PDA

View Full Version : Teflon Tape



John1
01-21-2006, 11:03 AM
Putting a new fitting(gas outlet) in my argon/co2 mig gauge.

Is it o.k. to use teflon tape on the threads.

Seems like somewhere I read teflon tape was a no-no on something!

Thanks
John1

HazMat55
01-21-2006, 11:08 AM
Just to be on the safe side, I'd use the teflon paste if needed. That will prevent a possible flake of the tape from entering your system. It is a "no-no" on a plasma cutter.

hankj
01-21-2006, 01:13 PM
John,

If you're talking the low pressure outlet, why bother with tape? There isn't enough pesuure there to leak past a loose fitting! I'd wrench it up snug and call it good.

Hank

Fishy Jim
01-21-2006, 01:57 PM
Hank, it will bleed down over time, which means that you're always wasting a little gas. If you do like I do, and occasionally forget to close the bottle at night, then you could wake up to it being empty.

I make sure my machines don't leak down and do whatever needs doing to fix it (like was the case on my tigmate) if they do. Pipe dope has always been my preferred method.

hankj
01-21-2006, 02:08 PM
Jim,

All three of my machines bleed down after they are shut off. The MM135 is the fastest, the TA the slowest. I've left the C-25 open on the 210 for a week (once!) and didn't seem to loose any appreciable amount of gas. It never seemed important enough to chase the leak. Maybe if I get boored today, I'll go play with it. Can't weld - no steel!

Hank

aametalmaster
01-21-2006, 02:24 PM
I use the tape, just don't wind it past the end of the fitting and it won't get in the hole....Bob

Fishy Jim
01-21-2006, 04:11 PM
I'm just **** like that I guess. :D I never closed the valve on my 130XP - it didn't leak at all. My new machines I just got back into the habit of closing them again, leaving them open got me into a bad habit and it has bit me at some other shops. They don't leak, I just close them.

ventureline
01-21-2006, 04:21 PM
Brass seals brass, so teflon tape is not needed. However, Telfon tafe should never be used, instead go for a small amount of paste on other fittings.

Meach
01-21-2006, 11:43 PM
Brass seals brass, so teflon tape is not needed. However, Telfon tafe should never be used, instead go for a small amount of paste on other fittings.

I certainly do not wish to put in my two cents, however (That means I'm gonna anyway :D ) I was (Still am) a master plumber for nearly 15 years and water hasnt been told that brass seals brass! Pipe dope (Rectorseal) hardens with time and can be a real bear when it comes time to remove fittings. Teflon paste is good, messy and ends up where you dont want it. On medium pressure Natural gas, low pressure Natural gas and high and low pressure LP (Propane) as well as water and air your best bet is good old teflon tape. Be sure not to wind the tape past the end of the thread and wind the tape on so when you screw in the fitting, it goes the proper direction. (Dont know how to explain it) If you wind in the wrong direction as you screw in the fitting, the tape may try to "Unwind" and end up inside the pipe.

MAC702
01-21-2006, 11:57 PM
I'm with Meach. Though I ain't been no plumber, I've used all the above. Teflon tape is the easiest, and I still have good fittings that were sealed with it decades ago.

Example of where to use it would be on the gauges where they thread into the regulator body. The threads do the sealing here.

Example of when not to use it would be where the regulator body mates to the valve on the cylinder. This is where the threads push two brass mating surfaces together, and they do the sealing, not the threads.

fastblast
01-22-2006, 12:28 AM
I certainly do not wish to put in my two cents, however (That means I'm gonna anyway :D ) I was (Still am) a master plumber for nearly 15 years and water hasnt been told that brass seals brass! Pipe dope (Rectorseal) hardens with time and can be a real bear when it comes time to remove fittings. Teflon paste is good, messy and ends up where you dont want it. On medium pressure Natural gas, low pressure Natural gas and high and low pressure LP (Propane) as well as water and air your best bet is good old teflon tape. Be sure not to wind the tape past the end of the thread and wind the tape on so when you screw in the fitting, it goes the proper direction. (Dont know how to explain it) If you wind in the wrong direction as you screw in the fitting, the tape may try to "Unwind" and end up inside the pipe.


ditto. they also sell 2 thicknesses of teflon tape. thin white tape and thicker yellow tape. and who came up with that brass seals brass...i've seen many brass fittings leak water at 70 psi....there are tapered fittings that seal themselves as you tighten them...i've only seen them on black iron however.

Roger
01-22-2006, 09:24 AM
There are 2 types of pipe threads. Common plumbing pipe threads have flat not sharp outer edges that leak if not sealed with pipe dope, tape or something. High pressure pipe threads come to sharp V at outer edge and sharp V at inner V so they seal better. Look at your Argon cylinder valve pipe thread connection. They don't use Teflon tape, dope or anything if it is steel cylinder. They just tighten real tight. Same is true for all the pipe thread fittings on my argon regulator. Cylinder valve is in so tight the threads are damaged and can't be reused many times. I've been told the cylinder valves with pipe threads are replaced after hydro. When I was using scuba cylinder valves with pipe threads with teflon tape the threads were so damaged I mught use old valve a couple of times. We had to visually inspect inside scuba cylinders once a year for rust. If your HP cylinder is aluminum then must use teflon tape or approved lubricant to prevent cylinder thread damage.

USN had someone use damaged pipe threads that would not seal until many layers of teflon tape was used. This cludge lasted long enough to cause an accident. They only allow 2 layers of teflon tape 1 to 2 threads away from end. Pipe dope and Teflon paste should also be placed 1 to 2 threads away from end. They all have to be removed from threads when they are taken apart. I have use brass O-ring pick made from brazing rod or awl to clean clean threads.

fyoung
01-22-2006, 09:45 AM
I've always had very good results using Harvey's paste with Teflon and other paste products with PTFEI. do use Teflon tape sometimes on small fittings but for bigger jobs such as 1/2 pipe and bigger I always use a paste with Teflon in it. I also have did plumbing for many years and we've run a bunch of 3/4 and 1 inch black pipe for gas installations with very few leaks..less than1%
just mt 2¢
Regards!

ventureline
01-22-2006, 10:44 AM
Teflon tape clogs up the solinoid screens and lines, don't use it. Teflon tape is NOT recommended on any (welding related)brass to brass connections. I merely mentioned that if you really had to use some sort of tape. then use a very small quantity of teflon paste. Works better and doens't clog up critical components.

Hmm, your brass tank connector seals and mates with your argon flow meter at 3000+ psi.


In aircraft, you won't find any teflon tap on any fittings, and brass does seal brass, providing the threads are the same. In the last 20 years of welder repair I don;t bother taping brass fittings. Though I'm not a plumber. I bubble check all my connections and haven't found a leak yet....

hankj
01-22-2006, 11:09 AM
It's hard to generalize threaded fittings.

You have to deal with each type as you encounter it. Brass flared fittings are designed to seal themselves. Inverted flare fittings are used on high pressure applications, like break lines, and are self sealing. Iron pipe unions have machined mating surfaces, and are self sealing on the union side, but the NPT (tapered) side will need teflon (or dope). The 9/16 - 18 fittng on O/A hoses is designed with a machined mating surface; self sealing. There are lots of applications for NPS (straight pipe thread) fittings, all of which need a sealant.

The generally accepted practice for welding gas fittings don't specify any sealant. Of course, there are those who do it their way, regardless of what the "standard" may be! ;)

Hank

calweld
01-22-2006, 11:47 AM
Putting a new fitting(gas outlet) in my argon/co2 mig gauge.

Is it o.k. to use teflon tape on the threads.

Seems like somewhere I read teflon tape was a no-no on something!

Thanks
John1

I think there's a warning on my tube of teflon paste recommending not to use it in oxygen-rich environments . . .

fyoung
01-22-2006, 07:34 PM
We all know oil and oxygen don't mix..explosive combination.

katarn444
01-23-2006, 11:20 AM
When I got my HH135 it was leaking all over the place. I used a friends regulator b/c my hose was leaking. That solved the problem and no gas would leak out over night. When I got the replacement hose from hobart I put my regulator back on and now It leaks out in less then 10 minutes. This means that the o-rings are ok, the hose is ok, so the only place left is the regulator itself. How do I find a leak in the regulator? I found the other leaks using soapy water.
Also while we are on the subject, when I try to tighten the hose going in the back of the welder, the connection on the back of the unit just starts to spin. Any thoughts.

Katarn

hankj
01-23-2006, 11:53 AM
444,

I'd say the leak is right there at the gas solenoid. If you can spin the connector, it doesn't sound like it's gas tight!

Hank

MAC702
01-23-2006, 11:56 AM
There should be a place to grab the machine's fitting with a wrench. Never expect the machine to keep the fitting from turning; you need two wrenches to make these connections.

10 minutes seems quicker than average, but as long as you keep your cylinder valve shut off while not welding, you probably aren't losing enough gas to poke in your eye. There is VERY LITTLE gas in the regulator and hose. It's a rare set-up that keeps the pressure there very long when the tank is off.

Fishy Jim
01-23-2006, 12:05 PM
Well Mac, then I've had three very rare welders from three different brands (even though miller and hobart are the same parent company). I think the solenoids are capable of sealing the low line pressure quite well - since they tend to be rated for 90psi and 20cfh ends up to be something like 7 psi (as I have been told - not that I have measured). I think if you have machines leak down, it's because you have leaky fittings.

My hobart leaked when I got it. Turned out to be a broken fitting at the solenoid (previous owner either over tightened it, or ran something into the air chuck he had attached for his bottle) - a little JB Weld and another fitting glued in the inlet later: no leaks. :)

MAC702
01-23-2006, 12:31 PM
Jim, I certainly agree that it seems that he has a loose fitting, probably the one that is spinning in the machine.

I usually see about a day or two in my regulators. BUT, if the incredibly small amount of gas in a reg and hose are leaking out in 10 minutes, the average small MIG user isn't losing any big money. A fuel gas would be a completely different story...

Fishy Jim
01-23-2006, 12:43 PM
I agree that it's not a detrimental expense incursion, but I do like being frugal with what I have paid for. You wouldn't just crack the valve on a tank and bleed off 20cf of gas because "it's only worth about 4 bucks." I don't want to waste anything. Over the life of my welding, that will add up to some savings, not much, but something. It's not like I have spent hours and hours to save pennies either. A couple more seconds with the dope on the fittings and there are no problems for the rest of the time I own the machine. Then if I do have a late night and forget to crank it closed (something I have never done with fuel gasses), I don't have to worry about it going empty on me. With my video business, I've been out of the state for months at a time (as I'm sure you have with your ministries). It just makes more sense to deal with the little leaks when they're discovered than to let them go and wind up not having any shielding gas saturday morning when you have a customer call up and say "I really need this done NOW." ;)

fyoung
01-23-2006, 02:30 PM
;)
Hi, I was just curious as to what kind of video business you have? Thanks, Farris

Mac, or jim or anyone reading this..Where do you think would be the cheapest place to buy some 035? I'm wanting some decent wire..I run 75/25co² gas
Thanks again, Farris

katarn444
01-23-2006, 06:24 PM
I will give a quick look tomorrow, like everyone else I agree that it is not much. But sometimes I am welding for four or five hours and do not want to keep opening and closing the valve. When I used the Lincoln regulator It held pressure overnight, so I know it is external. I will look at the rear fitting and the regulator. I have been meaning to intestigate for a while. Thanks
K