API Spec 6A Reference
Wellhead Flange Dimensions for 2000 PSI to 15,000 PSI
Complete reference table and slide rule selector for API Spec 6A Type 6B and 6BX wellhead and Christmas tree flanges. Covers all nominal bore sizes from 1-13/16" through 21-1/4".
- Type 6B flanges use standard Type R or RX ring joint gaskets.
- Type 6BX flanges use pressure-energized BX ring joint gaskets for 10,000 & 15,000 PSI.
- Materials conform to API 6A material classes AA, BB, CC, DD, EE, FF, and HH.
API 6A / API 16A Wellhead Flange Type 6B & Type 6BX Standard Assembly
API 6A Wellhead Flange Complete Selector Table
| Nominal Size | Pressure Rating (PSI) | Flange OD (in) | Flange Thk (in) | Ring Gasket No. | Bolt Circle (BCD) | Stud Bolt Size x Len |
|---|---|---|---|---|---|---|
| 1-13/16" | 2000 PSI | 6.12" | 1.31" | R-23 | 4.50" | 5/8" x 4-1/2" |
| 2-1/16" | 2000 PSI | 6.50" | 1.31" | R-23 | 5.00" | 5/8" x 4-1/2" |
| 2-1/16" | 3000 PSI | 8.50" | 1.56" | R-24 | 6.50" | 7/8" x 6-1/4" |
| 2-1/16" | 5000 PSI | 8.50" | 1.81" | R-24 | 6.50" | 7/8" x 6-1/2" |
| 2-1/16" | 10,000 PSI | 7.88" | 1.75" | BX-152 | 6.00" | 3/4" x 5-3/4" |
| 3-1/8" | 2000 PSI | 8.25" | 1.50" | R-31 | 6.62" | 3/4" x 5" |
| 3-1/8" | 3000 PSI | 9.50" | 1.56" | R-31 | 7.50" | 7/8" x 5-1/2" |
| 3-1/8" | 5000 PSI | 10.50" | 2.19" | R-35 | 8.00" | 1-1/8" x 7-1/4" |
| 3-1/16" | 10,000 PSI | 10.62" | 2.31" | BX-154 | 8.50" | 1" x 7-1/2" |
| 4-1/16" | 2000 PSI | 10.00" | 1.50" | R-37 | 7.88" | 3/4" x 5-1/4" |
| 4-1/16" | 3000 PSI | 11.50" | 1.81" | R-37 | 9.25" | 1-1/8" x 6-3/4" |
| 4-1/16" | 5000 PSI | 12.25" | 2.44" | R-39 | 9.50" | 1-1/4" x 8-1/2" |
| 4-1/16" | 10,000 PSI | 12.44" | 2.81" | BX-155 | 10.06" | 1-1/8" x 8-3/4" |
| 5-1/8" | 2000 PSI | 11.00" | 1.69" | R-41 | 9.00" | 7/8" x 5-3/4" |
| 5-1/8" | 5000 PSI | 14.75" | 3.12" | R-44 | 11.50" | 1-1/2" x 10-1/2" |
| 7-1/16" | 2000 PSI | 13.50" | 1.81" | R-45 | 11.00" | 1" x 6-1/2" |
| 7-1/16" | 3000 PSI | 15.00" | 2.19" | R-45 | 12.50" | 1-1/8" x 7-3/4" |
| 7-1/16" | 5000 PSI | 15.50" | 3.12" | R-46 | 12.50" | 1-1/2" x 10-3/4" |
| 7-1/16" | 10,000 PSI | 18.88" | 4.06" | BX-156 | 15.25" | 1-1/2" x 12-1/2" |
| 9" | 2000 PSI | 16.00" | 1.94" | R-49 | 13.50" | 1-1/8" x 7" |
| 11" | 3000 PSI | 19.50" | 2.69" | R-54 | 16.50" | 1-3/8" x 9-1/2" |
📌 API 6A Flange Technical Specification
API 6A flanges are not interchangeable with standard ASME B16.5 flanges even where bolt circles appear similar, due to differences in ring groove dimensions, hub tapers, and pressure rating design factors.
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