What’s the Difference between Steel Pipes and Steel Tubes?

Do You Know the Difference between Steel Pipes and Steel Tubes?

People often think that both are the same. They both can be seamless or welded. However, there are significant differences between steel pipe and steel tube. A pipe is round. A tube can be round, square, rectangular, or oval in shape. Pipes are primarily designed to carry fluids and gases, regardless of the industry in which they are deployed. Tubes can also transport fluids and gases but are typically designed for many more applications than the pipe, including industrial, medical, aerospace, military, transportation, architecture, and construction.

What are Steel Pipes?

Steel pipe has been produced in the US since the early 1800s. Pipe is a hollow section with a round cross-section, primarily made for the transportation of products including fluids, gas, pellets, powders, and more. But steel pipes are used in a variety of ways. They are used underground for transporting water and gas throughout cities and towns. They are also specified in construction to protect electrical wires. Steel pipes can be strong, but lightweight. This makes them great for bicycle frames. They are also used in the making of parts for automobiles, refrigeration units, heating and plumbing systems, flagpoles and street lamps, just to name a few.

The most important dimension for a pipe is the outer diameter (OD) together with the wall thickness (WT). OD minus 2 times WT (schedule) determines the inside diameter (ID) of a pipe, which determines the liquid capacity of the pipe.  In our industry, when we talk about pipe, we tend to call out an (ID) and schedule, like 2 inch schedule 40, or 14 inch extra heavy.  Examples of walls or schedules are Sch. 40, Sch. 80, Sch. Standard (STD), Sch. XS/XH, and Sch. XXS.  Most pipe is sold in 21 or 42 foot lengths.

What are Steel Tubes?

The word tube refers to round, square, rectangular, and oval hollow sections that are used for pressure equipment, for mechanical applications, and for instrumentation systems.

Steel tubing can be made from various raw materials, like iron, carbon, manganese, vanadium, and zirconium. Like pipe, tubing can be produced as either seamless or welded. Seamless tubing is a solid block of steel that is rolled into a round shape and then pierced and stretched into its final length. Think of having a wad of play dough and rolling it into a cylinder. Then push your finger through the middle and make it longer with the extra dough. That’s how it’s produced, but it’s hot and spinning and completely done with machines. Welded steel tubing, on the other hand, is made from the coil. The coil is slit and then rolled up into a round shape and the ends are welded together. From there, the tubing can simply be cut to a certain length as round tubing, or it can be further deformed into other shapes, such as square, rectangular, oval, etc.

Tubes are indicated with outer diameter (OD) and wall thickness (WT), in inches or in millimeters.  In our industry, buyers often refer to the item they want as an (OD) and a wall thickness (WT).  Examples of wall thicknesses are 11 gauge, 1/4”, 3/8” and 5/8”.  Tubing is sold in 20, 24, 40 and 48 foot lengths, but can be easily produced in custom lengths.