ASME B16 standards: what each one covers
The ASME B16 series standardizes the dimensions, tolerances and pressure classes of piping components. The material comes from another standard (ASTM), cited within each B16.
Standards in the B16 series
| Standard | What it covers | Range |
|---|---|---|
| ASME B16.5 | Pipe flanges and flanged fittings | NPS ½ to 24, classes 150 to 2500 |
| ASME B16.47 | Large-diameter flanges, Series A (formerly MSS SP-44) and Series B (formerly API 605) | NPS 26 to 60, classes 75 to 900 |
| ASME B16.9 | Butt-welding fittings: elbows, tees, reducers, caps | NPS ½ to 48 |
| ASME B16.11 | Forged socket-welding and threaded fittings | NPS ⅛ to 4, classes 2000 to 9000 |
| ASME B16.20 | Metallic gaskets: RTJ rings, spiral-wound and jacketed | For B16.5 and B16.47 flanges |
| ASME B16.21 | Non-metallic flat gaskets | For B16.5 and B16.47 flanges |
| ASME B16.25 | Butt-welding end preparation (bevel) | Pipes, fittings, flanges and valves |
| ASME B16.34 | Flanged, threaded and welding-end valves: class and minimum wall thickness | Classes 150 to 4500 |
| ASME B16.48 | Line blanks: spectacle blinds, paddle blanks and spacers | NPS ½ to 24, classes 150 to 2500 |
| MSS SP-97 | Forged branch outlets (olets): weldolet, sockolet, threadolet | Classes 3000 to 9000* |
| ASME B36.10M / B36.19M | Carbon/alloy steel and stainless pipe: diameter and schedule | NPS ⅛ to 80 / ⅛ to 30 |
Where the material comes from
- Forgings (flanges, B16.11 fittings, olets): ASTM A105 (carbon), A182 (alloy, stainless, duplex), A350 (low temperature), B564 (nickel).
- B16.9 butt-welding fittings: ASTM A234 (carbon and alloy), A403 (stainless), A815 (duplex), B366 (nickel).
- Bolts and nuts: ASTM A193, A320 and A194.
- The allowable pressure depends on the class and on the material group: see pressure classes.
Frequently asked questions
What is the difference between ASME B16.5 and B16.47?
B16.5 goes up to NPS 24. Above that, from NPS 26 to 60, B16.47 applies, which has two series with different dimensions: Series A is more robust and Series B more compact. Flanges of the two series are not interchangeable.
What is the difference between B16.9 and B16.11?
B16.9 covers butt-welding fittings, with the same wall thickness as the pipe (schedule). B16.11 covers small forged fittings, socket-welding or threaded, identified by class (3000, 6000, 9000).
ASME flanges and fittings in special alloysWe forge and machine non-standard items from your drawing.
Request a quote * Value to be confirmed in the current edition of the standard.
