Comprehensive analysis of pipe size chart, standard sizes, wall thicknesses and steel pipe speci

In industrial and construction projects, piping systems are a critical infrastructure whose design and selection directly impact the overall safety and efficiency of the project. Whether transporting fluids, gases, or other substances, the choice of pipe size, wall thickness, and steel pipe specifications plays a decisive role in ensuring the long-term stability of the system. Understanding and mastering the pipe size chart and the application of various standard sizes is crucial for professionals involved in piping engineering. This article provides a comprehensive analysis to help you gain a deeper understanding of these key elements, ensuring that your pipe system design and selection meet project requirements and comply with industry standards.

Basic Knowledge of Pipe Size Chart

1. Nominal Pipe Size (NPS) vs. Diameter Nominal (DN) Concept
Nominal Pipe Size (NPS):NPS is the pipe size standard used in the United States. It defines the nominal size of the pipe, typically in inches. NPS does not correspond directly to the actual internal or external diameter but serves as a reference for pipe size in engineering design and installation. For example, an NPS 6 pipe does not mean it has an internal diameter of 6 inches but is a nominal size used for identification.

Diameter Nominal (DN):DN is the international standard used by ISO (International Organization for Standardization), typically in millimeters, representing the nominal diameter of a pipe. Similar to NPS, DN also serves to designate the pipe size but corresponds more closely to the nominal outer diameter. For example, a DN 150 pipe has an outer diameter of approximately 150 millimeters.

Difference:
Unit difference: NPS is expressed in inches, while DN is expressed in millimeters.
Naming convention: NPS is used primarily in the U.S. and some other regions, while DN is more commonly used in Europe, Asia, and globally.
Correspondence of values: NPS and DN values are not identical, but they generally represent similar sizes. For example, NPS 6 is approximately equivalent to DN 150, though there are slight differences in the exact values.

2. Nominal Pipe Size vs. Outside Diameter (OD) and Inside Diameter (ID)
Outside Diameter (OD):OD refers to the external diameter of the pipe, which is the critical dimension for pipe installation and connection. Fittings and components such as flanges and joints are typically designed based on the OD of the pipe.

Inside Diameter (ID):ID is the internal diameter of the pipe, which determines the flow capacity of the pipe. It is the actual space through which fluids or gases are transmitted, and it affects the pipe’s ability to carry materials.

Difference:
Nominal Pipe Size (NPS) is a standard designation that may not exactly equal the pipe’s OD or ID, and it is used as a general reference for pipe sizing.
Outside Diameter (OD) and Inside Diameter (ID) are the actual physical measurements of the pipe, affecting installation, flow capacity, and system design.

3. Comparison Between ANSI/ASME and ISO Pipe Size Standards
ANSI/ASME Standard:The ANSI (American National Standards Institute) and ASME (American Society of Mechanical Engineers) pipe size standard is used primarily in the U.S. and other countries. It uses NPS to designate pipe size and defines wall thickness and pressure ratings using Schedule (e.g., Schedule 40, Schedule 80). The ANSI/ASME standard also covers materials, connection types, and performance specifications.

ISO Standard:The ISO pipe size standard, on the other hand, uses DN for pipe size and has different methods for defining pipe thickness and pressure ratings. It is used internationally, especially in Europe and Asia, to ensure consistent sizing standards across regions.

Comparison:
Naming Standard: ANSI/ASME uses NPS, while ISO uses DN.
Application Area: ANSI/ASME is mainly used in North America, whereas ISO is used worldwide, particularly in Europe and Asia.
Wall Thickness and Pressure Rating: ANSI/ASME uses Schedule numbers to define pipe wall thickness and pressure ratings, while ISO uses other specifications to define these parameters.

4. Definition and Function of Pipe Schedule (Pipe Schedule Chart)
Pipe Schedule:Pipe Schedule is a designation that defines the wall thickness of a pipe. The higher the Schedule number, the thicker the wall and the higher the pipe’s pressure tolerance. Common schedule numbers include Schedule 10, Schedule 40, and Schedule 80.

Function:
Wall Thickness Control: The Schedule defines the pipe wall thickness, ensuring that the pipe can handle the required pressure and application.
Pressure Rating: Different Schedule numbers correspond to different pressure ratings. Schedule 10 is for low-pressure systems, while Schedule 80 is used for high-pressure systems.
Selection Convenience: The Schedule provides an easy way for engineers to choose pipes that meet specific pressure and flow requirements.

5. Relationship Between Wall Thickness and Pressure Rating
The wall thickness of a pipe is directly related to its ability to withstand internal pressure. The thicker the wall, the higher the pipe’s pressure tolerance. By selecting pipes with the appropriate Schedule, engineers can ensure that the pipe will perform reliably under the expected pressure conditions.
Schedule 10: Suitable for low-pressure systems.
Schedule 40: Suitable for medium-pressure systems, widely used in construction and water supply.
Schedule 80: Suitable for high-pressure systems, commonly used in chemical, oil, and gas applications.

6. Comparison of Common Schedules: SCH 10, SCH 40, and SCH 80
SCH 10:
Thin wall thickness, suitable for low-pressure applications.
Commonly used in general fluid transport systems and lightweight industrial applications.
Suitable for low-pressure systems with lower stress requirements.

SCH 40:
Moderate wall thickness, suitable for medium-pressure applications.
Widely used in construction, water supply, and oil & gas industries.
Offers sufficient pressure tolerance for most common applications.

SCH 80:
Thick wall thickness, suitable for high-pressure applications.
Used in chemical, oil, and gas industries where higher pressure tolerance is required.
Provides higher strength and resistance to internal pressure.

The Dimensions and Characteristics of 40 and 80 Steel Pipes

1. 40 Steel Pipe
Pipe Size: Typically refers to a steel pipe with an outer diameter of 40mm, with wall thickness ranging from 1.5mm to 4mm, depending on the specific requirements.
Material Characteristics: 40 steel pipes are generally made from high-quality low-carbon steel or medium-carbon steel, offering good plasticity and toughness. They are commonly used in general mechanical structures, buildings, and low-pressure piping systems.
Applications: Widely used in power, mining, transportation, and construction industries, 40 steel pipes are suitable for making supports, load-bearing components, and low-pressure pipelines.

2. 80 Steel Pipe
Pipe Size: Typically refers to a steel pipe with an outer diameter of 80mm, with wall thickness ranging from 2mm to 6mm, depending on the specific requirements.
Material Characteristics: 80 steel pipes have higher strength than 40 steel pipes, making them suitable for higher pressure environments. They are stronger and have better compressive capacity, which makes them ideal for heavy-duty structural components.
Applications: 80 steel pipes are commonly used for water, oil, and steam pipelines that require higher pressure. They are also widely used in large industrial equipment, building structures, and machinery manufacturing.

Comparison
Size: 40 steel pipes have a smaller outer diameter, making them suitable for general low-pressure pipeline systems, while 80 steel pipes have a larger outer diameter and are designed to withstand higher pressures.
Strength: 80 steel pipes generally have higher compressive and tensile strength than 40 steel pipes, making them suitable for applications involving heavy loads.
Applications: 40 steel pipes are used for general construction and low-pressure applications, while 80 steel pipes are used in high-pressure and heavy-load industrial settings.

Cost: In terms of cost comparison, the differences between 40 steel pipes and 80 steel pipes are mainly reflected in the following aspects:
1. Raw Material Cost
40 Steel Pipe: With a smaller outer diameter and thinner wall thickness, the raw material required is less, resulting in a lower material cost.
80 Steel Pipe: Due to the larger outer diameter and thicker wall, more raw material is needed, leading to a higher material cost.

2. Production Cost
40 Steel Pipe: The production process is simpler, with lower material and energy consumption, resulting in a lower production cost.
80 Steel Pipe: The production process is more complex, requiring more energy and materials, which increases production costs.

3. Transportation Cost
40 Steel Pipe: Smaller size and weight mean lower transportation costs.
80 Steel Pipe: Larger size and weight increase transportation costs, especially for long-distance transportation, which may lead to higher fees.

4. Market Price
40 Steel Pipe: Due to lower production costs and suitability for general applications, 40 steel pipes are typically cheaper in the market.
80 Steel Pipe: Due to higher manufacturing and material costs, 80 steel pipes are priced higher in the market.

Pipe Size and Wall Thickness Chart Analysis

A pipe size and wall thickness chart is a crucial reference used to describe and standardize the dimensions of steel pipes, including outer diameter (OD), inner diameter (ID), and wall thickness (WT). This chart is important for pipe selection and application. Below is an analysis of the key components of this chart:

1. Outer Diameter (OD): The outer diameter refers to the external diameter of the steel pipe, typically measured in millimeters (mm) or inches (in). The outer diameter is one of the main factors in determining the size of the pipe and its fluid transport capacity.

2. Inner Diameter (ID)
The inner diameter is the internal diameter of the steel pipe. It is closely related to the outer diameter and wall thickness, calculated using the formula:Inner Diameter = Outer Diameter – 2 × Wall Thickness.
The inner diameter is crucial in determining the pipe’s flow rate and velocity.

3. Wall Thickness (WT): Wall thickness is the thickness of the pipe’s wall, which directly affects the strength, pressure-bearing capacity, and corrosion resistance of the pipe. Wall thickness is usually given in millimeters (mm) or inches (in), and it is a critical factor in determining the pipe’s suitability for different applications.

4. Standard Sizes
Steel pipes are standardized according to various norms. Common standards include:
DN (Nominal Diameter): Refers to the nominal internal diameter of the pipe. While nominal diameter differs from actual internal diameter, it is used to specify pipe sizes.
SCH (Schedule): Refers to the pipe’s wall thickness, which is typically indicated in the pipe’s designation (e.g., SCH40, SCH80). The higher the SCH number, the thicker the wall, which increases the pipe’s pressure capacity.

5. Common Pipe Sizes and Wall Thickness
Here is a reference information for common steel pipe sizes and wall thicknesses (measured in millimeters):
Outer Diameter (OD)Wall Thickness (WT)Example Applications
21.3mm 1.2mm Small fluid pipelines
33.7mm 1.5mm Small to medium pipelines
42.4mm 2.0mm Light structural components, oil and gas pipelines
48.3mm 2.5mm Medium structural components
60.3mm 3.0mm Heavy structural components, industrial pipelines
76.1mm 4.0mm High-pressure pipelines
219.1mm 6.0mm Large pipelines, steam transport

6. Common Steel Pipe Schedules (SCH)
SCH 40: A moderate wall thickness, widely used for low-pressure applications.
SCH 80: Thicker walls, used for medium-pressure applications.
SCH 160: Even thicker walls, suitable for high-pressure environments.

7. Pipe Standards and Pressure Capacity: The wall thickness of a steel pipe directly affects its pressure-bearing capacity. Thicker pipes (e.g., SCH 80, SCH 160) can withstand higher internal pressures, making them suitable for high-pressure fluid transport. Thinner pipes (e.g., SCH 40) are used for low-pressure applications.

8. Pipe Specifications and Applications
The choice of pipe size and wall thickness depends on the specific application and pressure requirements. For example:
Low-pressure environments: Such as water and gas pipelines, typically use pipes with thinner walls.
High-pressure environments: Such as steam pipelines and oil/gas pipelines, require thicker-walled pipes for strength and safety.

Key Factors and Steps to Choose the Appropriate Pipe Size

Choosing the right pipe size based on project requirements is crucial for ensuring the efficiency, safety, and cost-effectiveness of a piping system. The selection process involves considering various factors, including flow requirements, pressure ratings, fluid characteristics, installation environment, and budget. Below is an analysis of the key factors and steps to choose the appropriate pipe size:

1. Determine Flow Requirements
Flow requirements are the primary factor in selecting pipe size. The flow rate of the fluid (such as water, gas, or oil) will dictate the diameter and wall thickness of the pipe. The flow rate can be calculated using the following formula:
Q=A×VQ = A \times VQ=A×V
Where:
Q = Flow rate (m³/s or L/min)
A = Cross-sectional area of the pipe (m² or cm²)
V = Flow velocity (m/s or cm/s)
By calculating the flow rate, you can estimate the required inner or outer diameter of the pipe to ensure efficient flow of the fluid.

2. Consider Flow Velocity
Flow velocity is critical for pipe design. If the velocity is too high, it can result in excessive friction losses, increased energy consumption, and pressure drop. If the velocity is too low, sedimentation or blockage in the pipe may occur. Generally:
For liquid pipelines, flow velocity is usually between 0.9 m/s to 3 m/s.
For gas pipelines, the velocity can be higher, but adjustments should be made based on gas type and system design.

3. Determine Pressure Requirements
The pressure requirements dictate the pipe’s wall thickness and material. The higher the internal pressure the pipe must withstand, the thicker the wall should be to ensure the pipe’s strength and safety. High-pressure systems (such as steam pipelines or oil pipelines) typically require thicker-walled pipes (e.g., SCH 80 or SCH 160).

4. Fluid Characteristics
Corrosive Fluids: If the fluid is corrosive (such as acidic or alkaline solutions), a corrosion-resistant material may be necessary, and the pipe wall may need to be thicker or made from special materials (such as stainless steel or plastic pipes).
Temperature: High or low-temperature fluids will affect the pipe material and thickness. Materials resistant to high temperatures (such as alloy steel) may be required, or thermal insulation may be necessary.
Particulate Matter: If the fluid contains solid particles, the pipe material must be resistant to wear and tear. A thicker wall may be needed to handle abrasive conditions.

5. Pipe Length and Number of Bends
The total length of the pipe and the number of bends will affect the flow of the fluid. Longer pipes or more bends result in increased resistance to flow. It is essential to design the pipeline layout to minimize unnecessary losses and optimize flow efficiency.

6. Selection of Pipe Material
Different materials are suited for different applications:
Carbon Steel Pipes: Suitable for general liquid and gas transportation, typically used in standard temperature and pressure environments.
Stainless Steel Pipes: Used for transporting corrosive fluids and for high-temperature environments.
Plastic Pipes (e.g., PVC, PE): Used for low-pressure applications, offering corrosion resistance, and often used in water and drainage systems.
Alloy Steel Pipes: Used in high-pressure, high-temperature, or specialized applications (e.g., chemical transportation).

7. Economic Considerations
While selecting pipe size, it is important to balance performance and cost. Larger diameter pipes generally result in higher procurement, installation, and maintenance costs. Choosing the appropriate pipe size can help reduce overall costs while meeting system requirements safely and efficiently.

8. Compliance with Industry Standards
Ensure that the selected pipe size complies with local or international industry standards (such as ASTM, ISO, GB, etc.). These standards define pipe sizes, nominal pressures, wall thicknesses, and other parameters to ensure safety, reliability, and efficiency.

9. Pipe Design Software
For more complex projects, pipe design software can be used to simulate and calculate the most appropriate pipe size and material. These programs typically recommend optimal sizes based on factors such as flow rate, pressure, pipe length, temperature, and more.

Simplified Case Study: How to Apply Pipe Size Chart and Pipe Schedule Chart

Comparison of Pipe Selection for Low-Pressure vs High-Pressure Systems
Analysis:
Low-Pressure Transport System: Due to the lower pressure, the selected DN 50 pipe (outer diameter 60.3 mm) with SCH 40 wall thickness is sufficient to handle the pressure. SCH 40 is a cost-effective choice for a low-pressure system.
High-Pressure Transport System: For the high-pressure system, even though the flow rate is lower, the pressure is much higher, requiring a thicker pipe wall. The DN 40 pipe (outer diameter 48.3 mm) with SCH 80 wall thickness is necessary to safely handle the pressure.

Practical Tips for Cost-Saving and Improving Efficiency
Background
Low-Pressure Transport System: Used for cooling water in a factory, with a pressure of 4 bar and a flow rate of 200 L/min.
High-Pressure Transport System: Used for steam transport, with a pressure of 20 bar and a flow rate of 100 L/min.
Objective: Select appropriate pipe sizes and wall thicknesses for both systems.

Low-Pressure Transport System
Pipe Size Selection:
With a flow rate of 200 L/min, the required pipe size is DN 50.
From the chart: Outer diameter is 60.3 mm.
Wall Thickness Selection:
For low pressure (4 bar), SCH 40 (wall thickness 4.0 mm) is sufficient to meet the strength requirements while minimizing cost.

High-Pressure Transport System
Pipe Size Selection:
With a flow rate of 100 L/min, the required pipe size is DN 40.
From the chart: Outer diameter is 48.3 mm.
Wall Thickness Selection:
For high pressure (20 bar), a thicker wall is needed. SCH 80 (wall thickness 4.0 mm) ensures safety under high-pressure conditions.

Analysis of Pipe Size Chart Standardization and Future Development Trends

I. Current Standardization of Pipe Size Charts
Pipe size charts are globally standardized through several key systems, which include:
ASME/ANSI B36.10M and B36.19M:
Primarily used for steel pipes, including carbon steel and stainless steel, covering industrial transport and construction projects.
Defines standard pipe sizes (NPS, Nominal Pipe Size) and wall thickness series (Schedule, SCH).

ISO International Standards:
ISO 1127 and ISO 4200 specify dimensions for industrial stainless steel and carbon steel pipes and are somewhat compatible with ASME standards.

EN European Standards:
Standards like EN 10255 and EN 10220 are widely used in Europe, focusing on environmental sustainability and economic efficiency.

National and Regional Standards:
Countries have developed localized standards, such as China’s GB/T series and Japan’s JIS series. Although these differ from international standards, there is a trend toward alignment.

Advantages of Standardization:
High Compatibility: Unified dimensions and wall thickness standards facilitate international trade and project design.
Efficient Design: Engineers can quickly select the appropriate pipes, enhancing project efficiency.
Good Interchangeability: Reduces production and maintenance costs due to standardization of pipe fittings and pipes.

II. Future Development Trends of Pipe Size Charts
Greater Precision and Intelligence
Digital Tools: Future pipe size charts will likely integrate with CAD and BIM (Building Information Modeling) tools, allowing 3D modeling to directly generate pipe dimensions and select related components.
Smart Recommendations: With AI and big data, systems can automatically recommend optimal pipe sizes and wall thicknesses based on operating conditions, reducing human error.

Enhanced Global Standardization
As international engineering collaborations increase, national standards are likely to converge with ISO and ASME standards, eliminating discrepancies and lowering technical barriers in cross-border projects.

Incorporation of Green and Sustainable Practices
Material Optimization: Promote lightweight and high-strength materials like alloy steel, composites, and plastic pipes to reduce resource consumption during production.
Energy Efficiency: Design more efficient pipe sizes and fluid dynamics models to optimize flow rates and reduce operational energy consumption.

Sustainability and Circular Economy
Recycling and Reuse: Develop pipes using recyclable materials to extend their lifecycle.
Condition Monitoring: Implement health monitoring technologies to enable timely maintenance or replacement decisions before pipes fail.

Customization for Special Industries
Emerging industries (e.g., renewable energy, semiconductor manufacturing, and pharmaceuticals) demand more specialized pipe size charts, such as for ultra-thin pipes (used in precision instruments) or high-temperature, high-pressure applications.

Visualization and Augmented Reality (AR)
During design and construction, AR technology could display real-time pipe layout, dimensions, and wall thickness information, simplifying installation and maintenance.

Understanding the Pipe Size Chart, Pipe Schedule Chart, and the Steel Pipe Wall Thickness Chart is essential for optimizing pipeline selection in various applications. These tools provide crucial insights into pipe dimensions, wall thickness, and pressure-bearing capabilities, enabling engineers to make informed decisions that align with project requirements. In particular, SCH 40 and SCH 80 pipes offer distinct advantages for different scenarios. SCH 40 pipes, with their lighter weight and lower cost, are ideal for low-pressure systems, such as residential plumbing and irrigation. In contrast, SCH 80 pipes, with their thicker walls and higher pressure tolerance, are better suited for high-pressure or industrial applications, such as chemical transport and high-stress environments.

By effectively leveraging these charts and understanding the specific requirements of each project, businesses can achieve a balance between performance and cost, ensuring optimal outcomes. If you’re looking to enhance your pipeline selection strategy or explore how SCH 40 and SCH 80 pipes can be applied to your projects, feel free to reach out. We are here to provide insights and support to help you achieve success!