What is the difference between pipe and tube? Some people know that pipe is round, while the cross-sectional shape of tube varies. In addition to these, do you know other differences between them? Let’s introduce their differences:
What is Tube
- Tubes serve a multitude of purposes, including structural applications, mechanical components, precision instruments, and fluid transfer in heat exchangers.
- Tube sizes are typically determined by the outer diameter (OD) and wall thickness, which together define the inner diameter.
- Tube dimensions can be specified in either inches or millimeters (mm).
- Tubes provide an extensive array of material options, specifically tailored to meet distinct mechanical or engineering requirements, such as stainless steel, aluminum alloy, copper, titanium, and more.
- Tubes generally have tighter dimensional tolerances than pipes and are suitable for higher precision applications.
What is Pipe
- Pipes play a crucial role in efficiently transporting various fluids, such as water, oil, natural gas, and more. Additionally, they are versatile and can be used for structural purposes.
- Pipe size is typically defined by the inside diameter (ID) or nominal diameter (ND), and it adheres to a standard wall thickness (Schedule), such as SCH 40 or SCH 80.
- Pipe size is predominantly measured in inches.
- Various materials are utilized for pipes, including carbon steel, stainless steel, copper, PVC, and more, allowing for diverse applications.
- Pipe wall thickness is determined by the standard (Schedule), with thicker walls being well-suited for high-pressure applications.
Difference Between Pipe and Tube in OD
Outside diameter (OD) and wall thickness (WT) are essential dimensions of pipes. Inside diameter (ID) is critical in determining liquid capacity and is calculated by subtracting twice the wall thickness (2 × WT) from the outside diameter (OD). This relationship is critical when designing pipes to transport fluids because the inside diameter directly affects the system’s flow rate and pressure drop.
To better illustrate the difference between pipe OD and tube OD, we can compare them through a specific example:
Example
Suppose we have a 2-inch pipe and a 2-inch tube. Although their outside diameters (OD) are nominally 2 inches, the situation is different.
| Item | Pipe | Tube |
| Nominal Size | 2 inches | 2 inches |
| Actual OD | 2.375 inches (about 60.33 mm) | 2.000 inches (about 50.80 mm) |
| ID | Depends on wall thickness (e.g., SCH 40 with 0.154-inch wall thickness, ID = 2.067 inches) | Depends on wall thickness (e.g., 0.065-inch wall thickness, ID = 1.870 inches) |
| OD Characteristics | OD is usually fixed and independent of nominal size | OD is precisely measured and matches nominal size |
| Main Application | Focuses on inner diameter (ID) and fluid capacity, mainly used for fluid transportation | Focuses on outer diameter (OD) accuracy, suitable for applications requiring high precision |
Key Differences:
- The Pipe’s outer diameter (OD) is standardized and independent of the nominal size, mainly focusing on the inner diameter (ID) and fluid capacity.
- The Tube’s outer diameter (OD) is precisely measured and is a critical dimension, especially in applications requiring accuracy.
The above information shows that although both the Pipe and Tube are nominally 2 inches, the actual OD of the Pipe is larger than that of the Tube. This reflects that the Pipe is mainly used for fluid transportation, while the Tube is more concerned with dimensional accuracy.
10 basic differences between Pipe and Tube
| # | Criteria | Pipe | Tube |
| 1 | Definition | Used primarily for transporting fluids and gases, focusing on the internal diameter (ID). | Used for structural and mechanical purposes, focusing on the external diameter (OD). |
| 2 | Measurement | Typically measured by its nominal diameter (ND) and schedule (wall thickness). | Measured by its exact outer diameter (OD) and wall thickness. |
| 3 | Application | Commonly used in plumbing, pipelines, and gas systems where fluid flow capacity is crucial. | Often used in engineering, automotive, HVAC, and structural applications where precision is essential. |
| 4 | Size Tolerance | Looser tolerances, focusing on flow capacity. | Tighter tolerances for precise applications and fitment. |
| 5 | Standards | Governed by standards like ASTM, ASME, and API, focusing on the nominal size. | Governed by standards like ASTM and ISO, focusing on exact measurements and performance. |
| 6 | Shape | Typically round, as the round shape efficiently withstands internal pressure. | Can be round, square, rectangular, or custom shapes, depending on the application. |
| 7 | Strength | Strength measured based on its schedule and intended pressure rating. | Strength related to its precise dimensions, material grade, and structural integrity. |
| 8 | Connection | Connected using threaded, welded, or flanged joints designed for fluid tightness. | Connected using couplings, flanges, or specialized joints where alignment and fit are key. |
| 9 | Wall Thickness | Wall thickness varies with schedule; ID changes with different schedules for the same OD. | Wall thickness specified with minimal variation in OD, maintaining consistency across applications. |
| 10 | Cost | Generally less expensive due to simpler manufacturing and looser tolerances. | Typically more expensive due to tighter tolerances and precision requirements. |
Why SSM is Your Trusted Supplier of Steel Pipe and Tube
Choosing the right pipe or tube for your project is a critical decision, and at SSM, we understand that it can’t be left to chance. We’re more than just a supplier, we’re your reliable partner in metals that meet ASTM quality standards. We carefully source and offer a comprehensive range of metals that not only meet, but often exceed, stringent standards, and we ensure you can count on us.
Choose with confidence, choose quality, choose SSM. Contact us today for a free quote and experience the difference of working with a true metals expert.
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