Plumber's tape needed?

Page 3 of 5  


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
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
"Upscale" wrote:

=====================================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
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Thanks Lew. I'll dream tonight of fairy princesses all draped out in yellow Teflon tape. :)
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Uma is going to be pissed!
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

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.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote in message

What did you use on the old one?

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

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.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Correction, should have said brass.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote in message

FWIW, the compressor manufacturers say teflon tape. IIRC, Cambell Hausefeld includes a roll.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Upscale wrote:

I don't see any need for tape or dope on compression fittings. Non-compression fittings need tape or dope regardless of what they are made of?
I'm not a plumber though, but thats my take.
--
Jack
Using FREE News Server: http://www.eternal-september.org /
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Compressed air fittings are not the same as compression fittings.

Tape or dope should be used for all fittings for ease of proper assembly. The joint won't seal unless it's tight, and the tape or dope reduces friction, making it easier to get the joint tight. And it's pretty much mandatory for anything that might be disassembled later.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

> Jack Stein wrote:

Doug Miller wrote:

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.
--
Jack
Using FREE News Server: http://www.eternal-september.org /
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

??

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?

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Somebody wrote:

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 .
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Lew Hodgett wrote:

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.
--
Jack
Using FREE News Server: http://www.eternal-september.org /
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

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.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Doug Miller wrote:

I happen to have a hunk of 3/8 copper tubing with a compression fitting in my junk pile, which you made be go down and look at... couldn't see any notable issues that would preclude it's usage in a high flow situation, other than it was 3/8" in pipe. I guess there might be some negligible constriction which is difficult to see and might be important in super small pipe, but in normal home air systems in this discussion, a very non-issue.

I tend to think that the amount of air that would flow through a 3/8" pipe under 1000 lbs of pressure is more than would flow through the same pipe with 2 lbs of pressure? Is that wrong? I know volume and pressure are two different things, but I'd think one effects the other?
Most easily illustrated by example:

See, right there I don't get it? In my mind, to get high pressure you need to restrict the flow. I don't see a mountain stream or a river as high pressure? I admit I know next to nothing about fluid dynamics, but thats my point... For example, if I have a high pressure hose, and put a hole in the hose, the water will shoot out the hole into the air, and the more pressure, the higher it will go. The mountain stream is not shooting up in the air, just flowing... low pressure, high volume. My mind says the only way to get high pressure in a mountain stream is to force in through a pipe of some sort. I do realize that the deeper the stream, the higher the pressure at the bottom of the stream from the weight of the water.

Well, if you think about it, the main difference is a spring holds the compression fitting together instead of threads. Pipe dope is not needed anymore there than on a standard brass compression fitting.
--
Jack
Using FREE News Server: http://www.eternal-september.org /
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

One man's negligible is another man's noticeable, I suppose...

No, you're not wrong, and indeed the pressure does affect the flow rate -- but flow rate is also determined by the size of the pipe. You're going to get a higher flow rate through a one-foot diameter pipe at 2psi than you will through a 3/8"-diameter pipe at 1000psi.

That's not correct.

Steeper gradient = higher force (due to gravity).

I should have made it more clear that I meant that as an analogy to try to make the point. I did not mean that the mountain stream is literally under higher pressure.

Except that you won't be unscrewing one of those. Threaded fittings *are* from time to time unscrewed, and doping them on assembly makes disassembly easier.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Hey, guys, lets stick to topics we know something about, like electricity.
(paraphrasing a formerly prolific rw poster)
--
Better to be stuck up in a tree than tied to one.

Larry Wasserman - Baltimore Maryland - lwasserm(a)sdf. lonestar.org
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Jul 13, 1:36pm, snipped-for-privacy@sdf.lNoOnSePsAtMar.org (Larry W) wrote:

C'mon Larry, the plumbing, 'lectric & politico-religious threads allow those who know nothing about woodworking to pontificate.
L.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Related Threads

    HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.