Stud Bolt Lengths for ASME B16.5 Flanges
Stud bolt lengths for ASME B16.5 flanged joints depend on the flange pressure class, NPS, face type (raised face or ring joint), and gasket type. The tables below provide standard stud bolt lengths for the most common configurations: welding neck flanges with raised face (RF) and spiral wound gaskets.
Stud Bolt Length Table: Class 150 RF (Spiral Wound Gasket)
| NPS | Stud Bolt Dia. (in) | No. of Bolts | Stud Bolt Length (mm) | Stud Bolt Length (in) |
|---|---|---|---|---|
| 1/2 | 1/2 | 4 | 65 | 2-1/2 |
| 3/4 | 1/2 | 4 | 70 | 2-3/4 |
| 1 | 1/2 | 4 | 75 | 3 |
| 1-1/2 | 1/2 | 4 | 80 | 3-1/4 |
| 2 | 5/8 | 4 | 90 | 3-1/2 |
| 3 | 5/8 | 4 | 95 | 3-3/4 |
| 4 | 5/8 | 8 | 100 | 4 |
| 6 | 3/4 | 8 | 110 | 4-1/4 |
| 8 | 3/4 | 8 | 115 | 4-1/2 |
| 10 | 7/8 | 12 | 125 | 5 |
| 12 | 7/8 | 12 | 130 | 5-1/4 |
| 14 | 1 | 12 | 145 | 5-3/4 |
| 16 | 1 | 16 | 155 | 6 |
| 18 | 1-1/8 | 16 | 170 | 6-3/4 |
| 20 | 1-1/8 | 20 | 175 | 7 |
| 24 | 1-1/4 | 20 | 200 | 8 |
Stud Bolt Length Table: Class 300 RF (Spiral Wound Gasket)
| NPS | Stud Bolt Dia. (in) | No. of Bolts | Stud Bolt Length (mm) | Stud Bolt Length (in) |
|---|---|---|---|---|
| 1/2 | 1/2 | 4 | 70 | 2-3/4 |
| 3/4 | 5/8 | 4 | 80 | 3-1/4 |
| 1 | 5/8 | 4 | 85 | 3-1/4 |
| 1-1/2 | 3/4 | 4 | 95 | 3-3/4 |
| 2 | 5/8 | 8 | 100 | 4 |
| 3 | 3/4 | 8 | 110 | 4-1/4 |
| 4 | 3/4 | 8 | 120 | 4-3/4 |
| 6 | 3/4 | 12 | 130 | 5 |
| 8 | 7/8 | 12 | 145 | 5-3/4 |
| 10 | 1 | 16 | 170 | 6-3/4 |
| 12 | 1-1/8 | 16 | 190 | 7-1/2 |
| 14 | 1-1/8 | 20 | 195 | 7-3/4 |
| 16 | 1-1/4 | 20 | 215 | 8-1/2 |
| 18 | 1-1/4 | 24 | 225 | 9 |
| 20 | 1-1/4 | 24 | 240 | 9-1/2 |
| 24 | 1-1/2 | 24 | 280 | 11 |
Stud Bolt Length Table: Class 600 RF (Spiral Wound Gasket)
| NPS | Stud Bolt Dia. (in) | No. of Bolts | Stud Bolt Length (mm) | Stud Bolt Length (in) |
|---|---|---|---|---|
| 2 | 5/8 | 8 | 105 | 4-1/4 |
| 3 | 3/4 | 8 | 120 | 4-3/4 |
| 4 | 7/8 | 8 | 140 | 5-1/2 |
| 6 | 1 | 12 | 165 | 6-1/2 |
| 8 | 1-1/8 | 12 | 195 | 7-3/4 |
| 10 | 1-1/4 | 16 | 225 | 9 |
| 12 | 1-1/4 | 20 | 240 | 9-1/2 |
| 14 | 1-3/8 | 20 | 255 | 10 |
| 16 | 1-1/2 | 20 | 280 | 11 |
| 18 | 1-5/8 | 20 | 305 | 12 |
| 20 | 1-5/8 | 24 | 330 | 13 |
| 24 | 1-7/8 | 24 | 380 | 15 |
Stud bolt lengths are nominal and based on ASTM A193 B7 studs with ASTM A194 2H heavy hex nuts. Lengths include allowance for two nuts and minimum thread protrusion.
RTJ Face Adjustment
For ring joint type (RTJ) flanges, the stud bolt length is typically 6-12 mm (1/4 to 1/2 inch) shorter than the RF equivalent because the ring gasket sits inside the groove rather than adding thickness between the flanges. Always verify against the flange dimension tables for the specific RTJ groove depth.
For gasket type selection and bolt torque requirements, see the reference guides.
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