3-1/2 inch Class 150 flange dimensions
ASME B16.5 Class 150 flange dimensions for 3-1/2 inch (DN 90) pipe. The same bolting dimensions apply to weld neck, slip-on, blind, socket weld, threaded and lap joint flanges of this size and class.
| Nominal size | 3-1/2" (DN 90) |
| Pipe OD (bore end) | 101.6 mm |
| Flange outside diameter | 215 mm (8.46 in) |
| Minimum thickness (incl. 1.6 mm RF) | 22.3 mm (0.88 in) |
| Bolt circle diameter (PCD) | 177.8 mm (7.00 in) |
| Number of bolt holes | 8 |
| Bolt hole diameter | 0.75 in (19.0 mm) |
| Stud bolt diameter | 5/8" UNC |
| Raised face height | 1.6 mm (1/16 in) |
A complete 3-1/2" Class 150 joint needs 8 stud bolts of 5/8" diameter with 16 heavy hex nuts and one gasket.
Class 150 vs Class 300 — 3-1/2"
| Dimension | Class 150 | Class 300 |
|---|---|---|
| OD | 215 mm | 230 mm |
| Thickness | 22.3 mm | 28.6 mm |
| Bolt circle | 177.8 mm | 184.2 mm |
| Bolts | 8 × 5/8" | 8 × 3/4" |
Class 150 and Class 300 flanges do not bolt together — see 3-1/2" Class 300.
Frequently asked questions
What is the OD of a 3-1/2 inch Class 150 flange?
215 mm (8.46 in) per ASME B16.5.
How many bolts does a 3-1/2 inch Class 150 flange have?
8 bolts of 5/8 inch diameter in 0.75 inch holes on a 177.8 mm bolt circle.
What is the thickness of a 3-1/2 inch Class 150 flange?
The minimum flange thickness is 22.3 mm, including the 1.6 mm raised face.
Last updated 2026-11-02