This method is fast and accurate when preset torque wrenches are used. Consistent component selection is recommended so that the effects of dissimilar plating is not an adverse factor in joint integrity. This makes it desirable for high production assembly lines. However, a joint assembled using the torque method
can only be checked for proper tightening by torquing it again.
Note: This method should not be used if the type of plating on the fitting and mating parts (sleeve + nut or hose swivel) is not known. The torque method should not be used for lubricated or oily parts as improper clamping forces may result. Over-tightening and fitting damage may occur as a result

All straight thread fittings have this note.
Assembly Torque: Torque values are for unlubricated carbon steel components and properly lubricated stainless steel components. All stainless steel Triple-Lok tube nuts have an anti-seize lubricant to prevent galling during assembly.
No additional lubricant is needed unless the tube nuts are washed or heated above 150ºF. Stainless steel fittings use the upper limit of torque range

Pipe Thread R7
The proper method of assembling tapered threaded connectors is to assemble them finger tight and then wrench tighten further to the specified number of turns from finger tight (T.F.F.T.) given in Table R5. The following assembly procedure is recommended to minimize the risk of leakage and/or damage to components.
1. Inspect components to ensure that male and female port threads and sealing surfaces are free of burrs, nicks, scratches, or any foreign material.
2. Apply sealant/lubricant to male pipe threads if not pre- applied. For stainless steel fittings, the use of Parker Threadmate sealant/lubricant is strongly recommended.
(Pre-applied dry sealants are preferred over other sealants). With any sealant, the first one to two threads should be left uncovered to avoid system contamination.
If PTFE tape is used it should be wrapped 1-1/2 to 2 turns in clockwise direction when viewed from the pipe thread end.
Caution: More than two turns of tape may cause distortion or cracking of the port.
3. Screw the connector into the port to the finger tight position.
4. Wrench tighten the connector to the appropriate T.F.F.T. values shown in Table R5, making sure that the tube end of a shaped connector is aligned to receive the incoming tube or hose assembly. Never back off (loosen) pipe threaded connectors to achieve alignment.
5. If leakage persists after following the above steps, check for damaged threads and total number of threads engaged.

https://www.parker.com/content/dam/Parker-com/Literature/Tube-Fittings-Division/4300_Catalog_Cover.pdf

I was surprised about the comment for tape so I looked for another reference.
Rhino Ag in reference to installing hoses on a loader.
Apply sealant only to all tapered threads unless coupled with swivel adapters. When using Teflon tape, wrap tape clockwise (as viewed from end) and wrap only twice. Keep sealant away from first two threads of tapered end to prevent contamination of hydraulic fluid. Do not use sealant on O-ring or flare adapter threads.

https://www.rhinoag.com/wp-content/uploads/2017/03/2-7531-VALVE-PLUMBING-KIT-03-31-10.pdf

Based off what the manufactures state we should be assembling straight thread fittings dry and using pipe dope or tape on tapered threads. I was surprised that tape is an approved method of sealing. The folks at parker know more about sealing threads than almost anyone on the forum and have spent thousands testing the best methods. Feel free to link to reliable sources that state otherwise. The tape for tapered threads was new to me and I have been advising clients that tape was evil for years....

I see tape as safe until it has to be taken apart.

I don't know that I have ever seen a tapes joint, that didn't have tape residue inside the fittings on disassembly.

I can see how the tape residue could easily get in the oil upon reassembly.

It's very hard to make sure every little bit is removed.

This leads me to be anti tape for those types of fittings.

 

[Sodo]

jrsavoie your points are good.
Some items, the tape is of no concern. For example a simple gearbox.
But in some hydraulics circuits, cleanliness is crucial.

And when you see tape on a machine,,,,
and a crucial function is behaving like there is contamination,
to suspect the tape is logical.

But excess liquid sealant can shed residue into the system as well.

 

[jigs_n_fixtures]

If you use Teflon Tape, use the Yellow tape intended for gas and fuels. The white and pink will break down when exposed to hydrocarbons, including hydraulic and motor oils.

 

[joea99]

I don’t know that there’s a “right” answer with NPT. Pipe threads seal by deforming the threads EVER so slightly … Teflon tape actually functions as a lubricant more than as a sealant. Reducing friction between threads to achieve the right torque.

There is certainly a right answer with JIC and O-ring fittings. The seal is created by
-the two tapers coming together in the male and female (JIC)
-or the o-ring being squished “just enough” in O-ring boss or face seal
In either, the threads are just there to clamp. Threads hold the connection mechanically but there is no sealing done at threads.

If you THINK glopping stuff on threads in such instances “helps”… it’s at best a band aid for a damaged fitting or cut oring that needs replaced. If fluid is even GETTING to the threads when tight, you got bigger problems, and spackling over the threads isn’t a proper repair. Or safe.

If you’re worried about fittings coming loose, you don’t have a loctite issue, you have a torque issue. Or you have a hose installed with a twist in it that’s trying to loosen your connection under vibration or whatever

My only thought to "sealants" on non NPT fittings is not to seal but to prevent or reduce corrosion on the threaded, non sealing, parts. I've had a hard time removing some that lived out in the weather for years.

I'd never use anything other than hydraulic fluid on oring/mating surface or JIC mating surfaces.

 

[LittleBittyBigJohn]

For NPT fittings I've always just used some sort of PTFE pipe dope. Right or wrong I was told that the dope or tape on NPT fittings was basically just a lube to allow you to get the fitting tight enough to seal. I was also told that dope will dissolve in a hydraulic system. I just took it that the info was correct? I have used teflon tape on a black pipe fitting because I had it handy. It leaked and I tightened it for all I was worth and could not get it to quit. Found some dope, pulled the fitting apart, pulled the tape and added dope, re-assembled and no more leak.

 

[DarkBlack]

jrsavoie your points are good.
Some items, the tape is of no concern. For example a simple gearbox.
But in some hydraulics circuits, cleanliness is crucial.

And when you see tape on a machine,,,,
and a crucial function is behaving like there is contamination,
to suspect the tape is logical.

But excess liquid sealant can shed residue into the system as well.

I mostly agree. If someone is sloppy applying ptfe tape, causing issues, they’re the type of person who would also apply another sealant/lubricant sloppily too. I’ve seen sloppy applications of joint paste compounds that caused internal damage to parts of machines.
Good high pressure designs don’t employ NPT anyway, so it shouldn’t be a factor.
When someone learns how to properly apply teflon tape on low pressure NPT threads , it’s an easy, reliable, repeatable skill that someone can use thousands of times over a career, with great results

 

[joea99]

For what it's worth, when I first started working on my own tractor, "before I knew better", all the NPT joints I made up dry. Cleaned, but dry. Mainly because I did not see any sealant at all on the existing fitting.

Always just "good'n'tight". Can't recall a leak. But it always kind of bothered me, so embarked on a journey to "educated myself".

 

[WranglerX]

If you use Teflon Tape, use the Yellow tape intended for gas and fuels. The white and pink will break down when exposed to hydrocarbons, including hydraulic and motor oils.

Actually NOT quite true........ Yellow PTFE tape is for Natural Gas and Propane lines, not fuel/oils ...

Thread seal tape - Wikipedia

en.wikipedia.org

 

[WinterDeere]

Based off what the manufactures state we should be assembling straight thread fittings dry and using pipe dope or tape on tapered threads. I was surprised that tape is an approved method of sealing. The folks at parker know more about sealing threads than almost anyone on the forum and have spent thousands testing the best methods. Feel free to link to reliable sources that state otherwise. The tape for tapered threads was new to me and I have been advising clients that tape was evil for years....

Good post. Only NPT (tapered pipe) receives a thread sealant, as it has a spiral leak path formed by the flattened crest and filleted root of the thread. The sealant (tape or dope) is designed to fill this spiral leak path.

NPTF is a special variant of NPT, and can sometimes mate without leaking, as the crest and root are better matched to eliminate the classic NPT spiral leak path. But even there, sealant is recommended to provide sufficient lubrication to draw the tapered threads tight.

All other fittings, such as JIC, ORFS, and ORB, do not get thread sealant. The thread is not the sealing mechanism in these fittings, but rather only provides the mechanical clamping means, holding the two halves together around the o-ring or tapered cone seal. Using thread sealant on these fittings is more likely to cause, than to resolve, any problems.

As to tape versus dope, both work equally well, when used properly. The reason "tape is evil", is because it takes more skill to properly apply it, and so many do it wrong. Any idiot can slather dope on a fitting, and so it's become the preferred method, for most.