Steel pipes are found in various places. Since they are strong, they are employed underground for transporting water and gas throughout the cities and towns. They are also utilized in construction to protect electrical wires. Furthermore, steel pipes are robust and lightweight at the same time. This makes them perfect to be used in bicycle frame manufacture. Other places they find utility are in refrigeration units, automobiles,  heating and plumbing systems, street lamps, flagpoles, and medicine, to name a few.

Steel tubes are round, cylindrical forms that are hollow. Steel tubes are broadly used in structural and architectural areas. Steel tubes are measured by their outside diameter and wall thickness, unlike steel pipes.

Despite having primarily similar looks, pipes and tubes are, in fact, quite different in terminology and sizing. Also, we need to remember that pipes and tubes are rarely interchangeable.

The Differences between the Two:

1. Pipe Diameter and Tube Diameter

Steel tube is generally used for structural intents, and the OD is a significant and exact number. Steel tube size is defined by OD and the wall thickness (WT), and the calculated OD and stated OD are generally within very close tolerances of each other. However, steel tubes are usually more expensive than steel pipes due to more tight manufacturing tolerances.

Interestingly, while the stated and calculated OD's of steel tubes are almost the same in most of the cases, steel tube generally has a measured OD that is 1/8" larger than the stated OD.

Steel pipes are tubular containers used in pipeline and piping systems and commonly used in transporting gases or fluids. They are defined by "Nominal Pipe Size" (NPS) and Schedule (wall thickness). NPS is a size standard established by the American National Standards Institute (ANSI) and should NOT be confused with the different thread standards such as NPT and NPSC.

The manufacturing of Nominal Pipe Sizes from 1/8" to 12" is based on a standardized nominal outside diameter (OD) different from the measured OD. NPS pipe 14" and up have measured OD's corresponding to the nominal size.

For example, the actual outside diameter of 1¼" pipe is 1.625″ – while 1¼″ tube has a true 1.25″ outside diameter.

Tubing is more used in structures, so the OD is the important number. The strength of a steel tube counts on the wall thickness. So Tubing is defined by the outside diameter and the wall thickness. Steel tubes are also supplied in round sections and can be developed into square and rectangular tubes. Each square or rectangular steel tube has a separate mother tube created from the original round tube. The round tube will pass through a forming and a sizing section on the tube mill. It will continue through a couple of sets of Turks during the same process, which will turn the round tube into a square or a rectangular steel section.

Pipes are commonly used to transport gases or fluids, so knowing pipe's capacity. The internal cross-sectional area (defined by the ID) is essential. It's therefore not surprising that pipes are specified by the inside diameter (ID). It is common to identify pipes in inches using the measurement of NPS or "Nominal Pipe Size." The metric equivalent is called "diameter nominal" or DN. The metric designations conform to International Standards Organization (ISO) usage and apply to all plumbing, natural gas transporting, heating oil, and miscellaneous piping employed in buildings. A plumber always knows that the ID on the pipe label is only a *nominal* id. As an example, a (nominal) 1/8 wrought seamless steel pipe will typically have a *measured* id of 0.269 (schedule 40) or 0.215 (schedule 80).

2. Wall Thickness Difference

The wall thickness of pipes and tubes is essential to tell the difference. A gauge for thinner thicknesses often specifies the tubing thickness, and for thicker Tubing, it is indicated by fractions of an inch or millimetres. The normal range for Tubing is 20 gauge, which measures .035 inches, up to a thickness of 2 inches. The wall thickness of a pipe is referred to as a pipe schedule, which you can find the relevance between pipe schedule and thickness in millimetre or inch in specification ASME B36.10. The most common schedules are SCH 20, SCH 40, and SCH 80. Schedule 40 is the most common, and 80 is extra heavy. Which is needed to be noted, the pipe schedule is not set for all diameters; it varies. There is no formula between the pipe schedule and wall thickness. The only is to refer to the ASME B36.10 or relevant standards.

3. Pipes Tolerance & Tube Tolerance

Pipes are usually used for transporting or distributing, and then the properties of pressure or straightness roundness are strictly specified, the tolerance for pipes is looser than tubes comparatively. Here, tolerance refers to the diameter, wall thickness, straightness, roundness, etc.

4. Manufacturing Difference between Pipes and Tubes

As we mentioned above, tubes will require higher-level requirements. Consequently, the material production to the tube or pipe manufacturing process will be different. Tubes will require much more process, tests, inspection than pipes. The delivery time will be longer, too. The yield of tubes is comparatively much lower than pipes. Pipe manufacturing is easier than tubes, and it's in mass production.

5. Cost & Price

As per the above, manufacturing tubes will take much more labour, energy, material, etc., so the production cost is higher than pipes. And just because of the high-level requirement of tubes, the low yield of tubes will also increase the cost and price. In contrast, the process of pipes is more straightforward. And pipes are manufactured in large lots and cut the cost.

6. Use of Pipes and Tubes

Pipes are utilized for fluids and gases, such as water, oil, gas, propane, steam pipe, boiler pipe, etc. The outside & inside diameter is the crucial measurement — it suggests how much can flow through the pipe. Also, that's the reason why the pressure rating is so vital since the pressure must be under the transport or distribute pressure range.

Tubes, however, are often put to use in applications that have the requirement of precise outside diameters, like industrial parts, medical tubes, weapon parts, cooler tubes, boiler tubes, and heat exchanger tubes. Tubes are usually used in the medical sectors, construction industry, structure or load bearing, etc. The outside diameter is critical because it determines how much it can hold as a stability factor.

7. Material

Piping is usually made of carbon steel or low alloy steel. While Tubing is often made of mild steel, aluminium, brass, copper, chrome or stainless steel, etc. Different materials also lead to different costs and prices.

8. Mechanical Properties and Chemical Properties

The pressure rating, yield strength, and ductility properties are more important for pipes. However, high precision is the key to high quality for tubes, hardness, and tensile strength. Those elements like C, Mn, S, P, Si are the main chemical elements for pipes, and there are few microelements requirements. While for Tubing, the microelements are essential to the quality and process. 

9. Connections /Joint Welding

Connecting pipes is more labour-intensive as it requires welding, threading or flanges, and relevant types of equipment. Tubes can be joined quickly and easily with flaring, brazing, or couplings, but for this reason, they don't offer the same stability. Pipe welding is safer than "tube join."

10. Ductility

A pipe is available in rigid "joints," which come in various lengths depending on the material. In particular, Tubing comes in rigid complex tempered "joints" or soft tempered (annealed) rolls. Some tubing also comes in rigid "joints" or flexible rolls. The temper of the copper, whether it is a rigid "joint" or flexible roll, does not affect the sizing.

11. Surface Finish

Pipes need to be painted or coated for outdoor or underground transport to anti-corrosion or oxidation. Tubes are sour cleaning or special polish treatment for particular field use.

12. Packing

Pipes to be delivered are in a bundle or just bulk delivery. Because we need to protect the surface of the pipe from severe damage, there is no need to protect it from any light chafing. In contrast, tubes are usually wrapped with a wooden box or thin film for each tube, especially for medical purposes tubes.

13. Pipe End and Tube End

Pipe ends are usually in plain or beveled to welding. While tubes have coupling ends or specially end finish, like irregular ends, particular screw thread, etc.

14. Quantity

For long transport or distributing, piping is often used in mass quantity and for long-distance application. So, the order of pipes is usually significant. In comparison, tubes may be used in small quantities.

15. Application

Pipes accommodate larger applications with sizes that range from a half-inch to several feet. Tubes are generally used in applications that require smaller diameters. While 10-inch pipes are standard, you will rarely come across a 10-inch tube.

Each year, millions of tons of steel pipes and tubes are produced. Their indispensible usages and versatility make them the most often used products produced by the steel industry. The professional steel pipe and tube manufacturers and suppliers of India are more focusing on producing global standard products as the demand of these products are rapidly increasing worldwide.