Leaks in Air Compressor Lines - Black Iron Pipe

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Hi Gang
I've nearly completed my stationary compressor system, and I go to fill it with air and am greeted with a hissing sound from (at least) two locations. Luckily, I added enough unions to allow me to tighten and such, but my first attempts at tightening have done little good.
1.) Should I not have pressurized the lines until allowing the pipe sealant to firm up overnight. (does it even firm up?)
2.) Should I not have bought the pipe at Home Depot? It's probably made in China, and a poster warned me about that.
3.) How much torque is necessary to seal the joints? I cranked pretty hard on most of the joints. Is it possible to overtighten?
Any suggestions would be helpful. I guess as a last resort I could have a buddy come by and weld the problem joints, but that seems extreme.
Cheers Joe
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Probably should have used teflon tape instead of thread compound
John
On 19 Jan 2004 15:25:26 -0800, snipped-for-privacy@execpc.com (BIG JOE) wrote:

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IME, Teflon tape is not good for gas lines. I put one in my house using black pipe and Teflon tape; I couldn't get the joints to seal, even when I applied enough force with a pipe wrench to make the pipe egg-shaped.
I had to take the line apart and use pipe dope. That worked like a charm.
Bob S
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Was this gas, an in natural gas? There's a special yellow Teflon tape for that.
GTO(John)
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On 21 Jan 2004 02:22:33 GMT, snipped-for-privacy@aol.com (GTO69RA4) wrote:

It was natural gas. I was using the wrong kind of Teflon tape. But ... if it won't seal air (used for the pressure test) at 15 psi, how well does it really seal. Does Teflon tape depend on the surface tension of water to seal?
Bob S
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I use teflon tape to seal threads in 100+ psi lines. water isn't necessary for the tape to work, Bob.
dave
Bob Summers wrote:

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Dave
I use teflon tape on HP lines (3000psi and above) and they seal just fine.
John

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I haven't worked with that much air since working on F-106's
dave
John Crea wrote:

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Sounds like your joints were bad or you weren't using enough tape. I've used it for my 120+ PSI air systems for years. So has everyone else I know.
GTO(John)

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I use Gasoila soft set with PTFE:
http://www.gasoila.com/gasoila /
It's the blue can, works on about everything.
I elbowed and extended the drain valve in my 175 psi compressor, occasionally I will twist the elbow in the bottom of the tank when turning the drain valve, apparently it's not very tight. It has yet to spring a leak.
--
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Mark

N.E. Ohio
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1) The sealant should not need to set overnight to work. 2) HD's black pipe is just fine. 3) Apply enough torque necessary to achieve a seal. Just gonna have to tear back to the failed joints, re-apply thread sealant, and maybe cap off just after to pressure check before piping any further. I feel your pain...Tom Joe wrote:>Hi Gang

Someday, it'll all be over....
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I agree with Tom. The joints will have to be tightened until there is very little of the cut thread left exposed. If they are tightened enough the air leaks will stop - even the minute ones that cause the system to leak down over a period of several hours.

enough
sealant, and

feel
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Tom wrote:

You should use rector seal #9 for the sealing compound, depending on the pipe (say up to 1") size you are using you should be able to tighten the threads 3 to 4 turns for a hand tight fit, if less than 3 turns your threads wont seal! if more than 4 to 5 turns the pipe will screw in too far and possibly bottom out and not seal depending on the type of fitting it is going into. You should use sharp pipe dies to cut the threads if they are not sharp the threads will not be sharp and true you must use an ample amount of cutting oil when cutting the threads. You should only use pipe couplings that are steel with a designated as taper tap/ most couplings sold in hardware stores have straight pipe threads and don't seal as easy and taper tap couplings
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Ralph Roseburg suggested... You should use rector seal #9 for the sealing compound, depending on the

Funny you should mention that. After finishing up, I remembered I had some other pipe dope laying around, and sure enough, it's the rector stuff I'd used on some garden hose fittings and never had a problem. The stuff I used on the black pipe was greyish and of an inconsistent texture.
I will break down and clean the problem connections and use the rector stuff and maybe teflon tape as well as suggested hear by others. I probably need a bigger pipe wrench as well, mine is only about 15 inches long. When needing two wrenches, I substituted a vise-grip, which never slipped on me, but doesn't give me much leverage.
Joe
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JOE) wrote:

If you are depending on pipe dope to keep the joints from leaking, then you haven't made the joints tight enough.

Most stuff made in Communist China is crap. And even though it's pretty hard to screw up black pipe, you're still more likely to get pipe with the threads cut and tapered properly if you buy pipe that was made in a country with a capitalist economy.

Yes, it's possible to overtighten a joint so much that the fitting will crack. It takes a *lot* of force to tighten black pipe that much, though. Much more likely IMO that your joints are not tight enough, or that some of them are cross-threaded.

Squirt a little bit of liquid dish detergent or soap in a cup of water and stir it in well. Then use a paintbrush, or even your fingertip, to coat all of the joints with the soapy water. Pressurize the system, and you will see bubbles forming every place there's a leak. (BTW, this is the standard method of checking for gas leaks too.) Once you find out where the leaks are, you'll probably figure out why they're leaking too.
-- Doug Miller (alphageek at milmac dot com)
How come we choose from just two people to run for president and 50 for Miss America?
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    Greetings and Salutations.
On 19 Jan 2004 15:25:26 -0800, snipped-for-privacy@execpc.com (BIG JOE) wrote:

    Smart move. Leaks are a continual problem, and, having some flexibility to get rid of them is a good thing.

    I assume you mean pipe dope (the putty stuff?). It has been my experience that it should both stay flexible "forever" and if it is going to seal the pipe it should do it when the pipe is tightened up the first time.

    I have seen some variation in connectors from the BORG. I doubt it is a problem with the pipe, as that seems ok. There is a decent chance that the fitting has been threaded too far, though.

    Well, it is possible to overtighten, I suppose, although I have really only split a PVC fitting by overtightening. Metal pipe is pretty tough. I screw it in hand tight, then, crank another turn or so with a wrench.

    Yea...that is "iffy". I would suggest, first off, swapping out the leaking fitting for a new one. Kind of a hassle, but, might be easiest in the long run. Alternatively, you could switch over to teflon tape....     Regards     Dave Mundt
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I dont know is this is right or not but I used 2-3 wraps of teflon tape on my fittings and I only had one leak and that one was a nipple on my brad nailer. I either got really lucky or the tape works alot better than the goo. Something to think on.
Jim
(BIG JOE) wrote:

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Just out of curiosity .. .. is there anything wrong with using BOTH Teflon tape and flexible pipe dope sealant ?? ?? ?? I know a guy who swears by this method and uses it a;; the time !! !! !!
James D Kountz wrote:

-- I AM NOT PARANOID .. .. .. but EVERYONE thinks I am !! !! !!
<<<__ Bob __>>>
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I went with dope alone and the only leaks I have are at the quick disconnect couplers. (I chased them for a week or two) I did crank the pipe joints down to 1 1/2 - 2 threads showing per an old plumbing book I have. That took 24" pipe wrenches. I assembled as much as I could on the ground and made the last few joints in place with unions..
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A combination of non hardening Permatex and teflon makes a very durable joint sealant.
Tim
<<<___ Bob ___>>> wrote:

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