Knowing the differences between pipe and tube is essential for any engineering, manufacturing, or construction professional. In addition, knowing when to use each type of material and the varied performance characteristics of pipe and tube can be a critical factor in the success of any project. In this blog, we will explore the differences between pipe and tube and examine why a thorough understanding of the two is essential.
What is a Pipe?
Pipes are essential for various applications – from conveying fluids and gases such as oil, gas, propane, steam, acids, and water to providing structural support. The inside diameter (pipe I.D.) is the most crucial factor when selecting a pipe. This diameter indicates the rough fluid-conveying capacity of the pipe and is expressed in “NPS” or “D.N. (nominal pipe size).
The pipes outside diameter (O.D.) may vary depending on the nominal size and the pipe wall thickness. For example, a 2-inch pipe will have an inside diameter of approximately 2 inches but an outside diameter of 2.375 inches.
The pressure rating, yield strength, and ductility are the most critical mechanical parameters when selecting a pipe for a particular application. Therefore, choosing a pipe with the correct specifications for your specific application is essential.
As professional engineers and designers, we rely on the precise specifications of the ASME B36.10 and ASME B36.19 for the accurate design and implementation of pipe systems. These standards provide the necessary combinations of nominal pipe diameters and wall thicknesses (schedules) for carbon, alloy, and stainless-steel pipes.
What is a Tube?
The word “tube” refers to various hollow sections with different shapes and sizes, widely used in pressure equipment, mechanical applications, and instrumentation systems. Tubes are designated by precise measurements of their outside diameter and wall thickness, measured in either inches or millimeters. Knowing the outer diameter and the wall thickness allows you to calculate the inside diameter of the tube accurately.
Is It a Pipe or a Tube?
In some cases, the terms “tube” and “pipe” may be used interchangeably. However, the two have critical differences, especially regarding material order, tolerance, and application. Tubing is often used in structural applications, where the outside diameter is an essential factor. That is because it indicates the stability of the material. On the other hand, pipes are more commonly used for transporting gases or liquids, which means that the pipe’s capacity is crucial. The circular shape of the pipe allows for efficient handling of the pressure from the liquid flowing through it. Knowing the difference between tubes and pipes can help you make the right choice for your specific application.
Classification
Pipes are classified according to their nominal diameter and schedule number, which is the thickness of the pipe wall. To order a pipe, specify its Nominal Pipe Size (NPS) and the schedule number. While the schedule number remains the same for different size pipes, the actual wall thickness will vary. Therefore, knowing this information is essential for ensuring you get the suitable pipe for your project.
Tubes are typically ordered according to the outside diameter (O.D.) and wall thickness; however, they can also be ordered as O.D. & I.D. or I.D. and wall thickness. The strength of a tube depends on its wall’s thickness, typically indicated by a gauge number. The smaller the gauge number, the larger the outside diameter. Inside diameters are theoretical.
Tubes come in various shapes, such as square, rectangular, and cylindrical, while piping is always round. The round shape of pipes helps evenly distribute the pressure force. Pipes are used for larger applications ranging from a ½ inch to several feet. Tubing is generally used in applications when smaller diameters are required.
Ordering Your Tubing or Pipe
Tubing and piping can often be confusing to order. To make it easier, tubing is typically ordered to outside diameter and wall thickness, but it can also be ordered as O.D. & I.D. or I.D. and Wall Thickness. Although tubing has 3 dimensions (O.D., I.D., and wall thickness), only two may be specified with tolerances, while the third is theoretical. Therefore, tubing is usually ordered and held to tighter and more stringent tolerances and specifications than a pipe. On the other hand, pipes are typically ordered using the Nominal Pipe Size (NPS) standard, which requires specifying a nominal diameter (pipe size) and schedule number (wall thickness). Both tubes and pipes can be cut, bent, flared, and fabricated – but for more tips and tricks on how to get the best possible order, check out our top 10 tips for ordering tubing and piping.
Characteristics
The terms ‘tube’ and ‘pipe’ are often used interchangeably, but some subtle differences can make a significant impact when it comes to industrial applications.
Shape
While a pipe is always round, a tube can come in various shapes, including square, rectangular, or round. This means that when selecting the correct type of pipe or tube for your project, you must consider the most suitable shape for the job.
Measurement
To accurately measure a tube, it’s important to order it by its outside diameter and wall thickness. Tubing is usually held to more precise and stringent tolerances and specifications than the pipe, so it’s essential to use the exact measurements. When ordering a pipe, you should use the nominal pipe size (NPS) standard and specify the nominal diameter (pipe size) and schedule number (wall thickness) to ensure accuracy.
Telescoping Abilities
Tubes that can be telescoped are perfect for a variety of applications. Telescoping tubes are ideal for creating seamless connections between two pieces of material – allowing you to sleeve or expand one piece inside another. With telescoping tubes, you can easily achieve the exact fit and length you need for your project.
Rigidity
A pipe is rigid and cannot be easily shaped without special equipment, except for copper and brass tubes which can be shaped with some effort. Bending and coiling can be done without excessive distortion, wrinkling, or fracturing, allowing for greater project flexibility. With the proper tools and techniques, you can create the exact shape you need for your project.
Applications
Tubes and pipes are commonly used in medical applications that require a precise outside diameter. This outside diameter is critical because it directly impacts the device’s stability and capacity. Pipes are ideal for transporting gasses or liquids, as their circular shape makes them exceptionally efficient at handling pressure from the flowing liquid. Medical device manufacturers can ensure their products are safe and effective by using pipes and tubes with the correct outside diameter.
Metal Types
Tubes and pipes are both made from metal and can be galvanized, however, there are distinct differences between the two. Tubes are typically cold-rolled, meaning that they have been compressed and formed at a lower temperature, while pipes are only hot-rolled. The cold-rolling process creates a more robust and more durable metal that can better withstand higher pressures, making tubes an ideal choice for many applications. In addition, cold rolling allows for greater precision in size and shape than hot rolling. On the other hand, hot-rolling is faster and more cost-effective, making it the perfect option for pipes. Both tubes and pipes can be galvanized for added protection and durability.
Size
Pipes and tubing are two of the most versatile tools in modern plumbing and engineering applications. Pipes are typically used when larger diameters are required and can accommodate many applications. Tubing, on the other hand, is usually the preferred option when smaller diameters and tighter spaces are needed. By choosing the suitable material for the job, pipes and tubing can provide a reliable, efficient, and cost-effective way to complete any project.
Strength
Tubes are stronger and more durable than pipes, making them the ideal choice for applications that require superior strength and performance. Their superior strength and durability make them ideal for applications that require maximum durability and strength. With their superior strength and performance, tubes are the perfect choice for any application that requires superior strength and performance.
