air fitting

[hiram]

I got a coupler for my compressed air tank. I installed it using pipe dope on the threads. I have a slow leak. Was this the wrong stuff to use?

[dagger dog]

Teflon tape.

[runfiverun]

the dope is a lubricant so you don't tear the tape [sealant] which fills in the imperfections in the threads.
the first 4-5 threads is where the sealing occurs, if you tighten a fitting or pipe too much you will often times create a leak.

[starmac]

I never use tape anymore, and my trucks hold air for days, as does my compressor.
I never turn my compressor and it doesn't come on until I use it, and there is pipe dope on all connections. What brand fittings are you using, I have seen some cheap ones that nothing would seal.

[bearcove]

Dope and tape will seal pretty ruff threads. Either by itself works most of the time. Depending on what is in the line I have had to do it all 3 ways.

[Jeffrey]

There is "pipe dope" and then there is "PIPE DOPE". For refrigerant applications I use Loctite 567 UNDER standard teflon tape. Put only enough 567
http://www.useloctite.com/products/product_details_threadsealing4c67.html
to fill the threads. You should be able to lightly wipe the threads with your finger, just barely see the tops of the threads above the dope and then put the tape OVER the dope. Make sure you put the tape on in the correct direction so threading the fittings together does not "unwind" the tape, but makes it tighter instead. Less dope is better than more. A reasonably tight threaded fitting should not need more than 3 wraps with tape. Any more than that and you will not have the engagement (sp?) you need to make a good joint. In other words, you want the threaded parts to almost but not quite bottom out. Bottoming out is bad. The metal parts are loose against each other. Not enough penetration is bad too. Threaded metal against threaded metal with a sealant in between makes a seal.
Hope this helps. J

[MT Gianni]

Hit the teflon tape with a small spray of WD-40 and it shrinks in the threads. That helps to seal rough threads. You can also double dope as was mentioned, pipe dope over teflon tape. I have never much cared for teflon containing dope. The standard forever was Rectorseal #5 but it seems different than it was 20 years ago.

[edler7]

Rectorseal #5

+10 ! MT Gianni beat me to it. Good stuff.

[geargnasher]

Oatey Megaloc #15808. Best stuff I've ever found for sealing air and water, and I've tried just about every product there is.

The Rectorseal #5 is indeed not what it used to be.

Gear

[tomme boy]

You sure the coupler itself is not bad. Most all seem to leak.

[fatnhappy]

The standard forever was Rectorseal #5

My father was a steamfitter. I spent the first 4 years out of the Army working for the gas company. It was the .30-06 of pipefitters

[3006guns]

I've had the same problem with air fittings in the last few years and finally traced it to the manufacturer........China. Those things are mass produced, which is fine, but some point in the process actually crushes the fittings a bit resulting in an oval shaped opening. On some it seems like no matter how much teflon tape or dope you use it NEVER completely seals. The only solution is to try another fitting.

Sad state of affairs.

[CATS]

Stay back from the end one thread valley. This will leave a place for the dope or tape to squish to when you put it together. If you go all the way to the last thread, strips of tape and drops of cement hard dope will be extruded and likely damage your air device internals down stream and cause leaks and malfunctions.

[captaint]

Guess I have been lucky. A little teflon tape and I've been good to go. Mike

[Hardcast416taylor]

When I finally retired for the last time from my last job it was as a Steamfitter/Pipefitter/Plumber/Low Pressure Boiler Operator as my Journeymans card has it listed. For 35 1/2 years I plied that trade and assembled a piece of thread pipe or two and installed a few fittings. I worked in situations that didn`t always get the treatment that nice clean area jobs would recieve.to get machinery back up and running. I`ve used about anything you can imagine on threads to assemble and have as few leaks as possible. I`ve even used cotton thread in the threads, I have even once used some old paint in the threads to act as a sealant, or just assembled with no sealants at all. I also noticed the shoddiness of makers of fittings and iron fittings that can be traced to China and cheap cost cutting companies. A double wrap against the thread direction with a good name teflon tape usually ends the leak discussion.Robert