ASME/ANSI B16.5 Flange and Bolt Sizes – Class 150 to 2500
Diameters and Bolt Circles for Standard ASME B16.5 Flanges – 1/4 to 24 Inches – Class 150 to 2500
Flange size depends on the pipe size and the pressure rating required for the application. Flanges are standardized according to publications by organizations such as ASME, MSS, API, etc.
*Weld neck
*Pull-through
*Socket weld
*Threaded
*Lap joint
*Blind
Pipe flange sizes range from 1/2″ to 24″ – and classes range from 150 to 2500. Note that the classes are in steps in terms such as ASME Class or API.
Generally speaking, when pipes are butt welded to flanges, the specification (thickness) of the connected pipes needs to be specified. Socket welding and threaded connections are not affected by wall thickness and only the outer diameter needs to be specified.
ASME/ANSI B16.5 Flange and Bolting 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 | 1.25 | 29-1/2 |
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