Tape, dope or both for black pipe for compressed air

[SouthernIllinois]

I am using Rapid Air rigid aluminum piping for most of my compressed air plumbing but I will have some black pipe pieces.

What is consensus on sealant on the unions/joints?

Tape, pipe dope or both?

TIA

 

[Mr onetwo]

since this is not a production setting...clean the threads with Brake-Kleen, very thin coat of Blue Monster and 2 wraps of good teflon

 

[PCustoms]

Good pipe, good fittings and a little sealant.

Wipe the joint after you tighten it.

 

[NUTTSGT]

I forget what I used on mine but seems to do okay. I could probably look back though my Refurb thread and find out.

 

[PopcornSutton]

I use Oately pipe joint compound w/ teflon on any joint threaded I make. Especially with dissimilar metals. And while it isn't needed in most people's opinion, I use a light coating on coolant hoses when assembling. Even if the hose relaxes some in time under the clamp, it still holds.

 

[beltfeed]

If you have a bench grinder with a wire wheel on it use it to clean and de-bur all the male threads. Today's iron pipe and fittings are all imported from china or worse. The threads are very rough cut. Wire wheeling them smooths them out a lot and they seal much better. Sometimes I also will run a pipe tap into the fittings to clean the female thread out also. If the threads are smooth and clean, tape or pipe sealant will work fine.

 

[ZX3ST]

While I'm a sparky and don't deal with this type of stuff directly, I can share this: my company specifies to NOT use tape on any air/gas piping as bits of it tend to end up in equipment over time. Dope only.

 

[BrandonV]

Clean threads & quality dope.

I could turn that into a rap song.

 

[Packard V8]

My dad was a union pipefitter. He wiped with dope and then wrapped with tape, "If there was anything else, I'd be puttin' that on there too. You never want to have to come back to a job you did because of a leak, especially if it's 6" diameter and 50' in the air."

jack vines

 

[Fixr]

On pneumatic fittings, I mostly use a Loctite thread sealant that's made for hydraulic fittings. I've had both tape and pipe dope find their way into places where they don't belong.

 

[u2slow]

I'm in the both tape & dope camp. Especially so with iron and stainless.

 

[TurnipTruck]

American pipe cut with good dies screwed deep into American 3000psi fittings with five wraps of Blue Monster tape held back one thread from the tip, then whatever pipe dope is laying around. This air system would hold pressure for at least three months until I hooked up the most recent air hose reel.

 

[The Cobbler]

American pipe cut with good dies screwed deep into American 3000psi fittings

overtightening can cause leaks too . infact it's one of the most common reasons for leaks

 

[finn]

No tape. Might be ok in some places, but the last thing you want is tape strands in your paint gun or air tools.

The Blue stuff works well, although I typically use Oatey with the teflon paste, or whatever Menards has on the shelf. Resist the urge to buy large bottles if it’s a small project. The shelf life isn’t infinite.

Whatever you do, don’t use tape on Diesel fuel systems.

 

[andyvh1959]

Pipe tape or dope is fine, never had an issue with either on home plumbing, air systems. On anything hydraulic I don't use tape, only a thread sealant like Loktite. Problem with pipe tape is people figure two wraps is good, so four wraps must be better. Nope, two wraps does it, and the tape should be applied above the last thread on the male pipe. The first two threads of pipe thread thread do notihng for sealing, so no need to apply tape that far down on the tapered threads. And apply the tape CCW when looking at the end of the threads, so as the threads are turned in the tape doesn't get twisted off the threads.

 

[Junkdrawer Dog]

The last time I had a plumber out to do some work, he used both.

 

[The Cobbler]

The first two threads of pipe thread thread do notihng for sealing, so no need to apply tape that far down on the tapered threads. And apply the tape CCW when looking at the end of the threads, so as the threads are turned in the tape doesn't get twisted off the threads.

actually the first threads on the pipe are the perfect threads and infact do the sealing.
you mean wrap the tape CW so it wraps with the fitting

 

[grissom]

Good pipe, good fittings and a little sealant.

Wipe the joint after you tighten it.

American pipe cut with good dies screwed deep into American 3000psi fittings with five wraps of Blue Monster tape held back one thread from the tip, then whatever pipe dope is laying around. This air system would hold pressure for at least three months until I hooked up the most recent air hose reel.

So exactly where does one get quality pipe especially American made?

 

[PCustoms]

So exactly where does one get quality pipe especially American made?

I bought all my black iron for my gas lines at FW Webb, didn't have any issues.

Occasionally I buy pipe at home depot for small things, those threads look and feel like **** and usually want to weep.

 

[TurnipTruck]

So exactly where does one get quality pipe especially American made?

There is enough heavy industry supply around me that I bypass the residential and even the commercial supply houses and go the dedicated pipe and fitting businesses like Pacific Pipe&Supply or the larger hydraulic shops. Ferguson has some adequate pipe and OK fittings but won’t/can’t get the really stout fittings. Home Depot iron fittings have too many porosities and inclusions to be anything but shelf brackets.
Employee discounts and knowing people helps. Access to Dumpsters and industrial scrapyards helps a lot, too.

Five threads in, two threads showing.

 

[housewolf]

I started running screw pipe in 1978 using pipe dope only. Never found a more successful method. Good threads and good fittings don’t require good luck. Rectorseal #5 is my preferred pipe dope but it’s certainly not the only high quality dope out there. T plus 2 (rectorseal) & leak lock (blue stuff) are good too. I’ve used permatex for gasoline and fuel oil piping. Air/NG, rectorseal #5.

ETA; IME; the quality of the pipe/fittings and the country of origin have surprised me as often as not.

 

[twistedstang]

Union pipefitter here. The biggest variable is how the threads were cut. You should be able to spin a fitting onto the threads 3 to 3.5 revolutions by hand with no dope to check the settings. I like three wraps of tape and then a quality dope like loctite 567. It comes in a squeeze tube and smells great.

The argument against tape is it can plug a small orifice if it gets inside the pipe. Start your wrap 1 thread back when you wrap and wrap it clockwise so it doesn't come undone as you thead on a fitting.

 

[imagineer]

I used both when I did the compressed air loop around my pole barn (probably 9 or 10 years ago), and there are no leaks.

Regarding the tape, I didn't twist it to fit into the threads, but like mentioned, no leaks. For tape, i used basic plumbers tape (the white stuff). I don't recall the brand of pipe compound, but the stuff I used was yellow.

 

[Nvrplzd]

I’m in the same camp with a quality pipe thread tape and little bit of dope. Never have been a fan of the cheap pipe tape found in abundance at your big box stores

 

[4x4Pete]

Having dealt with threaded pipe fittings under high pressure, I suggest cleaning the male threads with a wire brush, then using the thickish pink teflon tape one (or two) threads back, wrapped clockwise, and then gently run the tape into the threads with the little lip on the tape roll cover (that's what its for). Add a small brush wipe of pipe dope, using a teflon variety as well, keeping the dope 3 threads back from the end. Tighten the joint firmly but not excessively. I have been successful in sealing a threaded y strainer thousands of times under 500 psi of water pressure leak free with a 12" pipe wrench. This strainer needed to be opened every 2 weeks to remove debris from it. If you were to get aggressive tightening it, good luck getting it back open without a 48" pipe wrench. For reference this was for a cooling loop that provided water to computer room cooling equipment. On the 3rd floor of a 85 story building. Static water pressure was just shy of 500 psi.

 

[Crazyjake8493]

Can't hurt to use both. Rectorseal and Blue Monster tape, not the cheapo white tape.

 

[RegeSullivan]

I did miles of residential gas pipe with my dad when I was a kid. He would call out the length, I'd cut the threads (no power vice) he would twist them together. Used tape then Teflon pipe thread compound. Never had a leak that wasn't a bad fitting. It was very rare but occasionally you would get a fitting that had a pin hole... of course that was my fault for not checking it.

 

[andyvh1959]

actually the first threads on the pipe are the perfect threads and infact do the sealing.
you mean wrap the tape CW so it wraps with the fitting

Maybe I need to clarify. The first threads I refer to are the smaller diameter at the begining of the taper, not the largest diameter at the bigger end of the taper. The 1st thread at the smaller diameter do little anything for sealing.
The OD of NPTF is measured on the 4th thread of the tapered thread, so the 1st and 2nd thread are smaller OD.

 

[Firebrick43]

Good pipe, good fittings and a little sealant.

Wipe the joint after you tighten it.

They days of good pipe are gone. We tried to source some USA made pipe a few years ago and couldn't. The Turkish pipe seemed to be better than the chinese pipe but not nearly as good as the old USA pipe that we saved if we had to take any down just to make small custom length end pieces as the other stuff threaded so poorly on the power threader even with new dies.

Anvil and ward still make excellent USA fittings however.

We always used monster tape and locktite 567 dope. On gas pipe rector seal #5

 

[Steve_P]

Teflon tape. I had one doped fitting after another fail over just a few months until I replaced it with tape. This is on 150+ PSI air lines, not natural gas. The high air pressure would blow the dope out over time. I was standing next to a fitting and actually saw it happen. 20 years later and no failures of the taped joints.

 

[rharman]

I despise plumbing work. But, when I have to do someting, I've had the best results with RectorSeal #5.
I really don't like teflon tape. But, I know I'm in the minority there.

 

[Dagny]

Fayett black pipe top notch ward and anvil fittings rectors no 5 dope. for high pressure it always works better if it can set a few days. the rectors no. 5 seems runny now days so I like to leave the cap loose for a few days but not in the truck. bad mess if it tips over.

 

[Dagny]

wheatland pipe is also usa

 

[Farmall450]

While I'm a sparky and don't deal with this type of stuff directly, I can share this: my company specifies to NOT use tape on any air/gas piping as bits of it tend to end up in equipment over time. Dope only.

Hold it back 2 threads. A good practice in general.

 

[Firebrick43]

wheatland pipe is also usa

At the time we could get wheatland ridged conduit but not A53 pipe?

 

[bluedog225]

Subscribed. Good info. Thanks

 

[The Cobbler]

Maybe I need to clarify. The first threads I refer to are the smaller diameter at the begining of the taper,

yes, they are the perfect threads and do the sealing...

 

[kwb]

Rectorseal no 5

 

[Death Row Dave]

Worked 36 years Stationary Engineer , good threads equal good seal . There is a great difference in the brands of tape you choose to use also . Yellow John Crane is the best I have ever used . We used Rector Seal with Teflon by the gallons also . We also had some type of sealer can not remember the brand , it dried metal to metal contact only . Once this stuff set it was as welded . The salesman said “ it will seal 150 lbs hand tight on 1 in fittings .” So I made some test stuff up , applied sealer and hand tight allowed to set over night . I pressure tested to 200 lbs . Guess what ? No leaks ! I then proceeded to tear down my test fittings and crushed a 1 in ****** with a 24in wrench , before it would turn to loosen , remember it was hand tighten . This is the stuff you see years ago on GM manual trans , instead of gaskets . I used it for years on fittings in steam process I knew that would never be removed again.

 

[housewolf]

I’m not exactly sure how it came to be, maybe experience(?), but over the years (40+) we came to use different pipe dope for different product. We always used Key Tite for steam.

Brazing threaded adapters on copper for medical gas equipment connections is probably the trickiest threaded connection I’ve ever encountered. Brazing anneals the copper so the threads eventually compress and begin leaking. We had some headwall units show up once that included green loctite for thread sealer. It worked great, is approved for O2 use, but you’re never taking it apart again without risking damage to very expensive equipment. Expando - powder mixed with water, is my go to now for something problematic. It never leaks and disassembly isn’t an issue but if I have a problem I’d rather address and correct the problem if possible. I don’t consider using a better sealing dope correcting the problem (bad threads/fittings) except in a very rare instance.