Among the general population, "pipe" and "tube" are interchangeable terms. They're even synonyms in Thesaurus.com. But, for manufacturers and others who work with pipes and tubes on a daily basis, they are very different.
For instance, we specify on our website that Tube Production & Tube Bending are some of our capabilities. When we say "tube," we mean tube.
So, what's the difference? Here are the biggest distinctions:
Pipes are purely vessels used for transporting liquids and gases.
Tubes are commonly used for structural purposes, though they can also transport fluids.
Pipes are always round, and can range from half an inch in diameter to several feet across. If you see a big hollow cylinder lying around on a construction site, it's a pipe.
Pipe sizes are generally more lenient than tube sizes - tubes are made to exact specifications (and tend to be more expensive because of it) while pipes can vary around an approximate schedule or diameter.
Tubes can be cylindrical, square, rectangular, and with the right manufacturer, any shape you can possibly imagine.
Tubes are much smaller than pipes - one of the largest standard sizes is ten inches in diameter.
Pipes are measured by their nominal pipe size (approximate outer diameter) and the schedule (wall thickness of the pipe).
Those are the two common pipe measurements, but they aren't the full story. To get the most important measurement, the inner diameter, the schedule must be subtracted from the NPS.
The inner diameter is most important because it indicates the capacity of the pipe - the volume of fluid it can hold at a given time. After all these measurements are taken, the capacity is what the customer cares about the most.
Tubes, on the other hand, are measured by wall thickness and their exact outer diameter. Since tubes are more commonly used in structural applications, their strength is the most important factor.
Wall thickness (also known as the "gauge") is the most reliable indicator of a tube's strength.
However, we've done some work for clients where we've increased the strength of the tube while keeping the walls thin. Here's the full story if you're curious.
If you're still a little confused about tube and pipe measurements, here is a helpful infographic by Commercial Metals:
Tubes and pipes are actually very different. Although, we probably sound like the person who has a strong preference for rainbow sprinkles over chocolate sprinkles.
Does it matter? Absolutely (to us, at least)!