What Are ASME B16.47 Series A Flanges?
ASME B16.47 Series A flanges are the traditional large-diameter flange design derived from MSS SP-44. Covering NPS 26 through NPS 60, Series A flanges have the larger outside diameter and bolt circle of the older MSS SP-44 heritage. They are not interchangeable with Series B flanges of the same size and class.
Series A Range
| Parameter | Series A (MSS SP-44 Heritage) |
|---|---|
| Size range | NPS 26 – NPS 60 |
| Pressure classes | Class 150 / 300 / 400 / 600 / 900 |
| Dimensional tables (SI) | Table 32 (150), Table 33 (300), Table 34 (400), Table 35 (600), Table 36 (900) |
| Raised face | 1.5 mm on Classes 150/300; 6.4 mm on Classes 400/600/900 |
| Flange types | weld neck, blind, hub (slip-on / threaded hub) |
Why Series A vs Series B?
Series A (MSS SP-44) uses a larger flange OD and a larger bolt circle with more, smaller-diameter bolting. Series B (API 605) is more compact with fewer, larger bolts. Match the flange series to your existing piping — drilling patterns are not interchangeable.
Materials
| Material | Grade | Temperature Range |
|---|---|---|
| ASTM A105 | Carbon steel forging | -29°C to 425°C |
| ASTM A182 | F304 / F316 | Up to 538°C |
| ASTM A350 | LF2 | -46°C to 425°C (low-temperature service) |
Pressure-temperature ratings follow the same material-group tables as ASME B16.5 (Rating Ceiling Values per Table A-1).
Dimensions
Full dimensional tables for Series A are in ASME B16.47-2025 Tables 32 through 36 (SI units): Table 32 Class 150, Table 33 Class 300, Table 34 Class 400, Table 35 Class 600 and Table 36 Class 900, covering NPS 26 through NPS 60. We manufacture to these tables — send us your size, class and series.
Related Standards
- ASME B16.47 — Large-Diameter Flanges Overview (NPS 26–60)
- ASME B16.47 Series B Flanges (API 605)
- ASME B16.5 — Flanges NPS 1/2–24
- ASME B16.20 — Metallic Gaskets for Large Flanges
- Our Flange Range
- ASTM A105 Carbon Steel Forgings
- ASTM A350 LF2 Low-Temperature Steel
FAQ
What does Series A mean in ASME B16.47?
Series A flanges follow the MSS SP-44 traditional design: larger outside diameter and bolt circle than Series B. They are used where existing piping or engineering calls for MSS SP-44 drilling.
What pressure classes do Series A flanges cover?
Class 150, 300, 400, 600 and 900, in NPS 26 through NPS 60. Dimensional tables are ASME B16.47 Tables 32 through 36.
Are Series A and Series B interchangeable?
No. The outside diameters, bolt circles and number/size of bolts differ — you must match the series already in your piping. Mixing Series A and Series B flanges will not bolt up.
Can Series A flanges be made in stainless steel?
Yes — A182 F304 and F316 forged stainless, A105 carbon steel and A350 LF2 low-temperature steel, all to the same Series A dimensional tables.
What sizes are covered?
NPS 26 through NPS 60. Smaller flanges up to NPS 24 are covered by ASME B16.5.