theoldwizard1
Well-known member
I know the difference in sizing (tubing is measured on the OD, pipe on the ID) and that pipe is typically galvanized but what other differences are there between the two (ignoring DOM and high alloy, like 4130) ?
Steel Tubing versus Pipe
- Thread starter theoldwizard1
- Start date
Richard D
Well-known member
Pipe is not really measured on the I.D., it is measure on the O.D., but the actual O.D. measurement is not the same as the "nominal size" of the pipe. Sometimes, in sch 40 pipe, the I.D. is pretty close to the nominal size, but not exactly. For example, 2" pipe is 2.375 O.D., with a wall thickness that varies. Sch 40 has a wall thickness of .154, which leaves an I.D. of 2.067, if I did my math right.
Pipe O.D.-Nominal vs. actual
1"-1.315 O.D.
1 1/2"-1.900 O.D.
3"-3.5 O.D.
4"-4.5 O.D
6"-6.625 O.D.
etc., etc. Until you get to 14" and up. Then the nominal size is the same as the actual O.D. I am also talking about pipe used in petro-chemical, hardware store plumber's pipe may be different.
Plus, pipe is made to withstand internal pressure of liquids and gasses, not to be a structural component, like DOM. That said, people build stuff out of pipe anyway because it is way cheaper and more readily available. I've done it myself, and I'm not dead yet.
P.S. That is a way simplified quick explanation. I am a piping designer, not an engineer.
Pipe O.D.-Nominal vs. actual
1"-1.315 O.D.
1 1/2"-1.900 O.D.
3"-3.5 O.D.
4"-4.5 O.D
6"-6.625 O.D.
etc., etc. Until you get to 14" and up. Then the nominal size is the same as the actual O.D. I am also talking about pipe used in petro-chemical, hardware store plumber's pipe may be different.
Plus, pipe is made to withstand internal pressure of liquids and gasses, not to be a structural component, like DOM. That said, people build stuff out of pipe anyway because it is way cheaper and more readily available. I've done it myself, and I'm not dead yet.
P.S. That is a way simplified quick explanation. I am a piping designer, not an engineer.
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NASTYZEN
Well-known member
Pipe is engineered for internal pressure whereas tubing is for structural use.
Beware, the id should never exceed the od with pipe.
Beware, the id should never exceed the od with pipe.
Richard D
Well-known member
That is not true at all. Petro-chem industry uses carbon and stainless steel pipe predominately. That may be true of some of the black and galvanized pipe in the hardware store, but I know I have MIG welded that stuff before, too. I don't think you can MIG cast iron without special wire.
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Kevin54
MEMBER EMERITUS
Pipe is engineered for internal pressure whereas tubing is for structural use.
Beware, the id should never exceed the od with pipe.
Yep, because if the I.D. is larger than the O.D. you turned your pipe inside out.
J/k
Pipe size is based on the OD, and the 'nominal' size is not what that OD is.
ex: 1/2" Sch 40 pipe has an OD of 0.840" and an ID (usually) of 0.622" (ID may vary depending on supplier and the pipe schedule , but the OD is supposed to be pretty consistent for the pipe 'size').
Tubing size (hydraulic or AC) is based on the ID, and is pretty much the stated/listed size.
Copper tube (aka copper 'pipe') size is based on the nominal OD, where the actual OD is 1/8" greater than the listed 'nominal' size. example: 1/2" copper 'pipe' has an OD of 5/8" and 3/4" copper 'pipe' has an OD of 7/8". The ID varies based on the "type" (similar to the "Schedule" for iron/steel/plastic piping)
Mechanical tubing (round, square, rectangular, etc) is based on the outside dimensions.
ex: 1/2" Sch 40 pipe has an OD of 0.840" and an ID (usually) of 0.622" (ID may vary depending on supplier and the pipe schedule , but the OD is supposed to be pretty consistent for the pipe 'size').
Tubing size (hydraulic or AC) is based on the ID, and is pretty much the stated/listed size.
Copper tube (aka copper 'pipe') size is based on the nominal OD, where the actual OD is 1/8" greater than the listed 'nominal' size. example: 1/2" copper 'pipe' has an OD of 5/8" and 3/4" copper 'pipe' has an OD of 7/8". The ID varies based on the "type" (similar to the "Schedule" for iron/steel/plastic piping)
Mechanical tubing (round, square, rectangular, etc) is based on the outside dimensions.
Pipe is engineered for internal pressure whereas tubing is for structural use.
Beware, the id should never exceed the od with pipe.
If you use this pipe it will leak very badly and make a mess.
Mike
kazlx
Well-known member
Like Nasty said, pipe is for piping things, liquid, gas, etc. Tubing is for building things. Not that it wouldn't hold liquid.
Pipe is typically threaded on the ends, either pre-done or by the user/installer. Angles are typically created by installed junctions, 90s, 45s, etc. Since most things that are followed are usually architectural (framing, concrete), the piping is typically run in the fastest route from A to B barring any other factors.
For tubing, the same tubing is typically bent up for all of the structure. The bends have a larger radius than a 90 elbow on a pipe joint. If you need a 90 degree turn in tubing, it's usually going to be a much more sweeping turn. It's fabricated based on need, looks, use and a host of other things.
Like everything else, there's exceptions to everything...
Pipe is typically threaded on the ends, either pre-done or by the user/installer. Angles are typically created by installed junctions, 90s, 45s, etc. Since most things that are followed are usually architectural (framing, concrete), the piping is typically run in the fastest route from A to B barring any other factors.
For tubing, the same tubing is typically bent up for all of the structure. The bends have a larger radius than a 90 elbow on a pipe joint. If you need a 90 degree turn in tubing, it's usually going to be a much more sweeping turn. It's fabricated based on need, looks, use and a host of other things.
Like everything else, there's exceptions to everything...
Richard D may be a “pipe fitter” and the drawing he works off of may be called “piping” lay outs.
But what he is working with is not what is commonly called pipe.
Plumbers work with pipes.
They rarely weld.
Pipe fitters work with tube. Even if they call it pipe.
They almost always weld.
(Sometimes in some of the worst conditions you can think of.)
There are union rules separating the work the two do.
Not sure of their exact limits and there may be some overlap.
I think there is a PSI limit for plumbers.
I don’t know what it is, but above it you need a pipe fitter.
There may also be a diameter size above which you need a pipe fitter.
It is a case of “common usage” vs. “engineering description.”
I have heard guys calling 8 foot diameter concrete culverts “pipe”
But that word was not on the drawing.
But what he is working with is not what is commonly called pipe.
Plumbers work with pipes.
They rarely weld.
Pipe fitters work with tube. Even if they call it pipe.
They almost always weld.
(Sometimes in some of the worst conditions you can think of.)
There are union rules separating the work the two do.
Not sure of their exact limits and there may be some overlap.
I think there is a PSI limit for plumbers.
I don’t know what it is, but above it you need a pipe fitter.
There may also be a diameter size above which you need a pipe fitter.
It is a case of “common usage” vs. “engineering description.”
I have heard guys calling 8 foot diameter concrete culverts “pipe”
But that word was not on the drawing.
Richard D
Well-known member
Sorry, but that is not accurate at all. In fact, I just read it to two fellow pipe designers, we all had a good laugh.
I look at pipe vs. tube only in terms of dimensioning. Pipe uses a nominal system whereas tube uses actual dimensions, often called out by OD & wall. You can't really go much beyond that because without reference to a specific ASTM spec like A53, A106, A513 we're just making general statements that may or may not apply to the material at hand.
koditten
Well-known member
The price of the fitting is what I notice first. Go buy a swadgelock 1/2" fitting and go buy a threaded 1/2" fitting. You can get lots of threaded pipe fittings for the price of 1 swagelock.
mattdwelder
Well-known member
sounds pretty confusing to me
Richard D
Well-known member
Average Joe probably won't be dealing with steel pipe unless he in in the petro chem industry
welder4956
Well-known member
A very entertaining thread.
Or the ammonia refrigeration industry
bsaint
Well-known member
pipe
- noun
1.
a tube of metal, plastic, or other material used to convey water, gas, oil, or other fluid substances.
Pipe is a tube. :|
- noun
1.
a tube of metal, plastic, or other material used to convey water, gas, oil, or other fluid substances.
Pipe is a tube. :|
Richard D
Well-known member
True, much as a Swanson Speed Square is technically a triangle.bsaint; said:
rshadd
Well-known member
Could they make the pipe sizing any more confusing?
Richard D
Well-known member
I've never really got a straight answer why it is done this way.
NASTYZEN
Well-known member
I would guess pipe was invented by an Englishman. They came up with threads and look what they did with that! Whit-worth!! Although probably the best thread, look how confusing it's all setup.
They can't even drive on the right side of the road...
They can't even drive on the right side of the road...
Alchymist
Well-known member
Yep, because if the I.D. is larger than the O.D. you turned your pipe inside out.
J/k
Actually when the ID is bigger than the OD, the pipe is used in situations where it is desirable to keep stuff OUT of the pipe, not inside it.
Move it all to metric?
Graham08
Well-known member
From what I've read, the OD is based on some obsolete schedule where the ID is the same as the nominal ID. Over time, the schedules evolved to their modern standards, but the OD was kept the same because it would have obsoleted all the existing threads, fittings, etc. to have changed it.
Pretty much all modern "iron" pipe is actually steel. ASTM standard A53 says so, which is what most black and galvanized pipe conforms to.
Richard D
Well-known member
^ This ^
offroadsteve
Well-known member
I agree this thread was an entertaining read... and its given me reason to step back and think about what we use here at work, and the best wayI can think of to sum this all up is to say "it depends". In shipbuilding we use both "pipe" and "tubing" to describe long, round things that carry fluids. Typically, "pipe" is relativly large diameter, heavy wall material (seawater, hydraulic, water, drain, "pipe" etc) where "tubing" is smaller diameter stuff (gauge line tubing, tygon tubing, etc), but thats not a hard and fast rule that I'm aware of.
We typically refer to steel or other metal used for structural purposes "shapes", mainly to avoid confusion between piping and structure. Probably also for this reason we use very very little round structural steel.
Anyway... like Richard said, what really matters is the specification a particular piece of material is manufactured to and its intended purpose. Sort of like the distinction between a bolt and a screw, for us at least, it depends on end-use.
We typically refer to steel or other metal used for structural purposes "shapes", mainly to avoid confusion between piping and structure. Probably also for this reason we use very very little round structural steel.
Anyway... like Richard said, what really matters is the specification a particular piece of material is manufactured to and its intended purpose. Sort of like the distinction between a bolt and a screw, for us at least, it depends on end-use.
Alchymist
Well-known member
OK, Who posted this and where did the post go?
"---Quote (Originally by NASTYZEN)---
They can't even drive on the right side of the road...
---End Quote---
Actually they DO drive on the right side of the road.
And you guys drive on the left side.
***************"
"---Quote (Originally by NASTYZEN)---
They can't even drive on the right side of the road...
---End Quote---
Actually they DO drive on the right side of the road.
And you guys drive on the left side.
***************"
buening
Well-known member
Typically the larger Sch 40 (AISC "standard weight") pipe's ID is closely based on the nominal pipe size. Its when you get to smaller pipe (like 3/4" and 1/2") is when the ID is larger than the nominal. Heavier wall pipe has ID's smaller than the nominal size. The OD is kept constant for the most part across all Schedule class pipe. I've used pipe and HSS round in structural applications, it just depends on material availability and the preference of the customer. Pipe has a lower yield strength at 35ksi compared to the 42ksi of the HSS. Pipe also has inconsistent wall thickness, so a reduction factor on the wall thickness is applied when using it for structural purposes.