Pipe Sizes and Pipe Schedule - A Complete Guide For Piping Professional

Summary

This video provides a comprehensive guide to understanding pipe sizes and pipe schedules. It explains key terms such as Nominal Pipe Size (NPS), Nominal Bore (NB), and Diameter Nominal (DN), detailing how they define pipe dimensions. The video also covers pipe schedules, with a focus on how wall thickness is represented, and how different schedules relate to pressure resistance. Additionally, it introduces the concept of schedule numbers and their application to stainless steel pipes. The viewer is encouraged to visit the website for downloadable charts and further resources.

Takeaways

• 😀 Nominal Pipe Size (NPS) refers to the size of the pipe, commonly expressed in inches, but does not correspond directly to the pipe's actual outside or inside diameter for sizes 1/8" to 12".
• 😀 NPS is also known as Nominal Bore (NB) in the U.S. and is frequently used interchangeably with DN (Diameter Nominal), which is the international metric equivalent.
• 😀 DN (Diameter Nominal) is used internationally, especially in Europe, and can be calculated by multiplying the NPS value by 25 (e.g., 2" NPS = DN 50).
• 😀 Pipe schedule refers to the wall thickness of the pipe, which determines how much pressure it can withstand. A higher schedule number indicates a thicker wall.
• 😀 Schedule 40 and Schedule 80 are common pipe schedules, with Schedule 80 having a thicker wall and higher pressure tolerance than Schedule 40.
• 😀 The schedule number is derived from a formula based on the service pressure and allowable stress of the pipe material.
• 😀 Pipes with larger schedule numbers are designed for higher pressure conditions due to thicker walls, which provide increased strength and durability.
• 😀 Stainless steel pipes have unique schedule numbers (marked with an 'S' suffix, e.g., Schedule 10S, 40S) to accommodate their higher cost and specialized uses, particularly for corrosion resistance.
• 😀 There is a distinction between Schedule 10 and Schedule 10S, with Schedule 10S specifically referring to stainless steel pipes with thinner walls for cost efficiency.
• 😀 You can access downloadable charts for Nominal Pipe Size (NPS) and pipe schedules on the channel's website, providing a helpful reference for piping dimensions in both metric and imperial units.

Q & A

What is Nominal Pipe Size (NPS)?

Nominal Pipe Size (NPS) is a number that defines the size of a pipe. For example, a 6-inch pipe has an NPS of 6 inches. However, for pipes between 1/8” to 12”, NPS is neither the outside diameter (OD) nor the inside diameter (ID) of the pipe.

How is the Nominal Pipe Size different from the actual diameter of the pipe?

The Nominal Pipe Size (NPS) does not directly correspond to the pipe's actual outside diameter (OD) or inside diameter (ID) for sizes between 1/8” to 12”. For instance, a 4” Schedule 80 pipe has an OD of 4.5” and a thickness of 0.337”.

What is the relationship between NPS and DN?

NPS (Nominal Pipe Size) and DN (Diameter Nominal) are essentially the same, but DN is used internationally, particularly in Europe. You can convert NPS to DN by multiplying NPS by 25. For example, a 2” NPS pipe is referred to as DN 50.

What does DN stand for, and how is it different from NPS?

DN stands for Diameter Nominal, which is an international designation for pipe sizes. It is equivalent to NPS but follows the metric system. For example, a pipe with NPS 8 would be listed as DN 200.

What is a Pipe Schedule?

A pipe schedule defines the wall thickness of a pipe. It is represented by a schedule number, such as Schedule 40 or Schedule 80. The schedule number helps determine the pipe's ability to withstand pressure based on its material and thickness.

How is the schedule number for a pipe calculated?

The schedule number is based on a modified Barlow’s formula for wall thickness, represented as 1000 x P/S, where P is the service pressure, and S is the allowable stress. A higher schedule number indicates a thicker pipe wall.

What is the difference between Schedule 40 and Schedule 80 pipes?

Schedule 80 pipes have thicker walls than Schedule 40 pipes. The thicker the wall, the higher the pipe’s pressure tolerance.

Why are stainless steel pipes more expensive than carbon steel pipes?

Stainless steel pipes are more expensive because of their superior corrosion resistance properties. Additionally, advancements in high alloy stainless steel and fusion welding techniques have allowed thinner pipes to perform adequately without failure, reducing costs.

What is the significance of the 'S' suffix in Schedule numbers for stainless steel pipes?

The 'S' suffix in Schedule numbers indicates pipes made from stainless steel. For instance, Schedule 10S or 40S is specific to stainless steel pipes. These schedules are different from carbon steel pipe schedules.

How can I easily convert between NPS and DN for pipe sizes?

To convert NPS to DN, simply multiply the NPS by 25. For example, an NPS 2 pipe becomes DN 50, and an NPS 8 pipe becomes DN 200.