The primary difference between pipe and tubing is how the size is designated. Pipe is designated by a "Nominal Pipe Size" based upon the ID (inside diameter) of the most common wall thickness. Tubing is designated by the measured OD (outside diameter). For Example: A 3/4 inch iron pipe has an OD of 1.050 inches, while a 3/4 inch steel tube has an OD of 0.75 inches.

The Copper industry calls all cooper tubular products "Tubes" but they designate a "Type". Each type has specified OD and ID dimensions

actually tube is used when we need to transfer heat from its walls and we want this to be happen while in pipes we try to stop the heat transfer such as we use tubes in boilers because we make steam we need to transfer the heat while when we transport steam we use pipes because we wana save heat energy.

tube, n--hollow wrought product that is long in relation to its cross

section, which is symmetrical and is round, elliptical, a regular

hexagon or octagon, or square or rectangular with sharp or rounded

comers, and has uniform wall thickness except as affected by

comer radii.

Alclad tube, n--a composite tube product comprised of an

aluminum-alloy core having on either the inside surface

(only) or outside surface (only) a metallurgically bonded

aluminum or aluminum-alloy coating that is anodic to the

core, thus electrolytically protecting the core against

corrosion.

arc-welded tube, n--tube made from sheet or plate formed by

positioning two opposite edges of the metal together and butt

welded by either the gas-tungsten or gas-metal arc-welding

method, with or without the use of filler metal; individually

fabricated tube may be welded together to produce the

ordered length.

drawn tube, n--tube brought to final dimensions by drawing

through a die.

extruded tube, n--tube formed by hot extruding.

finned tube, n--tube which has integral fins or projections

protruding from its outside surface.

heat exchanger tube, n--tube used in apparatus in which fluid

inside the tube will be heated or cooled by fluid outside the

tube, but the term is usually not applied to coiled tube or to

tube for use in refrigerators or radiators.

seamless tube, n--a tube that does not contain any junctures

(metallurgical welds) resulting from the method of

manufacture and may be produced by die and manrel, or by

hot piercer processes.

sized tube, n--tube that, after extrusion, has been cold drawn a

slight amount to minimize ovality.

structural tube, n--tube commonly used for structural purposes.

welded tube, n--tube produced by forming and seam-welding

sheet longitudinally. B 881, B07

tube, n--a hollow product of round or any other cross section having

a continuous periphery of uniform shape.

Noa~ The following standards use the same definition for "tube,"

less the words "of uniform shape."

pipe, n--tube in standardized combination of outside diameter and

wall thickness, commonly designated by "Nominal Pipe Sizes"

and "ANSI Schedule Numbers."

drawn pipe, n--pipe brought to final dimensions by drawing

through a die.

extruded pipe, n--pipe formed by hot extruding seamless pipe, n--extruded or drawn pipe which does not

contain any line junctures resulting from the method of

manufacture.

structural pipe, n--pipe commonly used for structural purposes.

B 881, B07

pipe, n--a tubular metal product, cast or wrought, of dimensions that

conform to those referred to commercially as standard pipe sizes.

B 899, B02

pipe--a tube or elongated hollow concrete structure intended to

transmit flow between locations. C 822, C13

pipe--See vitrified clay pipe. C 896, C04

pipe, n--as relatedto heating, ventilating, or air conditioning systems,

a cylindrical conduit for the conveyance of liquids or semi-solids.

E 176, E05

pipe, n--a tubular conduit for transport of fluids or finely divided

solids; also, a hollow structural member or safety barrier; a hollow

product of round cross section.

pipe railing system--See railing system. E 631, E06

pipe, n--hollow round section of metal or other material, the size of

which is usually designated by nominal size, in inches (millimeters),

as influenced by inside diameter and wall thickness.

E 1481,