Table of content
Introduction
Flange size is an important indicator for selecting flanges. Flanges have different production standards, such as ASME, ANSI, DIN, JIS, etc. The sizes of flanges produced according to different standards are slightly different. How to determine the flange sizes in these standards? Let’s answer this question.
What Are the Common Flange Sizes?
Flange sizes are expressed in different ways according to different standards: nominal pipe size NPS and nominal diameter DN.
Here are some common standard size data tables:
| Nominal Pipe Size (NPS) | Outside Diameter (OD) (inches) | Bolt Circle Diameter (inches) | Number of Bolt Holes |
|---|---|---|---|
| ½” (DN 15) | 3.50 | 2.38 | 4 |
| 1″ (DN 25) | 4.25 | 3.12 | 4 |
| 2″ (DN 50) | 6.00 | 4.75 | 4 |
| 4″ (DN 100) | 9.00 | 7.50 | 8 |
| 6″ (DN 150) | 11.00 | 9.50 | 8 |
| 8″ (DN 200) | 13.50 | 11.75 | 8 |
| 10″ (DN 250) | 16.00 | 14.25 | 12 |
| 12″ (DN 300) | 19.00 | 17.00 | 12 |
These flange sizes are used in various industries, including oil & gas, chemical processing, and water treatment.
Choosing the right size flange can be applied to various industries, such as oil pipelines, natural gas pipelines, chemical processing pipelines and water treatment systems.
How Are Flange Sizes Determined?
The specific size of the flange can be referenced by the following 5 aspects:
1. NPS or DN: Check the nominal diameter or nominal pipe size of the flange.
2. Outer diameter OD: the maximum outer diameter of the flange.
3. Bolt hole diameter: the center diameter of the bolt.
4. Number of holes: The number of bolt holes is used to fix the flange.
5. Pressure rating: The reference data of the highest pressure that the flange can withstand.
What Is the Difference Between NPS and DN?
NPS: Nominal pipe size, in inches, mostly used in American standards.
DN: Nominal diameter, in millimeters, mostly used in Europe.
Flange Pressure Ratings and Their Sizes
Flanges have different pressure ratings and different wall thicknesses. The higher the pressure rating, the thicker the wall thickness.
The following is a pressure rating table:
| Flange Class | Common Sizes Available | Pressure Rating (psi) |
|---|---|---|
| Class 150 | ½” – 24” | Up to 285 psi |
| Class 300 | ½” – 24” | Up to 740 psi |
| Class 600 | ½” – 24” | Up to 1,500 psi |
| Class 900 | ½” – 24” | Up to 2,250 psi |
| Class 1500 | ½” – 24” | Up to 3,750 psi |
| Class 2500 | ½” – 24” | Up to 6,250 psi |
Common Flange Sizes Based on Standards
There are three main common flange standards: ASME, DIN, JIS.
ASME B16.5
Mostly used in North America.
The sizes are mainly from ½” to 24”.
The pressure ratings are Class 150, 300, 600, 900, 1500, and 2500
Mostly used in the petroleum, chemical, and natural gas industries.
DIN
Mostly used in Europe.
The sizes are mainly from DN 10 to DN 3000.
Pressure levels include PN6, PN10, PN16, PN25, PN40, PN64, PN100, etc.
Mostly used in chemical plants and water treatment systems.
JIS
Mostly used in Japan.
Sizes are mainly from 10A to 1500A.
Pressure levels include 10K, 16K, 20K, 30K.
Mostly used in water treatment systems, oil pipelines, etc.
Choosing the Right Flange Size
When choosing flange size, you can refer to the following 5 points:
1. Size compatibility: see whether to choose NPS or DN standard.
2. Pressure: Choose the appropriate pressure flange according to the actual application.
3. Material: Choose carbon steel or stainless steel according to needs.
4. Bolts: Check the number and diameter of bolts.
5. Choose the right flange: see what type of flange is there: weld neck flange, slip-on flange, blind flange, or threaded flanges.
Summary
So when choosing flanges, you must understand the various standard flanges and flange sizes in detail. See whether it is American standard, German standard or Japanese standard. Because different standards have different representation methods and units. The pressure they can withstand is also different. Therefore, choosing the right flange is an important step to ensure that the pipeline does not leak. I hope this guide can help you choose the right industrial flange.
