← Back to Tools
Flange Dimension Lookup
Quick reference for flange outer diameter, bolt circle, number of bolts, bolt hole diameter, and face thickness.
Dimension Lookup Tool
Outer Diameter (OD)
6.5"
Bolt Circle (BC)
5"
Number of Bolts
8
Bolt Hole Diameter (BD)
0.75"
Face Thickness
0.88"
Pressure Class
Class 300
Understanding These Dimensions
- OD (Outer Diameter): Overall width of the flange. Use for flange-to-vessel clearance calculations.
- BC (Bolt Circle): Diameter on which bolt holes are centered. Critical for matching mating equipment.
- Bolts: Number of bolts in pattern. Must match mating equipment.
- BD (Bolt Hole Diameter): Diameter of each bolt hole. Determines bolt clearance.
- Thickness: Height of blind flange (or face thickness of other types). Affects weld strength.
Critical Verification Steps
- 1. Count bolts: Physically count bolt holes on mating equipment. One mismatch requires custom drilling.
- 2. Measure BC: Use calipers to measure bolt circle on mating equipment. Tolerance is typically ±1/16".
- 3. Check clearances: Verify OD doesn't interfere with vessel nozzles, saddles, or supports.
- 4. Confirm pressure class: Match pressure class to system design pressure and temperature rating.
When to Request Custom Flanges
If your equipment doesn't match standard ASME dimensions, request custom machining:
- • Non-standard bore diameter
- • Custom bolt pattern (off-pattern bolts)
- • Overbore (larger bore than standard)
- • Special hub extensions
- • Face modifications (raised face, ring joint, etc.)
Complete Dimension Reference (Class 300 PSI)
| NPS | OD | BC | Bolts | BD | Thickness |
|---|---|---|---|---|---|
| 1 | 4.88" | 3.5" | 4 | 0.625" | 0.69" |
| 2 | 6.5" | 5" | 8 | 0.75" | 0.88" |
| 3 | 8.25" | 6.62" | 8 | 0.875" | 1.12" |
| 4 | 10" | 7.88" | 8 | 0.875" | 1.25" |
| 6 | 12.5" | 10.62" | 12 | 0.875" | 1.44" |
| 8 | 15" | 13" | 12 | 1" | 1.62" |
| 10 | 17.5" | 15.25" | 16 | 1.125" | 1.88" |
| 12 | 20.5" | 17.75" | 16 | 1.25" | 2" |
| 14 | 23" | 20.25" | 20 | 1.25" | 2.12" |
| 16 | 25.5" | 22.5" | 20 | 1.375" | 2.25" |
| 18 | 28" | 24.75" | 24 | 1.375" | 2.38" |
| 20 | 30.5" | 27" | 24 | 1.375" | 2.5" |
| 24 | 36" | 32" | 24 | 1.625" | 2.75" |
| 1/2 | 3.75" | 2.62" | 4 | 0.5" | 0.56" |
All dimensions in inches per ASME B16.5 Table 8. Results are reference data only. For certified dimensions on production orders, call (281) 484-8325 or refer to the current ASME B16.5 spec.
Need Custom Flanges?
If your equipment requires non-standard dimensions, we can route custom-machined flanges from qualified suppliers to your exact specifications.
Request Custom Flanges →