sealing NPT threads, is there research tape vs. sealer? 11

[kcj]

The perennial discussion of teflon tape vs. anaerobic sealants for NPT threads goes on forever on boards. My opinion, your opinion, etc.

Is anyone aware of actual test research between the various methods? Teflon tape, Loctite PST, Megaloc, Rectorseal, etc?

kevin j

 

[Compositepro]

It's kind of like asking who is the best rock band. The discussion can go on forever. I hope it doesn't.

 

[kcj]

yup, and me too.
The Ford/Chevy, Miller/Bud, whateere debates that go on forever and lead nowhere.
That's why I am looking for actual test data comparing something, instead of just 'we have always used this.....'

I expect somethere in the last decades Cat/GM/John Deere et.al. have researched this to death to make a corporate decision on what to use, but I have never seen any SAE or NFPS papers or presentations or articles in HP magazine. Seems awfully common and generic not to have been addressed many times. Even papers by those selling the sealant would help.

kcj

 

[Compositepro]

What kind of test data will prove which rock band is best?

 

[hydtools]

I have not seen any comparative test reports.

I chose one or the other depending. Stuff like Loctite PST for production line assembly. Tape on fittings that are oily as when doing repair. Tape requires care to not get it wrapped over the end of the fitting putting shreds into the system. Loctite PST can be messy if the person applies too much, especially on products delivered to customers.

I like being able to chose for my designs and after sale support. Both seem capable of creating a seal on pipe thread. I saw one guy use both together.

Ted

 

[Cervantis]

I would like to see comparative tests that would be fair and well supported. Tape works if it is wrapped enough times, but not to excess, and importantly in the correct direction. Wrapping tape the wrong way will make the tape less effective. We use a prebaked on sealant on our plugs, but now there is a debate on where and how much is applied on the plug. Is there any standard information on where the sealant is applied on the thread. Is there a starter thread that does not have the sealant or should it be applied and covered on all threads from top to bottom?

 

[zdas04]

I did a comparative study 12 years ago (had three different crews each use tape on one location, tape and teflon paste on the next, and Coppercoat on the third, then repeat on 70 locations total--all locations had a similar number of fittings of similar size). I was assembling the data when Purchasing weighed in with 200 cases of Coppercoat and wouldn't buy anything else. The preliminary look showed that one crew had zero leaks with any of the sealants. One crew had multiple leaks at every location with every sealant. The third crew did marginally worse with the Coppercoat, but the tape vs. the tape and paste was indeterminate since both had zero leaks. Made me think that the teflon paste was overkill as long as the crew was able to properly wrap teflon and any sealant applied with the proper torque would work approximately equally as well.

I know there are any number of other options for field assembly of NPT threads, but I picked the three that were used most often in this area.

I always wished I could have published the results internally before purchasing "helped", but once their decision was made it was final and publishing became counter productive.

David

 

[kcj]

helpful, best 'data' so far. roughly in line with what I see, but still hoping for published tests.
why need high paid engineers when we have purchasing to help out....

tks, kcj

 

[Cervantis]

I see the question is more of what causes leaks and what can be done to identify the actual cause. Education, informational sharing, and data exchange could save tons of dollars if this was addressed more. Maybe it is, but I have not been able to find the information I needed. This is the best place so far and the particpants that reply are brilliant.

 

[moltenmetal]

With a good sealant system, for the right services, threaded pipe can be a very reliable, flexible, inexpensive and useful method. Unfortunately, due to the lack of data and standards that we're discussing here, the method gets a VERY bad rap from a great many people.

Just like everybody else here, all I can give you is our own experience:

Tape alone is too dependent on the skill of the pipefitter in applying it, the quality of the threads and other factors. It's also susceptible to leakage after repeated thermal cycling because it has limited "memory". With machined threads, the right tape and a skilled fitter, tape alone can give high reliability joints. With Chinese 150# stainless fittings, Home Depot 0.25 s.g. garbage tape and pipe threads cut with dull tooling, it's a TERRIBLE sealant!

Anaerobic paste alone is far more idiot-resistant, provided you select the right paste for the service. People should STOP calling it "liquid teflon" or "teflon paste", because that's a terrible description for what an anaerobic paste is. These pastes have nowhere nearly the corrosion resistance or other properties of teflon- and most of them contain far more other stuff than they do teflon particles. It has other disadvantages including the mess factor- the affectionate name the fitters have for it is "bird sh*t".

We use heavy (at least 1.1 s.g.) tape with an anaerobic paste as a top dressing. We VERY seldom encounter leaks. The tape provides full coverage to the male threads which helps resist galling in stainless parts if the fitter gets a little too aggressive with the pipewrench. The paste does the rest and helps the joint resist vibration and thermal cycling.

 

[zdas04]

I called it "Teflon Paste" because it is white and says "Teflon Paste" on the can. My mistake.

David

 

[JLSeagull]

I use Teflon tape for my home projects. Among the reasons for paste is that some people overlap the end of the nipple or fitting with the tape and the excess gets into the pipe or tube and blocks small pneumatic or analyzer components. Done properly both are fine products. I never use copper but have used "Never Seize" for hot joints.

Yes this discussion can go on forever. And the best rock and roll band was Yes.

 

[Cervantis]

Kevin,

Did you ever get your orginal question answered? Or have you found out any more information that you can share. I am also looking for information on use of a combination of sealants for some NPT parts.

 

[rmw]

In some applications the use of tape is forbidden; instrument air being one that comes to mind quickly. Along that line, any piping where there will be small passages somewhere downstream that the tape can become clogged in. Excessive paste be it Teflon or faux Teflon can do the same if slopped on to heavily.

I work for a company that has a policy against tape altogether due to the fact that there are several systems that would be impacted negatively if tape shreds ended up downstream.

Any and most of the above mentioned methods in this thread are operator dependent. A good operator can make a good joint that will seldom leak, and a bad operator can take the best sealant system and end up with a leaky joint as "Z" has pointed out above.

rmw

 

[Ron]

One consideration I have not seen mentioned here is that of corrosion resulting from improper use of paste sealants. I have seen corrosion resulting from the use of cheap sealant and from sealant that was not appropriate for the application. Both were on black steel pipe (fire sprinkler pipe) and caused extensive corrosion issues. Pastes can also clog downstream orifices as well as tape (someone noted that before).

I have not seen tape cause or contribute to corrosion.

 

[zdas04]

Some of the metalic based (e.g. Copperkote) pastes can create a galvanic cell, but the conditions have to be exactly right (pH is a big determiner) for it to happen. I've only seen it once and that was in water service with a 6.5 pH.

David

 

[kcj]

tks for info so far. I have been monitoring responses but not commenting.
Still looking for actual test data, but the responses have been pretty much in line with my personal experience.
I use good quality thick teflon tape when working from the toolbox (usually hydraulics), and Loctite PST when in one place for house construction (low pressure water and gas). I have not tried using both at once.

I don't have as much faith in the skills and meticulous nature of our shop assemblers, so have been specifying PST for shop assembly.

For new designs, I avoid NPT if at all possible. SAE oring boss, ORFS, split flange, JIC, or some sort of oring flanged joint if possible.

but would still like to know how the big boys made their decisions.....

tks to all. kcj

 

[hydtools]

The big boys made decisions based on experience(tryng, failing, succeding), lacking any 'standards' which are really the general concensus of an industry based on the collective member experience.

Ted

 

[kcj]

exactly. that is the experiance base I was hoping to be written up somewhere, but I think it is also a proprietory information, competetive advantage, etc.

Most of the few remaining OEM NPT adaptors I have seen use preapplied anaerobic coatings. Maybe for performance reasons, or more likely assembly line and skill reasons.

tks to all for their comments. That represents many years of experiences and industries.

kcj

 

[InfinityTech]

Just to add my rather chaotic experience:

I'm developing a very compact plumbing product that uses over 40 1" stainless fittings in a space of about 12" x 18". I used Weld-On White Seal to assemble the entire assembly. Upon testing I discovered a large, depressing, number of leaks. As this is a product in development, I treated it like data and forged ahead. I assembled it again thinking I was focusing better. Again, a bunch of leaks. I did it a third time, this time applying a little thread sealer onto the female threads. Leaks! I don't know at this point if it is the Weld-On sealer or the stainless. My experience with stainless is somewhat short.

Next, I tried standard thickness hardware store Teflon tape. I wrapped each thread very carefully 10 times, assembled everything and got leaks. Fewer leaks, but leaks. I disassembled and reassembled again but this time with 15 wraps. This time there were even fewer leaks, but still - leaks.

As a final repair to the last few leaks, I again wrapped the nipples with Teflon tape 15 times and applied some of the same problematic Weld-On White Seal onto the male and female threads. This solved the immediate problem, but provided no real data.

In the past I used Slic-Tite sealer which overall had a good success rate. However, I never tried it with stainless steel.

Hope this adds to the body of knowledge and experience.

Mark