In some instances the terms may be used interchangeably, however, there is some key difference between tube and pipe: 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 the outside diameter (“OD”) and wall thickness (“WT”), expressed in inches or millimeters.
Manufacturing Standards
The pipe is usually manufactured to one of several industry standards, both international and national, providing global consistency. This makes the use of fittings such as elbows, tees, and couplings more practical. The tube is more commonly manufactured to custom configurations and sizes using a wider range of diameters and tolerances and is different worldwide.
Diameter
The main difference between a pipe and a tube is that a pipe is usually specified by a nominal diameter with a constant outer diameter (OD) and a non-dimensional number for wall thickness called the “schedule”. The tube is specified by the OD and wall thickness.
There is often confusion as to Pipe Size or Tubing Size. The pipe size refers to a nominal – not actual – inside pipe diameter. The actual physical OD of a tube is just the same as its nominal OD. The size of a tube will keep the same OD no matter what the wall thickness is. So both the size of the tube and pipe is measured by their OD and thickness.
There’s an easy way to remember this: since the 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.
Telescoping Abilities
Tubes can be telescoped. Telescoping tubes are perfect for applications of different pieces of material to sleeve or expand inside one another. Remember to account for the flash weld inside the tube. Pipe, on the other hand, does not have a flash weld.
Rigidity
The pipe is rigid and cannot be shaped without special equipment. With the exception of copper and brass tubes can be shaped relatively easily, and tubes can be shaped with some effort. Bending and coiling tubing can be done without excessive distortion, wrinkling, or fracturing.
Applications
Heavy industry commonly uses piping rather than tubing. Pipes are used to transport something, and tubes to construct something; hence, tubes are defined by the outside diameter and wall thickness (for construction stability), and pipes are measured by inside diameter to allow a calculation for transportation viz., speed, volumes, etc.
Tubes are used in structural applications. The outside diameter is important since it will indicate how much it can hold as a stability factor.
Only pipes are pressure rated and intended to be used for the transference of fluids or gas, so making it is important to know the capacity. The circular shape of the pipe makes it efficient when handling pressure from the liquid flowing through.
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- Shape: Pipes are always round in shape. Tubes can be square, rectangular, or round.
- Metal Types: Tube is available in hot-rolled steel and cold-rolled steel. The pipe is only hot rolled. Both items can be galvanized.
- Size: Pipe is typically available in larger sizes than the tube. So pipes accommodate larger applications, and tubing is generally used where small diameters are required.
- Strength: The tube is stronger than the pipe. Tubes perform better in applications that require durability and strength.
More bending methods for metal profiles
Reference Reading: Best Beginner’s Guide to Metal Profile Bending