Flanges are chosen based on their corrosion resistance properties, erosion resistance properties, pressure temperature rating (Class), number of welds required for attachment, physical size (some flange designs may not fit into the space allowed) and cost. The most common flange types are:
- Welding Neck Flange
- Slip-on Flange
- Socket Weld Flange
- Lap Joint Flange
- Threaded Flange
- Blind Flange
|
Flange Type |
NPS (inch) |
ASME Class |
Faces |
Joint Integrity |
Weld |
ASME Standards |
|
Welding Neck Flange |
All |
All |
All |
High |
One butt weld. |
B16.5, B31.3 |
|
Slip-on Flange |
Many |
Generally, ≤ 600 |
FF, RF |
Medium |
One or two fillet welds. |
B16.5, B31.3 |
|
Socket Weld Flange |
Generally, Max ≤ 4 |
≤ 600 |
FF, RF |
Medium |
One fillet weld. |
B16.5, B31.3 |
|
Lap Joint Ring Flange |
Not used for small sizes. |
NA |
FF |
NA |
None |
B16.5, B31.3 |
|
Stub End of Lap Joint Flange |
150 to 2500 |
FF, RF, RTJ |
High |
One butt weld. |
B16.9, B31.3 |
|
|
Threaded Flange |
Generally, Max ≤ 4 |
≤ 300 |
FF, RF |
Low |
None |
B1.20.1, B31.3 |
|
Blind Flange |
All |
All |
All |
NA |
None |
B16.5, B31.3 |
Flange Type Summary Table
