Nothing. Didn't occur to me when I bought it some ten years ago. And yes, there was a small, discernable hiss right at the point of air exiting whatever male adapter I had inserted. Also, all the adapters appeared to be some type of silver coloured alloy. This time they're all copper as recommended.
Correction, should have said brass.
FWIW, the compressor manufacturers say teflon tape. IIRC, Cambell Hausefeld includes a roll.
Brass compression fittings certainly are common compressed air fittings?
Nope. Tape or dope is not needed at all for brass compression fittings commonly used in air lines, water lines etc.
The joint won't seal unless it's tight, and the tape or dope reduces friction,
I don't agree, brass compression fittings can easily be overtightened, and dope/tape could facilitate that. Also, tape/dope could contaminate the compression fitting resulting in leakage. Other than that, using dope/tape on a brass compression fitting is pretty much meaningless. If the oval ring in a compression fitting leaks, all the pipe dope or tape in the world will not help it, and a new ring/fitting is needed.
Tape/Dope should always be used on non-compression fitting, for the reasons you site. The original poster said only brass to brass, and didn't specify compression or non compression fittings.
Compression fittings are not at all common on air lines in my (admittedly limited) experience.
Where have you seen air lines with compression rings in the fittings?
Compression fittings require a metal to metal fit to work properly, thus tape or dope defeats the purpose except on the threaded portion of the fitting.
That said, compression fittings are a poor choice where high flow rates may be required.
Lew .
Any difference between plumber's dope and gasline dope?
These days Teflon paste serves both applications.
Lew
I don't think you can get high huffing PTFE. ;)
nb
Ok, I picked up a roll of the yellow tape today, but reading the instructions on the back a little more closely, I'm not sure if I should use it or if it's usable for my 150 psi compressor.
Here's what I got:
It's certainly yellow. The front description states "Gasline thread seal tape". On the back in finer print it states "Do not use on flared threads". And then the following blurb: "Got use in assemblies handling gasoline, petroleum oils, propane, butane and natural gas not exceeding 100 psig".
I'm guessing that 100 psig is gallons volume, so I'm not so concerned there, but the threads on the brass fittings *are* flared which to me means that the circumference gets gradually larger on the male part of the fittings. I guess I'll use it anyway since the only realistic problem I might get if there is one is the hiss of a little air.
Thanks
====================================== You are confusing oranges and apples.
In the USA, pipe threads are NPT (National pipe thread) which are tapered 1-1/2"/12".
For comparison, the Brits use BSP or straight (non tapered) pipe threads.
PSIG = Pounds per square inch gauge
Has nothing to do with volume, describes pressure..
"Flare" fittings involve flaring the copper tubing (usually 37-1/2 degrees) to provide a metal to metal seal which won't work if there is Teflon tape in the middle.
The 100 PSIG limit is to advise you not use Teflon tape on high pressure storage vessels.
IOW, for your applications, you can tuck your roll of tape under your pillow and sleep tight tonight.
Lew
It's a pressure measurement. "psig" = "pounds per square inch guage" as opposed to pounds per square inch absolute. To illustrate the difference, which is of interest only to scientists, normal atmospheric pressure is 14.7 psi absolute, at which pressure a guage will read zero. For practical purposes, "psi" and "psig" are freely interchangeable.
That would be a tapered thread. Gas-line pipe (black steel) uses tapered threads, which actually slightly expand the fitting when the pipe is seated properly, making a very tight seal. (If you've ever heard that gas-line fittings should not be reused after a joint is disassembled, that's why.)
Are you sure it says "flared" and not "flare"? I could understand the latter, in reference to flare fittings (which are used on gas-line *tubing*), but not the former.
Go ahead and use it. The warnings are all about avoiding any leaks of dangerous substances such as "gasoline, petroleum oils, ... natural gas". As you've already realized, since you're only using it for air, even if it does leak that presents no danger.
Not suggesting they're not used, just suggesting they're not common.
As long as you keep it on the threads, and off the ring, where's the harm?
Actually, they do. Take apart a compression joint in copper tube and take a look.
Pressure and flow rate are completely different. Pressure is the force moving a fluid (air, in this case) from one place to another; flow rate is the amount of fluid moving per unit time. Most easily illustrated by example: Low pressure, low flow rate -- the water in your rain gutters. High pressure, low flow rate -- a mountain stream. Low pressure, high flow rate -- the Mississippi. High pressure, high flow rate -- Niagara Falls.
Obviously a very different type from what we're discussing.
About 30 feet from where I'm sitting? Are you suggesting compression fittings are not used in air lines? I'm pretty certain I'm not the only one to use a compression fitting on an air, or a gas line.
Anyway, if one is using a compression fitting, pipe dope or tape is not needed, and may in fact be detrimental to the connection. I have seen compression fittings where pipe dope was used on the joint by someone who didn't know any better.
But, on the brass threaded portion the tape/dope is not needed, and probably should be avoided.
I never heard this before, and not sure I understand why? Not saying it's incorrect, just that I don't get it? They don't appear to restrict flow at all?
Compression fittings are used in high pressure conditions, which I guess would infer high flow rates?
Now that I think about it, for Doug, the disconnects at the end of your air hose are compression fittings. Not particularly the type we are discussing but thought I'd throw that in.
Typically compression fittings are brass which are self lubricating and the threads do not provide any seal.
Uma is going to be pissed!
I guess we could argue common, not common all day and get no where. I would guess it depends on what you are connecting together. Sometimes a compression fitting is common, sometimes not. Air lines commonly have flexible copper tubing for example and it is very common to use brass compression fittings where they connect to standard pipe. You would use pipe dope on the pipe thread, but not on the compression fitting.
No harm other than a waste of time. Brass compression fittings simply don't need dope on the threads. You could put pipe dope along the entire length of pipe and do no harm, but it begs the question, why?
Most of the air lines I've seen are black steel. YMMV.
As I've said several times before, taping or doping threads makes the joints easier to disassemble. There's no point at all, obviously, in putting it along the entire length of the pipe. But then, you're the only one who's suggested doing that.
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