Overview

If you use pipe products in your project, you will definitely come across the Nominal Pipe Size Schedule. Whether you are a pipe buyer or a pipe manufacturer, you need to use the Nominal Pipe Size Schedule to confirm the size of the pipe. However, do you clearly understand what the Nominal Pipe Size Schedule is?

This article will introduce the Nominal Pipe Size Schedule and the related ASME B36.10 / ASME B39.19 standards in detail. If you have questions in this regard, or you have just entered the pipe industry, I believe this article will help you.

How to Express Pipe Size

Before formally introducing the Nominal Pipe Size Schedule, we must clearly understand how to express pipe size.

The cross section of the pipe is a ring. The diameter of the outside of the ring is called the outer diameter (OD). The diameter of the inside of the ring is called the inner diameter (ID). The width of the ring is called the wall thickness (THK). The outer diameter, inner diameter and wall thickness determine the cross-sectional size of the pipe.

However, among the outer diameter, inner diameter and wall thickness, only two of the data are needed to determine the size of the pipe. The other data can be calculated by the following formula:

In addition, the length of the pipe is also an important part of the pipe size. However, the adjustment of the length can be achieved only by cutting. The specific outer diameter, inner diameter and wall thickness require complex processing to obtain.

Therefore, the Nominal Pipe Size Schedule mainly determines the outer diameter and wall thickness of the pipe. Now let's start to formally introduce the Nominal Pipe Size Schedule.

Nominal Pipe Size Schedule

What is Nominal Pipe Size Schedule?

The Nominal Pipe Size Schedule is a comparison table. It establishes a standard for the size of pipes. The following table is the Nominal Pipe Size Schedule:

NPS, DN, NB

NPS, DN, and NB determine the outer diameter of the pipe.

NPS is the abbreviation of Nominal Pipe Size. It is expressed in inches, such as: ⅛, ¼, ⅜, …, 44, 46, 48. It should be noted that NPS is not exactly equal to the outer diameter of the pipe. For pipes above NPS14, NPS can be directly equivalent to the outer diameter. For example: NPS14 means the outer diameter is 14 inches. However, for small-sized pipes, NPS is often smaller than the actual outer diameter. For example: the actual outer diameter corresponding to NPS2 is 2.375 inches. Therefore, in most cases we still need to refer to the table to confirm the specific outer diameter.

DN is the abbreviation of Diameter Nominal. NB is the abbreviation of Nominal Bore. They are the same and are expressed in millimeters. For example: 6, 8, 10, ..., 1100, 1150, 1200. Each NPS value has a corresponding DN or NB value. Unlike NPS, all DN/NB values have a certain gap with the actual outer diameter. For example: DN6 corresponds to an outer diameter of 10.3mm, and DN1200 corresponds to an outer diameter of 1219mm.

In general, NPS, DN, and NB are different ways of expressing the outer diameter. In practical applications, only one of them is needed.

SCH

SCH determines the wall thickness of the pipe. In the early days, it was difficult to make the pipe thin, so there were only three thicker SCH values, namely STD, XS, and XXS. Later, with the improvement of the process, more SCH values were introduced.

It should be noted that the SCH value cannot directly determine the wall thickness of the pipe, it represents the pressure bearing capacity of the pipe. For example: the wall thickness corresponding to NPS1, SCH40 is 3.38mm, while the wall thickness corresponding to NPS5, SCH40 is 6.55mm. Therefore, we need to determine the NPS value first, and then determine the corresponding wall thickness.

Why Use Nominal Pipe Size Schedule?

On the one hand, the production process of pipes (especially seamless pipes) is very complicated, and various different molds are required to achieve different sizes. Therefore, if there is no unified standard for the size of the pipe, the purchaser will propose various combinations of outer diameter and wall thickness. This greatly increases the number of molds and reduces production efficiency.

On the other hand, pipes are generally used with different pipe fittings and flanges. The sizes of pipe fittings and flanges are more complicated, and if there is no unified representation method, it will become very difficult to confirm their sizes.

How to Convert Nominal Pipe Size Schedule?

We have shown the table of Nominal Pipe Size Schedule above. So how to convert it specifically?

First, we need to find the row corresponding to the NPS, DN or NB value. The corresponding outer diameter can be found in the OD column. Then, find the corresponding wall thickness value according to the column corresponding to the SCH value. In this way, we have determined the size of the pipe.

However, if you need pipes of multiple sizes and have a long list, converting one by one not only wastes a lot of time, but is also prone to errors. For this purpose, we have developed a tool for batch conversion of Nominal Pipe Size Schedule, which is on this website. You can click the link below to use it directly. If you find it useful, you are welcome to bookmark this page:

Conversion / Calculator for Nominal Pipe Size Schedule

Here is the user guide for this tool:

Download Document

ASME B36.10 and B36.19

Both ASME B36.10 and B36.19 specify the conversion method of Nominal Pipe Size Schedule. However, they have different Schedule values. ASME B36.19 includes four Schedule values: SCH5S, SCH10S, SCH40S, and SCH80S. The remaining Schedule values are included in ASME B36.10. The subscripts organize the comparison tables of ASME B36.10 and B36.19 respectively:

Although they are different standards, they are inseparable. You may have discovered that SCH5, SCH10, SCH40, and SCH80 in ASME B36.10 correspond to SCH5S, SCH10S, SCH40S, and SCH80S in ASME B36.19 respectively. The wall thickness they represent on small-size pipes is the same. However, for large-size pipes, B36.19 corresponds to thicker wall thickness.

In fact, SCH5, SCH STD, SCH XXS in ASME B36.10 and SCH5S, SCH40S, SCH80S in ASME B36.19 are one-to-one correspondences. Their conversion results are exactly the same.

FAQ

Further Reading

What is Cold Rolling? What does Cold Rolling do in Nickel Alloy Pipes & Tubes?

Completely Understand the Hot Rolling of Nickel Alloy / Superalloy.

What is Cold Drawing? Which Materials need to be Cold Drawn?

Conclusion

Nominal pipe schedule is a collection of standard pipe sizes. It is actually a table that gives the corresponding outer diameter and wall thickness given the NPS (DN or NB) value and the SCH value. NPS, DN and NB correspond to different outer diameters of the pipe, and SCH corresponds to the wall thickness of the pipe. You can also use our tool to quickly convert it.

We can produce standard sizes of nickel alloy / superalloy pipes according to the Nominal Pipe Schedule, and of course, we can also customize the size according to your requirements. So if you have any needs in this regard, please contact us.