1. Scope & Application of ASME B16.5 Standard
The ASME B16.5 standard is the global benchmark for steel pipe flanges and flanged fittings. It covers pressure-temperature ratings, materials, dimensions, tolerances, marking, testing, and methods of designating openings for pipe flanges in sizes NPS 1/2 through NPS 24.
Sakshi Forge manufactures forged flanges in accordance with ASME B16.5 using closed-die drop forging and ring rolling processes to ensure optimal grain flow alignment along high-stress flange necks and bolt circle areas.
2. Material Group Classifications (ASTM Specifications)
Under ASME B16.5 Table 1A, flange materials are categorized into material groups based on metallurgical behavior under heat and pressure:
- Group 1.1 (Carbon Steel): ASTM A105, ASTM A350 Gr. LF2, ASTM A515 Gr. 70.
- Group 1.9 (Alloy Steel): ASTM A182 Gr. F11, ASTM A182 Gr. F22 (High temperature steam lines).
- Group 2.1 (Austenitic SS): ASTM A182 Gr. F304, F304L.
- Group 2.2 (Austenitic SS): ASTM A182 Gr. F316, F316L, F317L.
- Group 2.8 (Duplex SS): ASTM A182 Gr. F51 (UNS S31803), F53 (UNS S32750 Super Duplex).
3. ASME B16.5 Class 150 Flange Dimension Reference Table (NPS 1 to NPS 8)
Below are key nominal dimensions for ASME B16.5 Class 150 Weld Neck (WN) and Slip-On (SO) flanges manufactured by Sakshi Forge:
| NPS (Inches) | Outside Diameter (O) mm | Thickness (C) mm | Bolt Circle Diameter (W) mm | Number of Bolt Holes | Bolt Hole Diameter (Y) mm | Hub Diameter (X) mm |
|---|---|---|---|---|---|---|
| 1" | 108 mm | 14.3 mm | 79.4 mm | 4 | 15.9 mm (5/8") | 49.2 mm |
| 1-1/2" | 127 mm | 17.5 mm | 98.4 mm | 4 | 15.9 mm (5/8") | 65.0 mm |
| 2" | 152 mm | 19.1 mm | 120.7 mm | 4 | 19.1 mm (3/4") | 77.7 mm |
| 3" | 191 mm | 23.9 mm | 152.4 mm | 4 | 19.1 mm (3/4") | 108.0 mm |
| 4" | 229 mm | 23.9 mm | 190.5 mm | 8 | 19.1 mm (3/4") | 134.9 mm |
| 6" | 279 mm | 25.4 mm | 241.3 mm | 8 | 22.2 mm (7/8") | 192.1 mm |
| 8" | 343 mm | 28.6 mm | 298.5 mm | 8 | 22.2 mm (7/8") | 246.1 mm |
4. Maximum Allowable Working Pressure (MAWP) vs Temperature
For ASTM A182 F316L (Group 2.2), maximum working pressure drops as temperature increases:
| Temperature (°C / °F) | Class 150 (bar) | Class 300 (bar) | Class 600 (bar) | Class 1500 (bar) |
|---|---|---|---|---|
| -29 to 38 °C (-20 to 100 °F) | 19.0 bar | 49.6 bar | 99.3 bar | 248.2 bar |
| 100 °C (212 °F) | 16.2 bar | 42.2 bar | 84.4 bar | 211.0 bar |
| 200 °C (392 °F) | 13.7 bar | 35.6 bar | 71.3 bar | 178.2 bar |
| 300 °C (572 °F) | 10.2 bar | 31.6 bar | 63.2 bar | 158.0 bar |
| 400 °C (752 °F) | 6.5 bar | 29.4 bar | 58.9 bar | 147.2 bar |
5. Flange Facing Types & Machining Finish
- Raised Face (RF): Most common facing. 1.6 mm height for Class 150/300; 6.35 mm for Class 600+. Phonographic serrated finish (Ra 3.2 to 6.3 µm / 125 to 250 µin AARH) for spiral wound gaskets.
- Ring Type Joint (RTJ): Used in high pressure/high temperature oilfield lines (Class 600 to 2500). Utilizes octagonal or oval metallic ring gaskets.
- Flat Face (FF): Used when mating with cast iron or low-pressure pumps to prevent bending moments during bolt torquing.