Difference between steel pipe and steel tube

What is a steel pipe?

steel pipe is a round hollow section manufactured by drawing a solid billet (in carbon, alloy, stainless or nickel alloy steel) through a piercing rod. Seamless pipes are considered superior to welded pipes as they are built using monolithic steel billets, with intrinsic mechanical strength, without seam welds.

Seamless steel pipes are used for the transmission and distribution of oil, gas, steam, and chemicals. Stainless steel seamless pipes offer enhanced resistance to corrosion at high temperature and pressure.

What is a steel tube?

Steel tube can be divided into seamless steel tube and welded steel tube. Generally speaking, the outer diameter is less than 89 mm but the steel tube larger than 4 mm is referred to as the small diameter seamless steel tube.

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Seamless steel tube is a kind of hollow steel, with round, square and seamless rectangular shape. Seamless steel tube consists of steel ingot or solid tube, and then hot rolled, cold rolled or cold drawn seamless steel tube. Cross section, mainly used for conveying fluids. Compared with solid steel such as round steel, the bending and torsional strength of seamless steel tube are lighter. Seamless steel tube is widely used in manufacturing structural parts and mechanical parts, such as oil drill pipe, automobile transmission shaft, bicycle bracket and steel structure scaffold.

Difference between steel pipe and steel tube

1 Diameter 2 Wall Thickness 3 Tubular Shape 4 Production Range 5 Tolerances
6 Production Process 7 Cost 8 Uses 9 Materials 10 End Connections
Difference between steel pipe and steel tube STEEL PIPE STEEL TUBE
1 Diameter

Pipe diameter refers to a nominal diameter- not actual. Pipe Schedule refers to the pipe’s wall thickness (you can find the schedule chart and specification). The actual physical outside diameter is larger than it’s nominal ODPipes 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 a 10-inch pipe is common, it is rare that you will find a 10-inch tube.

The diameter of tubing on the other hand refer to the actual outside diameter. In other words, the actual physical OD of a tube is just the same as it’s nominal OD.

diameter 01 - Difference between steel pipe and steel tube

In short: Tube is measured by outside diameter, pipe is measured by inside diameter.
There is often confusion as to which size die the customer actually needs – Pipe Size or Tubing Size.
Keep in mind that pipe size refers to a nominal – not actual – inside pipe diameter. Schedule refers to the pipe’s wall thickness. The actual physical OD is larger than it’s nominal OD.
The dimensions provided for tubing on the other hand refer to the actual outside diameter. In other words, the actual physical OD of a tube is just the same as it’s nominal OD. The size of a tube will keep the same OD no mater what the wall thickness is.
For example: The actual outside diameter of 1¼″ pipe is 1.625″ – while 1¼″ tube has a true 1.25″ outside diameter.
Consequently, both the size of tube and pipe is measured by it’s OD and the thickness.

2 Wall Thickness

The wall thickness of a pipe is referred to as a pipe schedule thickness. The most common pipe schedules are:

  •  SCH20,

  •  SCH40,

  •  and SCH80.

SCH40 is the most common and SCH80 is quite heavy.

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The thickness of a tubing is often specified by a gauge for thinner thickness and for thicker tubing it is indicated by fractions of an inch or millimeter. The normal range of tubing is 20 gauge, which is 0.035 inch up to a thickness of 2 inches.
3 Tubular Shape

Pipe, on the other hand, is always round and rigid. It cannot be shaped easily without the use of a special equipment. Pipes are usually seamless and pressure rated to avoid leakages as they usually carry liquids or gases.

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A tube’s structure does not have to be round always. It can be square or rectangular too. They are usually seam welded.
4 Production Range Extensive (up to 80 inches and above) Narrower range for tubing (up to 5 inches), larger for steel tubes for mechanical applications
5 Tolerances (straightness, dimensions, roundness, etc)

Comparing the tolerance of both tubes and pipes, the tolerance for pipes is looser than tubes.

all icons 03 - Difference between steel pipe and steel tube 

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.
6 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. The production process of a pipe is easier in comparison to tubes and more often undergoes mass production.

Tubes require a higher level of processes, tests, inspection. As a result, the delivery period is longer too. The yield of tubes is comparatively much lower than the pipes.

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7 Cost The manufacturing of tubes utilizes much more labor, energy, and material. Therefore, in case of same material, the production cost of tubes is usually higher than pipes.

The manufacturing process of pipes is easier and they are always manufactured in large lots. This lead to a cutting in the cost of pipes. 

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8 Uses Pipes are used for fluids and gases, such as water, oil, gas or propane or as steam pipe, boiler pipe etc. Just because of this, the outside & inside diameter is the key measurement — it indicates how much can flow through the pipe. Also that’s the reason why the pressure rating is so important, because the pressure must be under the transport or distribute pressure range. Tubes, however, are often put to use in applications that require precise outside diameters, like with medical tubes, weapon part, industrial parts, cooler tubes, heat exchanger tubes and boiler tubes. Tubes are usually used in medical area, construction, structure or load bearing etc. This is why the outside diameter is important because it indicates how much it can hold as a stability factor.
9 Materials

Wide range of materials.

The difference in materials is also a reason for the difference in the cost and applications.

Some widely used steel pipe standards or piping classes are:

  •  The API range – now ISO 3183. E.g.: API 5L Grade B – now ISO L245 where the number indicates yield strength in MPa

  •  ASME SA106 Grade B (Seamless carbon steel pipe for high temperature service)

  •  ASTM A312 (Seamless and welded austenitic stainless steel pipe)

  •  ASTM A36 (Carbon steel pipe for structural or low pressure use)

  •  ASTM A795 (Steel pipe specifically for fire sprinkler systems)

Tubing is available in carbon steel, low alloy, stainless steel and nickel-alloys; steel tubes for mechanical applications are mostly of carbon steel
10 End Connections The most common are beveled and plain ends Tubes generally come with coupling ends or special end finishes like irregular ends, special screw thread etc.

Source: China Steel Pipe Manufacturer – Yaang Pipe Industry Co., Limited (www.ugsteelmill.com)

(Yaang Pipe Industry is a leading manufacturer and supplier of nickel alloy and stainless steel products, including Super Duplex Stainless Steel Flanges, Stainless Steel Flanges, Stainless Steel Pipe Fittings, Stainless Steel Pipe. Yaang products are widely used in Shipbuilding, Nuclear power, Marine engineering, Petroleum, Chemical, Mining, Sewage treatment, Natural gas and Pressure vessels and other industries.)

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