sealing leaks

[mechlectrician7]

Ok so our team uses pneumatics quite often and as im sure most teams have a similar problem, we always have a problem with leaks. The majority of our fittings are fairly new so we know its not that. And we use teflon tape(sp?) but that doesnt always do the trick, just wondering if anyone has any other tricks or products that do a better job?

[cmrnpizzo14]

The easiest way is to prevent leaks in the first place.

If you are using the plastic storage tanks, don't tighten the fittings too much, leave a thread or two visible. It is very easy to crack them.

Cut all of your tubing square on the end so that it fits in nice and snugly.

Make sure all of your tubing is fully plugged in.

Be liberal with teflon tape but don't overdue it. 2 or 3 wraps around the threading should be fine. Be careful that you are wrapping it the correct way as well. Counterclockwise I believe (someone correct me right away if I'm wrong).

Make sure that all of your components are nice and tight. Use a wrench, don't just hand tighten.

If you do have leaks, apply soap water to your pneumatics and look for the bubbles. That should show the problem region and then just check everything in that area for the above mentioned problems. Good luck!

[Big Ideas]

Are the leaks at the threaded joints, or elsewhere?

For pipe thread joints:
5 wraps of PTFE tape and 3/4+ turns after finger tight. Make sure that the first thread is not taped and that there is no tape on the front face of the male fitting. Clean off old tape and re-tape if the fitting is being reused. PTFE tape does not seal well if reused.

If the leaks are out of the "One Touch" style tube fittings--The NUMBER 1 OFFENDER is the tube ends NOT being cut square. If tubes are cut at a slant, or not cut cleanly, the o-ring seals at the bottom of the fittings will not make a good seal all around the tube.

[MrForbes]

It only takes one or maybe two wraps of tape on a threaded fitting to seal it, if you tighten the fitting properly.

Make sure the end of the tubing is cut square, and make sure it's pushed in all the way. If the tubing has been used for a while, you might need to cut off the end again and re insert it.

[mechlectrician7]

Helps a lot, thank you!

[donkehote]

If you have major leak issues, or students who are overzealous with teflon tape, you can use pipe sealant. Its much more forgiving and lass prone to develop leaks, at least in my experience.
http://toolmonger.com/wp-content/uploads/2009/10/loctite-thread-sealant-with-teflon.jpg
http://static.hardwarestore.com/media/product/673073_front500.jpg

You dont have to get the loctite brand, other brands work too, i know Brafasco carries it, possibly hardware stores as well.

[Al Skierkiewicz]

Use liquid with discretion, too much will pass into the cylinder and/or needle valve if you are using one. Tape has worked for us for many years. It isn't rocket science to wrap a few turns and tighten the fitting. Almost always, leaks occur at tubing that is not cut square or pushed fully into the fitting. A tubing cutter from McMaster or other source is worth every penny.

[MrForbes]

As Al says, it's not really difficult. I'd guess that 98% of the pneumatic leaks we get are a result of the tube not being pushed all the way into the fitting.

It's easy to check that...just firmly push in all the tubes, and see if the leaks stop.

Make sure the tubes are long enough, if they are bent to tightly, they will tend to leak, because they can't sit straight in the fitting. If necessary, replace with a longer piece of tubing.