The difference between a pipe, tube, and hollow bar

The difference between a pipe, tube, and hollow bar

 

Many people ask us the difference between a pipe, tube, and hollow bar so we’ve made this to explain the difference.

 

What is the difference 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.

Overall, the difference is the application and the way they are measured.

 

What is Pipe?

Pipes are typically used to transfer liquid or gas, and are constructed to withstand high pressure. Pipes are always round. boiler 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. = 3½” (88.9 mm)

NPS 4 actual O.D. = 4½” (114.3 mm)

NPS 12 actual O.D. = 12¾” (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?

Tubes are used for strength, mostly in structural applications, such as framing. Tubes can be round steel tube, square, or rectangle.

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.

Pipes are measured by its nominal (or inner) diameter and its wall thickness. The wall thickness is called a schedule. We typically use schedule 40 or schedule 80. A schedule is a fixed number based on the nominal diameter. For example a 0.75 inch nominal pipe, schedule 40, will always have a thickness of 0.113 inches. Tubes are measured by their outer diameter and will have a wall thickness, typically measured in inches or fractions.

Tubing is formed by running slit coils of metal through a tube mill to create a round, rectangular, or square tubular shape. The edges are then welded together using a process such as electric resistance welding or high-frequency welding. The method used depends on the type and thickness of the metal, as well as the preferences of the manufacturers. The tube is then refined with an annealing process to create the final product.

 

A hollow bar is always round and can look like a pipe or a tube, however, typically the walls are much thicker. A hollow bar has the strength of a solid round bar, but since there is no center, there is less weight per foot which can sometimes save money, without compromising strength.

A hollow bar, depending on the application, can be machined both on the inside and the outside.

Hollow bars are measured by giving an inner diameter (ID) and outer diameter (OD). Copper and Brass Sales offers pipe, tube and hollow bar in aluminum, stainless steel steel tube, copper, brass, and bronze.Hollow bar is not welded together. Instead, hollow bar is created using one of two processes. The first, called drilling, involves sending a drill through a solid bar stock. The second, called centrifugal casting, is when molten metal is poured into a cast as it undergoes high-speed rotation. The high-speed rotation forces the metal to the outside of the frame, where it hardens as it cools to create a dense, uniform final product. Hollow bar typically only come in bronze and stainless steel.

 

Uses for Tubes and Pipes

Tubes: The main use for tubing is for structural purposes. They are used in applications that call for precise outside diameters. They are defined by the outside diameter and wall thickness for construction stability. Tubes are always one whole piece from end to end. they can be flexible or orthogonal but continues in any case.

Tubes are used:

Gas line or hydraulic line

Water transferal

Protect fiber optics / wires and electrical cables

Liquid & gas transportation

Machine components

Vacuum tube in electrical circuits

Scaffolding

 

Pipes:Pipes are used mainly for transportation of fluids and gases like water, oil, gas, propane etc. The inside key measurement is the inside and outside diameter and pressure rating is important. Pipe Bollards use pipes because they require rigidity, resistance, and strength to cope with impact pressure. Pipes are the item that you lay in your house. in order to connect them, you weld (or screw) a flange to the end. They always go in straight lines. Pipes are used for:

Plumbing systems

Liquid & gas transportation

Compressed air systems

Fluid delivery systems

High-pressure storage units

Parking Bollards

 

Classification

The classification of pipes are schedule and nominal diameter. Pipe is typically ordered using the Nominal Pipe Size (NPS) standard and by specifying a nominal diameter (pipe size) and schedule number (wall thickness). The schedule number can be the same on different size pipe but the actual wall thickness will be different.
Tubes are typically ordered to outside diameter and wall thickness; however, it may also be ordered as OD & ID or ID and Wall Thickness. The strength of a tube depends on the wall thickness. The thickness of a tube is defined by a gauge number. Smaller gauge numbers indicate larger outside diameters. The inside diameter (ID) is theoretical. Tubes can come in different shapes such as square, rectangular and cylindrical, whereas piping is always round. The circular shape of the pipe makes the pressure force evenly distributed. Pipes accommodate larger applications with sizes that range from a ½ inch to several feet. Tubing is generally used in applications where smaller diameters are required.

 

Pipe vs Tube, 10 basic differences

PIPE vs TUBE	STEEL PIPE	STEEL TUBE
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
Materials	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

 

Quality

The difference in manufacturing makes for a big difference in quality. Hollow bar can be created to be flexible and fit into tight dimensions in a way that tube can’t. Tubing can also result in a lower quality product when the manufacturer is unskilled.

Avoid a reduction in quality by removing the excess weld metal and heat-treating, or annealing, the tube after welding. Otherwise, crystalline structures may affect the strength and structure of the metal that develop.

 

Materials

Most materials can be formed into tube using the welding process. This process is appropriate for any material that conducts electricity. While hollow bars can also be made out of most materials, it can be challenging to extrude strong and hard materials.

The choice between hollow bar or tube is ultimately up to you. Take into consideration what type of project you’re doing, your desired material, budget, and your project’s final application.

 

Measurement

Tube is typically ordered outside diameter and wall thickness. Tubing is usually held to tighter and more stringent tolerances and specifications than pipe. Pipe is typically ordered using nominal pipe size (NPS) standard and by specifying the nominal diameter (pipe size) and schedule number (wall thickness)

 

Telescoping Abilities

Tubes can be telescoped. Telescoping tubes are perfect for applications different pieces of material to sleeve or expand inside one another.

 

Rigidity

Pipe is rigid and cannot be shaped without special equipment. With the exception of copper and brass, tubes can be shaped with some effort. Bending and coiling tubing can be done without excessive distortion, wrinkling or fracturing.

 

Different Dimensional Tolerances

Achieving tight dimensional tolerances can be more challenging for steel tube but hollow bar can be made to be extremely homogeneous and can also possess very tight dimensional tolerances.Welding processes can create different crystalline structures near the weld zone which could affect the desired mechanical properties of the tubing.The excess weld metal should be removed to avoid stress concentrators in the welded tubing.The tube should be annealed or heat-treated after welding to ensure that a homogenous product is being created.Also, if care is not taken by the manufacturer, the welding process used for manufacturing tube can potentially create a lower quality product than desired.

 

Materials

A wide variety of materials can be formed into welded tubing. If the material can conduct electricity, electric resistance welding can be used to weld the material onto itself to create tubing. Hollow bar can be created out of most materials as well. However, harder and stronger materials may prove to be too difficult to extrude so the piercing method could be used instead.

In the end, the choice between using tube or hollow bar will ultimately come down to the application, as one is not universally better or cheaper than the other. Depending on the material type and tolerances, several design considerations should be taken into account before a choice between the two is made.

 

Fushun Metal LTD CO

Fushun Metal is a large special steel manufacturer and supplier. We are metal experts and have been providing quality customer service and products since 1998.

 

At Fushun Metal, we supply a wide range of metals for a variety of applications. Our products/stock includes: cold rolled steel tube, cold drawn steel tube, hollow bar, boiler tube, alloy steel tube, stainless steel tube, nickel alloy pipe,etc

 

We also can supply move services like heat-treatment(QT, +A, +N, +SR, +BKS), grounded, polished, cutting, beveled, painted, threaded, upsetting, boring, honing etc.

 

Send your inquiry information to us and get a free quotation today!