Detailed Explanation of Steel Pipe Wall Thickness: Classification, Standards, Pressure Ratings, and Common Selection Misconceptions

Table of contents

• Preface
• Steel Pipe Wall Thickness
• Relationship between Wall Thickness and Diameter
• Classification of Steel Pipe Wall Thickness
  • Thin-walled Steel Pipe
  • Medium-walled Steel Pipe
  • Thick-walled Steel Pipe
• Factors Affecting Steel Pipe Wall Thickness
• Standards for Steel Pipe Wall Thickness
• SCH40 Steel Pipe Wall Thickness
• SCH80 Steel Pipe Wall Thickness
• Common Misconceptions in Selecting Steel Pipe Wall Thickness
• Steel Pipe Wall Thickness and Installation Environment
• Summary

Preface

Steel pipes have a wide range of applications in modern engineering, from oil and gas pipelines to structural supports for urban buildings. As a fundamental building material, steel pipes bear critical responsibilities.

When selecting steel pipes, wall thickness is a crucial parameter that cannot be ignored, as it directly affects the pipe’s performance, durability, and applicable environments.

Today, this article will provide a detailed introduction to steel pipe wall thickness, focusing on classification, standards, and selection methods. We hope this will help you choose better and more suitable steel pipes.

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Steel Pipe Wall Thickness

The wall thickness of a steel pipe refers to the difference between its outer and inner diameters, usually measured in millimeters (mm). The wall thickness directly affects the pipe’s load-bearing capacity, pressure resistance, and corrosion resistance.

Relationship between Wall Thickness and Diameter

The wall thickness and diameter of a steel pipe are closely related. Increasing the wall thickness can enhance the load-bearing capacity of the steel pipe, but it will also increase the weight and cost.

Under certain working pressure, choosing the appropriate diameter and wall thickness can achieve the best balance between strength and economy.

Classification of Steel Pipe Wall Thickness

Generally speaking, steel pipes can be divided into two main categories according to their outer diameter and wall thickness: ordinary steel pipes and thick-walled steel pipes.

Thin-walled Steel Pipe

Thin-walled steel pipes typically have a wall thickness of less than 10mm and are commonly used in applications with lower pressure or lighter loads.

Their advantages include light weight, ease of processing and transportation, making them suitable for low-pressure applications or those with less stringent structural requirements.

Medium-walled Steel Pipe

Medium-walled steel pipes typically have a wall thickness between 10mm and 20mm, making them suitable for high-pressure applications.

These pipes offer good pressure resistance and corrosion resistance, making them suitable for most industrial piping systems.

Thick-walled Steel Pipe

Thick-walled steel pipes typically have a wall thickness greater than 20mm, making them suitable for projects requiring high pressure and heavy loads.

They possess superior compressive and bending resistance, enabling stable operation even in harsh environments.

Factors Affecting Steel Pipe Wall Thickness

Pressure Resistance Requirements: The pressure resistance required is directly related to the pipe wall thickness, depending on the specific project requirements. Under certain conditions, the higher the pressure inside the pipe, the thicker the wall needs to be.

Corrosion Resistance: In marine environments, steel pipes must withstand not only seawater corrosion but also oxidation reactions. Therefore, the pipe wall thickness must consider both load-bearing capacity and corrosion resistance.

Structural Strength Requirements: In projects involving high-intensity mechanical pressure, steel pipes must withstand internal and external pressures as well as external impacts and loads. A thicker pipe wall increases its bending and compressive strength.

High-Temperature Resistance: The selection of pipe wall thickness must fully consider its strength performance at high temperatures. Generally, a thicker pipe wall results in stronger high-temperature resistance.

Standards for Steel Pipe Wall Thickness

In practice, many countries and regions have strict standards and specifications for the selection of steel pipe wall thickness and diameter:

API 5L Standard: For oil and gas pipelines, the API 5L standard specifies the dimensions and wall thickness requirements for steel pipes to ensure that the pipelines can withstand the high pressure and corrosion that may occur during transportation.

ASTM Standard: The American Society for Testing and Materials (ASTM) also specifies the dimensions and wall thickness of steel pipes for different applications.

ISO Standard: The International Organization for Standardization (ISO) has developed globally applicable standards for steel pipe dimensions and wall thicknesses to ensure standardization across different countries.

SCH40 Steel Pipe Wall Thickness

The measured wall thickness data for different nominal diameters of SCH40 pipes are as follows (all measured using an ultrasonic thickness gauge):

DN15: Outer diameter 21.3mm, carbon steel pipe wall thickness 2.8-2.9mm;

DN25: Outer diameter 33.4mm, carbon steel pipe wall thickness 3.38mm;

DN50: Outer diameter 60.3mm, carbon steel pipe wall thickness 3.91mm;

DN80: Outer diameter 88.9mm, carbon steel pipe wall thickness 5.49mm;

DN100: Outer diameter 114.3mm, carbon steel pipe wall thickness 6.02mm.

The wall thickness and material of the steel pipe are related to its outer diameter; the actual measurement shall prevail for each batch of steel pipes.

SCH80 Steel Pipe Wall Thickness

Sch80 is an important wall thickness standard in American standard piping. The wall thickness increases with pipe diameter and is specifically designed for high-pressure applications. Below is an analysis of common specifications from DN15 to DN200:

DN15: Wall thickness 3.91mm, suitable for precision instruments, flexible pressure resistance, but pressure cannot exceed 25MPa.

DN20: Wall thickness 3.91mm, larger inner diameter, commonly used for connection pipes in chemical plant reactors.

DN25: Wall thickness 4.88mm, can withstand 30MPa pressure, mostly used in high-temperature steam pipelines in oil refineries; expansion allowance must be allowed during installation.

DN32 & DN40: Wall thickness 4.85mm and 5.08mm, respectively. The former is suitable for viscous liquids such as syrups in food factories, while the latter is suitable for circulating water systems.

DN50: Wall thickness 7.04mm, a mainstay in the chemical industry; flange connections require high-strength bolts to prevent leakage.

DN80 & DN100: Wall thickness 7.62mm, 10.31mm respectively. Mounting bracket spacing should not exceed 3 meters to prevent deformation.

DN150: Wall thickness 12.7mm. Commonly used in large buildings and industrial circulating water systems. Special lifting slings are required for handling to prevent scratches and corrosion.

DN200: Wall thickness 15.09mm. Specifically designed for long-distance transportation in petrochemical industries. Thicker wall thickness is required for harsh environments.

Common Misconceptions in Selecting Steel Pipe Wall Thickness

• Over-selection of thick-walled steel pipes
• Ignoring pipe corrosion and wear
• Disregarding installation and usage conditions

Steel Pipe Wall Thickness and Installation Environment

The installation conditions and operating environment of steel pipes also significantly influence the selection of wall thickness and diameter.

Installation Space: If installation space is limited, smaller diameter steel pipes should be selected to avoid excessively large pipes occupying too much space.

Ambient Temperature and Humidity: In high humidity or extremely cold environments, steel pipes may expand or contract; therefore, the appropriate wall thickness must be selected based on the ambient temperature.

Vibration and Impact: If the steel pipe is used to withstand vibration or impact loads (such as in the machinery manufacturing industry), the wall thickness needs to be increased to improve impact resistance.

Summary

Choosing the appropriate steel pipe wall thickness and diameter is a comprehensive decision-making process that must consider multiple factors, including the pipeline’s pressure resistance, the properties of the transported medium, the working environment, and installation conditions.

This article should have given you a clearer understanding of how to select the right steel pipe wall thickness.

If you still have questions about steel pipes, please contact Metleader engineers. We offer free technical support to help customers choose the most suitable steel pipe products.