Pipe and Tube

The key dimension for a pipe is its inside diameter.

The key dimension for a tube is its outside diameter.

The key dimension of pipe is neither its outside nor inside dia. Rather it is the nominal dia. The thickness varies according to schedule under which it is manufactured.

The 25mm pipe schedule 40 means its nominal dia is 25mm. its outside dia is 34mm where as its thickness is 3.4mm

The size designated to tube is generally its outside dia.

I had always been under the impression that pipes were ridgid while tubes were flexible.

Rigidity is a function of the materials of manufacture, the wall thickness, the diameter, and the distance between supports.

Tubing has thinner walls than pipe of the same size therefore it is more flexible. You need a larger tubing size than pipe to get the same strength. Pipe can be threaded whereas tubing cannot. It's easier to weld pipe than tubing. A tapped hole in pipe will be stronger than in tubing. You can put a self tapping screw into tubing, but I don't know if that is considered a tapped hole but it certainly won't be as strong as in pipe. What else?

In the particular case of tube used for boiler construction, the tube has to be sufficiently malleable to admit an expander to fit it to a tube plate while remaining sufficiently rigid to withstand the pressures seen in the boiler shell, and of sufficient thermal character to enable the effective transfer of heat from one side to the other while being of a metallurgy that will withstand scaling and corrosion sufficently to be an economic proposition at the temperatures, pressures, mineral content and acidities normally seen in the vessel.

Pipe can be joined in rather more ways than rigid tube: flanges, screwing, welding, swaging, cement and couplers being among the methods used.

The term "tubing" is sometimes used interchangeably with "hose" for diameters of flexible pipe below, say 20mm (3/4").

"The Tube" is an affectionate nickname for London's underground railway system.

Any more?

http://en.wikipedia.org/wiki/Tube

http://en.wikipedia.org/wiki/Pipe

Have you ever heard of a dictionary?

Wikipedia may be right in the general sense:

"The terms 'pipe' and 'tubing' are interchangeable." (Wikepedia)

but in specific applications, the terms pipe and tubing are not interchangeale

From the fluid mechanics point of view, the distinction was always made to point out that tubes have less friction than pipes due to the lower roughness of the inside wall (closer to ideal flow)

When you work in the actual world, the distinction is not so clear and therefore, you should go to the different standards (too many) to specify the features of the pipe / tube you need for a specific application.

So we have a clear difference when we deal with theory and lots of confussion in the actual practice.

Regarding the sizing issue, please always take into account that all size denominations are nominal and then it is a must to go to the sizing table for the particular standard to find out ID & OD. It changes according to the standard, schedule, size, materials, etc., etc.

One is pipular and the other is tubular, dude!!

The only difference is the spelling!

i think you r mentel

And where do conduits fit in to the picture?

Our local sanitary district refers to their 30' diameter (9 meter) concrete lined underground liquid conveyances as conduits.

I would agree that the terms are somewhat interchangable, and can vary depending on the audience you're facing.

You can pack a pipe with tobacco (or other more recreational substances) and smoke it.

If you try to smoke a tube, the burning rubber will likely spoil the experience, no matter how high a quality of tobacco you use.

Likewise, you may use a tube in some tires, but a pipe in the same application would be very noisy.

Here in the USA. Tubing is usually copper pipe - CTS = Copper Tubing Size. There are 3 types...M, L & K. Pipe is usually steel or PCV (IPS) (SDR26, 21, schedule, PIP, SDR35, C-900/C-905/C-909 and poly). It can also be Ductile Iron pipe, or asbestos cement.

I get my pipe repair and hot tap saddles from www.pipemanproducts.com. They have a big selection for all types of tubing and pipes.

Sozoman

pipe is used only for mass transfer where as tube is used for heat transfer along with mass transfer.