Steel Pipe Dimensions & Sizes Chart Schedule 40, 80 Pipe

Steel Pipe Dimension: 3 Elements

To fully describe a steel pipe’s dimensions, three critical elements must be included: the outer diameter (OD), wall thickness (WT), and pipe length.

1. Outer Diameter (OD): This measures the distance across the pipe’s outermost edges. It is crucial for determining the pipe’s size and compatibility with fittings and other components.
2. Wall Thickness (WT): This measures the thickness of the pipe wall. It is essential for assessing the pipe’s strength and its ability to withstand internal and external pressures.
3. Pipe Length: Pipes are typically supplied in standard lengths, such as 20 feet (approximately 6 meters) or 40 feet (approximately 12 meters).

These three elements—OD, WT, and length—are vital for several reasons. They allow us to calculate the pipe’s weight, determine its pressure-bearing capacity, and estimate the cost per foot or meter. Accurately knowing these dimensions ensures you select the right pipe for your application, preventing costly errors and ensuring the pipe meets performance requirements.

By understanding and specifying these key elements correctly, you can ensure the steel pipes you select are fit for purpose and cost-effective.

Steel Pipe Dimensions Chart (Size Chart)

Dimension Standards for Steel Pipe

There are various standards used to describe steel pipe sizes, outer diameters (OD), and wall thicknesses. The main standards are ASME B36.10 and ASME B36.19.

Relevant Standard Specifications: ASME B36.10M and B36.19M

ASME B36.10M

ASME B36.10M covers the standardization of steel pipe dimensions and sizes, including both seamless and welded types, which are used in high or low temperatures and pressures. This standard is specifically used for pipeline systems and the transmission of fluids such as oil, gas, water, and slurry.

• Pipe vs. Tube: In this context, “pipe” is used for pipeline systems and fluid transmission, while “tube” refers to other applications. For pipes, the standard used is ASME B36.10M.
• Outer Diameter (OD) Less than 12.75 in (NPS 12, DN 300): For pipes with an OD smaller than 12.75 inches, the actual diameter is larger than the nominal pipe size (NPS) or nominal diameter (DN).
• Steel Tube Dimensions: For tubes, the actual outside diameter matches the pipe number for all sizes.

Why Pipes with Sizes Smaller than NPS 12 (DN 300) Have Different OD

1. Nominal Pipe Size (NPS): All pipe sizes are identified as nominal pipe size (NPS).
2. Standard Outside Diameter (O.D.): From NPS 1/8 (DN 6) to NPS 12 (DN 300), sizes are based on a standard outside diameter. Initially, the OD specified the pipe dimensions. However, due to the wall thickness and internal diameter (ID), the difference between OD and ID varies for smaller pipes. As pipe dimensions increase, OD and ID become approximately equal.
3. No Direct Relationship: There’s no direct relationship between the old standard thickness (OD) and nominal size, so both are accepted according to ASME B36.10M.

Steel Pipe Schedule

In ASME B36.10M, the pipe schedule is identified as Standard (STD), Extra-Strong (XS), or Double Extra-Strong (XXS), or with schedule numbers 5, 10, 20, 30, 40, 80, 120, and 160.

ASME B36.19M

ASME B36.19M specifies the dimensions for stainless steel pipes, including both seamless and welded types. This standard is similar to ASME B36.10M with some differences:

• NPS 14 to NPS 22 (DN 350-550): Schedule 10S
• NPS 12: Schedule 40S
• NPS 10 and NPS 12: Schedule 80S

The “S” suffix indicates these differences in pipe thickness compared to ASME B36.10M.

Ways to Express Pipe Dimensions

1. Pipe Wall Thickness: Expressed using the Steel Pipe Schedule (e.g., Schedule 40 steel pipe, Schedule 80 pipe).
2. Pipe Diameters: Described by Nominal Pipe Size (NPS) and DN (Nominal Diameter).
3. Pipe Weight Class: Given in LB/FT (pounds per foot) or KG/M (kilograms per meter).

What is the Steel Pipe Dimensions Schedule?

The steel pipe schedule, indicated by “Sch,” is a method defined by ASME B 36.10 to represent the wall thickness of steel pipes. It is commonly used in American steel pipe standards. For example, “Sch 80” signifies a specific wall thickness from the ASME B 36.10 chart.

Importance of Steel Pipe Schedule

Steel pipes are primarily used to transport fluids under pressure. Therefore, the internal diameter, or nominal bore (NB), is critical. The pipe must have enough strength and wall thickness to withstand the pressure. This is why wall thickness is specified in schedules, abbreviated as “Sch.”

Pipe Schedule Formula

The formula for determining pipe schedule is: Sch.=P[σ]t×1000\text{Sch.} = \frac{P}{[\sigma]_t} \times 1000Sch.=[σ]t​P​×1000

Where:

• P is the designed pressure (in MPa).
• [σ]t[\sigma]_t[σ]t​ is the allowable stress of materials under design temperature (in MPa).

Understanding SCH in Steel Pipe Dimensions

When describing steel pipe parameters, the pipe schedule represents the wall thickness using a number. Pipe schedule (Sch.) is a series, not a specific wall thickness. Different schedules mean different wall thicknesses for pipes of the same diameter. Common schedules include SCH 5, 10, 20, 30, 40, 60, 80, 100, 120, 140, and 160. Generally, the larger the schedule number, the thicker the pipe wall and the higher its pressure resistance.

Schedule 40 and 80 Steel Pipe Dimensions

If you’re new to the pipe industry, you might wonder why Schedule 40 or 80 steel pipes are so prevalent. What materials are these pipes made from?

Understanding Schedule 40 and 80

As mentioned earlier, Schedule 40 and 80 refer to the wall thickness of steel pipes. These designations are common in various industries because they indicate the pipe’s ability to withstand typical pressures. Pipes with these schedules are often requested in large quantities due to their widespread use and reliable performance.

Reasons for Popularity

• Pressure Handling: Schedule 40 and 80 pipes are designed to handle higher pressures, making them suitable for many industrial applications.
• Versatility: These pipes are used in diverse industries, from construction to manufacturing, because of their robustness.

Material Standards

The material standards for Schedule 40 and 80 pipes are flexible. You can find these schedules in various materials:

• Stainless Steel: For example, Schedule 40 stainless steel pipes, like ASTM A312 Grade 316L.
• Carbon Steel: Common options include API 5L, ASTM A53, ASTM A106B, A179, A252, A333, among others.

These materials ensure that Schedule 40 and 80 pipes meet the specific requirements of different applications, providing durability and reliability.

What is Nominal Pipe Size (NPS)?

Nominal Pipe Size (NPS) is a North American standard for specifying pipe sizes used in various pressure and temperature applications. NPS is a non-dimensional number that combines a nominal size in inches with a schedule (Sched. or Sch.) number. The schedule indicates the wall thickness, and the nominal size helps identify the pipe’s general dimensions, facilitating the selection and specification of pipes for different applications.

What is DN (Nominal Diameter)?

Nominal Diameter (DN), also known as outside diameter, represents the general diameter of pipes and pipeline accessories. Due to the thin wall of the pipe, the outside and inside diameters are nearly identical, so the average of both is used as the nominal diameter.

Key Points about DN:

• Interchangeability: DN ensures that pipes and fittings with the same nominal diameter can be connected, promoting standardization and interchangeability.
• Representation: The nominal diameter is denoted by the symbol “DN” followed by a number, indicating the size in millimeters. The DN value is close to the inside diameter of the pipe but does not precisely represent the pipe’s actual diameter.

Example:

• DN50: A pipe with a nominal diameter of 50 mm, allowing for easy identification and compatibility with other DN50 fittings and accessories.

DN (mm) and NPS (inch) conversion

Nominal diameter DN (mm) and NPS (inch) conversion

Conversion DN ( mm ) that requires separate memory

Greater than or equal to DN100 diameter and NPS conversion

DN=25*NPS;
NPS=DN/25

Exact conversion

1 inch =25.4 mm

Pipe Weight Class Schedule

The pipe weight class (WGT class) is a historical system that indicates the wall thickness of pipes, a practice still in use today. This system categorizes pipes into three grades: STD (Standard), XS (Extra Strong), and XXS (Double Extra Strong). Initially, each pipe size had a single wall thickness specification known as standard tube (STD). As the need for pipes capable of handling higher pressure fluids grew, the thicker XS (Extra Strong) pipes were introduced, followed by the even thicker XXS (Double Extra Strong) pipes for handling even greater pressures.

With advancements in materials processing technology, the demand for more cost-effective, thin-walled pipes increased, leading to the development and introduction of these various pipe grades. The ASME B36.10 and ASME B36.19 specifications outline the corresponding relationships between pipe schedules and these weight classes, ensuring that the right pipe thickness is chosen for specific pressure conditions. This evolution highlights the balance between maintaining structural integrity under pressure and optimizing material usage for cost efficiency.

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