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What is the difference between Pipe and Tube?

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.

What is Pipe?

Pipe is a hollow section with round cross section for the conveyance of products. The products include fluids, gas, pellets, powders and more.

The most important dimensions for a pipe is the outer diameter (OD) together with the wall thickness (WT). OD minus 2 times WT (SCHEDULE) determine the inside diameter (ID) of a pipe, which determines the liquid capacity of the pipe.

EXAMPLES OF ACTUAL O.D. AND I.D.

ACTUAL OUTSIDE DIAMETERS

• NPS 1 actual O.D. = 1.5/16" (33.4 mm)
• NPS 2 actual O.D. = 2.3/8" (60.3 mm)
• NPS 3 actual O.D. = 3.1/2" (88.9 mm)
• NPS 4 actual O.D. = 4.1/2" (114.3 mm)
• NPS 12 actual O.D. = 12.3/4" (323.9 mm)
• NPS 14 ACTUAL O.D. = 14" (355.6 MM)

ACTUAL INSIDE DIAMETERS OF A 1 INCH PIPE.

• NPS 1-SCH 40 = O.D.33,4 mm - WT. 3,38 mm - I.D. 26,64 mm
• NPS 1-SCH 80 = O.D.33,4 mm - WT. 4,55 mm - I.D. 24,30 mm
• NPS 1-SCH 160 = O.D.33,4 mm - WT. 6,35 mm - I.D. 20,70 mm

Such as above defined, the inside diameter is determined by the oudside diameter (OD) and wall thickness (WT).

The most important mechanical parameters for pipes are the pressure rating, the yield strength, and the ductility.

The standard combinations of pipe Nominal Pipe Size and Wall Thickness (schedule) are covered by the ASME B36.10 and ASME B36.19 specifications (respectively, carbon and alloy pipes, and stainless steel pipes).

What is Tube?

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

Tubes are indicated with outer diameter and wall thickness, in inches or in millimeters.

In order to understand pipe class and piping specification, one must primarily understand the piping basics.

Pipe covers a very large part of any process plant. I am sure most of us have seen the complex piping system at the Oil Exploration platform, Refinery and Petrochemical complex.

Pipes are used to carry liquids, gases, slurries, or fine particles.

A piping system is generally considered to include the complete interconnection of pipes, including in-line components such as pipe fittings and flanges. Pumps, heat exchanges, valves and tanks are also considered part of piping system. Piping systems are the arteries of our industrial processes and the contribution of piping systems are essential in an industrialized society.

The pipe is a straight pressure tight cylindrical hollow, used in the piping system to transport liquid, gas and sometimes solids.

Different types of pipes used in various design conditions, considering technical and commercial parameters. For small & medium sizes requirement, seamless pipes are more popular whereas, for larger diameter, welded pipes are more economical.

Based on the way pipe manufacturing, Pipes are mainly classified into two categories seamless and welded. Welded pipes are further classified based on the method of welding. There are two ways to weld pipe 1st is with filler metal and 2nd is without filler metal.

Submerged Arc Welding process is with filler metal welding whereas ERW/EFW and HFW are no filler welding methods to weld the pipe. SAW pipes are further classified as straight seam and spiral seam pipe. Straight seam pipes are also known as L-SAW or long seam SAW pipes. Medium diameter straight SAW pipe has single seam whereas large diameter pipe has a two-weld seam.