Posted by Wayne Moncla on Aug 18, 2015

You may have wondered:what is the difference between pipe and tube? We reached out to our friends at Federal Steel Supply, Inc for this guest post.

Pipes and Tubes may look similar because they are both of similar shape, with a hollow vacuum running through the center of them.  But, you would be surprised that there are many differences between them.

Diameter and Thickness

Pipe and Tube diameters differ in how they are measured.  The diameter of a pipe is referred to its nominal internal diameter and not the actual outside diameter.  In contrast, the diameter of tube is measured by the actual outside diameter of the tube.

An important factor is how the wall thickness of the pipe and tube is measured.  Pipe wall thickness is denoted by schedules; there are multiple schedules for each diameter.  The larger the schedule number, the thicker the wall.  The outside diameter remains constant over the entire schedule range.

Tubing wall thickness is measured by gauge number (example 20 gauge is roughly 0.035” thickness) for thinner tubes and by fractions for thicker walled tubes.

Tolerances

The tolerances of pipe and tube differ as well.  Pipe has a looser tolerance than tube, which are commonly tighter in tolerances. Tolerance refers to diameter tolerance, wall thickness tolerance, straightness tolerance, and roundness tolerance.  

Manufacturing difference

The fabrication of pipe is easier than tube; most pipes are made from a flat strip of steel that is formed into a round shape and welded together.  There is also seamless pipe that is not welded. This particular pipe is made from a solid round and more expensive; these are typically heavier wall pipe. 

Tubing requires many more production operations to make a finished product. It is normally of a lot higher quality than pipe, resulting in increased testing and inspections. Pipe production far outweighs tubing production.

Connection

Pipes are typically connected by threading the ends and screwing together with couplings, T’s, or elbows. Another common way of connecting pipes is welding them together or to other components, such as flanges.

Tubes can be connected by flaring, brazing, tube couplings, or welding.  Pressures within the tube normally dictate the type of coupling used.

Uses of pipes and tubes

Pipe is used for the transport of liquids and gases such as water, oil, natural gas, or propane.  Pipe sizes and schedules are specified for the application depending on the internal pressure required of the material being transported, the volume of flow required and the material it is made of (if corrosion is an issue). 

Tube, on the other hand, is used for many applications including structural, high pressure hydraulic systems, medical & food systems, boilers & heat exchangers, as well as several others.  Tubing is made in many more grades of material and sizes than pipe; it can also be square or rectangular in shape, in addition to round.

Cost and price

Due to the ease of manufacturing pipe, it is far less expensive and is manufactured in vast amounts, which also reduces the cost.  Tubing, as mentioned above, is of a higher quality requiring more steps in the manufacturing process and thus is comparatively more expensive.  

Conclusion

It’s easy to see why the two are thought to be interchangeable, but everything from the way they measured to their actual use differs dramatically.  Before beginning a project, make sure you know what you need and that you get the right type of pipe or tube

Jessica Kane is a professional blogger who writes for Federal Steel Supply, Inc., a leading supplier of carbon, alloy and stainless steel in pipe, tube, fittings and flanges.

 

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Topics: pipe fabrication

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