Pipes and tubes: is the difference still taught?

[Syncopator]

Many decades ago, at about the time I acquired my first pair of long trousers, a cousin started work in one of the then most prestigious boilermakers in the U.K. (

http://www.localhistory.scit.wlv.ac.uk/Museum/Engineering/JohnThompson/johnthompson00.htm#menu)

After he had worked there for a while he was taught the difference between a pipe and a tube and asked me if I knew. No. So he told me.

I forget which is which now, but the difference is that one is rolled and therefore has a seam, while the other is drawn or extruded and therefore does not have a seam.

I have seen the question posted elsewhere and it attracted many answers, none of them in accordance with the above and most of them totally illogical and based on common (mis) use.

So, is the proper distinction no longer taught?



Equal rights for equal responsibilities.
Equal opportunities for equal abilities.

 

[jte]

Syncopator-

I beg to differ with your cousin's distinction. Pipes and tubes can be seamless or welded.

The way I've been taught... for a given nominal diameter, piping has constant OD regardless of wall thickness, tubing has constant ID regardless of wall thickness.

jt

 

[IRstuff]

And perhaps, it's just an anachronism. One might argue that modern manufacturing tolerances are tight enough that ID and OD variations are about the same.

TTFN

FAQ731-376

 

[drawoh]

Syncopator,

Can you extrude hollow steel sections?

I would claim that a pipe is anything that conforms to offical pipe sizes. I am too lazy at the moment to search my Machinery's Handbook. I think 1/4" pipe is Ø.540", and 1/2" pipe is Ø.840", etc.

I have been told that pipes are sized by inside diameter, which actually makes a lot of sense. Unfortunately for all that sense, pipes have fixed outside diameters, and wall thicknesses that vary depending on the schedule.

This sounds a lot like the old bolts versus screws debate which has taken place on here many times.

JHG

 

[TenPenny]

My understanding is that Pipe has a consistent OD for a given size, and the ID changes for differentwall thicknesses, whereas for tube, it's the reverse.

My Machinery's Handbook says, "The word pipe as distinguished from tube is used to apply to the tubular products of dimensions commonly used for pipelines and piping systems. Pipe dimensions of sizes 12 inches and smaller have outside diameters numerically larger than the corresponding nominal sizes, whereas outside diamters of tubes are identical to nominal sizes."

 

[SnTMan]

Well, I use O.D. tube all the time. I would say the distinction is completely based on dimensional schedules and perhaps specifications, if it meets SA-106 its a pipe, it it meets SA-178 its a tube.

Then there is stuctural tubing.

Regards

Mike

 

[GregLocock]

A pipe gives a wise man time to think, and a fool something to stick in his mouth.



Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

http://eng-tips.com/market.cfm?

 

[rmw]

To spice it up, I work for a company that utilizes drafting and engineering services from a country where in their native language they use the same word for both pipe and tube. Some strange stuff comes from that.

I too, use constant OD tubing with various wall thicknesses, and it in no way is confused with pipe. I use pipe in seamless and welded versions, and the same with tubing, so that is no determining factor.

SnTMan gave the correct answer above.

rmw

 

[metengr]

Basic definition I learned from an an ASME code brother is pipe conveys fluids, tubes are for heat transfer or for structural purposes.

 

[geesamand]

We design with mechanical tubing and pipe regularly. In some cases, tubing and pipe sizes are effectively identical and they are cross-listed.

In cases where the tubing and piping do not match sizes, the piping has poorer dimensional control (roundness, runout) than the mechanical tubing. For my needs that can be important.

 

[CorBlimeyLimey]

A wise man would have no need for a pipe.

 

[IRstuff]

Who needs a pipe if you already have a joint?

TTFN

FAQ731-376

 

[SnTMan]

Frivolity! Frivolity!

 

[moltenmetal]

We use inch dimension OD tubing for plenty of fluid-carrying services other than heat transfer, but it is by no means PIPE!

Tube is sized by OD and wall thickness. Pipe is ALSO sized by OD and wall thickness- to a totally different standard. Below 14", the NPS pipe OD sizes are NOT whole inches or even simple fractions of inches for some of the smaller sizes, and the wall thicknesses are organized into "schedules" rather than by the nominal gauge of stripstock the welded form is made from.

Tube for fluid handling purposes meets its own set of ASTM specs for ovality, OD and wall thickness tolerance etc. etc. Pipe meets a different set of ASTM specs with different tolerances.

The carbon steel structural stuff does have a proper name, which is "hollow structural steel" (HSS). Some people do call it "structural tube" or "box tubing" for rectangular sections. And yes, you can find this with the same weird OD dimensions as pipe, but meeting different ASTM specs and with different (fractional inch) wall thicknesses. We like this stuff particularly for guardrail/handrail as it's both cheaper than and has a nicer surface finish than A53 carbon steel pipe.

 

[rmw]

Metengr,

Front standards of many your turbines are full of hydraulic tubes that are conveying fluids to various parts of the controls.

rmw

 

[metengr]

All perspective, rmw. The definition I was referring too was for boilers.

 

[rmw]

metengr,

Chuckle, chuckle.

In that context, naturally, your statement would be the gold standard.

One of my designers, many years ago, had a hand lettered sign posted at his board (pre cube days):

"Tubing, or not tubing - that is the question."

rmw

 

[bobble293]

Hi,

To me, tube is defined primarily by its O.D, then by its wall thickness, pipe by its NOMINAL bore, then by its wall thickness, though not the measurement, just the "weight" light, medium, heavy. Pipe O.D must necessarily remain more or less constant for a given nominal bore, or threading and mating with other parts would be a nightmare.

Tenpenny was not quite right!

It's a pity so many lines of type are expended upon basics like this. I've taken up, late in life, part time employment in a training establishment, and am finding younger members of staff have been taught using different terms to those which I was. It causes confusion, and sometimes confrontation!

Machinery's, by the way, being American, is packed with terms we never used this side of the pond, despite the almost universal adoption of it as our "bible"

C&G, for instance, now refer to the saddle of a lathe as a carriage! Perhaps in the US of A! If you teach using new, or different terms rather than those which have been used historically, reference books become useless, or will need an additional glossary or interpreter.

Click only once.

 

[Syncopator]

An interesting mixture of opinions, as I anticipated.

With the exception of the last post, bobble293's, they all serve to answer my question in the negative.

No. The difference is no longer taught.

Equal rights for equal responsibilities.
Equal opportunities for equal abilities.

 

[bobble293]

Hi,

My last post failed, I'm ashamed to say, answer your question, and only stated what I was taught.

However, conversations with others over the past couple of years, have led me to the conclusion that their ignorance of some basic aspects of their trade is not necessarily due to their not having been taught it, merely to their having forgotten that they've been taught it.

This could be due to never having had to use the knowledge, or because the subject had been glossed over by the tutor, or because it was found, by the student, to be less than fascinating.