You use nominal pipe size schedule to describe pipe diameter and wall thickness without relying on exact measurements. ASME B36.10 and ASME B36.19 set standards for pipe size, schedule, and diameter in your projects. When you work with NPS, you ensure that fittings and pipes match correctly. Understanding these terms helps you select the right pipe for your application.
Note: Accurate conversion between NPS and actual diameter keeps your pipe selection reliable.
Key Takeaways
- Nominal pipe size (NPS) is a standard way to identify pipe sizes without exact measurements. It helps ensure compatibility between pipes and fittings.
- Understanding pipe schedules is crucial. Higher schedule numbers indicate thicker walls, which provide greater strength and pressure ratings.
- ASME B36.10 applies to carbon and alloy steel pipes, while ASME B36.19 focuses on stainless steel pipes. Each standard has different wall thicknesses and schedule numbers.
- Always check the nominal pipe size, schedule, and material type before selecting pipes. This practice helps avoid costly mistakes and ensures safety.
- Use pipe charts to compare nominal sizes, outer diameters, and wall thicknesses. These charts guide you in selecting the right pipe for your project.
Nominal Pipe Size Basics
What Is Nominal Pipe Size?
You often see the term nominal pipe size when you select pipes for a project. This term does not describe the exact diameter of a pipe. Instead, it gives you a convenient way to identify and compare different pipe sizes. The nominal pipe size system started with the iron pipe size system. In the past, people used the internal diameter to classify pipes, such as IPS-6 for a 6-inch internal diameter pipe. As technology advanced, the industry needed a better way to handle new materials and higher service demands. The nominal pipe size system evolved to meet these needs. In 1927, the American Standards Association formalized the system for wrought steel and wrought iron pipes.
The nominal pipe size schedule helps you match pipes, pipe fittings, and flanges, even when the actual measurements differ.
You should remember that nominal pipe size is a non-dimensional number. It does not match the actual outer diameter or inner diameter of the pipe. For example, a 2-inch nominal pipe size does not mean the pipe has a 2-inch outer diameter. The table below shows how nominal pipe size compares to actual outer diameter for common pipes:
| Nominal Pipe Size | Outside Diameter | Nominal Wall Thickness | |||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| NPS | DN | OD | SCH5/5S | SCH10S | SCH10 | SCH20 | SCH30 | SCH40S/STD | SCH40 | SCH60 | SCH80S/XS | SCH80 | SCH100 | SCH120 | SCH140 | SCH160 | XXS |
| â…› | 6 | 10.3 | – | 1.24 | 1.24 | – | 1.45 | 1.73 | 1.73 | – | 2.41 | 2.41 | – | – | – | 3.15 | 4.83 |
| ¼ | 8 | 13.7 | – | 1.65 | 1.65 | – | 1.85 | 2.24 | 2.24 | – | 3.02 | 3.02 | – | – | – | 3.68 | 6.05 |
| â…œ | 10 | 17.1 | – | 1.65 | 1.65 | – | 1.85 | 2.31 | 2.31 | – | 3.2 | 3.2 | – | – | – | 4.01 | 6.40 |
| ½ | 15 | 21.3 | 1.65 | 2.11 | 2.11 | – | 2.41 | 2.77 | 2.77 | – | 3.73 | 3.73 | – | – | – | 4.78 | 7.47 |
| ¾ | 20 | 26.7 | 1.65 | 2.11 | 2.11 | – | 2.41 | 2.87 | 2.87 | – | 3.91 | 3.91 | – | – | – | 5.56 | 7.82 |
| 1 | 25 | 33.4 | 1.65 | 2.77 | 2.77 | – | 2.90 | 3.38 | 3.38 | – | 4.55 | 4.55 | – | – | – | 6.35 | 9.09 |
| 1¼ | 32 | 42.2 | 1.65 | 2.77 | 2.77 | – | 2.97 | 3.56 | 3.56 | – | 4.85 | 4.85 | – | – | – | 6.35 | 9.7 |
| 1½ | 40 | 48.3 | 1.65 | 2.77 | 2.77 | – | 3.18 | 3.68 | 3.68 | – | 5.08 | 5.08 | – | – | – | 7.14 | 10.15 |
| 2 | 50 | 60.3 | 1.65 | 2.77 | 2.77 | – | 3.18 | 3.91 | 3.91 | – | 5.54 | 5.54 | – | – | – | 8.74 | 11.07 |
| 2½ | 65 | 73 | 2.11 | 3.05 | 3.05 | – | 4.78 | 5.16 | 5.16 | – | 7.01 | 7.01 | – | – | – | 9.53 | 14.02 |
| 3 | 80 | 88.9 | 2.11 | 3.05 | 3.05 | – | 4.78 | 5.49 | 5.49 | – | 7.62 | 7.62 | – | – | – | 11.13 | 15.24 |
| 3½ | 90 | 101.6 | 2.11 | 3.05 | 3.05 | – | 4.78 | 5.74 | 5.74 | – | 8.08 | 8.08 | – | – | – | – | – |
| NPS | DN | OD | SCH5/5S | SCH10S | SCH10 | SCH20 | SCH30 | SCH40S/STD | SCH40 | SCH60 | SCH80S/XS | SCH80 | SCH100 | SCH120 | SCH140 | SCH160 | XXS |
| 4 | 100 | 114.3 | 2.11 | 3.05 | 3.05 | – | 4.78 | 6.02 | 6.02 | – | 8.56 | 8.56 | – | 11.13 | – | 13.49 | 17.12 |
| 5 | 125 | 141.3 | 2.77 | 3.40 | 3.40 | – | – | 6.55 | 6.55 | – | 9.53 | 9.53 | – | 12.7 | – | 15.88 | 19.05 |
| 6 | 150 | 168.3 | 2.77 | 3.40 | 3.40 | – | – | 7.11 | 7.11 | – | 10.97 | 10.97 | – | 14.27 | – | 18.26 | 21.95 |
| 8 | 200 | 219.1 | 2.77 | 3.76 | 3.76 | 6.35 | 7.04 | 8.18 | 8.18 | 10.31 | 12.7 | 12.7 | 15.09 | 18.26 | 20.62 | 23.01 | 22.23 |
| 10 | 250 | 273.1 | 3.4 | 4.19 | 4.19 | 6.35 | 7.8 | 9.27 | 9.27 | 12.7 | 12.7 | 15.09 | 18.26 | 21.44 | 25.4 | 28.58 | 25.4 |
| 12 | 300 | 323.9 | 3.96 | 4.57 | 4.57 | 6.35 | 8.38 | 9.53 | 10.31 | 14.27 | 12.7 | 17.48 | 21.44 | 25.4 | 28.58 | 33.32 | 25.4 |
| 14 | 350 | 355.6 | 3.96 | 4.78 | 6.35 | 7.92 | 9.53 | 9.53 | 11.13 | 15.09 | 12.7 | 19.05 | 23.83 | 27.79 | 31.75 | 35.71 | – |
| 16 | 400 | 406.4 | 4.19 | 4.78 | 6.35 | 7.92 | 9.53 | 9.53 | 12.7 | 16.66 | 12.7 | 21.44 | 26.19 | 30.96 | 36.53 | 40.49 | – |
| 18 | 450 | 457.2 | 4.19 | 4.78 | 6.35 | 7.92 | 11.13 | 9.53 | 14.27 | 19.05 | 12.7 | 23.83 | 29.36 | 34.93 | 39.67 | 45.24 | – |
| 20 | 500 | 508 | 4.78 | 5.54 | 6.35 | 9.53 | 12.7 | 9.53 | 15.09 | 20.62 | 12.7 | 26.19 | 32.54 | 38.1 | 44.45 | 50.01 | – |
| 22 | 550 | 559 | 4.78 | 5.54 | 6.35 | 9.53 | 12.7 | 9.53 | – | 22.23 | 12.7 | 28.58 | 34.93 | 41.28 | 47.63 | 53.98 | – |
| 24 | 600 | 610 | 5.54 | 6.35 | 6.35 | 9.53 | 14.27 | 9.53 | 17.48 | 24.61 | 12.7 | 30.96 | 38.89 | 46.02 | 52.37 | 59.54 | – |
| NPS | DN | OD | SCH5/5S | SCH10S | SCH10 | SCH20 | SCH30 | SCH40S/STD | SCH40 | SCH60 | SCH80S/XS | SCH80 | SCH100 | SCH120 | SCH140 | SCH160 | XXS |
| 26 | 650 | 660 | – | – | 7.92 | 12.7 | – | 9.53 | – | – | 12.7 | – | – | – | – | – | – |
| 28 | 700 | 711 | – | – | 7.92 | 12.7 | 15.88 | 9.53 | – | – | 12.7 | – | – | – | – | – | – |
| 30 | 750 | 762 | 6.35 | 7.92 | 7.92 | 12.7 | 15.88 | 9.53 | – | – | 12.7 | – | – | – | – | – | – |
| 32 | 800 | 813 | – | – | 7.92 | 12.7 | 15.88 | 9.53 | 17.48 | – | 12.7 | – | – | – | – | – | – |
| 34 | 850 | 864 | – | – | 7.92 | 12.7 | 15.88 | 9.53 | 17.48 | – | 12.7 | – | – | – | – | – | – |
| 36 | 900 | 914 | – | – | 7.92 | 12.7 | 15.88 | 9.53 | 19.05 | – | 12.7 | – | – | – | – | – | – |
| 38 | 950 | 965 | – | – | – | – | – | 9.53 | – | – | 12.7 | – | – | – | – | – | – |
| 40 | 1000 | 1016 | – | – | – | – | – | 9.53 | – | – | 12.7 | – | – | – | – | – | – |
| 42 | 1050 | 1067 | – | – | – | – | – | 9.53 | – | – | 12.7 | – | – | – | – | – | – |
| 44 | 1100 | 1118 | – | – | – | – | – | 9.53 | – | – | 12.7 | – | – | – | – | – | – |
| 46 | 1150 | 1168 | – | – | – | – | – | 9.53 | – | – | 12.7 | – | – | – | – | – | – |
| 48 | 1200 | 1219 | – | – | – | – | – | 9.53 | – | – | 12.7 | – | – | – | – | – | – |
| 52 | 1300 | 1321 | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – |
| 56 | 1400 | 1422 | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – |
| 60 | 1500 | 1524 | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – |
| 64 | 1600 | 1626 | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – |
| 68 | 1700 | 1727 | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – |
| 72 | 1800 | 1829 | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – |
| 76 | 1900 | 1930 | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – |
| 80 | 2000 | 2032 | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – |
NPS, DN, NB
You can also see this relationship in the chart below:
Nominal pipe size gives you a standard way to talk about pipe size, even when the actual measurements do not match the name.
NPS, DN, NB Explained
You will encounter several terms when you work with pipes: NPS, DN, and NB. Each term helps you specify pipe size in different regions or industries.
| Term | Definition | Usage | Example |
|---|---|---|---|
| NPS | North American standard for pipe sizes, indicating nominal size without exact measurements. | Used in the US and Canada for various applications. | A 2-inch NPS pipe has an outside diameter of 2.375 inches. |
| NB | Interchangeable with NPS, used primarily in the UK and British standards. | Important for compatibility in international projects. | A 2-inch NB pipe has the same meaning as a 2-inch NPS pipe. |
| DN | European standard for pipe sizing using metric measurements. | Commonly used in Europe and metric regions. | A DN50 pipe has an approximate internal diameter of 50 millimeters. |
NPS stands for Nominal Pipe Size. You use NPS in North America to describe the size of pipes. DN means Nominal Diameter. You see DN in Europe and other metric-based countries. NB, or Nominal Bore, is similar to NPS and appears in British standards. When you work on international projects, you must understand these terms to ensure that pipes, pipe fittings, and flanges fit together correctly.
Tip: Always check if your project uses NPS, DN, or NB. This step helps you avoid mistakes and ensures that your piping system works safely and efficiently.
Pipe Schedule Meaning
You need to know more than just the nominal pipe size when you select a pipe. The schedule tells you the wall thickness of the pipe. The schedule is a non-dimensional number, just like the nominal pipe size. You use the schedule to determine how thick the pipe walls are and how much pressure the pipe can handle.
- Pipe schedule refers to a standard classification system for defining pipe dimensions, especially wall thicknesses required to withstand fluid pressure.
- The calculation of pipe schedule uses both pipe size and wall thickness to find the right schedule number.
- The formula for pipe schedule is SCH = 1000 * p / S, where ‘p’ is the internal pressure and ‘S’ is the maximum allowable tension of the material.
- Barlow’s formula helps you calculate wall thickness: t = pD / 2S + c, where ‘t’ is the thickness, ‘c’ is the corrosion allowance, and ‘D’ is the inside diameter.
As the schedule number increases, the wall thickness also increases. This change gives the pipe more strength and a higher pressure rating. For example, a pipe with schedule 80 has thicker walls than a pipe with schedule 40 of the same nominal pipe size. You must select the right schedule to ensure the pipe can handle the pressure in your system.
| Schedule Number (SCH) | Maximum Internal Pressure (P) | Allowable Stress (S) |
|---|---|---|
| 40 | Varies | Varies |
You will find that higher schedule numbers lead to thicker walls. Thicker walls give the pipe more mechanical strength and a higher pressure rating. Other factors, such as material, temperature, and pipe diameter, also affect the pipe’s performance.
Note: The nominal pipe size schedule, including schedule values, helps you choose the right pipe for your application. Always refer to standards like ASME B36.10 and ASME B36.19 for accurate information.
Pipe Schedule and Conversion
Schedule Numbers
You use schedule numbers to describe the wall thickness of a pipe. These numbers help you compare different pipes with the same nominal pipe size. The most common schedule numbers include SCH 5, SCH 10, SCH 20, SCH 40, SCH 80, and SCH 160. Each schedule number gives you a different wall thickness, which affects how much pressure the pipe can handle. For example, SCH 40 is popular for moderate pressure, while SCH 80 and SCH 160 work for higher pressures.
| Schedule Number | Application Description |
|---|---|
| SCH 40 | Commonly used for moderate pressure applications. |
| SCH 80 | Used for higher pressure applications due to its thicker walls. |
| SCH 160 | Designed for very high-pressure systems. |
You find that the nominal pipe size schedule system lets you select the right pipe for your needs. The schedule values show you which pipe will work best for your pressure and safety requirements. When you look at a pipe chart, you see the nominal size, outer diameter, and wall thickness for each schedule.
Wall Thickness Conversion
You often need to convert wall thickness between inches and millimeters. ASME B36.10M-2018 gives you clear rules for this process. You round wall thickness in inches to the nearest 0.001 inch. When you convert to millimeters, you round to the nearest 0.01 mm. This rule helps you keep your measurements accurate when you work with both imperial and metric systems.
| Measurement Type | Rounding Specification |
|---|---|
| Wall Thickness (inches) | Nearest 0.001 in. |
| Wall Thickness (mm) | Nearest 0.01 mm |
You use these rounding rules to make sure your nominal pipe size schedule matches the requirements in both NPS and DN systems. This step is important when you select pipes, pipe fittings, and flanges for international projects.
Practical Pipe Sizing
You need a clear process to choose the right pipe size and schedule for your piping system. Start by checking your project’s pressure, temperature, and fluid type. Next, add a safety margin to your calculations. Make sure your pipes meet the standard for quality and testing. Use pipe charts to compare nominal pipe size, outer diameter, and wall thicknesses. These charts help you match the right schedule to your needs.
| Specification | Description |
|---|---|
| Nominal Pipe Size (NPS) | Standardized designation for pipe diameter, essential for compatibility. |
| OD (Outer Diameter) | Actual external measurement, crucial for fitting and installation. |
| Pipe Schedule | Defines wall thickness; lower numbers for thinner walls, higher for thicker. |
| Schedule Numbers | Indicates wall thickness and pressure rating, ensuring safety and performance. |
Tip: Always check the nominal pipe size, schedule, and DN when you select pipes and pipe fittings. This habit helps you avoid mistakes and keeps your piping system safe.
You see that understanding the nominal pipe size schedule, wall thickness, and conversion rules helps you select the right pipes, fittings, and flanges for any application.
ASME B36.10 and ASME B36.19 Standards
ASME B36.10 Overview
You use ASME B36.10 when you work with seamless and welded carbon steel pipes. This standard gives you the dimensions for nominal pipe size, outer diameter, wall thickness, and schedule numbers. You find that ASME B36.10 covers both welded and seamless pipes, making it essential for many industrial piping systems. The standard helps you distinguish between pipe and tube, which is important for correct sizing and installation.
You see updates to ASME B36.10 over time. The last major update happened in 2004. The standard focuses on the dimensions of wrought steel pipe, including both carbon and alloy steel. You rely on ASME B36.10 to ensure that your pipes, pipe fittings, and flanges match the required specifications for pressure and safety.
- ASME B36.10 covers welded and seamless wrought steel pipe.
- You use this standard for carbon steel and alloy steel piping systems.
- The standard helps you select the right nominal pipe size schedule for your project.
- You find thicker wall thicknesses in ASME B36.10, which support higher pressure and temperature applications.
- The standard provides clear guidance for nps, dn, and nominal bore conversions.
ASME B36.19 Overview
You use ASME B36.19 when you work with stainless steel pipes. This standard gives you the dimensions for nominal pipe size, outer diameter, wall thickness, and schedule values specific to stainless steel. ASME B36.19 focuses on stainless steel piping system components, including common grades like Type 304, Type 304L, Type 316, and Type 316L.
- ASME B36.19 covers stainless steel pipes and their fittings.
- You use this standard for projects that require corrosion resistance and clean environments.
- The standard provides thinner wall thicknesses compared to ASME B36.10.
- You find schedule numbers like 5S, 10S, 40S, and 80S in ASME B36.19.
- The standard helps you select the correct nominal pipe size schedule for stainless steel piping systems.
You rely on ASME B36.19 to ensure compatibility and safety in your stainless steel piping projects. The standard supports international trade by providing consistent specifications for diameter, wall thickness, and size.
Key Differences
You need to understand the differences between ASME B36.10 and ASME B36.19 before you select pipes for your system. The main difference comes from the material type and the wall thicknesses specified in each standard.
| Standard | Material Type | Wall Thickness Characteristics | Schedule Numbers |
|---|---|---|---|
| ASME B36.10 | Carbon Steel | Thicker wall thicknesses | Various schedules |
| ASME B36.19 | Stainless Steel | Thinner wall thicknesses | 5S, 10S, 40S, 80S |
You see that ASME B36.10 applies to carbon steel and alloy steel pipes, while ASME B36.19 applies to stainless steel pipes. The wall thicknesses in ASME B36.10 are usually thicker, which makes these pipes better for high-pressure and high-temperature applications. ASME B36.19 gives you thinner wall thicknesses, which work well for lower pressure and clean environments.
You also notice that the schedule numbers differ. ASME B36.10 uses a wide range of schedule numbers, including sch 40 and sch 80. ASME B36.19 uses schedule numbers with an “S” suffix, such as 10S and 40S, which indicate thinner walls for stainless steel pipes.
Impact on Pipe Selection
You must choose the correct standard when you select pipes for your project. The choice between ASME B36.10 and ASME B36.19 affects the safety, reliability, and compliance of your piping system. If you select the wrong standard, you risk serious problems.
- ASME B36.10M is designed for carbon and alloy steel pipes. You use these pipes for high-pressure and high-temperature applications because they have thicker wall thicknesses and greater strength.
- ASME B36.19M focuses on stainless steel pipes. These pipes have thinner wall schedules and work best in environments where corrosion resistance is more important than high pressure.
- You must match the nominal pipe size schedule to the material and application. This step ensures that your system meets safety and performance requirements.
If you select the wrong standard, you face health risks, compliance issues, and safety hazards. Mislabeled pipes can cause cross-contamination, environmental damage, and equipment failure. In healthcare, wrong labeling of medical gas systems can lead to severe injuries or fatalities. In industrial settings, mislabeling can result in dangerous chemical reactions, fires, or explosions.
You reference ASME B36.10 and ASME B36.19 in industrial piping projects to ensure compatibility, safety, and reliability. The standards help you match nominal pipe size, dn, nps, and nominal bore for your pipes, pipe fittings, and flanges. You use these standards to avoid mistakes and keep your piping system safe.
| Standard | Focus Area | Contribution to Standardization |
|---|---|---|
| ASME B36.10 | Carbon and Alloy Steel Pipes | Provides dimensions and weights ensuring consistency in manufacturing. |
| ASME B36.19 | Stainless Steel Pipes | Ensures compatibility across industries, facilitating international trade. |
Tip: Always check the nominal pipe size schedule, wall thickness, and schedule numbers in ASME B36.10 and ASME B36.19 before you select pipes for your project. This habit helps you avoid costly mistakes and keeps your system safe and compliant.
You improve your project results when you understand nominal pipe size, schedule, and the ASME standard. Many engineers make mistakes by confusing diameter with nominal pipe size or by choosing the wrong pipe fittings. You avoid these errors and select the right pipes for your system. ASME standards guide you in choosing pipe materials, checking inspection steps, and confirming size for safe operation. For more details, use guides based on ASME B36.10 and B36.19. These resources explain pipe schedules, dimensions, and international standards.
FAQ
What does “nominal pipe size” mean?
Nominal pipe size gives you a standard way to identify pipes. You do not use it for exact measurements. It helps you match pipes and fittings easily.
How do you choose the right pipe schedule?
You check your system’s pressure and temperature. You use pipe charts to compare wall thickness. Higher schedule numbers mean thicker walls and more strength.
Why do ASME B36.10 and B36.19 use different schedule numbers?
You see different schedule numbers because each standard covers different materials. ASME B36.10 uses regular schedules for carbon steel. ASME B36.19 uses “S” schedules for stainless steel.
Can you convert NPS to DN easily?
You can convert NPS to DN by multiplying the NPS value by 25. For example, NPS 2 equals DN 50. Always check the standards for exact conversions.
What happens if you select the wrong pipe schedule?
You risk leaks, bursts, or system failure. Always match the schedule to your pressure and safety needs. Double-check your selection with ASME standards.
