Difference Between Tube and Pipe

people use the words pipe and tube interchangeably, and they think that both are the same. however, there are significant differences between pipe and tube.

the short answer is: a pipe is a round tubular to distribute fluids and gases, designated by a nominal pipe size (nps or dn) that represents a rough indication of the pipe conveyance capacity, a tube is a round, rectangular, squared or oval hollow section measured by outside diameter (od) and wall thickness (wt), expressed in inches or millimeters.

the difference between pipe and tube includes the following points:

shape

pipes are always round in shape. tubes can be square, rectangular or round.

measurement

pipes are only provided with an inside (nominal) diameter and a “schedule” (which means wall thickness). there’s an easy way to remember this: since pipe is used to transfer fluids or gas, the size of the opening through which the fluids or gas can pass through is probably more important to you than the outer dimensions of the pipe. tube measurements, on the other hand, are provided as an outside diameter and set ranges of wall thickness.

tolerance 

pipes are usually used for transporting or distributing, then the properties of pressure or straightness, roundness are strictly specified, the tolerance for pipes is more loose than tubes comparatively. here the tolerance refers to diameter tolerance, wall thickness tolerance, straightness tolerance, roundness tolerance etc.

applications

pipes are used for fluids and gases, such as water, oil, gas or propane or as steam pipe, boiler pipe etc. just because of this, the outside & inside diameter is the key measurement — it indicates how much can flow through the pipe. also that’s the reason why the pressure rating is so important, because the pressure must be under the transport or distribute pressure range. tubes, however, are often put to use in applications that require precise outside diameters, like with medical tubes, weapon part, industrial parts, cooler tubes, heat exchanger tubes and boiler tubes. tubes are usually used in medical area, construction, structure or load bearing etc. this is why the outside diameter is important because it indicates how much it can hold as a stability factor.

metal types

tube is available in hot rolled steel and cold rolled steel. pipe is typically black steel (hot rolled). both items can be galvanized.

size

pipe is typically available in larger sizes than tube.

strength

tube is stronger than pipe.