Class 1500 Weld Neck Flange Dimensions
ASME B16.5 dimensions and bolting for the Class 1500 weld neck flange, NPS 1/2 through NPS 24.
- Standard
- ASME B16.5
- Flange type
- Weld Neck Flange
- Pressure class
- Class 1500
- Size range
- NPS 1/2 – NPS 24
- Raised face height
- 0.25 in (6.3 mm)
- Rating at 100 °F (A105)
- 3705 psig (255.5 bar)
Dimensions are given in inches, with the millimetre equivalent beneath in grey.
| Size | Flange OD | Thickness | Bolt circle | Bolts | Bolt dia. | Raised face OD |
|---|---|---|---|---|---|---|
| NPS 1/2 | 4.75120.65 mm | 0.8822.35 mm | 3.2582.55 mm | 4 | 3/4 in | 1.3835.05 mm |
| NPS 3/4 | 5.12130.05 mm | 1.0025.40 mm | 3.5088.90 mm | 4 | 3/4 in | 1.6942.93 mm |
| NPS 1 | 5.88149.35 mm | 1.1228.45 mm | 4.00101.60 mm | 4 | 7/8 in | 2.0050.80 mm |
| NPS 1 1/4 | 6.25158.75 mm | 1.1228.45 mm | 4.38111.25 mm | 4 | 7/8 in | 2.5063.50 mm |
| NPS 1 1/2 | 7.00177.80 mm | 1.2531.75 mm | 4.88123.95 mm | 4 | 1 in | 2.8873.15 mm |
| NPS 2 | 8.50215.90 mm | 1.5038.10 mm | 6.50165.10 mm | 8 | 7/8 in | 3.6291.95 mm |
| NPS 2 1/2 | 9.62244.35 mm | 1.6241.15 mm | 7.50190.50 mm | 8 | 1 in | 4.12104.65 mm |
| NPS 3 | 10.50266.70 mm | 1.8847.75 mm | 8.00203.20 mm | 8 | 1 1/8 in | 5.00127.00 mm |
| NPS 4 | 12.25311.15 mm | 2.1253.85 mm | 9.50241.30 mm | 8 | 1 1/4 in | 6.19157.23 mm |
| NPS 5 | 14.75374.65 mm | 2.8873.15 mm | 11.50292.10 mm | 8 | 1 1/2 in | 7.31185.67 mm |
| NPS 6 | 15.50393.70 mm | 3.2582.55 mm | 12.50317.50 mm | 12 | 1 3/8 in | 8.50215.90 mm |
| NPS 8 | 19.00482.60 mm | 3.6291.95 mm | 15.50393.70 mm | 12 | 1 5/8 in | 10.62269.75 mm |
| NPS 10 | 23.00584.20 mm | 4.25107.95 mm | 19.00482.60 mm | 12 | 1 7/8 in | 12.75323.85 mm |
| NPS 12 | 26.50673.10 mm | 4.88123.95 mm | 22.50571.50 mm | 16 | 2 in | 15.00381.00 mm |
| NPS 14 | 29.50749.30 mm | 5.25133.35 mm | 25.00635.00 mm | 16 | 2 1/4 in | 16.25412.75 mm |
| NPS 16 | 32.50825.50 mm | 5.75146.05 mm | 27.75704.85 mm | 16 | 2 1/2 in | 18.50469.90 mm |
| NPS 18 | 36.00914.40 mm | 6.38162.05 mm | 30.50774.70 mm | 16 | 2 3/4 in | 21.00533.40 mm |
| NPS 20 | 38.75984.25 mm | 7.00177.80 mm | 32.75831.85 mm | 16 | 3 in | 23.00584.20 mm |
| NPS 24 | 46.001168.40 mm | 8.00203.20 mm | 39.00990.60 mm | 16 | 3 1/2 in | 27.25692.15 mm |
Flange thickness excludes the raised face. Bolt diameter is nominal; stud bolts are normally ASTM A193 B7 with A194 2H nuts.
Each size above links to its own page, with the flange bore for every schedule of pipe it can be welded to.
Common questions
How many bolts does a Class 1500 weld neck flange use?
NPS 1/2 takes 4 × 3/4 in; NPS 3/4 takes 4 × 3/4 in; NPS 1 takes 4 × 7/8 in; NPS 1 1/4 takes 4 × 7/8 in; NPS 1 1/2 takes 4 × 1 in. Bolt count rises with size — see the table above for the full range.
What pressure is a Class 1500 flange rated for?
Class is a designation, not a pressure. A Class 1500 flange in A105 carbon steel is rated 3705 psig (255.5 bar) at 100 °F, and that rating falls as metal temperature rises. In stainless the same class starts lower at ambient but holds up far better in the heat — see the P-T rating tables.
Will a Class 1500 flange bolt to a Class 150 flange?
No. Bolt circle diameter, bolt count and bolt size all change with class, so flanges of different classes in the same NPS will not mate. The only exceptions inside B16.5 are the deliberate ones the standard calls out, such as Class 400 sharing Class 600 dimensions in NPS 1/2 through 3 1/2.