Carbon Steel Pipe: SCH20，SCH40，SCH80 etc.

Carbon steel pipe is an important material widely used in various industrial fields. To meet the requirements of different scenarios, carbon steel pipe wall thickness grades vary.

The wall thickness grade generally refers to the ratio of the pipe's outer diameter to its wall thickness, expressed numerically. Common wall thickness grades include SCH10, SCH20, SCH30, SCH40, SCH60, SCH80, SCH100, SCH120, SCH140, SCH160, STD, XS, and XXS, among others. SCH stands for standard wall thickness, STD for standard wall thickness grade, XS for heavy wall thickness grade, and XXS for extra heavy wall thickness grade.

Carbon Steel Pipe Wall Thickness Grading System

There are three main internationally accepted steel pipe wall thickness grading systems:

1. SCH Designation System

The US ANSI standard uses the SCH value to represent wall thickness. The calculation formula is (design pressure/material allowable stress) × 1000, rounded to the nearest whole number. A typical application involves SCH40 carbon steel seamless pipe with a pressure of 3.68 MPa at 350°C. This calculation requires consideration of factors such as corrosion allowance in conjunction with the Barlow formula.

2. Weight Notation

The MSS standard categorizes wall thicknesses into STD (standard pipe), XS (extended thickness pipe), and XXS (extra-thick pipe). For example, SCH80 pipes below DN200 correspond to XS pipes, which are specifically designed for high-pressure systems.

3. Direct Marking

Standards such as China's GB/T 3091 use the "outer diameter × wall thickness" notation (e.g., φ60.5 × 3.8 mm) to intuitively display geometric parameters. This is primarily used for low-pressure fluid pipelines.

Comparison of Common SCH Series

SCH20, SCH30, SCH40, SCH60, SCH80, SCH100, SCH120, SCH140

Applications of Carbon Steel Pipes of Different Schedules

1. SCH10 and SCH20

These two wall thickness grades of CS pipe generally have a wall thickness range of ≤3mm and are suitable for general industrial applications, such as transporting water, gas, and low-pressure steam.

2. SCH30, SCH40, SCH60, SCH80, and SCH100

These wall thickness grades of carbon steel pipe generally have a wall thickness range of ≤12.7mm and are suitable for medium-pressure applications, such as transporting steam, gas, oil, and natural gas.

3. SCH120, SCH140, and SCH160

These three wall thickness grades of CS pipe generally have a wall thickness range of ≤ 21.44 mm and are suitable for high-pressure applications, such as transporting high-pressure oil and natural gas.

4. STD, XS, and XXS

STD is a standard wall thickness grade, one of the most common CS pipe wall thickness grades; XS and XXS are heavy and extra heavy wall thickness grades, suitable for high-pressure and high-temperature applications.

How to Identify Carbon Steel Pipes of Different Schedules

1. Marking Method

The pipe body is sprayed with a code or labeled (e.g., "ASTM A106 Sch. 40").

Some steel pipe ends are color-coded (e.g., Sch. 40 carbon steel pipe has no special color, but stainless steel pipe may be marked green).

2. Measurement Verification

Use a caliper to measure the outside diameter and wall thickness and compare them to the standard size table (e.g., the wall thickness for NPS 1" Schedule 40 should be 3.38mm).

FAQ

1. What Is The Difference Between SCH40s and SCH40?

SCH40 carbon steel pipe is a commonly used pipe wall thickness standard with a relatively standard wall thickness.

SCH40s carbon steel pipe adds an additional layer of wall thickness to the standard SCH40.

2. Are SCH40 and "STD" The Same?

For NPS ≤ 10", they are the same; for NPS ≥ 12", "STD" has a slightly thinner wall thickness than SCH40.

3. What Is The Difference Between Schedule 40 and Schedule 80 Carbon Steel Pipe?

Schedule 40 pipe has a thinner wall than Schedule 80 pipe. Therefore, Schedule 80 pipe can withstand higher pressures than Schedule 40 pipe.

4. How Do I Know If Schedule 40 Pipe Can Withstand The Pressure?

A mathematical formula can help you determine whether Schedule 40 is appropriate for your project.

SCH = (1,000) * (P/S)

In this equation, P equals the pipe's internal operating pressure, and S represents the pressure the material can withstand.

Summary

In summary, the wall thickness grade of carbon steel pipe is closely related to the pipe's application and pressure rating. When selecting CS pipe, choosing the appropriate wall thickness grade not only ensures proper performance, but also reduces costs and improves safety.