Flange sizes are essential for a perfect fit and smooth function in piping systems. This guide simplifies the complex dimensions and standards of flanges. By exploring different approaches and their tradeoffs, you’ll understand how to make informed decisions, balancing factors to ensure the best performance and safety.
Flanges Size Chart
ASME/ANSI B16.5 Flanges and Bolt Dimensions – Class 150
| Nominal Pipe Size NPS (inches) | Class 150 | ||||
|---|---|---|---|---|---|
| Diameter of Flange (inches) | No. of Bolts | Diameter of Bolts (inches) | Diameter of Bolt Holes (inches) | Bolt Circle (inches) | |
| 1/4 | 3-3/8 | 4 | 1/2 | 0.62 | 2-1/4 |
| 1/2 | 3-1/2 | 4 | 1/2 | 0.62 | 2-3/8 |
| 3/4 | 3-7/8 | 4 | 1/2 | 0.62 | 2-3/4 |
| 1 | 4-1/4 | 4 | 1/2 | 0.62 | 3-1/8 |
| 1-1/4 | 4-5/8 | 4 | 1/2 | 0.62 | 3-1/2 |
| 1-1/2 | 5 | 4 | 1/2 | 0.62 | 3-7/8 |
| 2 | 6 | 4 | 5/8 | 0.75 | 4-3/4 |
| 2-1/2 | 7 | 4 | 5/8 | 0.75 | 5-1/2 |
| 3 | 7-1/2 | 4 | 5/8 | 0.75 | 6 |
| 3-1/2 | 8-1/2 | 8 | 5/8 | 0.75 | 7 |
| 4 | 9 | 8 | 5/8 | 0.75 | 7-1/2 |
| 5 | 10 | 8 | 3/4 | 0.88 | 8-1/2 |
| 6 | 11 | 8 | 3/4 | 0.88 | 9-1/2 |
| 8 | 13-1/2 | 8 | 3/4 | 0.88 | 11-3/4 |
| 10 | 16 | 12 | 7/8 | 1 | 14-1/4 |
| 12 | 19 | 12 | 7/8 | 1 | 17 |
| 14 | 21 | 12 | 1 | 1.12 | 18-3/4 |
| 16 | 23-1/2 | 16 | 1 | 1.12 | 21-1/4 |
| 18 | 25 | 16 | 1-1/8 | 1.25 | 22-3/4 |
| 20 | 27-1/2 | 20 | 1-1/8 | 1.25 | 25 |
| 24 | 32 | 20 | 1-1/4 | 1.38 | 29-1/2 |
ASME/ANSI B16.5 Flanges and Bolt Dimensions – Class 300
| Nominal Pipe Size NPS (inches) | Class 300 | ||||
|---|---|---|---|---|---|
| Diameter of Flange (inches) | No. of Bolts | Diameter of Bolts (inches) | Diameter of Bolt Holes (inches) | Bolt Circle (inches) | |
| 1/4 | 3-3/8 | 4 | 1/2 | 0.62 | 2-1/4 |
| 1/2 | 3-3/4 | 4 | 1/2 | 0.62 | 2-5/8 |
| 3/4 | 4-5/8 | 4 | 5/8 | 0.75 | 3-1/4 |
| 1 | 4-7/8 | 4 | 5/8 | 0.75 | 3-1/2 |
| 1-1/4 | 5-1/4 | 4 | 5/8 | 0.75 | 3-7/8 |
| 1-1/2 | 6-1/8 | 4 | 3/4 | 0.88 | 4-1/2 |
| 2 | 6-1/2 | 8 | 5/8 | 0.75 | 5 |
| 2-1/2 | 7-1/2 | 8 | 3/4 | 0.88 | 5-7/8 |
| 3 | 8-1/4 | 8 | 3/4 | 0.88 | 6-5/8 |
| 3-1/2 | 9 | 8 | 3/4 | 0.88 | 7-1/4 |
| 4 | 10 | 8 | 3/4 | 0.88 | 7-7/8 |
| 5 | 11 | 8 | 3/4 | 0.88 | 9-1/4 |
| 6 | 12-1/2 | 12 | 3/4 | 0.88 | 10-5/8 |
| 8 | 15 | 12 | 7/8 | 1 | 13 |
| 10 | 17-1/2 | 16 | 1 | 1.12 | 15-1/4 |
| 12 | 20-1/2 | 16 | 1-1/8 | 1.25 | 17-3/4 |
| 14 | 23 | 20 | 1-1/8 | 1.25 | 20-1/4 |
| 16 | 25-1/2 | 20 | 1-1/4 | 1.38 | 22-1/2 |
| 18 | 28 | 24 | 1-1/4 | 1.38 | 24-3/4 |
| 20 | 30-1/2 | 24 | 1-1/4 | 1.38 | 27 |
| 24 | 36 | 24 | 1-1/2 | 1.62 | 32 |
ASME/ANSI B16.5 Flanges and Bolt Dimensions – Class 400
| Nominal Pipe Size NPS (inches) | Class 400 | ||||
|---|---|---|---|---|---|
| Diameter of Flange (inches) | No. of Bolts | Diameter of Bolts (inches) | Diameter of Bolt Holes (inches) | Bolt Circle (inches) | |
| 1/4 | 3-3/8 | 4 | 1/2 | 0.62 | 2-1/4 |
| 1/2 | 3-3/4 | 4 | 1/2 | 0.62 | 2-5/8 |
| 3/4 | 4-5/8 | 4 | 5/8 | 0.75 | 3-1/4 |
| 1 | 4-7/8 | 4 | 5/8 | 0.75 | 3-1/2 |
| 1-1/4 | 5-1/4 | 4 | 5/8 | 0.75 | 3-7/8 |
| 1-1/2 | 6-1/8 | 4 | 3/4 | 0.88 | 4-1/2 |
| 2 | 6-1/2 | 8 | 5/8 | 0.75 | 5 |
| 2-1/2 | 7-1/2 | 8 | 3/4 | 0.88 | 5-7/8 |
| 3 | 8-1/4 | 8 | 3/4 | 0.88 | 6-5/8 |
| 3-1/2 | 9 | 8 | 7/8 | 1 | 7-1/4 |
| 4 | 10 | 8 | 7/8 | 1 | 7-7/8 |
| 5 | 11 | 8 | 7/8 | 1 | 9-1/4 |
| 6 | 12-1/2 | 12 | 7/8 | 1 | 10-5/8 |
| 8 | 15 | 12 | 1 | 1.12 | 13 |
| 10 | 17-1/2 | 16 | 1-1/8 | 1.25 | 15-1/4 |
| 12 | 20-1/2 | 16 | 1-1/4 | 1.38 | 17-3/4 |
| 14 | 23 | 20 | 1-1/4 | 1.38 | 20-1/4 |
| 16 | 25-1/2 | 20 | 1-3/8 | 1.5 | 22-1/2 |
| 18 | 28 | 24 | 1-3/8 | 1.5 | 24-3/4 |
| 20 | 30-1/2 | 24 | 1-1/2 | 1.62 | 27 |
| 24 | 36 | 24 | 1-3/4 | 1.88 | 32 |
ASME/ANSI B16.5 Flanges and Bolt Dimensions – Class 600
| Nominal Pipe Size NPS (inches) | Class 600 | ||||
|---|---|---|---|---|---|
| Diameter of Flange (inches) | No. of Bolts | Diameter of Bolts (inches) | Diameter of Bolt Holes (inches) | Bolt Circle (inches) | |
| 1/4 | 3-3/8 | 4 | 1/2 | 0.62 | 2-1/4 |
| 1/2 | 3-3/4 | 4 | 1/2 | 0.62 | 2-5/8 |
| 3/4 | 4-5/8 | 4 | 5/8 | 0.75 | 3-1/4 |
| 1 | 4-7/8 | 4 | 5/8 | 0.75 | 3-1/2 |
| 1-1/4 | 5-1/4 | 4 | 5/8 | 0.75 | 3-7/8 |
| 1-1/2 | 6-1/8 | 4 | 3/4 | 0.88 | 4-1/2 |
| 2 | 6-1/2 | 8 | 5/8 | 0.75 | 5 |
| 2-1/2 | 7-1/2 | 8 | 3/4 | 0.88 | 5-7/8 |
| 3 | 8-1/4 | 8 | 3/4 | 0.88 | 6-5/8 |
| 3-1/2 | 9 | 8 | 7/8 | 1 | 7-1/4 |
| 4 | 10-3/4 | 8 | 7/8 | 1 | 8-1/2 |
| 5 | 13 | 8 | 1 | 1.12 | 10-1/2 |
| 6 | 14 | 12 | 1 | 1.12 | 11-1/2 |
| 8 | 16-1/2 | 12 | 1-1/8 | 1.25 | 13-3/4 |
| 10 | 20 | 16 | 1-1/4 | 1.38 | 17 |
| 12 | 22 | 20 | 1-1/4 | 1.38 | 19-1/4 |
| 14 | 23-3/4 | 20 | 1-3/8 | 1.5 | 20-3/4 |
| 16 | 27 | 20 | 1-1/2 | 1.62 | 23-3/4 |
| 18 | 29-1/4 | 20 | 1-5/8 | 1.75 | 25-3/4 |
| 20 | 32 | 24 | 1-5/8 | 1.75 | 28-1/2 |
| 24 | 37 | 24 | 1-7/8 | 2 | 33 |
ASME/ANSI B16.5 Flanges and Bolt Dimensions – Class 900
| Nominal Pipe Size NPS (inches) | Class 900 | ||||
|---|---|---|---|---|---|
| Diameter of Flange (inches) | No. of Bolts | Diameter of Bolts (inches) | Diameter of Bolt Holes (inches) | Bolt Circle (inches) | |
| 1/2 | 4-3/4 | 4 | 3/4 | 0.88 | 3-1/4 |
| 3/4 | 5-1/8 | 4 | 3/4 | 0.88 | 3-1/2 |
| 1 | 5-7/8 | 4 | 7/8 | 1 | 4 |
| 1-1/4 | 6-1/4 | 4 | 7/8 | 1 | 4-3/8 |
| 1-1/2 | 7 | 4 | 1 | 1.12 | 4-7/8 |
| 2 | 8-1/2 | 8 | 7/8 | 1 | 6-1/2 |
| 2-1/2 | 9-5/8 | 8 | 1 | 1.12 | 7-1/2 |
| 3 | 9-1/2 | 8 | 7/8 | 1 | 7-1/2 |
| 4 | 11-1/2 | 8 | 1-1/8 | 1.25 | 9-1/4 |
| 5 | 13-3/4 | 8 | 1-1/4 | 1.38 | 11 |
| 6 | 15 | 12 | 1-1/8 | 1.25 | 12-1/2 |
| 8 | 18-1/2 | 12 | 1-3/8 | 1.5 | 15-1/2 |
| 10 | 21-1/2 | 16 | 1-3/8 | 1.5 | 18-1/2 |
| 12 | 24 | 20 | 1-3/8 | 1.5 | 21 |
| 14 | 25-1/4 | 20 | 1-1/2 | 1.62 | 22 |
| 16 | 27-3/4 | 20 | 1-5/8 | 1.75 | 24-1/2 |
| 18 | 31 | 20 | 1-7/8 | 2 | 27 |
| 20 | 33-3/4 | 20 | 2 | 2.12 | 29-1/2 |
| 24 | 41 | 20 | 2-1/2 | 2.62 | 35-1/2 |
ASME/ANSI B16.5 Flanges and Bolt Dimensions – Class 1500
| Nominal Pipe Size NPS (inches) | Class 1500 | ||||
|---|---|---|---|---|---|
| Diameter of Flange (inches) | No. of Bolts | Diameter of Bolts (inches) | Diameter of Bolt Holes (inches) | Bolt Circle (inches) | |
| 1/2 | 4-3/4 | 4 | 3/4 | 0.88 | 3-1/4 |
| 3/4 | 5-1/8 | 4 | 3/4 | 0.88 | 3-1/2 |
| 1 | 5-7/8 | 4 | 7/8 | 1 | 4 |
| 1-1/4 | 6-1/4 | 4 | 7/8 | 1 | 4-3/8 |
| 1-1/2 | 7 | 4 | 1 | 1.12 | 4-7/8 |
| 2 | 8-1/2 | 8 | 7/8 | 1 | 6-1/2 |
| 2-1/2 | 9-5/8 | 8 | 1 | 1.12 | 7-1/2 |
| 3 | 10-1/2 | 8 | 1-1/8 | 1.25 | 8 |
| 4 | 12-1/4 | 8 | 1-1/4 | 1.38 | 9-1/2 |
| 5 | 14-3/4 | 8 | 1-1/2 | 1.62 | 11-1/2 |
| 6 | 15-1/2 | 12 | 1-3/8 | 1.5 | 12-1/2 |
| 8 | 19 | 12 | 1-5/8 | 1.75 | 15-1/2 |
| 10 | 23 | 12 | 1-7/8 | 2 | 19 |
| 12 | 26-1/2 | 16 | 2 | 2.12 | 22-1/2 |
| 14 | 29-1/2 | 16 | 2-1/4 | 2.38 | 25 |
| 16 | 32-1/2 | 16 | 2-1/2 | 2.62 | 27-3/4 |
| 18 | 36 | 16 | 2-3/4 | 2.88 | 30-1/2 |
| 20 | 38-3/4 | 16 | 3 | 3.12 | 32-3/4 |
| 24 | 46 | 16 | 3-1/2 | 3.62 | 39 |
ASME/ANSI B16.5 Flanges and Bolt Dimensions – Class 2500
| Nominal Pipe Size NPS (inches) | Class 2500 | ||||
|---|---|---|---|---|---|
| Diameter of Flange (inches) | No. of Bolts | Diameter of Bolts (inches) | Diameter of Bolt Holes (inches) | Bolt Circle (inches) | |
| 1/2 | 5-1/4 | 4 | 3/4 | 0.88 | 3-1/2 |
| 3/4 | 5-1/2 | 4 | 3/4 | 0.88 | 3-3/4 |
| 1 | 6-1/4 | 4 | 7/8 | 1 | 4-1/4 |
| 1-1/4 | 7-1/4 | 4 | 1 | 1.12 | 5-1/8 |
| 1-1/2 | 8 | 4 | 1-1/8 | 1.25 | 5-3/4 |
| 2 | 9-1/4 | 8 | 1 | 1.12 | 6-3/4 |
| 2-1/2 | 10-1/2 | 8 | 1-1/8 | 1.25 | 7-3/4 |
| 3 | 12 | 8 | 1-1/4 | 1.38 | 9 |
| 4 | 14 | 8 | 1-1/2 | 1.62 | 10-3/4 |
| 5 | 16-1/2 | 8 | 1-3/4 | 1.88 | 12-3/4 |
| 6 | 19 | 8 | 2 | 2.12 | 14-1/2 |
| 8 | 21-3/4 | 12 | 2 | 2.12 | 17-1/4 |
| 10 | 26-1/2 | 12 | 2-1/2 | 2.62 | 21-1/4 |
| 12 | 30 | 12 | 2-3/4 | 2.88 | 24-3/8 |
Types of Flanges
Flanges come in various types, each designed for specific applications. Here’s a breakdown of the most common types.
Slip-On Flanges
Slip-on flanges easily slide over the pipe and are welded both inside and outside, creating a robust joint. This type is often chosen for its simplicity and ease of installation. However, the tradeoff is that it can be less durable under high-pressure conditions compared to other types.
Weld Neck Flanges
Weld neck flanges are securely attached to pipes through welding, ensuring a strong, permanent connection. While they offer superior strength and are ideal for high-pressure applications, they require precise welding skills and can be more expensive due to the additional labor and materials.
Blind Flanges
Blind flanges are used to close off the end of a piping system, effectively sealing it to prevent flow. They are crucial for isolating sections of a system for maintenance or testing. However, their use can be limited to situations where the system does not need frequent access.
Threaded Flanges
Threaded flanges feature internal threads that allow them to be screwed onto the pipe, eliminating the need for welding. This design simplifies installation and makes them a convenient choice for applications where welding might be impractical. Nonetheless, they are typically used for lower-pressure applications, as they can be less robust than welded options.
In choosing the right flange type, consider the impact of factors such as installation ease, pressure requirements, and cost. Balancing these elements helps ensure you select the most appropriate flange for your specific needs, addressing both practical and economic challenges.
How to Read a Flange Size Chart
Interpreting a flange size chart can be straightforward once you understand the key components and measurements involved.
Dimensions Explained
A typical flange size chart provides several important dimensions, including diameter, thickness, and bolt-hole pattern. To start, the diameter measurement tells you the size of the flange’s opening, which must match the pipe it will connect to. Next, the thickness indicates how robust the flange is, which affects its ability to withstand pressure.
Lastly, the bolt-hole pattern details the arrangement and size of holes for bolting the flange to other components. Each dimension plays a crucial role in ensuring a proper fit and function. However, balancing these dimensions can be challenging, as incorrect measurements may lead to leaks or mechanical failures.
Pressure Ratings
Pressure ratings on a flange size chart show the maximum pressure the flange can safely handle. These ratings are essential for selecting the right flange for your system’s operational pressures. High-pressure ratings generally mean a more robust and costly flange, whereas lower-pressure ratings might be sufficient for less demanding applications. Understanding these ratings helps avoid potential failures and ensures the flange’s performance under pressure. When making decisions, weigh the tradeoffs between cost and pressure requirements to find the most suitable flange for your needs.
By thoroughly understanding these components and their implications, you can make informed decisions that balance performance, safety, and cost-effectiveness in your piping system.
Choosing the Right Flange Size
Selecting the correct flange size involves more than just matching dimensions. Consider these factors to ensure optimal performance.
Pipe Size Compatibility
First, ensure that the flange size matches the diameter of the pipe it will connect to for a proper fit. A correct match is crucial for maintaining the integrity of the connection and preventing leaks. While it might seem straightforward, the challenge lies in accurately measuring and selecting the flange that aligns perfectly with the pipe’s dimensions. Balancing this precision with other factors, such as pressure and temperature requirements, can be complex but is essential for effective system operation.
Pressure and Temperature Ratings
Next, choose flanges that can handle the pressure and temperature conditions of your system. Flanges with higher pressure and temperature ratings offer better performance but can be more expensive. Conversely, selecting a flange with inadequate ratings might lead to system failures or safety issues. Therefore, assessing the tradeoffs between cost and performance is vital. It’s important to choose a flange that not only fits but also withstands the operational conditions it will encounter.
Material Considerations
Finally, consider the material of the flange. The flange material should be compatible with the substances it will come into contact with to prevent corrosion and ensure durability. For instance, a flange exposed to corrosive chemicals needs to be made from a material resistant to those chemicals. Choosing the right material involves weighing the costs against the benefits of enhanced durability and resistance. Ensuring material compatibility helps avoid long-term maintenance issues and extends the life of your piping system.
By carefully evaluating these factors and their tradeoffs, you can make informed decisions that enhance the performance, safety, and cost-effectiveness of your piping system.
FAQ
1. What is the most common type of flange used in piping systems?
Answer:
The most common type of flange used in piping systems is the Slip-On Flange. It is favored for its ease of installation and cost-effectiveness. Slip-on flanges slide over the pipe and are welded both inside and outside, providing a secure connection. However, they are typically used for lower-pressure applications compared to Weld Neck Flanges, which are more robust but also more expensive.
2. How do I determine the correct flange size for my piping system?
Answer:
To determine the correct flange size, first measure the diameter of the pipe it will connect to, ensuring the flange’s size matches this measurement for a proper fit. Next, check the pressure and temperature ratings of the flange to ensure it can handle your system’s operational conditions. Finally, consider the flange material to ensure it is compatible with the substances in your system. Balancing these factors is crucial for optimal performance and safety.
3. What should I do if I can’t find a flange size that matches my requirements?
Answer:
If you can’t find a flange size that matches your requirements, consider contacting a manufacturer or supplier who can offer custom flanges. Custom fabrication allows you to get a flange with precise dimensions, pressure ratings, and materials that meet your specific needs. Additionally, consult with a piping systems engineer to ensure that your custom solution will perform effectively and safely within your system.