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What is difference between pipe and tube?

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What is Pipe?

The pipe is a pressure-tight circular hollow section that used in piping systems to transport gases or fluids.

Pipes are used in all kinds of process fluids and services. Tubes are generally used for heat transfer applications such as heat tracing lines, heat exchange, and fired heater and also used as instrument connection lines.

What is Tube?

Tube is a circular structural member,In oil and gas industries, tubes are not just used as a structural part but also used in the heat exchanger and fired heater for a process application.

There are some differences as follows




Key Dimensions (Pipe and Tube Size Chart)

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. The NPS does not match the true diameter, it is a rough indication

The most important dimensions for a steel tube are the outside diameter (OD) and the wall thickness (WT). These parameters are expressed in inches or millimeters and express the true dimensional value of the hollow section.

Wall Thickness

The thickness of a steel pipe is designated with a "Schedule" value (the most common are Sch. 40, Sch. STD., Sch. XS, Sch. XXS). Two pipes of different NPS and same schedule have different wall thicknesses in inches or millimeters.

The wall thickness of a steel tube is expressed in inches or millimeters. For tubing, the wall thickness is measured also with a gage nomenclature.

Types of Pipes and Tubes (Shapes)

Round only

Round, rectangular, square, oval

Production range

Extensive (up to 80 inches and above)

A narrower range for tubing (up to 5 inches), larger for steel tubes for mechanical applications

Tolerances (straightness, dimensions, roundness, etc) and Pipe vs. Tube strength

Tolerances are set, but rather loose. Strength is not the major concern.

Steel tubes are produced to very strict tolerances. Tubulars undergo several dimensional quality checks, such as straightness, roundness, wall thickness, surface, during the manufacturing process. Mechanical strength is a major concern for tubes.

Production Process

Pipes are generally made to stock with highly automated and efficient processes, i.e. pipe mills produce on a continuous basis and feed distributors stock around the world.

Tubes manufacturing is more lengthy and laborious

Delivery time

Can be short

Generally longer

Market price

Relatively lower price per ton than steel tubes

Higher due to lower mills productivity per hour, and due to the stricter requirements in terms of tolerances and inspections


A wide range of materials is available

Tubing is available in carbon steel, low alloy, stainless steel, and nickel-alloys; steel tubes for mechanical applications are mostly of carbon steel

End Connections

The most common are beveled, plain and screwed ends

Threaded and grooved ends are available for quicker connections on site


The two variables that are associated with pipe size are -

The inner diameter of the pipe is measured in inches. The metric equivalent is called DN, or “nominal diameter”

Measurements for the wall thickness are taken using the schedule.  No unit of measurement is implied by the value.

pipe wall thickness increases as schedule number increases. However, you may find that schedule numbers are assigned to different wall thicknesses for different pipes. Because the NPS (number of passes) is built into the thickness, it is accounted for. If the schedule numbers on two pipes are different but the NPS is the same, the ID will be different from the OD.

Generally, tube diameters are measured in outside diameter (OD), which shows the true outer size of the tube. Industrial pipe suppliers say that one can measure the thickness of a wall in millimeters, inches, or the “gauges.” Measurements in millimeters are used to measure the thin-walled tubes in the United States, whereas thicker tubes are measured in inches.

So, Even though pipe and tube look almost identical, they are designed to serve different purposes.For more questions, Feel free contact us




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