The dimensions of a Class 150 Welding Neck Flange, as per ASME B16.5 standards, can vary based on the size of the flange. Here are the general dimensions for a Class 150 Welding Neck Flange for some common sizes:
| Flange NPS | Inside | Outside | Bolt Circle | Raised Face | Raised Face | H | H1 | Raised Face | T1 | Flat Face | Bolt Hole | No. of |
| Diameter | Diameter | (BC) | (R) | (RF) | Thickness (T) | Thickness (T2) | (B) | Bolt Holes | ||||
| 1/2″ | 0.62″ | 3.50″ | 2.38″ | 1.38″ | .063″ | 1.19″ | 0.84″ | 1.88″ | .38″ | 1.82″ | .62″ | 4 |
| 3/4″ | 0.82″ | 3.88″ | 2.75″ | 1.69″ | .063″ | 1.50″ | 1.05″ | 2.06″ | .44″ | 2.00″ | .62″ | 4 |
| 1″ | 1.05″ | 4.25″ | 3.12″ | 2.00″ | .063″ | 1.94″ | 1.32″ | 2.19″ | .50″ | 2.13″ | .62″ | 4 |
| 1-1/4″ | 1.38″ | 4.62″ | 3.50″ | 2.50″ | .063″ | 2.31″ | 1.66″ | 2.25″ | .56″ | 2.19″ | .62″ | 4 |
| 1-1/2″ | 1.61″ | 5.00″ | 3.88″ | 2.88″ | .063″ | 2.56″ | 1.90″ | 2.44″ | .62″ | 2.38″ | .62″ | 4 |
| 2″ | 2.07″ | 6.00″ | 4.75″ | 3.62″ | .063″ | 3.06″ | 2.38″ | 2.50″ | .69″ | 2.44″ | .75″ | 4 |
| 2-1/2″ | 2.47″ | 7.00″ | 5.50″ | 4.12″ | .063″ | 3.56″ | 2.88″ | 2.75″ | .82″ | 2.69″ | .75″ | 4 |
| 3″ | 3.07″ | 7.50″ | 6.00″ | 5.00″ | .063″ | 4.25″ | 3.50″ | 2.75″ | .88″ | 2.69″ | .75″ | 4 |
| 3-1/2″ | 3.55″ | 8.50″ | 7.00″ | 5.50″ | .063″ | 4.81″ | 4.00″ | 2.81″ | .88″ | 2.75″ | .75″ | 8 |
| 4″ | 4.03″ | 9.00″ | 7.50″ | 6.19″ | .063″ | 5.31″ | 4.50″ | 3.00″ | .88″ | 2.94″ | .75″ | 8 |
| 5″ | 5.05″ | 10.00″ | 8.50″ | 7.31″ | .063″ | 6.44″ | 5.56″ | 3.50″ | .88″ | 3.44″ | .88″ | 8 |
| 6″ | 6.07″ | 11.00″ | 9.50″ | 8.50″ | .063″ | 7.56″ | 6.63″ | 3.50″ | .94″ | 3.44″ | .88″ | 8 |
| 8″ | 7.98″ | 13.50″ | 11.75″ | 10.62″ | .063″ | 9.69″ | 8.63″ | 4.00″ | 1.06″ | 3.94″ | .88″ | 8 |
| 10″ | 10.02″ | 16.00″ | 14.25″ | 12.75″ | .063″ | 12.00″ | 10.75″ | 4.00″ | 1.13″ | 3.94″ | 1.00″ | 12 |
| 12″ | 12.00″ | 19.00″ | 17.00″ | 15.00″ | .063″ | 14.38″ | 12.75″ | 4.50″ | 1.19″ | 4.44″ | 1.00″ | 12 |
| 14″ | 13.25″ | 21.00″ | 18.75″ | 16.25″ | .063″ | 15.75″ | 14.00″ | 5.00″ | 1.32″ | 4.94″ | 1.12″ | 12 |
| 16″ | 15.25″ | 23.50″ | 21.25″ | 18.50″ | .063″ | 18.00″ | 16.00″ | 5.00″ | 1.38″ | 4.94″ | 1.12″ | 16 |
| 18″ | 17.25″ | 25.00″ | 22.75″ | 21.00″ | .063″ | 19.88″ | 18.00″ | 5.50″ | 1.50″ | 5.44″ | 1.25″ | 16 |
| 20″ | 19.25″ | 27.50″ | 25.00″ | 23.00″ | .063″ | 22.00″ | 20.00″ | 5.69″ | 1.63″ | 5.63″ | 1.25″ | 20 |
| 22″ | 21.25″ | 29.50″ | 27.25″ | 25.25″ | .063″ | 24.25″ | 22.00″ | 5.88″ | 1.75″ | 5.82″ | 1.38″ | 20 |
| 24″ | 23.25″ | 32.00″ | 29.50″ | 27.25″ | .063″ | 26.12″ | 24.00″ | 6.00″ | 1.82″ | 5.94″ | 1.38″ | 20 |
Nominal Pipe Size (NPS): 1/2 inch (DN 15) to 24 inches (DN 600) and larger.
Outside Diameter (OD): Varies with NPS. For example, the OD of a 1/2-inch flange is approximately 3.5 inches, while the OD of a 24-inch flange is around 32 inches.
Bolt Circle Diameter (BCD): This is the diameter of the circle that passes through the center of the bolt holes. It increases with the size of the flange. For example, the BCD of a 1/2-inch flange is approximately 2.38 inches, while the BCD of a 24-inch flange is around 29.5 inches.
Number of Bolt Holes: Varies with NPS. Typically, smaller sizes have fewer bolt holes (e.g., 4), while larger sizes may have more (e.g., 20).
Bolt Hole Diameter: The diameter of the bolt holes varies with the NPS. For example, the bolt hole diameter for a 1/2-inch flange is approximately 0.88 inches.
Hub Diameter: The diameter of the raised face at the base of the flange. It increases with the size of the flange.
Overall Length Through Hub (LTH): This is the distance from the face of the flange to the end of the hub. It also increases with the size of the flange.
Flange Thickness: This is the thickness of the flange and can vary based on the pressure class.
It's important to note that these are general dimensions, and specific dimensions may vary based on the manufacturer and standards in use. For accurate and detailed dimensions, it is recommended to refer to the ASME B16.5 standard or consult the manufacturer's specifications for the specific flange size and class.
